KSB Know-how, Volume 5
Pressure Boosting
Planning information for pressure boosting November 2007 edition Subject to technical modifications.
© Copyright by KSB Aktiengesellschaft Publisher: KSB Aktiengesellschaft
All rights concerning public distribution through film, radio, television, video, photo-mechanical reproduction, sound and data storage devices of any kind, the printing of excerpts, and the saving, accessing and manipulation of data in any way, shape or form are only granted with the expressed permission of the manufacturer.
Division: Building Services Pumps D-91253 Pegnitz
KSB – the complete range! Pumps and systems for pressure boosting and fire fighting
Hya-Solo E
Hya-Solo D/DV
Hya-Eco K/VP
Hyamat K/V/VP
Contents
Page 1
Foreword
3
2
Fundamentals
4
3
Calculating the hydraulic data of pressure boosting units
8
3.1
Calculating the flow rate of a pressure boosting unit
8
3.1.1
Calculation example (1) – Drinking water supply system for a residential building
3.2
Calculating the pressure values and pressure zones
9
3.2.1
Connection types
9
3.2.2
Calculating the available pressure upstream of the PBU (pinl)
9
3.2.2.1 Determining the pressure zone upstream of the PBU 3.2.2.2 Calculation example for direct connection; continuation of (1)
9 10
3.2.3
Calculating the required pressure downstream of the PBU (pdischarge)
12
3.2.4
Calculating the discharge head of the PBU
13
3.2.5
Determining the pressure zone(s) downstream of the PBU
13
4
Calculation example (2) – Calculating the hydraulic data of a PBU for the supply of fire-fighting water for wall-mounted fire hydrants
14
5
Choosing the correct PBU variant (Pump type) – with calculation examples (3) + (4)
15
5.1
PBU with cascade control (Hya-Eco and Hyamat K)
15
5.2
PBU with one variable speed pump (Hyamat V)
20
5.3
PBU with speed control on all pumps (Hyamat VP)
26
6
Overview – Connection types for drinking water and service water installations
28
7
Overview – Connection types for fire-fighting systems, wet risers
30
8
Overview – Connection types for combined installations (drinking and fire-fighting water supply as well as service and fire-fighting water supply)
32
9
Overview – Connection types for wet- / dry-type systems
33
10
Accumulator selection / calculations
34
11
Dry running protection, selection criteria for PBUs
37
11.1
Protection of the supply network
37
11.2
Protection of pressure boosting unit
37
12
Effects of inlet pressure fluctuations
39
12.1
Indirect connection
39
12.2
Direct connection
39
1
Contents
Page 13
Causes of pressure surges
42
13.1
Pressure surges caused by valves
42
13.2
Pressure surges as a result of inlet pressure fluctuations
42
14
Standards, directives and statutory regulations
43
15
Inspection, maintenance and repair
46
16
Nomenclature
47
17
References
50
18
Annex Worksheet 1, Calculation flow rates and minimum flow pressures
52
Worksheet 2, Calculating the peak flow rate
53
Worksheet 3, Flow rates
54
Worksheet 4, Water meters
55
Worksheet 5, Filters, drinking water heating systems, pressure losses in consumer supply pipes 56
2
Worksheet 6, Conversion of discharge head H into pressure increase ⌬p
57
Worksheet 7, Head losses of steel pipes
58
Worksheet 8, Head losses of low-friction pipes
59
Worksheet 9, Permissible flow rate criteria of a PBU
60
1
Foreword
1 Foreword
Pressure boosting units have the following typical applications:
This brochure is intended for all involved with the planning, design and service of pressure boosting units (PBU).
• Residential buildings
Pressure boosting units are often found in modern office, residential and hotel buildings for general water provision and fire-fighting purposes. Considering the various PBU design concepts such as • cascade control (Hya-Eco, Hyamat K) • variable-speed control for one pump (Hyamat V) • variable-speed control for all pumps (Hyamat VP) • etc. it is particularly important to select the right PBU concept for the specific project at the planning stage. This brochure offers design guidance for pressure boosting units ensuring easy installation and uninterrupted water supply. KSB justifies its status as a full-line supplier of pumps for building services by constantly developing its range of products according to the requirements of its customers.
• Office buildings • Hotels • Department stores • Clinics/hospitals • Trade and industry plants • Spray and conventional irrigation • Rainwater harvesting • Small-scale domestic water supply units A pressure boosting unit is required when the minimum pressure supplied by the local water provider, see Fig. 1, is insufficient. Pressure boosting units and their ancillary components must be designed and operated in such a way that neither the public water supply nor any other consumer units are interfered with – any degradation in the quality of drinking water must likewise be ruled out. The regulations referred to in the brochure are based upon regulations in force in Germany at the time of writing. To ensure compliance, reference should be made to LOCAL and current regulations.
3
2
Fundamentals
2 Fundamentals Drinking water is a consumable product, and is therefore subject to strict legal regulations. The essential requirements for drinking water quality are laid down in: DIN 2000 Central drinking water supply
DIN EN 805 Water supply – Requirements for units and components outside buildings (if agreed upon) DIN EN 806 Specifications for installations inside buildings conveying water for human consumption (if agreed upon) (Public drinking water supply, for which KSB also offers an extensive pump programme, is not dealt with here.)
DIN 2001 Drinking water supply from small units and non-stationary plants
In terms of the origins of drinking water, a difference must be made between centralized and/or local individual water supply units.
IfSG Protection Against Infection Act
The following discussion deals with both possible applications.
LMBG Foodstuffs and Commodities Act
In all cases where the minimum supplied water pressure (pmin,V) does not enable an unconditional supply to all extraction points, i.e.:
TrinkwV Drinking Water Ordinance
pmin,V < ∆pgeo + pmin,flow + Σ(R · l+ Z) +
[1]
∆pwm + ∆pap [bar]
The regulations for adequate water provision to consumers which are applicable to units situated in buildings and property are as follows:
the deployment of a PBU is necessary.
AVB Wasser V General Water Supply Terms Ordinance
pmin,V = Minimum pressure available at the local water provider’s hand-over point
DIN 1988 Drinking water supply units
∆pgeo =
Legend for [1]:
Static pressure loss
pmin,flow = Minimum flow pressure at the least hydraulically favourable extraction point
PBU pmin,V
Fil 000
m3 Mains water supply pipe Water meter
Consumer supply pipe upstream of the PBU
PBU= Pressure boosting unit and ancillary components
Service pipe Hand-over point-local water provider (public/private)
Fig. 1: Flow diagram, pressure boosting unit (PBU): direct connection
4
Installation within the building
Consumer supply pipe upstream of the PBU
2
Fundamentals
Σ(R·l+Z) = Pipe friction and other losses ∆pwm = Water meter pressure loss ∆pap
= Apparatus pressure loss
The configuration and function of the PBU are described in DIN 1988 Part 5. This standard applies to centralized and individual water provision units. It prescribes, amongst other things, built-in stand-by pumps suitable for immediate operation for the transportation of drinking water. Permanent operating reliability is required according to DIN EN 806 Part 2. Omitting the installation of a stand-by pump alongside a PBU for drinking water supply may be justified when the breakdown of a PBU does not seriously affect residents’ requirements, e.g. in the case of weekend houses. Here, a PBU may be installed and operated without a stand-by pump. Permission must however always be sought from the responsible Water Authority. As a rule, the integration of the PBU (Fig. 1) must be performed in such a way that adverse hydraulic effects on the public water supply network are minimized. This is facilitated through the selection of suitable components which in turn relies on knowledge of inlet pressure fluctuation and the maximum connection capacity of the service pipe together with an examination of the flow velocity in the house service pipe. Anti-vibration mounting of the PBU (e.g. expansion joints with length limiters, anti-vibration mounts) markedly contributes to a reduction in solid-borne sound transmission.
If the inlet pressure fluctuations lie beyond +0.3/-0.2 bar, the following remedial action is possible and may be necessary: • Pressure controller / reducer upstream of the PBU (type series Hyamat K, Hyamat V, Hya-Eco) • PBUs with variable speed base load pump (type series Hyamat V) (see also section 5.5.2) • for large inlet pressure fluctuations: PBUs with speed control on all pumps (type series Hyamat VP)
Distribution of flow volume Decisive for sizing the individual pumps of a PBU is the relationship between the PBU’s design flow rate and the maximum connection capacity of the service pipe. Particularly in the case of PBUs with cascade control (Hya-Eco and Hyamat K range) it is important to ensure that the velocity change in the service pipe does not exceed 0.15m/s when the individual pumps are started and stopped. This can be achieved by distributing the design flow rate across several pumps. Possible remedies: • Incorporating membrane-type accumulators on the inlet side • Indirect connection via unpressurized inlet tank • PBU with one variable speed base load pump (Hyamat V) • PBU with speed control on all pumps (Hyamat VP)
Fluctuating inlet pressures Fluctuations in the supply pressure have a considerable effect on the operating characteristics of the PBU. These range from a dramatic rise in switching frequency (excessive on/off) to increased levels of discharge pressure fluctuation. In certain cases, the rated pressure of the unit components can be exceeded. This leads in all cases to pressure surges and consequent wear on all associated parts.
Demand fluctuations Sudden changes in demand downstream of a PBU can lead to pressure surges/noises in the dischargeside distribution unit. Pressure surges can sometimes trigger safety devices or even cause damage to apparatus or lead to burst pipes and increased wear on pumps, valves, and piping. Reduction in the highly dynamic levels of consumption is the most effective
5
2
Fundamentals
remedy (e.g. through the replacement of solenoid valves with motor-operated valves). Just as important is the adequate sizing of the pump in relation to its nominal flow rate. ∆QPu > ∆Qmax,dyn [m3/h]
[2]
Legend for [2]: ∆Qmax,dyn = Change of flow of a highly dynamic consumer ∆QPu = Change of flow rate of each pump In addition, membrane-type accumulators fitted directly upstream of dynamic consumers reduce the aforementioned effects. These must be of the direct-flow type. PBUs incorporating continuously variable speed control on all pumps (Hyamat VP) can respond better to high consumer fluctuations due to the synchronized operating mode of the pumps.
Noises Modern PBUs are expected to operate with a minimum of noise. Operating noise (airborne sound) is mainly generated by the electric motor fans. Cladding can considerably reduce noise emission. The selection of an appropriate location is likewise an important factor (away from recreation rooms and bedrooms). In operation, pumps create vibrations, flow noise and solid-borne noise. The provision of adequate sound insulation of the piping from the PBU is therefore of primary importance, and every PBU must be separated from the piping and structure surrounding it by suitable sound insulation (i.e. expansion joints with length limiters, anti-vibration mounting using rubber-bonded metal elements). Expansion joints must be easily replaceable. With regard to flow noises, a moderate flow velocity in piping, apparatus and pipe fittings should be ensured.
6
Hygiene In view of hygiene requirements, a distinction should be made between units dealing with drinking water and those handling service water. Drinking water: According to the Drinking Water Ordinance (excerpt) drinking water is referred to as “water for human consumption and use”. Drinking water is to be understood as water in its original condition or after treatment which is used for drinking, cooking, preparing meals and beverages, for personal hygiene and the cleaning of objects which are destined to be used with food and those which are temporarily in contact with the human body. Service water: “Water to serve commercial, industrial, agricultural or similar purposes with varying levels of quality which can include drinking water”. When operating a PBU it is important that water quality is not impaired. An essential requirement is: operation of the PBU and its associated components should not allow stagnation. As a closed unit rules out any health risk resulting from external contamination of drinking water, units with direct connection should be preferred to those with indirect connection. The following measures reduce the chance of water stagnating: • Direct-flow membrane-type accumulators (dual connection) • Automatic switchover between all pumps • Smallest possible dead spaces in components handling water • Forced flushing of pipe sections where stagnation could occur A further aspect of hygiene is the temperature of the fluid. The following factors can lead to a temperature increase of the water inside PBU components – unpressurized inlet tank, pumps, pipe components and membrane-type accumulators:
2
Fundamentals
• Increased ambient temperature at the site of installation • Long periods of minimum consumption (office buildings at the weekend) • Temperature increase due to the pumping operation (heat losses). These factors can be eliminated through the selection of an appropriate location and the prompt stopping of pumps at minimum/zero consumption. The materials and auxiliary equipment used in the construction of a PBU must be in line with the relevant regulations regarding the compatibility with drinking water (as stipulated, for example, by the German LMBG, KTW, DVGW regulations). Cleanliness during construction, transport, installation and commissioning of a PBU und its associated equipment, together with a final flushing of the entire unit according to DIN 1988 Part 2 or ZVSHK technical instruction leaflet, are mandatory requirements for water according to DIN 2000 which is: • Absolutely hygienic • Cool • Neutral in terms of taste and odour • Clear • Free from foreign substances
7
3
Calculating the flow rate of the PBU
3 Calculating the hydraulic data of pressure boosting units 3.1 Calculating the flow rate of a pressure boosting unit 3.1.1 Calculation example (1) Drinking water supply system for a residential building The calculation is performed on the basis of DIN 1988 (1988 edition). The assumptions are as follows: High-rise residential building with basement, ground floor and a further 14 floors, see Fig. 4. 97 identically equipped living units have to be supplied with drinking water. The living units (LU) are equipped as follows: Per living unit (LU): 2 toilets with cisterns, DN 15 1 bath tub, DN 15 1 shower, DN 15 2 sink units, DN 15 1 bidet, DN 15 1 washing machine, DN 15 1 dishwasher, DN 15 1 kitchen sink, DN 15
· The required total flow ΣVR should as a rule be established on the basis of the specifications made by the taps, showerheads and fittings manufacturers. If in a specific case such information is not available, the total flow can be calculated by means of Worksheet No. 1 in the Appendix. · According to this Worksheet ΣVR is as follows: Appliance flow rates 2 toilets 1 bath tub 1 shower 2 sink units 1 bidet 1 washing machine 1 dishwasher 1 kitchen sink
0.26 l/s 0.3 l/s 0.3 l/s 0.28 l/s 0.14 l/s 0.25 l/s 0.15 l/s 0.14 l/s
This gives a required total flow per living unit of: 1.82 l/s The total calculated flow for 97 living units is: · ΣVcal = 97 · 1.82 l/s = 176.5 l/s In practice, total flow is never required. · For the determination of a realistic peak flow Vpeak use Worksheet 2, curve A, in the Appendix.
