BS en 12845-2004 Fixed Firefighting Systems — Automatic Sprinkler Systems — Design, Installation and CRACK

EN 12845:2004 (E) The distance from the end of the shelf parallel to the range pipe lines to the nearest sprinkler shall be half the sprinkler spacing along the range lines or 1,4 m, whichever is the less. Table 21 — Location of intermediate sprinklers in type ST5 and ST6 storage Shelf width - s

Rows of sprinklers

Maximum distance between sprinklers along rows m

Maximum distance between rows of sprinklers m

1 1 2

2,8 2,8 2,8

2,8

m ST5: s ≤ 1,0 ST6: 1,0 < s ≤ 3,0 ST6: 3,0 < s ≤ 6,0

13 Pipe sizing and layout 13.1 General 13.1.1 Pipe sizing Pipe sizes shall be determined using one of the following methods: ⎯

pre-calculated systems, where the diameters are partly taken from tables and partly calculated (see 13.3);

⎯

fully calculated systems, where all diameters are determined by hydraulic calculation (see 13.4).

The designer may choose between the two systems, except in the following cases, where full calculations shall always be used: ⎯

layouts with intermediate level HHS sprinklers;

⎯

gridded or looped layouts.

13.2 Calculation of pressure losses in pipework 13.2.1 Pipe friction loss Calculations of pipe friction loss shall be not less than those derived from the Hazen-Williams formula:

p=

6,05 x 105 x L x Q1,85 1,85 4,87 x C d

where: p is the pressure loss in the pipe, in bar; Q is the flow through the pipe, in litres per minute; d is the mean internal diameter of the pipe, in millimetres; C is a constant for the type and condition of the pipe (see Table 22);

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EN 12845:2004 (E) L is the equivalent length of pipe and fittings, in metres. The values of C indicated in Table 22 shall be used. Table 22 — C values for various types of pipe

NOTE

Type of pipe

Value of C

cast iron ductile iron mild steel galvanized steel spun cement cement lined cast iron stainless steel copper reinforced glass fibre

100 110 120 120 130 130 140 140 140

The list is not exhaustive

The pressure loss due to velocity may be ignored. 13.2.2 Static pressure difference The static pressure difference between two inter-connecting points in a system shall be calculated from: p = 0,098h where: p is the static pressure difference, in bar; h is the vertical distance between the points, in metres.

13.2.3 Velocity The equilibrium water velocity shall not exceed: ⎯

6 m/s through any valve or flow monitoring device;

⎯

10 m/s at any other point in the system,

for the stabilized flow condition at the demand point the total number of sprinklers assumed to be in simultaneous operation. 13.2.4 Pressure loss through fittings and valves The pressure loss due to friction in valves, and in fittings where the direction of water flow is changed through 45o or more, shall be calculated using the formula specified in 13.2.1. The appropriate equivalent length shall be one of the following: a)

as specified by the equipment supplier;

b)

as taken from Table 23, if a) is not available.

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EN 12845:2004 (E)

If there is a bend, tee or cross where there is a change in direction of flow and there is also a change in diameter at the same point, the equivalent pipe length and pressure loss shall be determined by using the smaller diameter. Table 23 — Equivalent length of fittings and valves a

Equivalent length of steel straight pipe for a C value of 120 (m)

Fittings and valves

Nominal diameter (mm) 20

25

32

40

50

65

80

100

150

200

250

1,0

1,2

90º Screwed elbow (standard)

0,76 0,77

1,5

1,9

2,4

3,0

4,3

5,7

7,4

90º Welded elbow (r/d = 1,5) 45º Screwed elbow (standard)

0,30 0,36 0,49 0,56 0,69

0,88

1,1

1,4

2,0

2,6

3,4

0,34 0,40 0,55 0,66 0,76

1,0

1,3

1,6

2,3

3,1

3,9

Standard screwed Tee or cross (flow through branch)

1,3

1,5

2,1

2,4

2,9

3,8

4,8

6,1

8,6

11,0

14,0

-

-

-

-

0,38

0,51 0,63 0,81

1,1

1,5

2,0

-

-

-

-

2,4

3,2

5,1

7,2

9,4

12,0

-

-

-

-

12,0

19,0 19,7 25,0 35,0 47,0

62,0

-

-

-

-

2,2

2,9

8,6

9,9

-

-

-

-

16,0

21,0 26,0 34,0 48,0 64,0

84,0

Gate valve - straight way Alarm or non-return (swinging type)

valve

Alarm or non-return (mushroom type)

valve

Butterfly valve Globe valve

3,9

3,6

4,6

6,4

a

These equivalent lengths may be converted as necessary for pipes with other C values by multiplying by the following factors: C value100 110 120 130 140 Factor 0,714 0,85 1,00 1,16 1,33

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