Pipenet Vision Spraysprinkler Module

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PIPENET VISION SPRAY/SPRINKLER MODULE CHAPTER 1 INTRODUCTION AND BASIC PRINCIPLES

1.

Introduction

The Spray/Sprinkler Module of PIPENET VISION was specifically developed for the type of fire protection systems that are used in process plants and similar plants, such as refineries, petrochemical plants, offshore plants, and terminals. Such systems are characterised by complex firewater ringmains, deluge systems, sprinkler systems, foam injection systems, etc. For these systems, it is usually necessary to perform calculations under several scenarios, such as different fire scenarios and different pump scenarios. With PIPENET VISION, it is simple and fast to perform these calculations. The objective is to ensure that pipes, pumps, hydrants, nozzles and other items perform satisfactorily. Where necessary, PIPENET VISION can be used to size orifice plates in order to balance or reduce the flow rates. The Spray/Sprinkler Module is a steady-state modelling program for designing systems, with the objective being to ensure that the sizes of pumps, pipes, nozzles, etc. are adequate. The Spray/Sprinkler Module complies with the NFPA rules, which are the universal rules governing the design of fire protection systems in the process plant industry, as far as hydraulic calculations are concerned. One of the differences between the Spray/Sprinkler Module and the other modules of PIPENET VISION is that, with the Spray/Sprinkler Module, it is not possible to enter a network until either (a) a Sunrise Data File (“*.SDF”) has been entered and saved or (b) an existing Sunrise Data File is opened. In the suite of training manuals for the PIPENET VISION Spray/Sprinkler Module, Chapters 2 and 3 are the core of the training course, whereas Chapters 1 and 4 provide useful reading material. Most of the concepts and capabilities introduced in “Chapter 1 – User Interface of PIPENET VISION” are relevant to this module and should be read prior to reading the training manuals for this module. In this document, the main concepts and features that are specific to the Spray/Sprinkler Module are described.

2.

Concepts

2.1

Pressure Drop Model

The pressure loss, P, in a pipe is described as

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P = Pfric + Pelev + Pplat where Pfric is the pressure loss due to friction and fittings, Pelev is the pressure loss due to elevation change, Pplat is the pressure loss due to any orifice plate fitted. Full details of the equations that are used to calculate these pressure losses are described below.

2.1.1 Friction Pressure Losses – Darcy Pfric is determined using the Bernoulli Equation, which is a theoretical equation that gives the pressure in pipes, ignoring frictional effects. The pressure drop due to friction effects can be found by comparing the theoretical results from the Bernoulli Equation with results obtained in experiments. Based on the work of the French engineer Henri Darcy (1803–58) the following equation is obtained.

Pfric

2 f ( L + Le ) ρ u 2 = D

where D is the internal diameter of the pipe, L is the pipe length, Le is the equivalent length of any pipe fittings, f is the Fanning friction factor, u is the fluid velocity, ρ is the fluid density. The Fanning friction factor depends on the relative roughness of the pipe (i.e., pipe roughness divided by pipe diameter) and the Reynolds Number, Re, which is defined as

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Re =

SPRAY: CHAPTER 1 REVISION 2.1, SEP 2010

ρuD µ

where µ is the fluid viscosity. The standard values for f can be obtained from a graphical representation known as the Moody Diagram. The friction factor is represented in PIPENET VISION by the following empirical formulae (in which r is the surface roughness of the pipe). Laminar flow (Re < 2000):

f =

16 Re

Transitional flow (2000 < Re< 3000): The value of f is obtained by interpolating between the laminar value for Re = 2000 and the turbulent value at Re = 3000. Turbulent flow (Re > 3000):

 0.27 r 1.252 1 = −1.768 ln +  D f Re f 

   

2.1.2 Friction Pressure Losses - Hazen-Williams Method With this method, the pipe C-factor is used in the calculations, and so the C-factor must be supplied. It should be noted that, for maximum flexibility, the user is allowed to override the roughness or C-factor value of the pipe type when entering the individual pipe data. However, by default, the roughness or C-factor of each pipe will be determined by the pipe type of a particular pipe. The Hazen-Williams Equation is an empirical formula that gives an explicit expression for the frictional pressure loss. SI Units The frictional losses are given by

Pfric where

6.05 × 105 ( L + Le )Q1.85 = C 1.85 D 4.87

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L is the pipe length in metres, Le is the equivalent length of any pipe fittings in metres, Q is the (volumetric) fluid flow rate in l/min, D is the pipe diameter in mm, C is the Hazen-Williams constant (or C-factor) for the pipe. Imperial Units The frictional losses are given by

Pfric

4.52 ( L + Le )Q1.85 = C 1.85 D 4.87

where L is the pipe length in feet, Le is the equivalent length of any pipe fittings, in feet, Q is the (volumetric) fluid flow rate in UK gallons per minute, D is the pipe diameter in inches, C is the Hazen-Williams constant (or C-factor) for the pipe.