Flow rate in m3/h (l/s) Drinking water demand
1)
2)
4 5 (1.11) (1.39)
6 1.67
8 2.22
9 (2.5)
10 2.78
11 3.06
12 3.33
13 3.61
14 3.89
15 4.17
25 6.94
30 8.33
40 11.1
50 13.9
420
560
Residential buildings 1) up to ... living units
4
6
10
30
45
60
75
95
115
140
180
Hospital 2) up to ... beds
30
40
50
65
75
85
95
100
115
125
135
180
230
300
Office buildings 2) up to ... employees
160
200
240
340
380
440
480
540
600
660
730
1100
1500
2000
Hotel 2) up to ... beds
20
25
30
40
45
50
55
60
65
70
75
100
125
155
210
280
Department store 2) up to ... employees
40
50
60
85
95
105
115
125
135
150
160
220
300
400
750
1400
· These are reference values for living units with standard equipment (Vcal < 1 l/s); for living units with more “luxury” installations higher values must be considered and/or a detailed calculation performed. These reference values serve merely as a guideline. To determine the water consumption, the design engineer has to calculate the expected max. consumption taking the installations and their usage into account.
Table 1: Data for approximately calculating the flow rate of a PBU
8
20 5.56
3
Calculating the flow rate of the PBU
The resultant peak flow is: · Vpeak = 4.4 l/s The PBU to be selected must be capable of handling at least this peak flow.The following equation is therefore applied: · ^ Vmax,P = ^ QD = 4.4 l/s Vpeak = 앒 15.9 m3/h · In pumping technology, the peak flow (Vpeak) corresponds to the design flow rate of the PBU (QD). For an approximate calculation of the flow rate, below table 1 can be used.
3.2 Calculating the pressure values and pressure zones 3.2.1 Connection types As a rule, a distinction is made between the direct and indirect connection of a PBU to the water supply unit. The water provider will determine the type of connection permitted.
3.2.1.1 Direct connection of a PBU, Fig. 2 This type of connection is characterized by a specific inlet pressure (pinl) available upstream of the PBU.
pmax,V pmin,V
As the supply pressure level at the hand-over point can vary between pmin,V and pmax,V, the resultant inlet pressure pinl upstream of the PBU has to be established according to the example in section 3.2.2.2.
3.2.1.2 Indirect connection of a PBU, Fig. 3 As the unit is separated through the installation of an unpressurized inlet tank (indirect connection type), the existing supply pressure is reduced to the ambient pressure; hence installing the PBU on the same level as the inlet tank means that only the filling level of the inlet tank is the available hydrostatic inlet pressure (pinl 앒 0.1 bar). Hence, an inlet pressure (pinl) of 0 bar is assumed for the design of the PBU. N.B. If the installation level of the unpressurized inlet tank is lower than that of the PBU, the PBU must be designed for suction lift operation.
3.2.2 Calculating the available pressure upstream of the PBU (pinl) 3.2.2.1 Determining the pressure zone upstream of the PBU The number of floors can be established through the following equation:
Fil 00 0
m3 pinlet
Mains water supply pipe Service pipe
Water meter
Consumer pipes upstream of the PBU
PBU
Consumer pipes downstream of the PBU
Hand-over point (local water provider)
Fig. 2: Flow diagram, direct connection of a pressure boosting unit (PBU)
9
3
Calculating the flow rate of the PBU
Fil
pmax,V
000
m3
pmin,V
pinlet 0 bar
Mains water supply pipe Service pipe
Water meter
Consumer pipes upstream of the PBU
PBU
Consumer pipes downstream of the PBU
Hand-over point (local water provider)
Fig. 3: Flow diagram, indirect connection of a pressure boosting unit (PBU)
pinl, min – pflow – ∆pdyn NwithoutPBU 울 ––––––—––––––––– ∆pfl 2.47 – 1.0 – 0.2 ––––—––––––– 0.3
NwithoutPBU 울 NwithoutPBU =
[3]
3.2.2.2 Calculation example for direct connection; continuation of (1) The local water provider provides the following information for a drinking water installation as per section 3.1.1:
4.23
Rounded down
pmin,V
Nwithout PBU = 4
pmax,V = 4.8 bar
= 2.8 bar
Nom. diameter of service pipe: DN 80 Direct connection of PBU Counting from the branch (upstream of the PBU inlet pipe), the first 4 floors (ground floor, 1st, 2nd and 3rd floor) can be supplied directly, Fig. 4. Water supply by means of a PBU is required from the 4th floor, Fig. 4.
Woltmann-type water meter
15th . . pressure zone, here pressure reduction measures are not required
. . .
Legend for [3]:
. .
Nwithout PBU= Number of floors which can be supplied without PBU
. . . 5th
pinl,min
= Minimum pressure available upstream of the PBU
pflow
= Flow pressure at consumer
⌬pdyn
= Dynamic pressure difference
⌬pfl
= Pressure loss per floor
4th 3rd 2nd
Nflpr = 6
1st
Nwithout PBU = 4
Ground floor Basement PBU
Fig. 4: Diagram depicting pressure zones
10
3
Calculating the flow rate of the PBU
Calculation of minimum, maximum and inlet pressure fluctuations upstream of the PBU.
pinl,min = pmin,V – Σ(R · l + Z)inl – ∆pwm – ∆pap [bar]
Σ(R·l+Z)inl = 0.1 bar (assumption made by engineering consultant)
Result, Fig. 5:
⌬pwm
· Vpeak 2 = ––––– · ⌬p ·
⌬pwm
15.9 2 1 = ––––– · 600 · ––––– bar 30 1000
[ ] [ ]
pinl,min = 2.8 – 0.1 – 0.17 – 0.06 = 2.47 bar
Vmax
pinl,min 앒 2.5 bar pinl,max = 4.8 bar ⌬pinl
= 0.17 bar (Woltmann-type water meter, vertical, DN 50, see Worksheet 4, Appendix) · VS ⌬pap = ––––– ·
2
[ ] [ ] Vmax
[4]
· ⌬p
15.9 2 1 ⌬pap = ––––– · 200 ·––––– bar 30 1000 = 0.06 bar (Filter: nom. throughflow 30 m3/h, see Worksheet 5, Appendix)
= 4.8 – 2.5 = 2.3 bar
The PBU must be able to operate reliably with an inlet pressure fluctuation of ⌬pinl = 2.3 bar. The inlet pressure pinl upstream of the PBU fluctuates to a greater extent than the supply pressure at the hand-over point. Therefore, it must be possible to operate the PBU with a supply pressure fluctuation ⌬pinl. This must be examined for each specific unit and, if necessary, appropriate measures should be taken to properly protect the unit (e.g. pressure reducers).
Maximum pressure: Minimum pressure: This level is reached under min. supply pressure pmin,V and simultaneous max. water consumption · Vpeak conditions. This requires that the dynamic pressure losses in the installation between handover point (local water provider) and PBU inlet be taken into account.
pmax,v = 4.8 bar pmin,v = 2.8 bar
Fil
This level is reached under maximum supply pressure pmax,V and simultaneous minimum water consumption conditions. The dynamic pressure losses in the supply-side installation can be disregarded. pinl,max = pmax,V
[bar]
pinl,max = 4.8 bar
00 0
m3 pinl,min = 2.5 bar
Mains water supply pipe Service pipe
[5]
Water meter
Consumer pipes upstream of the PBU
PBU
Consumer pipes downstream of the PBU
Hand-over point (local water provider)
Fig. 5: Flow diagram, direct connection of PBU including pressure values
11
3
Calculating the flow rate of the PBU
∆pinl = pinl,max – pinl,min
[bar]
[6]
Legend for [4], [5], [6]: pinl,min = Minimum available pressure upstream of the PBU pmin,V = Minimum available pressure at the local water provider’s hand-over point Σ(R·l+Z)inl = Pipe friction and other losses from the supply pipe to the PBU ⌬pwm = Water meter pressure loss ⌬pap
15 · 3 ⌬pgeo = ––––––– 10
= 4.5 bar
Σ(R·l+Z)discharge =
70 · 15 –––––– = 1.05 bar 1000
(Estimation, see Appendix, Worksheet 5) The measured pipe length from the PBU to the least hydraulically favourable extraction point is approx. 70 m. (Exact calculation acc. to DIN 1988, Part 3) pmin,flow = 1.0 bar (see Appendix, Worksheet 1)
= Apparatus pressure loss
pinl,max = Maximum pressure upstream of the PBU
The tap requiring the highest pressure determines the required minimum flow pressure (pmin,flow).
pmax,V = Maximum available pressure at the local water provider’s hand-over point
⌬pap = 0 (assumption: no further apparatuses built into piping)
⌬pinl
Above values inserted into the formula:
= Pressure fluctuation upstream of the PBU
pdischarge = 4.5 + 1.05 + 1.0 + 0 3.2.3 Calculating the required pressure downstream of the PBU (pdischarge) Calculation example: The residential building as per section 3.1.1 is provided with 97 identical living units. All floors – basement, ground floor and a further 14 floors – have a floor height of 3 m. pdischarge = ∆pgeo + Σ(R · l + Z)discharge + pmin,flow + ∆pap [bar]
[7]
= 6.55 bar ≈ 6.6 bar
Legend for [7], [8]: pdischarge = Required pressure downstream of the PBU ⌬pgeo = Pressure loss from static head difference Σ(R·l+Z)discharge = Pipe friction and other losses downstream of the PBU ⌬pwm = Water meter pressure loss pmin,flow = Minimum flow pressure at consumer ⌬pap
= Apparatus pressure loss (e.g. individual water meter)
N
= Number of floors
Hfl
= Floor height
Calculation procedure: The static head loss is calculated on the basis of the number of floors (N) and the floor height (Hfl). N · Hfl ∆pgeo = ––––––– 10
[bar]
see also Appendix, Worksheet 6
12
[8]
3
Calculating the flow rate of the PBU
3.2.4 Calculating the discharge head of the PBU In the case of direct PBU connection, the inlet pressure pinl can generally be used, under certain conditions (see sections 5.2 and 5.3) even fully. The minimum permissible inlet pressure pinl,min (or the inlet pressure fluctuation) depends on the PBU control mode: • for cascade controlled PBUs (Hya-Eco, Hyamat K) installing a pressure reducer upstream of the PBU is often essential (see section 2). This is assumed for our example. The overall pressure reduction achieved by the pressure reducer is ⌬ppressred 0.7 bar.
H = [6.6 – (2.5 – 0.7)] · 10 = 48 m • for variable speed PBUs (Hyamat V, Hyamat VP) installing a pressure reducer on the inlet pressure side is normally not required.*) In general, the following equation applies for the calculation of the pump’s discharge head H: [m]
Assuming a constant supply pressure downstream of the PBU of pdischarge 앒 6.6 bar, a rough check of protective measures required can be made as follows. The maximum permissible static pressure in residential buildings is max. 5.0 bar (safety valves, noises, toilet cisterns). Since this maximum pressure of 5.0 bar must not be exceeded and the highest static pressure level will be reached at zero consumption (Q 앒0), the dynamic pressure losses will be Σ(R·l+Z) = 0. In order to find out up to which floor the consumers have to be protected by means of pressure reducers against a pressure of 욷 5.0 bar, the following calculation can be applied:
Above values inserted into the formula [9]:
H = (pdischarge – pinl,min) · 10
3.2.5 Determining the pressure zone(s) downstream of the PBU
[9]
Above values inserted into the formula [9]: H = (6.6 – 2.5) · 10 = 41 m
pdischarge – pmax,flow Nflpr 욷 ––––––––––––––––– ⌬pfl
Nflpr 욷
Legend for [10]:
Legend for [9]: = Pump discharge head
6.6 – 5.0 –––––––– = 5.3 0.3
(This value must be rounded up to 6.)
Nflpr
H
[10]
= Number of floors which have to be protected against inadmissible pressures by means of pressure reducers
pdischarge = Required pressure downstream of the PBU
pdischarge = Required pressure downstream of the PBU
pmax,flow = Maximum permissible flow pressure at consumer
pinl,min = Minimum available pressure upstream of the PBU
⌬pfl
*) Whether this approach is hydraulically permissible must, however, be checked by means of the KSB documentation.
= Pressure loss per floor
At least the first 6 floors have to be protected with pressure reducers installed in the consumer pipes downstream of the PBU. In this case, this applies to floors 4 and 5, since the lower floors are supplied directly, cf. Fig. 4, page 10. This consideration only applies to pressure boosting units with a constant, variable-speed controlled discharge pressure.
13
4
Supply of fire-fighting water for wall-mounted fire hydrants
4 Calculation example (2): Calculating the hydraulic data of a PBU for the supply of fire-fighting water for wall-mounted fire hydrants The residential building as per section 3.1.1 is equipped with 18 fire hydrants including standard fire service connections which must be supplied with fire-fighting water by a PBU. · The peak flow (Vpeak) for the fire-fighting water supply is calculated exclusively on the basis of the calculated flow rate per hydrant multiplied by the simultaneity factor (f). The calculated flow per wall-mounted fire hydrant · is Vcal = 100 l/min = 6 m3/h (Worksheet 3, Appendix) for a hydrant marked “F”. A simultaneity factor of f = 3 according to DIN 14461 part 1 has been laid down. · In the example, the peak flow (Vpeak) and therefore the design flow rate (QD) of the PBU for the supply of fire-fighting water is: · · Vpeak = Vcal · f = QD [m3/h]
[11]
Using the discharge head calculation for drinking water, the discharge pressure and head of the firefighting PBU can be established with the following formula: ∆pP = ∆pgeo + Σ(R · l + Z)discharge + pmin,hydr – pinl,min [bar]
[13]
Legend for [13]: ⌬pgeo = Pressure loss from static head difference Σ(R·l+Z)discharge = Pipe friction and other losses down-stream of the PBU pmin,hydr = Minimum flow pressure at the least hydraulically favourable hydrant pinl,min
H
= Minimum available pressure upstream of the PBU
= (4.5 + 1.05 + 3.0 – 1.8) m · 10 = 67.5 m
Selected: Hya-Solo D 1807 / 1.8 (1 Pump, 7.5 kW, pco = 9.6 bar, pci = 11.6 bar, pressure-dependent control)
· Vpeak = 6 m3/h · 3 = 18 m3/h = QD Legend for [11]: · Vpeak = Peak flow of a PBU · Vcal = Calculated flow rate per hydrant f
The standard applied for the pressure boosting units is DIN 1988-5 or, if agreed upon, DIN EN 806-2. In addition, the requirements for the respective fire-fighting concept are applicable.
= Simultaneity factor
QD = Design flow rate of a PBU
According to EN 806-2: 2005 the following applies to PBUs for water supply and firefighting: The flow rate of the PBU should be the higher value of both supply requirements.
Calculating the pump discharge head H: H = (pdischarge – pinl,min) · 10
14
[m]
[12]
5
Choosing the correct PBU variant
This is particularly noticeable in the case of pumps with fewer stages (flat pump curve)
5 Choosing the correct PBU variant (Pump type) – with calculation examples (3) + (4)
• In the case of inlet pressure fluctuations, potential use of the inlet pressure is limited
5.1 PBU with cascade control (Hya-Eco and Hyamat K)
• Therefore, upstream pressure reducers are frequently required
5.1.1 Features
• Adverse hydraulic impact on the mains supply network is relatively high
• Pumps are started / stopped as a function of pressure • Pumps run at full speed • Auto-changeover of pumps
5.1.2 Calculation example (3) Discharge head of PBU
• Output pressure fluctuates by min. (pco – pci) by max. (p0 – pci) + ⌬pinl
Calculating the required pressure downstream of the (pdischarge) pdischarge = ⌬pgeo + Σ(R · l + Z) + pmin,flow [bar] [14]
• Excessive on/off ("hunting") occurs when the water demand falls below a min. capacity Qmin (pco)
pdischarge = 3.3 + 1.1 + 1.0 (assumed values)
• The range of excessive on/off operation is enlarged with increasing pinl (inlet pressure).
pdischarge = 5.4 bar
Cascade control p Hyamat K
pco
p(co-ci)
pci
The discharge pressure(pdischarge) required of a PBU with cascade control is the cut-in pressure (pci). Depending on the design of the pump, the discharge pressure can rise up to the value p0 = pinl + H0 / 10.
Q
This increase in pressure always depends on the type of pumps selected (flat/steep characteristic curve).
On/Off
H p0 pco Fluctuation range of discharge pressure p(co-ci) pci
Qmin (pco)
Q
Excessive on/off
According to the local water provider, the supply pressure at the hand-over point may vary between a minimum value of pmin,V = 2.2 bar and a maximum value of pmax,V = 3.5 bar. As the inlet pressure fluctuations are too high for cascade control, it is necessary to install a pressure reducer. Due to the pressure reduction of approx. 0.7 bar achieved by the pressure reducer, the available inlet pressure is lowered to pinl = 1.5 bar.
Fig. 6: Performance chart of a PBU with cascade control (type series: Hya-Eco and Hyamat K)
15
5
Choosing the correct PBU variant
The pump’s discharge head is therefore established as follows: [15]
H = (pdischarge – pinl) · 10 [m]
The following pumps have been selected 1. Hyamat K 5/0407/1.5
(5 pumps),
2. Hyamat K 6/0406/1.5
(6 pumps),
both options with stand-by pump
H = (5.4 – 1.5) · 10 H = 39 m (Fig. 7)
5.1.3 Determining the pressure zones
Legend for [14], [15]:
Calculating pmin and pmax per floor:
pdischarge = Required pressure downstream of the PBU
(Refer to Fig. 8)
⌬pgeo
The max. discharge pressure pdischarge = p0 = pinl + H0 /10 is assumed for the PBU’ discharge pressure (pdischarge).
= Static pressure loss
Σ(R·l+Z) = Pipe friction and other losses pmin,flow = Minimum flow pressure at the consumer H
= Pump discharge head
pinl
= Available inlet pressure upstream of the PBU
The available pressure upstream of the PBU (pinl) is to be understood as the pressure reducer’s output pressure. If a pressure reducer has not been installed, the max. possible supply pressure (pmax,V) is to be used for pinl
Selecting the appropriate PBU size(s): · = QD = 24 m3/h Vpeak (assumed)
pdischarge – pmax Nflpr = –––––––––––––– ⌬pfl
H = 39 m
Pressure increase of pump incl. inlet pressure p inl
We assume that the installation of an upstream pressure reducer for a PBU in cascade operation is always compulsory.
Nflpr =
Pump discharge head for p inl = 0 bar
pdischarge [bar]
H [m]
p0 = 8.0 pco= 7.7 Fluctuation range for p discharge at constant inlet 6.0 pressure pci = 5.4
65 50
4.5
30
Nflpr
39
= Number of floors which have to be protected against inadmissible pressures by means of pressure reducers
pdischarge = Required pressure downstream of the PBU
3.0 10 Qmin (pco )
QN
pmax
= Maximum permissible flow pressure at consumer
⌬pfl
= Pressure loss per floor (hfl = 3m)
Q
0
Fig. 7: Performance chart of a PBU with cascade control including pressure values for a specifically chosen pump with inlet pressure (pinl )
16
= 10
Legend for [16]:
20 Output pressure from the pressure p inl = 1.5 reducer
8.0 – 5.0 ––––––––– 0.3
[16]
5
Choosing the correct PBU variant
Calculating the max. flow pressure on a random floor pmax,fl
Where ⌬pgeo,fl = 0.3 bar
Assumption:
pmax = pdischarge – ∆pgeo (floor X) = p0 – ∆pgeo (floor X) [bar]
⌬pgeo = 11 · 0.3 bar = 3.3 bar
Water consumption is zero or very low. Therefore, the head loss is HL ≈ 0
For example for the 10th floor
Calculation:
pmax = 8.0 bar – 3.3 bar = 4.7 bar
The max. floor pressure (pmax,fl) is calculated by deducting the static pressure loss ⌬pgeo (floor X) of the respective floor from the PBU discharge pressure (pdischarge).
In general, the following calculation applies to the max. floor pressure:
The static pressure loss of a building with N = 11 floors, meaning ground floor + 10 floors, amounts to: ∆pgeo = N · ∆pgeo,fl [bar]
[18]
pdischarge= p0 [bar]
[19]
pmax = p0 – ⌬pfl · N [bar]
[20]
[17]
160 H m 150
pA bar Characteristic curve values and tolerances to ISO 9906
041 5
14.4
140 130
041 3
12.4
120 0411
9.5
0410
0409
90
8.5
0408
80
0407
70
0406
60
0405
50
0404
40
0403
30
0402
20
7.5 6.6 5.6 4.6 pP = 3.9 bar
110
10.5
3.6
100
2.6 1.7
Pumps per PBU
10
with stand-by pump without stand-by pump according to DIN 1988
0
0
/
2
2
3
4
5
6
7
8
9
2
3
4
6
8
10
12
14
16
18
3
4
6
9
12
15
18
21
24
27
4
5
8
12
16
20
24
28
32
36
5
6
10
15
20
25
30
35
40
45
6
/
12
18
24
30
36
42
48
54
0
1
Q m3/h
Fig. 8: Selection chart Movitec 4
17
5
Choosing the correct PBU variant
Legend for [17], [18], [19], [20]
The calculated total pressure loss per floor is
⌬pgeo = Pressure loss from static head difference ⌬pfl,tot = ⌬pgeo,fl + ⌬pdyn,fl [bar]
⌬pgeo,fl = Pressure loss from static head difference per floor pdischarge = Required pressure downstream of the PBU p0
= Maximum pump pressure at zero flow rate (Q = 0)
pmax
= Maximum pressure
⌬pfl
= Pressure loss per floor
N
= Number of floors
[22]
⌬pfl = 0.3 bar + 0.1 bar ⌬pfl = 0.4 bar In general, the following applies to the flow pressure at a floor:
pmin,flow(N) = pdischarge – ⌬pfl · N [bar]
[23]
⌬pgeo (floor X) = Static pressure loss for floor X
Calculating the minimum flow pressure on a random floor
Legend for [21], [22], [23] ⌬pdyn,fl
= Dynamic pressure loss per floor
Assunption:
Σ(R·l+Z) = Pipe and other losses
1. The PBU discharge pressure (pdischarge) corresponds to the cut-in pressure pci. · 2. Water consumption is max QN = Vpeak.
N
= Number of floors
⌬pfl,tot
= Total pressure loss per floor
⌬pgeo,fl
= Static pressure loss per floor
3. The dynamic pressure losses Σ(R·I+Z) correspond to the maximum value.
pmin,flow (N)= Minimum flow pressure at the consumer on floor N
4. For simplification we assume a linear distribution of the pressure loss across the individual floors. This applies both to the static and dynamic pressure loss.
pdischarge = Required pressure downstream of the PBU
Example: Determining the available flow pressure for the 5th floor:
Calculation: The following applies to a building with 11 floors (N = 11):
N = 6 (ground floor + 5 floors)
⌬pgeo,fl = 0.3 bar per floor
using the values as per Fig. 9 gives:
A dynamic pressure loss of
pmin,flow (6) = 5.4 bar – 0.4 bar · 6
Σ(R·l+Z) = 1.1 bar
pmin,flow (6) = 3.0 bar
gives a dynamic pressure loss per floor of Σ(R·l+Z) ⌬pdyn, fl = –—––––– [bar] N 1.1 ⌬pdyn, fl =–—––––– = 0.1 bar 11
18
[21]
5
Choosing the correct PBU variant
5.1.4 Pressure zone calculation for a building equipped with a PBU using cascade control (Hya-Eco and Hyamat K)
As a result of the pressure loss inherent in the reducer (here = ⌬p 0.7 bar) the minimum available inlet pressure pinl drops to 1.5 bar. The nominal discharge head required of the pumps is thereby increased by 7 m.
Outcome: In the event of pump failure, consumers are not affected since appropriate measures (installation of pressure reducers on the inlet side, establishing pressure zones on the consumer side) have been taken.
• Consumer-side pressure reducer On floors 3 to 8, the max. permissible pressure pmax = 5 bar would be exceeded (Fig. 9). For this reason, these floors require protection from pressure reducers. The available pressures are then set to a uniform pressure of 1.3 bar.
• Inlet pressure reducer: Required as the inlet side pressure fluctuations are too high for cascade operation.
5.1.5 Summary pmax = 4.7 bar 10th
pmin = 1.0 bar
+ 33.0 m
pmax = 5.0 bar 9th
pmin = 1.4 bar
Top pressure zone, directly supplied via PBU
+ 30.0 m
pmax = 5.3 bar 8th
1.3 bar pmin = 1.8 bar pmax = 5.6 bar
7th
+ 27.0 m 1.3 bar
pmin = 2.2 bar
+ 24.0 m
pmax = 5.9 bar 6th
1.3 bar pmin = 2.6 bar pmax = 6.2 bar
5th
+ 21.0 m 1.3 bar
pmin = 3.0 bar pmax = 6.5 bar 4th
3rd
+ 18.0 m 1.3 bar
pmin = 3.4 bar pmax = 6.8 bar
Middle pressure zone, supplied via PBU, protected by a pressure reducer per floor
The cascade-controlled PBU is favourably priced. However, tackling this unit’s negative consequences (pressure fluctuations, excessive on/off operation, hydraulic impact on the water supply network…) requires the installation of various additional components (pressure controller, membrane-type accumulator…).