2.1.3 Pressure Loss due to Elevation Change The pressure drop caused by the difference in elevation of the two ends of the pipe is given by

Pelev = ρ g Z in which g is the acceleration due to gravity, Z is the change in elevation.

2.2

Pumps

In the simple pump model, the pump performance curve is used. The user inputs the flow rate against head data at 100% rpm. PIPENET VISION can then calculate the performance curve at other speeds, using the homologous relationships for pumps. This curve is normally intended only for use only in the positive quadrant; in other words, when the flow and the head are positive. Three options are available for defining pump curves: Quadratic function,

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Cubic function, Cubic spline functions. These functions are applicable to values of Q that lie between the specified minimum and maximum values (namely, Qmin and Qmax respectively).

2.2.1 Data Required for Entering a Pump Into the Library The standard method for entering pump data is to use points from the performance curve. These points are then used by PIPENET VISION to calculate the coefficients that define the appropriate curve (i.e., quadratic, cubic, or cubic spline). An alternative method, which is seldom used, is for the user to enter the coefficients A, B, and C that define the pump-performance curve. In this case, the minimum and maximum values for the flow rate must also be given.

2.2.2 Some Useful Tips If the user knows the performance coefficients for a pump, but does not wish to use a pump library, the user can define the pump as a non-library pump, by supplying the values of A, B, C, Qmin, and Qmax. In order for the calculator to function correctly, it is necessary to ensure that there is only one flow rate that corresponds to each pressure gain, and so the following restrictions apply: •

For flow rates between Qmin and Qmax, the slope of the performance curve must be negative or zero.

•

For flow rates between Qmin and Qmax, there must not be a flow rate that gives no pressure change (that is, all flow rates must correspond to a non-zero pressure change, and so the performance curve must not cross the horizontal axis).

If a flow rate lies outside the range Qmin to Qmax, PIPENET VISION issues an appropriate warning message, and then extrapolates the performance curve using the tangent to the curve at either the minimum or maximum flow rate (whichever is appropriate). PIPENET VISION calculates the power required by a pump based on an efficiency value. If this efficiency value is not supplied, the pump is assumed to be 100% efficient for the purpose of this calculation.

2.2.3 Pumps - Coefficients Unknown In the PIPENET VISION Spray/Sprinkler Module, data for pumps and fans can be created in a library. In this case, PIPENET VISION performs a curve fit, and uses the curve coefficients in the calculations. The input data must be in the form of data pairs, taken from the performance curves.

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Typically, the units for the pump curves are not the same as the units in which pressure-drop calculations are to be made. For example, it is usual to specify the pump curve in head of fluid, rather than psi. For this reason, the pump/fan module accepts data in its own units. The dialog box for inputting a pump curve can be obtained by choosing “Pumps – Coeffs. unknown” from the Libraries Menu (which is denoted by Libraries | Pumps – Coeffs unknown in the PIPENET VISION training manuals). The resulting dialog box is shown below.

PIPENET VISION takes into account the fact that the head generated by a pump is independent of the density of the fluid, and so PIPENET VISION makes an appropriate density correction in converting the head into a pressure. Similarly, the pressure generated by a pump depends on the fluid, and when the pump curve is defined in terms of pressure, an appropriate density correction is applied. This is the reason why, when the pumpperformance curve is defined in terms of pressure, the performance curve is interpreted to be that of water.

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Creating a New Pump 1. Select the New Button, and provide a name and description. 2. Select the desired flow-rate and pressure units from the drop-down menus. 3. Provide minimum and maximum values of the flow rate. 4. Provide at least three points for the curve. 5. Select the type of curve to be fitted (from, quadratic, cubic and cubic spline). 6. Click on the Apply Button to add the pump to the library. 7. The coefficients are then calculated and displayed, along with the pump curve. Note that the definition of the pump curve is accepted only if at least three points are supplied, and that the slope of the calculated curve is negative everywhere between the minimum and maximum values.