+ 15.0 m 1.3 bar
pmin = 3.8 bar
+ 12.0 m pmax = 2.6 bar
2nd
pmin = 1.0 bar
+ 9.0 m
2.9 bar 1st
1.4 bar
+ 6.0 m
Bottom pressure zone, directly supplied via supply pressure
3.2 bar
Ground floor
1.8 bar p0 = 8.0 bar Hyamat K Basement pci = 5.4 bar
F
pinl =1.5 bar
W
+ 3.0 m p max,V = 3.5 bar p min,V = 2.2 bar ±0m
Fig. 9: Schematic drawing of a PBU operating with cascade control incl. pressure values and pressure zones
19
5
Choosing the correct PBU variant
5.2 PBU with one variable speed pump (Hyamat V)
• Hydraulic impact on the water supply network is low
5.2.1 Features
• Inlet side pressure reducer is normally not required
• One variable speed base load pump • Peak load pumps cut in depending on the pressure (⌬p-range) • Peak load pumps run at full speed • Pump change-over of variable speed base load pumps is possible • Discharge pressure is largely constant
5.2.2 Calculation example (4) Discharge head of PBU The discharge pressure pdischarge is calculated as follows
• Inlet pressure fluctuations can be compensated for
pdischarge = ⌬pgeo + Σ(R·l+Z) + pmin, flow [bar] [24]
• In the event of a malfunction of the speed control, unit operates like a cascade
pdischarge = 3.3 bar + 1.1 bar + 1.0 bar = 5.4 bar
• Under low flow conditions, the base load pump is shut down irrespective of the inlet pressure
Legend for [24] pdischarge= Required pressure downstream of the PBU ⌬pgeo = Static pressure loss
One pump with continuous speed control
Σ(R·l+Z) = Pipe friction and other losses
p
pmin,flow = Minimum flow pressure at consumer
Hyamat V const.
pci
Q On / Off
continuously controlled
pump change-over
The required discharge pressure (pdischarge) on pressure boosting units with one variable speed pump is also referred to as the cut-in pressure (pci). Under normal operating conditions, the discharge pressure is almost constant.
H p0 Almost constant discharge pressure
When peak load pumps are started or stopped, the discharge pressure may slightly deviate from pci (e. g. ± 0.5 bar) for a short period of time.
pci
Note: n -1 pumps
n pumps
Q Excessive on/off
Fig. 10: Performance chart of a PBU with one variable speed pump (Type: Hyamat V)
20
In the event of a malfunction (speed control failure) the unit automatically changes over to cascade operation. As a pressure reducer is not normally installed in the case of a PBU with one variable speed pump, the discharge pressure can rise to a maximum value of pdischarge = p0 = pinl,max +H0 / 10.
5
Choosing the correct PBU variant
Possible remedial measures:
The installation of an additional temperature monitoring device in the by-pass (hygiene!) ensures the pump is shutdown in the event of a prolonged period of low water demand.
Option 1
p0 = 9.1 bar
Calculating the discharge head of the PBU
PBU Hyamat V
pci = 5.4 bar ppr = 6.2 bar
Fig. 11 Central pressure control (e.g. pressure reducer) One central pressure reducer on the discharge side of the PBU Setting the pressure reducer to the output pressure ppr = 6.2 bar ensures that the pressure reducer is fully open under normal operating conditions. Only in the event of a fault is the pressure thus limited to the value set (ppr = 6.2 bar).
The supply pressure at the hand-over point varies between the minimum pmin,V = 2.2 bar and the maximum value pmax,V = 3.5 bar. Pressure boosting units with one variable speed pump are capable of handling supply pressure fluctuations (see Fig. 13 and 14) thus eliminating the need for pressure reducers. The discharge head is determined on the basis of the minimum supply pressure pmin,V. The pump head is calculated as follows: H = (pdischarge - pinl,min)·10 [m]
[25]
H = (5.4 bar - 2.2 bar) · 10 H = 32 m (i.e. 7 m less than Hyamat K)
Option 2 Legend for [25]: Tmax
= Pump discharge head
pdischarge= Required pressure downstream of the PBU
pmon = 6.2 bar PBU pdischarge ≥ 6.2 bar
H
pinl,min = Minimum available pressure upstream of the PBU
Hyamat V
pci = 5.4 bar
Fig. 12 Pressure control using a by-pass valve
A pressure-controlled by-pass valve between inlet and discharge side of the PBU with additional temperature monitoring. The by-pass valve opens as soon as the set pressure is reached or exceeded (pdischarge 욷 6.2 bar). If consumer demand is low, the excess flow is routed to the PBU inlet.
21
5
Choosing the correct PBU variant
Pressure increase of pump(s) incl. max. inlet pressure
Discharge head of pump(s) for pinl = 0 bar
pinl,max Discharge pressure pdischarge [bar]
60 without protection p0 = 9.1
Fig. 13: Performance chart of a PBU with one variable speed pump, incl. pressure values for operation with max. inlet pressure pinl,max.
Pump discharge head H [m]
H0 = 56
50
Rotational speed = 100 %
40 with protection ppr = pvalve = 6.2
30
pci = 5.4
19 10 Rotational speed = 58 %
pinl,max = 3.5 QN Q max. inlet pressure
0
Pressure increase of pump(s) incl. min. inlet pressure pinl,min Discharge pressure pdischarge [bar]
Discharge head of pump(s) for pinl = 0 bar
Pump discharge head H [m] 60
without protection p 0 = 7.8 with protection p pr = p valve = 6.2
H0 = 56
50
Rotational speed = 100 %
40
pE = 5.4
32 20 10
Rotational speed = 76 %
pinl,min = 2.2 QN
min. inlet pressure 0
22
Inlet pressure reducers are not normally installed with this type of system! The max. inlet pressure pinl,max, is critical for calculating the max. discharge pressure p0. The max. discharge pressure p0 can only occur in the case of a fault in the continuous speed control. (Change-over to cascade operation).
Q
Fig. 14: Performance chart of a PBU with one variable speed pump, incl. pressure values, for a specific pump with inlet pressure pinl,min
5
Choosing the correct PBU variant
2. Hyamat V 6/0405/2,2 (6 pumps) ⌬pinl,perm = 1.5 bar, with stand-by pump for each option
Selecting the appropriate PBU size(s): · Vpeak = QD = 24 m3/h (assumed) H
= 32 m
In this case (⌬pinl = 1.3 bar) both PBU sizes can operate without a pressure reducer on the inlet pressure side.
The pumps selected 1. Hyamat V 5/0406/2,2 ⌬pinl,perm = 1.3 bar,
(5 pumps)
160 H m 150
pA bar Characteristic curve values and tolerances to ISO 9906
041 5
14.4
140 130
041 3
12.4
120 0411
9.5
0410
0409
90
8.5
0408
80
0407
70
0406
60
0405
50
0404
40
0403
30
0402
20
7.5 6.6 5.6 4.6 pP = 3.2 bar
110
10.5
3.6
100
2.6 1.7
Pumps per PBU without stand-by pump
with stand-by pump according to DIN 1988
10 0
0
/
5
–
–
8
12
16
20
24
28
32
36
5
6
–
–
10
15
20
25
30
35
40
45
6
/
–
–
12
18
24
30
36
42
48
54
Max. useful inlet pressure rise pinl,max . in bar in relation to the pump curve
Movitec 0415
8
7
7
Movitec 0413 6
Movitec 0411
6
6
5
Movitec 0409
Movitec 0405
2
3
Movitec 0406
2
3
Movitec 0404
2
Movitec 0403
1.5
Movitec 0402
1
1
2
3
4
Movitec 0407
1
2
3
4
Movitec 0408
1
2
3
4
1.5 1 1
0
1
0
1
2
3
4
Movitec 0410
2
3
4
5
0
1
2
3
4
1
2
3
4
5
5
Q m3/h
0 0 0
bar
0
1.3 1
0
1
0 0 0 0
Fig. 15: Selection chart Movitec 4
23
5
Choosing the correct PBU variant
5.2.3 Determining the pressure zones
all floors connected to the PBU must be protected (see also section 5.2.2).
Under normal operating conditions, a unit using continuous speed control ensures an almost constant discharge pressure pdischarge = 5.4 bar (see also section 5.2.2).
Legend for [26], [27]:
The following equation applies to the number of floors requiring protection (Nflpr):
pdischarge = Required pressure downstream of the PBU
pdischarge - pmax Nflpr = –––––––––––– ⌬pfl
pmax
= Maximum pressure
⌬pfl
= Pressure loss per floor
p0
= Maximum pump pressure at zero flow rate (Q = 0)
Nflpr
[26]
5.4 bar - 5.0 bar = –––––––––––––– 0.3 bar
Nflpr =
= Number of floors which have to be protected against inadmissible pressures by means of pressure reducers
pinl,max = Maximum pressure upstream of the PBU
1.3 앒 2
From this equation can be deduced that the lowest two floors, namely the basement and the ground floor, would require protection. However, the basement, ground floor as well as 1st and 2nd floors are not connected to the PBU. Floors 3 to 10 do not, in principle, require any protection. In the event of a fault: Speed control failure In this case, the following applies due to changeover to cascade operation: H0 pdischarge = p0 = pinl,max + –––––– 10
Nflpr
[bar]
[27]
pdischarge = p0 = 3.5 bar + 5.6 bar = 9.1 bar
H0
= Maximum discharge head at zero flow rate (Q = 0)
Determining the max. floor pressure (pmax,fl) As in section 5.1.3, we take a static approach meaning we do not assume any flow losses Σ(R·l+Z). Normal conditions: pdischarge = pci In the event of a fault: pdischarge = p0 pmax,fl = pdischarge - ⌬Hgeo (floor x) [bar] Example:
Result of [27] inserted into equation no. [26]:
Floor 10 requires: ⌬pgeo,10th floor = 3.3 bar
pdischarge - pmax Nflpr = –––––––––––– ⌬pfl
Normal conditions:
Nflpr
9.1 bar - 5.0 bar = –––––––––––––– 0.3 bar
pmax,10th floor = 5.4 bar - 3.3 bar pmax,10th floor = 2.1 bar
In the event of a fault: Nflpr =
13.6
pmax,10th floor = 9.1 bar - 3.3 bar pmax,10th floor = 5.8 bar
This means that while in principle no floors require protection, in the event of a malfunction,
24
[28]
5
Choosing the correct PBU variant
The other floor pressures can be calculated using the respective ⌬pgeo values. Legend for [28]: pmax,fl
= Maximum pressure per floor
pdischarge = Required pressure downstream of the PBU
5.2.4 PBU with one variable speed pump (Hyamat V) – Possible effects In the event of a fault (breakdown of the variable speed control), the pressure rises on those floors not provided with additional safety equipment!
⌬Hgeo(floor X) = Static pressure loss for floor X. Conclusion: Calculating the minimum flow pressure per floor The same calculation as the one described in section 5.1.3 (Calculating the minimum flow pressure per floor) can be used.
In the event of a fault (variable speed control breakdown), the max. static pressure from floors 4 to 10 considerably exceeds the maximum set pressure of 5 bar.
The following applies to the 5th floor: pmin,fl = 3.0 bar Possible effects:
Normal operation Fault
pmax = 2.1 bar 10th
pmin = 1.0 bar pmax = 2.4 bar
9th
pmin = 1.4 bar
• Considerably increased flow velocity
5.8 bar + 33.0 m 6.1 bar
• Float valves of cisterns cease to close
+ 30.0 m
pmax = 2.7 bar 8th
pmin = 1.8 bar
6.4 bar + 27.0 m
pmax = 3.0 bar 7th
pmin = 2.2 bar
6.7 bar + 24.0 m
pmax = 3.3 bar 6th
pmin = 2.6 bar pmax = 3.6 bar
5th
pmin = 3.0 bar pmax = 3.9 bar
4th
pmin = 3.4 bar pmax = 4.2 bar
3rd
pmin = 3.8 bar
7.0 bar + 21.0 m 7.3 bar + 18.0 m 7.6 bar + 15.0 m 7.9 bar
Possible remedial measures:
+ 12.0 m pmax = 2.6 bar
2nd
pmin = 1.0 bar
+ 9.0 m
pmax = 2.9 bar 1st
pmin = 1.4 bar
+ 6.0 m
Bottom pressure zone, directly supplied via supply pressure
pmax = 3.2 bar
Ground floor
Basement
Top pressure zone, supply via PBU
• At a pressure of 6 bar, the safety valves on the water heaters open. As a result of possible fluctuations, increased switching frequency of the pumps and even pressure surges are to be expected.
pmin = 1.8 bar Hyamat V pdischarge = 5.4 bar p 0,max = 9.1 bar in the event of a fault
F
W
+ 3.0 m pmax,V = 3.5 bar pmin,V = 2.2 bar ±0m
possible remedial measures: Section 5.2.2
• Installation of a central pressure reducer downstream of the PBU (the value set for this downstream pressure must be > pci) • Installation of a by-pass valve + temperature monitor in the by-pass pipe from the consumer to the inlet side
Fig. 16 Schematic drawing of a PBU with one variable speed pump incl. pressure values and pressure zones
25
5
Choosing the correct PBU variant
5.2.5 Summary The disadvantages of cascade operation are avoided. Generally, pressure reducers and large membrane-type accumulators are not necessary. Making full use of the inlet pressure saves electrical drive energy.
• With regard to fluctuations during operation, the adverse hydraulic effects on the public water network are very low
5.3.2 Calculation example (also see section 5.2.2) All calculations are performed as per section 5.1.2 and 5.2.2 in accordance with example (4) pdischarge = pci = 5.4 bar
5.3 PBU with speed control on all pumps (Hyamat VP)
Even in the event of a fault, inadmissible pressure rises cannot occur with this type of PBU concept.
5.3.1 Features • All pumps are variable speed • Number of operating pumps depends on flow rate • No pressure rise in the event of a fault/variable speed pump breakdown
Therefore, floors 3 to 10 can be directly connected to the PBU (Fig. 11) without any protective measures. A constant discharge pressure pdischarge is guaranteed at all times.
• Broad regulating range, optimum conditions when all pumps are running
5.3.3 Determining the pressure zones
• Constant discharge pressure
see also section 5.2.3
• Compensation for very high inlet pressure fluctuations possible
Nflpr = 1.3 앒 2
Speed control on all pumps p Hyamat VP pci
const. Q
continuously variable
H p0 constant discharge pressure p discharge pci
n -1 pumps
A special feature of this PBU concept is that even in the event of a fault (e.g. breakdown of one variable speed pump) a pressure rise is not to be expected. All other variable speed pumps continue operating. If required, the stand-by pump (also equipped with variable speed control) can be started up. Hence, floors 3 to 10 are supplied with water without needing additional protective equipment.
n pumps
Q excessive on/off
Fig. 17: Performance chart of a PBU with speed control on all pumps (Hyamat VP)
26
From this equation can be deduced that the lowest two floors, namely the basement and the ground floor, would require protection. As, however, the basement, ground floor as well as 1st and 2nd floors are not connected to the PBU anyway this can be disregarded.
Determining the maximum floor pressure pmax,fl As in section 5.1.3, we take a static approach meaning we do not assume any flow losses Σ (R x l + Z).
5
Choosing the correct PBU variant
Legend for [29], [30]:
The following is therefore applicable: pdischarge = pci = constant [bar]
[29]
pdischarge
= Required pressure downstream of the PBU
pmax,fl = pdischarge - ⌬pgeo (floor X) [bar]
[30]
pmax,fl
= Maximum pressure per floor
pci
= Cut-in pressure / setpoint
Example:
⌬pgeo (floor X) = Static pressure loss for floor X
The following is applicable for the 5th floor: N = 6;
⌬pgeo,fl = 0.3 bar; pdischarge = 5.4 bar
Determining the minimum floor pressure pmin,fl
⌬pgeo (floor 5) = N · ⌬pgeo,fl = 6 · 0.3 bar
The following is also applicable for floor 5:
⌬pgeo (floor 5) = 1.8 bar
pmin (floor 5) = 3.0 bar
therefore, pmax (floor 5) = 5.4 bar - 1.8 bar
5.3.4 PBU with speed control on all pumps (Hyamat VP) – Possible effects
pmax (floor 5) = 3.6 bar
All pumps are variable speed. In the event of a fault (breakdown of one variable speed pump), the Hyamat VP unit continues operating with the available variable speed pumps.
pmax = 2.1 bar 10th
pmin = 1.0 bar
+ 33.0 m
pmax = 2.4 bar 9th
pmin = 1.4 bar
+ 30.0 m
pmax = 2.7 bar 8th
pmin = 1.8 bar
The supply pressure is not subjected to any fluctuations.
+ 27.0 m
pmax = 3.0 bar 7th
pmin = 2.2 bar
+ 24.0 m
pmax = 3.3 bar 6th
pmin = 2.6 bar
Top pressure zone, supply via PBU
Additional measures are not required.
+ 21.0 m
pmax = 3.6 bar 5th
pmin = 3.0 bar
+ 18.0 m
In buildings with more than 10 floors, it is normal to define pressure zones.
pmax = 3.9 bar 4th
pmin = 3.4 bar
+ 15.0 m
pmax = 4.2 bar 3rd
pmin = 3.8 bar
Conclusion:
+ 12.0 m pmax = 2.6 bar
2nd
pmin = 1.0 bar
+ 9.0 m
pmax = 2.9 bar 1st
pmin = 1.4 bar
+ 6.0 m
Bottom pressure zone, directly supplied via supply pressure
pmax = 3.2 bar
Ground floor
pmin = 1.8 bar
+ 3.0 m
Hyamat VP Basement pdischarge = 5.4 bar
F
W
pmax,V = 3.5 bar pmin,V = 2.2 bar ±0m
5.3.5 Summary Even if one frequency inverter unit breaks down, the discharge pressure remains constant (in the Hyamat V concept, by contrast, the PBU would automatically change over to cascade operation). Any hydraulic equipment limiting the pressure is not required.
Fig. 18 Schematic drawing of a PBU, all pumps are variable speed controlled, incl. pressure values and pressure zones
27
6
Overview – Connection types for drinking water installations
6
Overview – Connection types for drinking water installations
6 Overview – Connection types for drinking water (to DIN 1988, always with stand-by pump) and service water installations Inlet side Indirect connection
Pressure boosting unit
Consumer side
Service water
Direct connection
Unpressurized tank for volume balancing
Arrangement example PBU
No adverse effects on supply network Demand peaks are covered
Inlet pressure fluctuation must be limited
No risk of contamination Additional pressure loss
Constant inlet pressure
Constant inlet pressure Wasted energy
Risk of contamination
Pressure-dependent cascade control
Exploitation of design inlet pressure
Dampened impact on supply network
p pco
Hyamat K
pci
(max. +0,3/-0,2 bar)
Q
One pump is variable speed
Inlet pressure may fluctuate slightly
Tank is not required
Full exploitation of inlet pressure Normally not required
p
Hyamat V
Const.
pci
Observe pump curve profile
Q
Greater inlet pressure fluctuation permitted Full exploitation of inlet pressure
p pci
Observe pump curve profile
Constant discharge pressure
Constant discharge pressure
Pressure peaks are reduced
Wasted energy
No risk of contamination Reduction of switching frequencies Additional pressure loss
Low pressure losses at high flow rates
Reduction of switching frequency Excessive on/off is avoided
Const. Q
Excessive on/off is avoided Throttled filling
Unthrottled re-filling Balancing of dynamic fluctuations in consumption
Minimum energy demand
Thottled filling See also section 9
All pumps are variable speed
Hyamat VP
Flow is distributed across pumps according to demand Discharge pressure fluctuation
Unthrottled re-filling
Constant discharge pressure Minimum Not required energy demand Highly dynamic regulating potential
Legend Optimum
Supply network
Membrane-type accumulator
Unpressurized inlet tank
Direct-flow membrane-type accumulator with dual connection
Cascade-controlled pump
Non-return valve
Variable speed pump
Solenoid valve (dyn. consumer)
Good Possible Unfavourable
Drinking water DW
28
Pressure reducer Drinking water valve Service water valve
Service water SW
29
7
Overview – Connection types for fire-fighting units, wet risers
7
Overview – Connection types for fire-fighting units, wet risers
7 Overview – Connection types for fire-fighting units, wet risers
Consumer side
Pressure boosting system
Inlet side Indirect connection
Direct connection pressure-dependent control
Unpressurized tank for volume balancing
Hya-Solo D *)
WC
WC
p pco
Signal line
WC
pci Q
Hydraulic separation
Dampened effects on supply network
Storage of water No adverse effects on supply netword Constant inlet pressure
Q FfW No DIN recommendation for pressure reducers
pressure-dependent cascade control
Exploitation of design inlet pressure must be
lower than
Hya-Eco + Hyamat K*)
Qnetw
Risk of contamination due to water stagnation.
p
Tapping drinking water is not possible
pco pci
Inlet pressure fluctuation has an influence on the system’s characteristics
Q
Constant discharge pressure
Switching frequency is limited (e. g. toilet flushing)
Pressure zones decentralized
Adverse effects when tank is being filled and in the case of direct connection
No DIN recommendation for pressure reducers
Start-up via remoteelectric controlled contact possible No excessive on/off during firefighting duty
*Limited volume balancing as a standard, full volume balancing on option *)
To reduce the risk of back contamination it is important to ensure that time-controlled flushing of the fire-fighting system (1.5 x the pipe contents per week) takes place in directly connected pressure boosting units.
Legend
WC
Optimum
Supply network
Membrane-type accumulator
Unpressurized inlet tank
Direct-flow membrane-type accumulator with dual connection
Good Possible Unfavourable
Cascade-controlled pump
Toilet used regularly ensures exchange of water
Pressure reducer
Fire hydrant
Time-controlled solenoid valve
Fire hydrant with electric contact
DW
30
Drinking water
FfW Fire-fighting water
31
8
Overview – Connection types for combined installations
9
Overview – Connection types for wet- / dry-type units
8 Overview – Connection types for combined installations: Drinking water and fire-fighting water Service water and fire-fighting water
9 Overview – Connection types for wet- / dry-type units
N.B.: Depending on the specific unit conditions, the requirements for pressure boosting units must be agreed with the manufacturer.
NB:
The connection types and the installation of accumulators must be realized in compliance with the water provider’s and manufacturer’s specifications for the specific unit.
*)
Pressure boosting unit
Fire-fighting operation is activated via the contacts on the wall-mounted fire hydrants
Arrangement example
If special solutions are involved, specific unit requirements must be agreed with the manufacturer! The connection types must be determined in compliance with the water provider’s and manufacturer’s requirements.
Pressure boosting unit
*)
Contact Signal line
Arrangement example
PBU
To reduce the risk of back contamination it is important to ensure that time-controlled flushing of the fire-fighting unit (1.5 x the pipe contents per week) takes place in directly connected pressure boosting units.
PBU*) Cascade control p pA
Hyamat K
**)
pE Q
To reduce the risk of contamination in the connection pipe it is important to ensure that time-controlled flushing of the fire-fighting pipe branch (1.5 times the pipe contents per week) takes place in drinking water operation (direct connection).
W/ D
Cascade-controlled pump Cascade control p pA
Cascade control for all pumps
pE
p
Hyamat K
Hyamat K Hya-Solo D
*) FL
*)
W/D
Q
TW TW
Hya-Solo D **)
Wet/dry valve station
Δp
Wall-mounted fire hydrant
FL Q
Selection of economically determined pump sizes
Cascade-controlled pump
Drinking water valve
Variable speed pump
Wall-mounted fire hydrant
One variable speed pump and pressure-dependent control of fire-fighting pump Hyamat V
p *) Ftw
p pA pE
DW Ftw Q Selection of economically determined pump sizes
One variable speed pump Hyamat V
p Set value Ftw Set value DW Q
32
Δp Filling pump
DW
Hya-Solo D **)
Fire-fighting pumps
Hyamat K Legend
*) Q
Legend Optimum
Optimum
Good
Good
Possible
Possible
Unfavourable
Unfavourable
33
10
Accumulator selection / calculations
10
Accumulator selection / calculations
10 Accumulator selection / calculations Some of the following design information is taken from the DIN 1988 standard and other parts are specific KSB infomation. They are to be considered as KSB recommendations.
Determing the tank sizes of the PBU
Inlet side
Consumer side
Unpressurized inlet tank
Pressure boosting units with pressure-dependent or cascade control (e. g. Hyamat K, Hya-Solo)
Membrane-type accumulator for direct
for indirect connection
connection
Pressure boosting units with variable speed control on one or all pumps (e. g. Hyamat V, Hyamat VP)
Sizing the accumulator Standard i.e. the water supply network is capable of providing Vmax at any time.
Total volume of accumulators on inlet pressure side of PBU Maximum flow rate of a PBU pump
Tank selection VIT = 0.03 ·Vmax (QD) [m3]
3
N.B.: The size of the tank is proportional
Vtot
m3/h
m3
to that of the re-fill valve.
0.3 0.5 0.75
Selection of re-fill valve by means of pinl,min and QD
The minimum volume should not be
2 x 2”
Q
less than 0.3 m3
2” 1 1/2î
Selection on the basis
consumer behaviour
of the Qcrit. limit In the case of consumers with very low demand
Qconsumer, small Residential buildings Office and administration buildings Hotels Department stores Hospitals Schools Fire-fighting systems with water exchange lines
1.1
m3/h
0.4
m3/h
2.2 m3/h 2.3 m3/h 3.6 m3/h 4.7 m3/h
Industrial operations
p p0 Pco
In compliance with PBU manufacturer’s requirements we recommend the installation of a
p(co-ci)
Pci
Consumers with quick ON/OFF characteristics (solenoid valves) Q
80 l standard accumulator
t Qcrit.
Q
1.8 m3/h Obtain information or perform selection on the basis of the Qcrit limit
selected nominal diameter
In the case of highly dynamic consumers
Unstable
Determining the max. re-fill volume
Stable
area
Duration of extraction
area
1”
QD pinl,min
3
Selection on the basis of the
Total accumulator volume on inlet pressure side of pumps
Vmax,p
Membrane-type accumulators are normally not required in variable speed pump systems. They have a negative influence on the control characteristics of a PBU.
t Flow volume extracted
Q
Determining accumulator efficiency p
Yes
This selection allows for a buffer
Legend:
volume sufficient for approx. 100 s in the
Pinl,min = Minimum available pressure on filling side
case of maximum water consumption and if re-filling does not take place. Determining the storage volume by the volume difference / time method. 3
VIT = (QD - Qmin) · t [m ]
Vtot = Qconsumer, small
·
pco + 1 p(co-ci)
Legend:
No
Qconsumer, small < Qcrit .