Type of curve fitted

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Editing an Existing Pump 1. Select the name of the pump from the drop-down list. 2. Make the required changes to the pump parameters. 3. Click on the Apply Button to commit the changes. Deleting a Pump 1. Select the name of the pump from the drop-down list. 2. Click on the Delete Button.

2.2.4 Pumps - Coefficients Known This capability is hardly ever used. In this case, the pump coefficients that define the performance curve can be obtained from the manufacturer. These coefficients are then entered into PIPENET VISION using Libraries | Pumps – Coeff. Known, and a pump-performance curve is produced.

2.3

Non-Return Valves

Non-return valves allow unrestricted flow of fluid in a positive direction, and prevent all flow in the reverse direction. Positive flow is taken to be in the direction from the valve's input node to its output node, in which case there is no pressure drop across the component. Caution should be exercised to avoid positioning a non-return valve such that it would isolate a portion of the network. If this were to happen, the calculator could report the error message “network cannot be solved". Note that, even if the solution to the problem involves the valve being open, PIPENET VISION can still generate this error message. Occasionally, a non-zero "leakage flow" may be reported through a closed valve. This flow, which arises from rounding errors that are smaller than the requested convergence accuracy, is usually negligible. Modelling Equations Open valve:

P1 = P2 Fully closed valve:

Q1 = 0

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Continuity Equation:

Q1 = Q2 The following variables are used in the above equations. P1 is the inlet pressure, P2 is the outlet pressure, Q1 is the inlet flow rate, Q2 is the outlet flow rate.

2.4

Filters

Strainers are usually modelled as equipment items. However, if the user wishes to model them more accurately and the required data is available, the filter model can be used. Filters are used in most of the networks to collect residue and dirt particles from the flow medium. The filters can also be generated in PIPENET VISION by supplying the values of the coefficients, A and B, in the modelling equations. Modelling Equation The modelling equation is

P = AQ Q + BQ where P is the pressure increase from the inlet to the outlet, Q is the (volumetric) flow rate through the filter, A is a coefficient (which is less than or equal to zero), B is a coefficient (which is less than zero). This equation is valid for values of Q whose modulus is less than a given maximum flow, Qmax. Note that filters are reversible (i.e., Q may be negative), in which case, since

A ≤ 0 and B < 0 the pressure drops in the direction of the flow.

2.5

Nozzles

Nozzle models in PIPENET VISION represent both the spray and sprinkler nozzles. The modelling equation for the nozzle is

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Q=K P where Q is the (volumetric) flow rate through the nozzle, P is the drop in pressure across the nozzle, K is a constant for the nozzle. This equation holds for values of P between specified minimum and maximum values (Pmin and Pmax respectively). The range from Pmin to Pmax is known as the working pressure range of the nozzle. Note that the value of K depends on the units used for P and Q. When the K value of a nozzle is referred to, the standard units for P and Q are bar and litres per minute respectively. Data Required In the library, the following data is required. 1. A nozzle descriptor to identify the type of nozzle (usually the manufacturer’s nozzle name is used). 2. The nozzle K-factor. 3. The values of Pmin and Pmax.

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The data for the input is as follows. 1. The nozzle status (i.e., “on” or “off”). Note that, if a nozzle is off, there is a small solid circle inside the nozzle symbol (in the schematic diagram), as indicated below. 2. 3. 4. 5.

The nozzle label. The input node. The name of the nozzle in the library. The flow rate required through the nozzle.

Notes 1. Nozzles do not have to be stored in a library. Instead, they can be defined by specifying the values of K, Pmin and Pmax. However, when there are several nozzles of the same type in the same network, it is easier to define the type in a library, as described above.

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2. The flow rate required through a nozzle is used in the Design Facility of PIPENET VISION.

2.6

Deluge Valves

Typically, users prefer to model a deluge valve as an equipment item, since an equipment item requires only an equivalent length. This length value can be either calculated or obtained from the vendor of the deluge valve. For the sake of completeness, this section contains an introduction to the deluge valve model. Before a deluge valve can be added to a network, the valve must first be defined in the private data file (via Libraries | Deluge valves). The dialog box for this option contains a list of defined valve types. A descriptor, manufacturer supplied K-factor and X-factor, and bore must be supplied.