Vtot = Total accumulator volume Qconsumer, small = Low or permanent consumption dependent on usage Vtot = Qcrit. ·
pA + 1 p(co-ci)
Pinl,max = Maximum inlet pressure on filling side Vmax,p = Maximum volume flow of a PBU pump Vtot
= Total accumulator volume in m3
QD Qmin
= Design flow rate of PBU
Qmax VIT
= Maximum permissible re-fill volume flow (= network extraction) = Usable volume of atmospheric inlet tank
t
= Buffering period of inlet tank in h
= Re-fill volume flow under minimum inlet pressure (pinl,min) conditions
Switching operations/h 23
Pump size
Number of stages
2
Number of stages 2 to 10
10
8 to 20
9
2
11 to 25
14
18
2 to 7
17
4
2 to 10
23
18
8 to 16
9
4
11 to 25
14
32 - 45
2 to 6
14
10
2 to 7
17
32 - 45
7 to 12
9
Pump size
Switching operations/h
Qcrit. Pco
= Critical minimum flow of PBU = PBU cut-out pressure
Pci p(co-ci)
= PBU cut-in pressure = Difference between cut-in/-out pressures
n
= Number of pumps (incl. stand-by pump)
S
= Switching frequency
Efficiency 10
pci = Inlet pressure, accumulator p = Pressure drop = Accumulator efficiency
8 6 4
Pci = 5 bar Pci = 2 bar Pci = 1 bar
2 0
0.5
1
1.5
2
2.5
3
p [bar]
Approximate estimation of the required accumulator efficiency with given inlet pressure pci and permissible pressure drop (p) Determining the gross accumulator volume Vaccum. =
Example: t = 25 s ,
Q = 1.5 l/s
Pci = 2 bar , pperm. = 1.0 bar
V = 1.5 l/s · 25 s = 37.5 l from diagram
=4
tank efficiency Vaccum. = 37.5 l · 4 = 150 l Chosen
34
180 l standard accumulator
35
Highest office tower in Europe WATER
WASTE WATER
INDUSTRY
ENERGY
BUILDING SERVICES
MINING
Commerzbank headquarters Frankfurt on the Main/Germany
CPK
The Commerzbank headquarters in Frankfurt on the Main is the highest office building in Europe and dominates the skyline with its accomplished architectural features. Impressive, too, is the number of KSB products integrated in the building’s various service systems that reliably fulfil their daily tasks
to their owner’s complete satisfaction: approximately 300 pumps and 2,000 valves of a wide variety of types and sizes have safeguarded safe and reliable fluid transport since 1997. Our extensive product scope, the know-how of our specialists and KSB’s uncompromising quality management convinced the
Mr. Muschelknautz
Hyamat
customer to place his order with us. This is without doubt a reference we can be proud of. For further information, contact us on phone number +49 69 94208-221, by email at
[email protected] or visit our website at www.ksb.com.
Scope of supply and technical data
0127.1031-10
bdf
05/05
Customer: Commerzbank AG Fields of application: Heating, air-conditioning, water supply and disposal, fire-fighting and sprinkler systems
Scope of supply: 294 pumps and some 2,000 valves. Pumps: Ama-Drainer, CPK, Compacta, Etanorm, Eta-R, Etaline, Hyamat with Movitec, Hyatronic, Rio and Riotec
Valves: BOA-Control IMS, BOA-Compact, BOA-Compact-EKB, BOA-H, BOA-S, SISTO, BOAX Commissioned: 17.5.1997
11
Dry running protection
11 Dry running protection Selection criteria for PBUs “Dry running protection” is the protection of the pumping station against inadmissible operation (such as lack of water) and the timely shutdown of the PBU to protect the supply network. The following presents an overview of the various dry-running protection concepts.
An inlet pressure monitoring device is installed on the PBU inlet side in order to monitor and observe the required minimum pressure of pmin,V = 1 bar. Depending on the unit, this monitoring equipment can either be a pressure switch or an analog pressure transmitter. Whenever the minimum pressure is reached the PBU should reduce the number of operating pumps. Simultaneous stopping of all operating pumps must be avoided. Alternatively, the possibility of an indirect connection of the PBU providing sufficient protection should be examined.
11.1 Protection of the supply network By stipulating minimum pressures, the General Water Supply Terms Ordinance (AVB Wasser V), the DIN 1988 and the future DIN EN 806 standards endeavour to prevent consumers directly supplied via a house connection being inadmissibly compromised as a result of PBU operation. Possible causes for an inadmissible pressure drop at the house connection are for example: • Insufficient supply network. The pressure of the mains water pipe drops when considerable quantities of water are extracted. • If the service pipe’s diameter is insufficient, the supply pressure drops at the hand-over point when considerable quantities of water are consumed.
11.2 Protection of pressure boosting unit High-pressure centrifugal pumps are mainly employed for PBUs and, apart from a few exceptions, these are non-self priming pump types. This means that the inlet / suction pipe must be constantly filled with water. In essence, all protection concepts aim to prevent inadmissible rises in temperature or, in the worst case, the dry running of the pumps. A distinction should be made between direct and indirect protection methods. Direct protection:
• Pressures drop at the hand-over point if considerable quantities of water are pumped via the PBU (e. g. due to large pumps and/or a large membrane-type accumulator downstream of the PBU).
pmin,V
1.0 bar
p1 ≤ 0.5 pmin,V
Indirect protection:
Permissible pressure
• Inlet pressure control upstream of the PBU – particularly in the case of cascade control (Hya-Eco and Hyamat K) – by making sure that the pumps can reach or exceed the cutout pressure pco.
increase p2 ≤ 1.0 bar
• Water level control in the inlet tank
Run-down time
p1
Permissible pressure drop
p2
Pump start- Period of up phase operation
• Flow control on the PBU inlet side
• Pump performance monitoring (electrically) 0.0 bar
• Temperature monitors on each pump (alternatively)
Fig. 17: Pressure development at the consumer end of the service pipe, i. e. upstream of the PBU, during start-up and shutdown of pumps
37
11
Dry running protection
Conclusion: Generally, PBUs must be protected against operating with a lack of water. As a whole host of connection types for PBUs and different operating conditions exists, there is no such thing as a standard solution. The protection concept chosen must always suit the individual operating conditions (see Fig. 20).
PBU protection concepts
Indirect connection
Direct connection
Suction lift operation
Suction head operation
Options
Options
Options Pressure monitoring using a digital pressure transmitter 욷 0.5 bar
P
Flow monitoring + pressure monitoring downstream of the PBU
Q
PBU
P
PBU
Pressure monitoring using an analog pressure transmitter 욷 0.5 bar
e.g. BMS
Water level monitoring using a float switch
PBU not self-priming
PBU
Water level monitoring using electrodes
After “lack of water” tripping manual reset required
P
PBU
Fig. 20: PBU protection concepts
38
PBU
12
Effects of inlet pressure fluctuations
12 Effects of inlet pressure fluctuations Supply pressure fluctuations at the hand-over point (water meter) influence the operating behaviour of pressure boosting units.
70
500
2 x 2”
Q m3/h
Q m3/h
50
DN 100 300
40 2” 30
12.1 Indirect connection, Fig. 21
14 10 0
PBU
200 1 1/2 ”
20
1”
0
DN 80 100
1 2 3 4 5 Inlet pressure p bar
0
0
1 2 3 4 5 Inlet pressure p bar
Fig. 22 Selection diagram for filling devices The PBU’s function is not impaired as long as water is available. Fig. 21 Indirect connection The PBU takes the required quantity of water from an unpressurized inlet tank situated upstream. The tank filling device is usually sized such that the PBU’s nominal flow rate QN is reached under normal inlet pressure (pinl) conditions. If the inlet pressure drops to the minimum inlet pressure pinl,min this may lead to a significant reduction of the filling volume. Example: pinl,min = 1.0 bar pinl,max = 3.1 bar pinl
= 2 bar (angenommen)
QN
= 20 m3/h
Selection of float valve for pinl = 2 bar, Fig. 22 QN
= 20 m3/h
at pinl,min = 1 bar
씮 11⁄2 ” 씮 Q = 14 m3/h
This results in a filling volume reduction of 30%. It should be noted that the stored volume will be used up under minimum inlet pressure conditions and a water consumption of more than 14 m3/h over a prolonged period of time (risking a lack-ofwater condition).
12.2 Direct connection, Fig. 23 12.2.1 Inlet pressure fluctuations in the form of pressure increase PBU
Fig. 21: Direct connection When PBUs with cascade control are used (Hya-Eco, Hyamat K, Hya-Solo D) inlet pressure fluctuations (in this case in the form of pressure increases) will directly influence the PBUs’ discharge pressure. Since cascade-controlled PBUs have an inherent discharge pressure fluctuation of ⌬p(co-ci) + 0.3 bar (Fig. 24), the sum of discharge pressure fluctuation and inlet pressure fluctuation must be examined to ensure that it is acceptable for the consumers downstream. The maximum fluctuation range recommended by DIN 1988 is 2.5 bar. ⌬pPBU,max = ⌬p(co-ci) + 0.3 + ⌬pinl,max [bar]
[31]
39
12
Effects of inlet pressure fluctuations
Legend for [31]: ⌬pPBU,max = Maximum pressure difference downstream of the PBU ⌬p(co-ci)
= Switching pressure difference
⌬pinl,max
= Maximum pressure upstream of the PBU
If this is not the case, it is important to use an inlet side or discharge side pressure controller / reducer.
Impact of inlet pressure increase of 0.3 bar H0
Discharge pressure
pA p(co - ci) pE
Qco
Qco
+ pinl,min + 0.3 bar
Pressure fluctuation inherent to PBU
QD
p(co - ci) + 0.3 bar
Example: A negative effect of inlet pressure increase Pressure development of a system with 3 pumps is the shifting of the minimum flow rate for with increasing flow rate (consumption) continuous operation (Qco at pco) and the with decreasing flow rate (consumption) minimum inlet pressure pinl,min to considerably larger cut-out flow rates at Fig. 24: increased inlet pressure, especially in the The operating characteristics of a pressure boosting unit case of PBUs with a low number of with cascade control, i. e. without speed control stages.
The consequences are as follows (Fig. 24): • Low flow rates (> Qco for pinl,min) lead to the risk of excessive on/off operation (very high switching frequency of the PBU pumps). • As a result of the cut-out of the last pump in operation at flow rates > Qco audible pressure surges in the pipes are to be expected. Example: Impact of inlet pressure increase on a real pump curve (Fig. 25), Hyamat K series. Pump size: 0406 Qco = 1.5 m3/h at pinl,min
In the case of direct PBU connection, the respective inlet pressure is added to the discharge head of the pump(s). The factory-set value for the cut-out pressure pco is normally 0.3 bar lower than the maximum discharge pressure of the pump (at Q = 0 m3/h). Point 1 on the pump curve (Fig. 25) characterizes the cut-out flow rate of the pump for the design inlet pressure pinl,min (not considering possible after-run time). As a pump is always stopped whenever the cut-out pressure pco is exceeded, the conclusion in the case of increased inlet pressure is that the pump stops with a lower discharge pressure.
After an inlet pressure increase of 0.5 bar pinl = pinl,min + 0.5 bar the cut-out flow rate is Qco = 3 m3/h. Cascade-controlled PBUs have fixed pressuredependent switching points for pump cut-in and cut-out.
40
Point 2 demonstrates the increased cut-out flow rate at the lower pump discharge pressure. The characteristic curves used as an example clearly show that especially with flat pump curves (fewer stages) one can expect an excessive flow rate increase at the cut-out point.
12
Inlet pressure fluctuations in the form of pressure decrease
pumps in operation can no longer reach the cutout pressure!
12.2.2 Inlet pressure fluctuations in the form of pressure decrease Inlet pressure fluctuations (in this case in the form of pressure decreases) which fall below the minimum inlet pressure are particularly dangerous for PBUs. Cascade-controlled PBUs have a nominal cut-out pressure margin of 0.3 bar. This means that the maximum pump discharge head is 0.3 bar above the cut-out pressure pco. As soon as the minimum inlet pressure drops by more than 0.3 bar, the PBU
160 H m 150
pA bar Characteristic curve
041 5
14.4
valvues and tolerarances
140
to ISO 2548, Annex B
130
041 3
12.4
120 110
10.5
0411
9.5
0410
0409
90
8.5
0408
80
0407
70
0406
60
7.5 6.6 5.6
100
0405 Point 1
4.6
0404
3.6
50 Point 2
0.5 bar
Specifically selected PBU for p inl,min
40
0403
30
0402
20
2.6 1.7
Pumps per system without standby pump
with standby pump
10 0
1.5
0
/
2
2
3.0 3
4
5
6
7
8
9
2
3
4
6
8
10
12
14
16
18
3
4
6
9
12
15
18
21
24
27
4
5
8
12
16
20
24
28
32
36
5
6
10
15
20
25
30
35
40
45
6
/
12
18
24
30
36
42
48
54
0
1
Q m3/h
Fig. 25: Pump selection chart for Movitec V 4
41
13
Causes of pressure surges
This means when the pressure wave returns and the valve is closed, the pressure surge according to Joukowsky fully develops.
13 Causes of pressure surges 13.1 Pressure surges caused by valves All kinds of valves can, when they close quickly, lead to pressure surges. The theoretic basis for calculating this phenomenon is described in the formula by Joukowsky:
⌬⌯ =
a — · ⌬v g
Remedy: TC must be markedly longer than TR. e.g.: TC 욷 2 · TR
[32]
[m]
13.2 Pressure surges as a result of inlet pressure fluctuations in the case of PBUs with cascade control
Legend for [32] ⌬H = Pressure increase a
= Propagation of a pressure wave at approx. 1000 - 1200 m/s
g
= Acceleration due to gravity, approx. 10 m/s2
If the inlet pressure increases, the pump curves shift upwards and the base load pump is stopped at a higher volume flow (Fig. 27). This results in an increased flow velocity change as the pump stops, thus generating pressure surges!
⌬v = Velocity difference The full impact of the pressure surge can be mathematically expressed by the following formula: 2·l TC 울 TR = ——— a
[33]
[s]
Remedy: A pressure reducer/controller has to be installed upstream of the pressure boosting unit to prevent detrimental effects.
Legend for [33]
Impact of inlet pressure increase by 0.3 bar
TC = Valve closing time
H0
TR = Reflection time in the piping l
= Length of piping up to the location of disturbance
Discharge pressure
pA p(co -ci) pE
Qco, normal
Q co, inlet pressure increase by 0.3 bar
QD
pressure wave Location of disturbance, e.g. T-piece
Valve
Example: Pressure development of a system with 3 pumps with increasing flow rate (consumption) with decreasing flow rate (consumption)
l
Fig. 26: Pressure surge caused by valves
42
Fig. 27: Operating characteristics of a pressure boosting unit with cascade control, i. e. without speed control
14
Standards, directives and statutory regulations
14 Standards, directives and statutory regulations
DIN 1988 (December 1988 edition) Codes of practice for drinking water installations (TRWI); general; - DVGW1 code of practice Part 1, General includes among others: Competences, technical terms, graphic symbols and designations Part 2, Planning and operation; component parts, apparatus and materials includes among others: Piping units, valves, apparatus, drinking water heating units, drinking water tanks, drinking water treatment equipment, measuring and metering instruments. Part 2, Sheet 1 Compilation of standards and other technical specifications regarding materials, components, apparatus. Part 3, Calculating the pipe diameters includes among others: Calculation flow rate and flow pressure, application of conversion curve(s) of total flow to peak flow, selection of piping diameter, circulation pipes and circulation pumps, calculation examples; Annex A: forms for calculation Part 3, Sheet 1, Calculation examples Part 4, Protection of drinking water, drinking water quality control includes among others: Causes for impairment and endangering of drinking water quality, equipment preventing back flow, protection of drinking water in water heating units Part 5, Boosting and pressure reduction includes among others: Pressure boosting units and pressure reducers Part 6, Fire-fighting and fire protection installations includes among others: Terms, configuration and requirements, commissioning Part 7, Prevention of corrosion damage and calcareous deposit formation includes among others: Prevention of damage due to interior and exterior corrosion and calcareous deposit formation
1
German Gas and Drinking Water Association
43
14
Standards, directives and statutory regulations
Part 8, Operation of plants includes among others: Commissioning, operation, damage and faults, maintenance information Annex A Information on maintenance measures Annex B Inspection and maintenance schedule Annex C Sample forms for commissioning and instruction reports DIN 2000 (November 1973 edition) Centralized drinking water supply; principles for drinking water requirements, planning, construction and operation of units DIN 2001 (February 1983 edition) Individual drinking water supply; principles for drinking water requirements, planning, construction and operation of units; DVGW code of practice DIN 4109, Part 5 (October 1989 edition) Sound insulation in building construction EN 1717 (February 1995 edition) Protection against pollution of potable water installations and general requirements of devices to prevent pollution by backflow DIN 4807, Part 5 (March 1997 edition) Direct flow membrane pressure vessels in drinking water installations DIN 14200 (June 1979 edition) Nozzle discharge IfSG – Protection Against Infection Act (01.2001) Act regulating the prevention of and protection against communicable diseases in humans LMBG – Foodstuffs and Commodities Act (09.1997) Official food control law for food, tobacco, cosmetic products and other commodities to protect health and to safeguard consumers’ rights TrinkwV 2001 – Drinking Water Ordinance Regulation for the quality of water for human use VDI Directives Directives issued by the Association of German Engineers
44
14
Standards, directives and statutory regulations
Regulation governing plant safety (BetrSichV, 27.09.2002 edition) Excerpt (special, manufacturer-related aspects have to be considered) Group classification
Group I
울 PN 25 p · V 울 200
Single tests
Group III
Group IV
p · V > 200; p · V 울 1000 Operating pressure > 1 bar
p · V > 1000; > 1 bar Operating pressure > 1 bar
Pressure vessel code (DruckbehV) § 9, Testing prior to commissioning
not applicable
In the case of a pressure vessel which has been subjected to an acceptance test at another location – excluding the installation test – and provided with an acceptance certificate accordingly, it is sufficient that the installation at the place of operation is checked by an expert and that this is confirmed in writing, e. g. through a commissioning/acceptance report Pressure vessel code (DruckbehV) § 10 Regular testing (1) In accordance with sections 4 to 9, a group IV pressure vessel must be subjected to regular testing carried out by an expert (e. g. TÜV) at defined intervals.
Regular testing
not applicable
not applicable (4) Groups IV and VII pressure vessels must be subjected to internal tests every five years; pressure tests must be carried out every ten years and external tests must be performed every two years.
Allocation of membrane type pressure vessel (accumulator) sizes
Accumulator (PN 16; 12 l)
PN 10 ; 80 l
PN 10; 180 l, 300 l, 400 l, 800 l, 1000 l PN 16; 80 l, 180 l, 300 l, 400 l, 800 l, 1000 l
Table 2: Allocation of membrane-type pressure vessels (accumulators) and tests according to pressure vessel code
45
15
Inspection, maintenance and repair
15 Inspection, maintenance and repair to DIN 1988, Part 8
Inspection, maintenance and repair:
According the manufacturers’ operating instructions
Carried out by:
Installation contractor
Interval:
Annually unless otherwise specified by the manufacturer
46
16
Nomenclature
16 Nomenclature Description
Symbols
Unit
Propagation velocity of a pressure wave
a
m/s
Simultaneity factor
f
-
Acceleration due to gravity (9.81 m/s2)
g
m/s2
Pump discharge head
H
m
Max. pump discharge head at zero flow rate (Q = 0)
H0
m
Static head loss
Hgeo
m
Floor height
Hfl
m
Head loss
HL
m
Head increase
∆H
m
Static pressure loss for floor X
∆Hgeo (floor X)
m
Number of pumps (incl. stand-by pump)
n
-
Number of floors which have to be protected against inadmissible pressures by means of pressure reducers
Nflpr
-
Number of floors which can be supplied without PBU
Nwithout PBU
-
Pressure
p
bar
Maximum pump pressure at zero flow rate (Q = 0)
p0
bar
Cut-out pressure, pressure at which one pump of a pressure-controlled PBU cuts out
pco
bar
Cut-in pressure, pressure at which one pump of a pressure-controlled PBU cuts in
pci
bar
Flow pressure at consumer
pflow
bar
Minimum flow pressure at consumer
pmin,flow
bar
Minimum flow pressure at consumer in floor N
pmin,flow(N)
bar
Minimum supply pressure (at hand-over point between local provider and consumer)
pmin,V
bar
Maximum pressure
pmax
bar
Maximum flow pressure at consumer
pmax,flow
bar
Maximum pressure per floor
pmax,fl
bar
Maximum supply pressure (at hand-over point between local provider and consumer)
pmax,V
bar
Required pressure downstream of the PBU
pdischarge
bar
Available pressure upstream of the PBU
pinl
bar
Minimum available pressure upstream of the PBU
pinl,min
bar
Maximum pressure upstream of the PBU
pinl,max
bar
Opening pressure of a by-pass valve
pvalve
bar
Setpoint (of a speed controlled PBU)
47
16
Nomenclature
Description
Symbols
Unit
Pressure drop during pump start-up
∆p1
bar
Pressure increase during pump shutdown
∆p2
bar
Apparatus pressure loss
∆pap
bar
Difference between cut-in/-out pressures
∆p(co-ci)
bar
Maximum pressure difference downstream of the PBU
∆pPBU,max
bar
Dynamic pressure difference
∆pdyn
bar
Dynamic pressure loss per floor
∆pdyn,fl
bar
Static pressure loss
∆pgeo
bar
Static pressure loss per floor
∆pgeo,fl
bar
Static pressure loss for floor X
∆pgeo (floorX)
bar
Pressure loss per floor
∆pfl
bar
Total pressure loss per floor
∆pfl,tot
bar
Pressure fluctuation upstream of the PBU
∆pinl
bar
Water meter pressure loss
∆pwm
bar
Permissible pressure loss
∆pperm.
bar
Mean pressure drop in consumer supply pipes
∆p/l
mbar/m
Cut-out flow rate of the last pump in operation (without after-run period) · PBU design flow rate = nominal flow rate of a PBU (Vmax)
Qco
m3/h
QD
m3/h
Maximum volume flow of a PBU incl. stand-by pump
QDS
m3/h
Fire-fighting water volume flow
QFfw
m3/h
Critical minimum flow rate of pressure-dependent cascade control
Qcrit
m3/h
Minimum flow rate
Qmin
m3/h
Maximum permissible volume flow of filling device
Qmax
m3/h
Maximum permissible volume flow from water supply network
Qmax,netw
m3/h
Nominal flow rate of water meters
Qn
m3/h
Nominal flow rate of PBU
QN
m3/h
Filling volume flow
Qfill
m3/h
Water supply network volume flow
Qnetw
m3/h
Low or permanent consumption dependent on usage
Qconsumer, small
m3/h
48
16
Nomenclature
Description
Symbols
Unit
Volume flow difference
∆Q
m3/h
Volume flow change of a highly dynamic consumer
∆Qmax,dyn
m3/h
Change of nominal flow rate per pump
∆QPU
m3/h
Switching frequency
S
-
Period of time required to fill a hydrant pipe up to the wall-mounted fire hydrant which is most unfavourably located
t
s
Inlet tank buffering period
t
h
Time difference
∆t
s
Closing time of valve
TC
s
Reflection time in the pipeline
TR
s
Flow velocity
v
m/s
Flow velocity difference
∆v
m/s
Usable volume of the atmospheric inlet tank
VIT
m3
Accumulator volume
Vaccum.
m3
Gross accumulator volume
Vgross
m3
Total accumulator volume
Vtot
m3
Contents of network piping
Vpipe
m3
Calculation flow rate of a tap/fitting
Vcal
m3
Total accumulator volume
Vtot
m3
Volume difference
m3
Sum of all calculation flow rates of all taps/fittings to be supplied
∆V · Vn · Vmin · Vmax · Vmax,p · Vcal · Vpeak · ΣVcal
Pipe friction and other losses
Σ(R · I+Z)
bar
Pipe friction and other losses from supply pipe up to PBU
Σ(R · I+Z)inl
bar
Pipe friction and other losses downstream of PBU
Σ(R · I+Z)discharge
bar
Mean pressure drop in a pipe
R
bar/m
Individual friction losses
Z
bar
Pipe length
I
m
Sum of pipe length from PBU to the hydraulically least favourable extraction point
ΣIdischarge
m
Accumulator efficiency
e
-
Temperature factor
j
-
Nominal flow rate of water meters Minimum flow rate Nominal flow rate of a PBU = design flow rate of a PBU (QD) Maximum volume flow of a PBU pump Calculation flow rate of a wall-mounted fire hydrant Peak flow rate of a PBU
m3/h m3/h m3/h m3/h l/s l/s l/s
49
17
References
17 References
–
DIN 1988 Codes of practice for drinking water installations
–
DIN EN 806, Parts 1 und 2 Codes of practice for drinking water installations
–
Kommentar zu DIN 1988, Teil 1 bis 8 1st edition 1989
–
Feurich Sanitärtechnik 1999 (Sanitation Engineering)
–
50
KSB brochure / manual “Selecting centrifugal pumps” 5th edition 2005
51
Worksheet 1
Calculation flow rates and minimum flow pressures
Worksheet 1 Calculation flow rates and minimum flow pressures Step 1: Determining the calculation flow rates of all taps/fittings and apparatus to be connected according to manufacturer’s specifications (Rough evaluation on the basis of reference values according to DIN 1988, Part 3, Table 11). Minimum flow pressure
Calculation flow rate for extraction of cold or heated mixed water1) drinking water only
Type of drinking water extraction point
· Vcal
· Vcal
cold l/s
warm l/s
DN 15 DN 20 DN 25 DN 10 DN 15
– – _ – –
– – _ – –
0.30 0.50 1.00 0.15 0.15
pmin,flow bar 0.5 0.5 0.5 1.0 1.0
l/s Water tap without spray2)
with spray
· Vcal
1.0
Showerheads
DN 15
0.10
0.10
0.20
1.2 1.2 0.4 1.2
Flush valve to DIN 3265 Part 1 Flush valve to DIN 3265 Part 1 Flush valve to DIN 3265 Part 1 Flush valve for urinals
DN 15 DN 20 DN 25 DN 15
– – – –
– – – –
0.70 1.00 1.00 0.30
1.0 1.0
Domestic dishwasher Domestic washing machine
DN 15 DN 15
– –
– –
0.15 0.25
1.0 1.0 1.0 1.0 1.0
Mixer for combined bathtubs/shower bathtubs kitchen sinks sink units bidets
DN 15 DN 15 DN 15 DN 15 DN 15
0.15 0.15 0.07 0.07 0.07
0.15 0.15 0.07 0.07 0.07
– – – – –
1.0
Mixer tap
DN 20
0.30
0.30
–
0.5
Cistern to DIN 19 542
DN 15
–
–
0.13
1.0
Electric water heater
DN 15
–
–
0.10 3)
)
1
The temperatures for the calculation of flow rates for mixed water extraction were assumed to be 15°C for cold and 60°C for heated drinking water. 2) Taps with screwed hose connections (without spray): the pressure loss in the hose (up to 10 m) and in connected apparatus (e. g. lawn sprinkler) is generally taken into account via the minimum flow pressure. In this case, the minimum pressure is increased by 1.0 bar to 1.5 bar. 3) With fully opened throttle screw
Table 3: Reference values for minimum flow pressure and calculation flow rates of common drinking water extraction points Comment: In the case of similar extraction points and apparatus with larger flow rates or minimum flows which have not been specified in this table, information should be obtained from the respective manufacturers in order to calculate the piping diameter
Step 2: · Adding the calculation flow rates = ΣVcal
52
Worksheet 2
Calculating the peak flow rate
Worksheet 2 Calculating the peak flow rate Step 3: · Calculating the peak flow Vpeak in accordance with diagram (from DIN 1988, Part 3, Fig. 3) below. (For more accurate calculations, we recommend using tables 12 to 17 of DIN standard 1988, Part 3, especially when higher outputs are required) The simultaneity of water extraction in particular must be considered – if required, upon consultation with the operator – for all drinking water installations which have not been specified here.