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Modelling Equation

P = QX / K where P is the pressure drop across the valve, Q is the (volumetric) flow rate through the valve, K is a constant for the valve, X is a constant for the valve (with typical values being 1 and 2). Typical Performance Curves

2.7

Overboard Dump Valves

Overboard dump valves (or pressure safety valves) operate with a trigger pressure, PS. When the pressure upstream of the valve is below the trigger pressure, PS, the valve remains shut; on the other hand, when the pressure rises above PS, the valve opens. Once the valve is open, the upstream pressure stabilises at the trigger pressure, PS. In PIPENET VISION, an overboard dump valve is modelled as a special kind of outlet, and there is no need to model the network downstream of the point at which the trigger pressure is measured.

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3.

SPRAY: CHAPTER 1 REVISION 2.1, SEP 2010

Rules Governing Specifications

The rules that govern specifications in the Spray/Sprinkler Module are important. The following notes will help the user to understand them. These rules are mainly concerned with applying specifications to firewater ringmains. Before a simulation can be performed, the user must provide PIPENET VISION with information about pressures and/or flow rates at a number of nodes in the network. These specifications must obey the rules described in this section. PIPENET VISION runs the simulation in two phases; namely, the Design Phase and the Calculation Phase. The aim of the Design Phase is to find suitable diameters for one or more pipes in the network, so that the fluid velocity in each pipe and the pressure drop per unit length of pipe remain within the design criteria. Even if all of the diameters are known, PIPENET VISION still performs this phase. In the Calculation Phase, PIPENET VISION performs the final analysis calculations. For both phases, the user must specify the pressure and/or flow rate in various parts of the network. The user must also specify the input and output nodes in the network. There are two sets of specifications for each simulation: the design-phase specifications and the calculation-phase specifications. So that the problem is mathematically solvable, these two sets of specifications must obey certain rules. It should be noted that, in some simulations, the user may not be interested in the results of one of the phases; however, both phases are still run in PIPENET VISION, and so two sets of specifications need to be supplied. The specifications have to adhere to the following rules. 1. There must always be at least one pressure specification. (If there is at least one nozzle in the system, PIPENET VISION will automatically set its outlet pressure to 0 bar G, in which case a pressure need not be set by the user.) 2. The actual number of specifications must obey the rules in the following table.

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Phase

Np

Nf

Design

1 (set by PIPENET VISION)

Nio – 1

Analysis

Np

Nio - Np

The following parameters are used n the above table. Nio is the sum of the number of inputs and the number of outputs (ignoring nozzles), Np is the number of pressure specifications, Nf is the number of flow specifications.

3.1

The Design Phase

When a network is being designed, it is a general requirement that the velocity of the fluid in each pipe does not exceed a given value (known as the design velocity of the pipe). The velocity of the fluid in a pipe depends on: • •

The flow rate through the pipe, The diameter of the pipe.

It is, therefore, important that all of the pipes are correctly sized, so that the fluid velocity does not exceed the design velocity. This problem is addressed in the design phase of the simulation. Given the required flow rates in and out of the network, PIPENET VISION will find optimal diameters for each pipe in the network, so that the velocity of the fluid does not exceed the design velocity. The user must supply the required flow rate for (a) all nozzles and (b) all but one of the input and output nodes in the network. PIPENET VISION can then determine the flow rates required throughout the network, and thus calculate optimal sizes for the pipes. The total number of Design Phase flow-rate specifications must be one less than the number of input/output nodes. This point is especially important for firewater ringmains, as they typically have more than one input/output node. The following points must be noted. By virtue of mass balance, the flow rates through all of the input/output nodes can be calculated if the flow rate at one input/output node is left unspecified. Moreover, the pipe diameters must be sized adequately to handle the required flow rates, which is the reason why all the specifications during the design phase are flow rates.

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The following points should also be noted: •

If desired, the user can set the diameter of some (or all) pipes in the network. PIPENET VISION will then size only those pipes whose diameter has not been set.

•

If the user wants certain pipes in the network to be given the same diameter, then the Pipe Groupings facility should be used.

•

When a pipe (or group of pipes) is being sized, PIPENET VISION will choose the smallest pipe size that ensures that the design velocity is not exceeded by the fluid.

•

In the design phase, it is assumed that all nozzles discharge at the minimum required rate. In most systems, there will be some nozzles that actually discharge at a rate greater than the minimum requirement, and so flow rates and velocities in the system will rise. Consequently, the velocity of the fluid may rise above the design velocity in some pipes in the system. These pipes will be identified during the calculation phase, and a warning will be issued. The user can resolve this problem by setting the diameters of these pipes to be slightly larger than the design diameters.

In order to size all the pipes in a network, it may be necessary to perform more than one simulation.

3.2

The Calculation Phase

In the calculation phase, all the diameters of the pipes are known, as they are either (a) set by the user or (b) determined by PIPENET VISION during the design phase. PIPENET VISION simulates the behaviour of the network under the pressure and flow-rate conditions set by the user. All nozzles in the network are assumed to discharge to atmospheric pressure. The user must supply flow rates and/or pressures at various parts of the network by making Calculation Phase Specifications (which are described in the next section). PIPENET VISION will then calculate the pressures and flow rates throughout the network. The total number of Calculation Phase flow-rate and pressure specifications must be equal to the number of input/output nodes. This point is especially important for firewater ringmains, as they typically have more than one input/output node. Usually, the pressures at pump inlets are known and the flow rates at outlets are known. However, this is not a strict rule. For example, if a pump-selection case is to be run, the pressure and flow rate will typically be specified at the most remote output, and the input node would be left simply as an input (but with no pressure or flow rate specified). Typically, the calculation phase is used for one or more of the following purposes: • • •

Determine what pressures are needed to produce the required flow rates. Select suitable pumps for the network. Check that all demands made on the network can be satisfied. (A warning is issued for any nozzle supplying at less than its required rate.)

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Check that the fluid velocity in each pipe does not exceed the design velocity of the pipe. (A warning will be issued for any pipe for which the fluid velocity exceeds the design velocity.)

The User Interface and the Design and Calculation Phases

When a calculation is run, a pipe-sizing operation is performed if (a) there are unset pipe sizes and (b) the user has requested that the Design Phase be run. However, the user will generally perform a pipe sizing-operation, possibly make some changes to the network, and then perform another pipe-sizing operation, repeating these steps as required. Only when the user is satisfied will he/she perform a calculation. The controls relating to the Design and Calculation Phases are located on the Calculation Toolbar:

The sequence of operations will typically proceed as follows: 1. The two buttons D and C correspond to the Design and Calculation Phases respectively. If a Design Phase is required then the D Button is selected by default and the pipe-sizing button (i.e., the third button) is enabled. 2. The user enters the network and, if he/she requires PIPENET VISION to perform a Design Phase, then pipes may be entered with undefined bores. 3. When the user has entered the network he/she will select the Pipe Sizing Button to size the undefined pipes. The calculated pipe sizes are returned to the user, where they are displayed along with other pipe attributes. Note that, if another pipe-sizing operation is performed, the sizes may change if changes are made to the network. 4. Steps 2 and 3 are repeated as required. 5. When the user is satisfied with the network, he/she should select the C Button (in which case, the Pipe Sizing Button is disabled) to fix the designed pipe sizes, and then perform a calculation (by pressing the fourth button on the Calculation Toolbar). 6. The user can revert to the Design Phase by selecting the D Button; however, the bores of pipes that were fixed in Step 5 do not become unset.

4.1

Assumptions

1. The input and output nodes of a network are those points where fluid enters or leaves the network. 2. Internal nodes are those nodes that are neither input nodes nor output nodes.

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3. Sub-networks may be created by the presence of breaks and/or blocks. 4. If a node is at one end of a break then it is considered to have an attached pressure specification. 5. If a node is at one end of a block then it is considered to have an attached flow specification. 6. In the Design Phase, an arbitrary pressure of 50 bar is associated with one of the nodes. Therefore, a user-supplied pressure specification is not used in this phase.

4.2

Design Phase

1. There must be one (and only one) pressure specification, which may be applied at an input node, an output node, or an internal node. This specification is automatically set in PIPENET VISION, and so the user does not need to input it. 2. In a network, all but one of the input and output nodes must have a flow specification.