100
100 Range of application:
70
Vcal < 20 l/s
70
Vcal > 0.5 l/s
50
Vcal < 0.5 l/s
50
Residential buildings
40
40
Office and administration buildings
30
30
Hotels 20
15
Hospitals (wards equipped with beds only) Vcal = Vpeak from 0.1 to 1.5 l/s Schools
10
10
Vcal > 1.5 l/s
7 Peak flow Vpeak in l/s
20
Department stores
15
7
5 4.4 4
5
3
3
2
2
4
1.5
1.5
1.0
1.0 Range of application:
0.7
Vcal > 20 l/s
0.7
Residential buildings 0.5
0.5
Office and administration buildings
0.4
0.4
Hotels
0.3
0.3
Department stores Hospitals (wards equipped with beds only)
0.2 0.15
0.2 0.15
Schools 0.1 0.1
0.15 0.2
0.3 0.4 0.5
0.7
1.0
1.5
2
3
4
5
7
Total flow rate
10
15
20
30
40 50
70
100
150 200 176.5
0.1 300 400 500
Vcal in l/s
Fig. 26: · · Peak flow rate Vpeak in l/s as a function of total flow rate ΣVcal in l/s
· A rough evaluation can be made for residential buildings on the basis of a total flow rate of ΣVcal = 2.0 l/s per living unit.
53
Worksheet 3
Flow rates
Worksheet 3 Flow rates Water flow rate of fire-fighting hose nozzles1) according to DIN 14 200 Pressure p
Internal diameter d in mm 4 3)
6 6)
8
bar
) ) 6 ) 7 )
9 4)
10
12 7)
Water flow rate Q in 1/min
3.0
18
41
73
93
115
165
3.5
20
45
79
100
125
180
4.0
21
48
85
105
130
190
4.5
22
50
90
115
140
200
5.0
24
53
95
120
150
215
6.0
26
58
105
130
160
235
7.0
28
63
110
140
175
250
3
Corresponds to fire-fighting hose nozzle DM (d5 = 4)
4
Corresponds to fire-fighting hose nozzle CM (d5 = 9) Corresponds to fire-fighting hose nozzle DM (d2 = 6)
to DIN 14 365, Part 1
Corresponds to fire-fighting hose nozzle CM (d2 = 12)
Table 4: Flow rates of fire-fighting hose nozzles
Frequently applied flow rates for fire hydrants Requirements as per the following standards DIN 14 461-1 (Delivery valve installation with semi-rigid hose) requires water volumes of 100 l/min at 3 bar and simultaneous operation of three wall-mounted fire hydrants (3 x 1.67 l/s). DIN 1988/6: The piping system must be designed to deal with a maximum water volume of 2 x 24 l/min (2 x 0.4 l/s) at 2 bar (wall-mounted fire hydrant, type S).
54
Worksheet 4
Water meters
Worksheet 4 Water meters Pressure losses ⌬pwm of water meters Standard values
Nominal flow rate · Vn(Qn) m3/h
Pressure loss ⌬p · at Vmax (Qmax) to DIN ISO 4064, Part 1 mbar max.
Turbine flowmeter
< 15
1000
Woltman type flowmeter (vertical)
욷 15
600
Woltman type flowmeter (parallel)
욷 15
300
Flowmeter type
As a rule, the water meter type, quantity and size are determined by the local water provider. If the local water provider determines the size of the water meter, then the water meter pressure loss specified by the provider must be applied. The following applies according to DIN ISO 4064, Part 1: · · Vn (Qn) = 0.5 Vmax (Qmax)
Table 5 Water meter pressure losses
[34]
· Vn (Qn) applies to permanent consumption · Vmax (Qmax) applies to short-term peak consumption
Connection, nominal and maximum flow rate of water meters to DIN ISO 4064, Part 1
Flowmeter type
Connection Thread size Connection size to (nominal flange size) DIN ISO 228, Part 1 DN
Nominal flow rate *) · Vn (Qn)
Maximum flow rate · Vmax (Qmax)
m3/h
m3/h
G 1/2 B
–
0.6
1.2
Positive
G 1/2 B
–
1
2
displacement
G 3/4 B
–
1.5
3
and turbine
G1B
–
2.5
5
flowmeters
G 1 1/4 B
–
3.5
7
G 1 1/2 B
–
6
12
G2B
–
10
20
–
50
15
30
–
50
15
30
–
65
25
50
–
80
40
80
–
100
60
120
–
150
150
300
–
200
250
500
Woltman flowmeter
*) The nominal flow rate is a water meter specification. According to DIN ISO 4064, Part 1, thread sizes for a given nominal flow V·n (Qn) can also be taken from the class directly above or below those indicated in the table for the respective values.
Table 6 Flow rates for water meters
55
Worksheet 5
Filters, drinking water heating systems, pressure losses in consumer supply pipes
Worksheet 5 Filters, drinking water heating systems, pressure losses in consumer supply pipes
Filter-induced pressure losses
Pressure losses of consumer supply pipes downstream of the PBU
A reference value of 200 mbar can be applied for filters · · with Vmax = Vpeak.
Pressure loss ⌬pDH of drinking water heating systems for several extraction points Reference values:
Heater type
Pressure loss ⌬pDH 1) bar
Electric through-flow water heater, thermally controlled hydraulically controlled 2)
0.5 1.0
Electric or gas water heater with storage tank, nom. volume up to 80 l
0.2
Gas through-flow water heater and combined gas heater for warm water and heating systems to DIN 3368, Parts 2 and 4
0.8
)
These values do not include the pressure loss caused by safety and connection valves/fittings
)
Corresponds to the required switching pressure difference
1
2
Table 7 Pressure losses of drinking water heaters
To calculate the pressure loss of further apparatus (e. g. water softening or dosing equipment) obtain relevant manufacturer’s data, if required.
56
Evaluation to DIN 1988, Part 3: Pipe length from PBU to Mean pressure drop in least hydraulically favourable consumer supply pipes extraction point ⌬p (R · l + Z)downstream — = ———————— Σldownstream l Σldownstream m
mbar/m
울 30
20
> 30 울 80
15
> 80
10
Table 8 Pressure loss evaluation of consumer supply pipes downstream of PBU
In the planning phase the system designer is however required to perform a detailed calculation of the pressure losses.
Conversion of discharge head H into pressure increase ⌬p
Worksheet 6
Worksheet 6 Conversion of discharge head H into pressure increase ⌬p
⌬p = · g · H
[35]
⌬p = pressure increase in pa (1pa = 1 N/m2) (1bar = 100 000 pa)
= Density in kg/m3
g
= Acceleration due to gravity = 9.81 m/s2
H = Discharge head per pump in m In practice, the value assumed for acceleration due to gravity (g) is 10 m/s2 and for density ␦ 1000 kg/m3 The above equation is therefore simplified: H ⌬p 앒 —— 10
[bar]
[36]
⌬p = Pressure increase in bar H = Discharge head in m Both equations also apply to static pressure losses, e. g. ⌬pgeo , and the static head losses, e. g. Hgeo. Therefore: Hgeo ⌬p geo 앒 —— 10
[bar]
[37]
57
Head loss HL
Fig. 27: Head losses HL for new unmachined steel pipes, seamless (k= 0.05 mm)
0,01 0,5
0,02
0,05
0,1
0,2
0,5
1
2
5
20
0,5
2 1
32
5
40
2
10 5
2 10
5
2,0
2,5
20
50
2
m/s
Flow rate Q
102
15 0
m
d
=1 5m
1
0,3
50
0,4
0,6
65
0,5
1,5 1,2 5 1,0
80
0,8
0 10
4,0 3,5 3,0
5,0
17 5 20 0
10
5 12
v=
5 200
30 0 35 0 40 0
100
0 25
20
0
103
50
50 m 100 m
60 0 70 0
500
2
2000
104
5000
2
l /s Source: Selecting centrifugal pumps, KSB
1000
5
m3/h
New unmachined steel pipes, seamless
80 0 90 0 00 10
58 12 00 14 00 16 0 18 0 0 20 0 00
100
Worksheet 7 Head losses of steel pipes
Worksheet 7 Head losses of steel pipes
25
Head loss H L
0,01 0,5
0,02
0,05
0,1
0,2
0,5
1
2
5
d
= 1 5m m
1
20
0,5
2 1
32
5 2
0,3
40
10
0,4
50 0,6 0, 5
5
2
1,0
65 0,8
80
10
1,5 1,2 5
2,0
5 20
12 5
10
10 0
4,0 3,5 3,0 2,5
v= 5,0 m/s
50
2
30 0
100
25 0
Flow rate Q
102
15 0
20
17 5 20 0
50 m 100 m
200
35 0 40 0
5
50 0
103
500
2
0
5 2000
104
5000
2
20 40 oC 60 Temperature t
HL-correction for plastic pipes
l /s
m3/h
Source: Selecting centrifugal pumps, KSB
1000
0,8
0,9
1,0
1,1
Plastic and drawn metal pipes
Temperature factor
100
Head losses of low friction pipes
Worksheet 8
Worksheet 8 Head losses of low friction pipes
Fig. 28: Head losses HL for low-friction pipes (k ≈ 0) (For plastic pipes when t ⫽ 10°C multiply by the temperature factor ).
59
25
Worksheet 9
Permissible flow rate criteria of a PBU
Worksheet 9 Permissible flow rate criteria of a PBU
Nominal service
Max. total flow upstream of
Max. permissible flow rates for direct connection
pipe diameters
PBU and consumer
of a PBU without pressurized inlet tank
pipes without PBU DN
I
IIa
IIb
Qmax at v < 2.0 m/s
Qmax at v < 0.15 m/s
Qmax PBU at v < 0.5 m/s
m3/h 25 / 1"
3.50
0.26
0.88
32 / 1 1⁄4"
5.80
0.43
1.45
40 / 1 1⁄2"
9.00
0.68
2.30
50 / 2"
14.00
1.06
3.50
65
24.00
1.80
6.00
80
36.00
2.70
9.00
100
57.00
4.20
14.00
125
88.00
6.60
22.00
150
127.00
9.50
32.00
200
226.00
17.00
57.00
250
353.00
26.50
88.00
300
509.00
38.00
127.00
Permissible flow velocity in service pipe (to DIN 1988 Part 5, section 4.4.1) I:
The total flow velocity upstream of the PBU and upstream of the consumer pipes without PBU must not exceed 2.0 m/s. For direct connection to a PBU without pressurized inlet tank the difference in flow velocity in the service pipe as a result of starting and stopping the PBU pumps must not exceed the following values:
IIa: v < 0.15 m/s by one (the largest) single pump IIb: v < 0.5 m/s by simultaneously stopping all PBU duty pumps
The table provides information on flow rate criteria for the specified nominal service pipe diameters depending on the following: – permissible flow velocity ( IIa) and – its change as a result of the number of pumps started / stopped (IIb) and – total flow rate (I).
60
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P u m p C o n t r o l / Sy s t e m A u t o m a t i o n
1
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