4.3

Calculation Phase

1. There must be at least one pressure specification. 2. Pressure specifications may be applied to input nodes, output nodes, or internal nodes. 3. The total number of pressure and flow specifications must be equal to the total number of input and output nodes (but note Points 4 and 5). 4. If there is at least one nozzle present, a user-supplied pressure specification is not required in the Analysis Phase. The rule that the total number of specifications must equal the total number of input and output nodes still holds. 5. If the Most Remote Nozzle Option is selected, one flow specification is added to the Analysis Phase. Therefore, the user must only provide n - 1 pressure or flow specifications, where n is the number of input and output nodes.

4.4

Simple Example

For a system with two inlets (pumps) and one outlet (deluge system), the specifications would be as follows.

4.4.1 Specifications for the Two Inlets (Pumps) Suppose that both pumps have Design Phase flow rates of 0 and Analysis Phase pressures of 0 barg.

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4.4.2 Specification for the One Output (Deluge System) For the output node, there are no Design Phase specifications and one Analysis Phase flowrate specification.

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General Concepts of Fire Protection System

Fire protection piping systems convey a fire-extinguishing substance from the source of supply to devices and equipment for applying it in fire fighting and fire protection. Water (owing to its effectiveness, availability, and low cost) is used most extensively as a fireextinguishing material. Other substances that are piped for fire fighting special types of fire are foam, carbon dioxide (or other inert gases), vaporizing liquid, or dry chemicals in an inert gas carrier. The detailed procedures followed by fire-protection specialists in determining anticipated water flows, in establishing pipe sizes, and in planning pipe locations and arrangement for particular private installations are too highly specialised and too limited in application to be allocated space for more than a brief mention here. Detailed information is available in the publications included in the references that appear later in this section.

5.1

Standard, Rules and Regulations

Some of the rules followed in fire protection systems are as follows. 1. National Fire protection association rules (NFPA) - most universally used. 2. Tariff Advisory Committee rules (TAC) - mostly followed in India. 3. Oil Industry Safety Directorate rules (OISD) - for oil and gas industries in India.

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4. GB Standard - mostly followed in China. The generally recognized standards that cover fire-protection piping are those developed by the National Fire Protection Association and by insurance organizations such as the American Insurance Association, the Factory Mutual Engineering Corporation and the Factory Insurance Association. The general recognised standards that relate to fire protection piping are listed below. Note that the fire protection hand books in References 1 and 2 contain much of the information in the individual standards, and may provide all the information that is required. 1. “NFPA Handbook of Fire Protection”, National Fire Protection Association, 60 Battery March St., Boston, Mass. 02110. The following standards are all available in the National Fire Protection Association. 2. “Handbook of Industrial Loss Prevention”, Factory Mutual Engineering Corporation. 3. Standard for the installation of Sprinkler Systems, NFPA No. 13. 4. Standard for the installation of Stand Pipe and Hose Systems, NFPA No.14. 5. Standard for the installation of Water Tanks for Private Fire Protection, NFPA No. 22. 6. Standard for the installation of Centrifugal Fire Pumps, NFPA No. 20. 7. Standard for Carbon-dioxide Extinguishing Systems, NFPA No. 12. 8. Standard for Foam Extinguishing Systems, NFPA No. 11. 9. Standard for Dry Chemical Extinguishing Systems, NFPA No. 17. 10. Standard for Outside Protection, NFPA No. 24. The following general references relate to certain aspects of the problems that are involved in the design and specification of the fire protection system. 11. “Automatic Sprinkler Hydraulic Data”, by Clyde M. Wood. Automatic Sprinkler Corporation of America. 12. “Hand Book of Cast Iron Pipes,” Cast Iron Pipe Research Association, Chicago. 13. “Approved Equipment and Materials for Industrial Fire Safety,” Factory Mutual Engineering Corporation. 14. “Fire Protection Equipment List,” Underwriter Laboratories Inc, Chicago. 15. “List of Inspected Appliance and Equipment and Materials,” Underwriter Laboratories of Canada.

5.2

Tariff Advisory Committee

The Tariff Advisory Committee has compiled rules to provide minimum requirements for fixed water spray systems, based on good engineering practices. While formulating the rules, due consideration has been shown to the International Standards.

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According to the TAC Manual, full details on the Common Requirements to High Velocity Water Spray and Medium Velocity Water Spray Systems are explained in the TAC manual, and they are: 1. Water supplies. 2. Pumps - general requirements for electric driven, compression ignition engine driven pumps, pump room, etc. 3. Detection system. 4. General requirements. 5. Piping. 6. Fittings. 7. Deluge valves. 8. Drainage. Similarly, high-velocity water-spray systems and medium-velocity water-spray systems are also explained in TAC Manual.

5.3

Oil Industry Safety Directorate (OISD)

For “Fire Protection Facilities for Petroleum Refineries & Oil/Gas processing plants”, the Oil Industry Safety Directorate staffed from within the industry for formulating and implementing a series of self regulatory measures aimed at removing obsolescence, standardizing and upgrading the existing standards to ensure safer operations. OISD constituted a number of committees comprising of experts nominated from the industry to draw up standards and guidelines on various areas of concern. This standard covers the design criteria and the details of the various fire protection facilities to be provided in petroleum refineries and oil/gas processing plants.

5.4

Classification of Petroleum Products

5.4.1 General Classification of Petroleum Products Petroleum products are classified according to their closed-cup flash points, as follows: Class 'A' Petroleum: Liquids that have a flash point below 23 degrees C. Class 'B' Petroleum: Liquids that have a flash point of 23 degrees C or above, but below 65 degrees C. Class 'C' Petroleum: Liquids that have flash point of 65 degrees C or above, but below 93 degrees C. Excluded Petroleum: Liquids that have a flash point of 93 degrees C or above. Liquefied gases, including LPG, do not fall under this classification but form a separate category.

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5.4.2 Classification for Heated Products At locations where the handling temperatures are higher than the flash point of the product in circumstances where the product handled is artificially heated to above its flash point, a class 'C' product shall be considered as a Class 'B' product and a Class 'B' product shall be considered as a Class 'A' product.

5.5

Classification Of Fires

Class 'A' Fires: Fires involving combustible materials of organic nature, such as wood, paper, rubber and any plastics, etc., where the cooling effect of water is essential for extinction of such fires. Class 'B' Fires: Fires involving flammable liquids, petroleum products, or the like, where a blanketing effect is essential. Class 'C' Fires: Fires involving flammable gases under pressure, including liquefied gases, where it is necessary to inhibit the burning gas at a fast rate with an inert gas, powder or vaporizing liquid for extinguishment. Class 'D' Fires: Fires involving combustible materials such as magnesium, aluminium, zinc, sodium, potassium, when the burning metals are reactive to water and water-containing agents, and in certain cases carbon dioxide, halogenated hydrocarbons and ordinary dry powders. Special media and techniques are required to extinguish these fires.

5.6

Fire Protection Philosophy

The Fire Protection Philosophy is based on Loss Prevention and Control. The importance of adequate fire protection facilities for hydrocarbon processing plants need not be emphasised, as none of the plant is absolutely safe (because of the inherent hazard it carries). A fire in one part/section of the plant can endanger other sections of the plant as well. If a fire breaks out, it must be controlled/extinguished as quickly as possible, to minimize the loss to life and property and to prevent further spread of fire.

5.6.1 Design Criteria The following shall be the basic design criteria for a fire protection system. 1. Facilities should be designed on the basis that city firewater supply is not available close to the installation. 2. Fire protection facilities shall be designed to fight two major fires simultaneously, anywhere in the installation. Fire-water requirements will be decided as per guidelines given in the Annexure of OISD.

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5.6.2 Fire Water System Water is an essential medium for fire protection, and is the most important medium available for this purpose. Water is used for fire extinguishment, fire control, cooling of equipment and protection of equipment and personnel from heat radiation. For these purposes, water is used in various forms, such as straight jet, water fog, water curtain, water spray, deluge/sprinkler, for foam making, etc. The main components of the fire water system are fire water storage, fire-water pumps, and distribution piping network, along with hydrants and monitors.

5.6.3 Design Basis The fire water system in an installation shall be designed to meet the fire water flow requirement for fighting two fires simultaneously, requiring largest water demand.

5.6.4 Fire Water Demand Various areas that can be under fire shall be considered, and fire water demand for each area shall be calculated on the design basis. Consider different cases (for example, the fire water rate of five different cases), and calculate the flow rate for each case. Then, the total design fire water rate is the sum of water rates for the two major fires.

6.

Additional Information on the User Interface

6.1

Spray Options

The dialog box obtained from Options | Module options allows the user to control a number of modelling and calculation options for the Spray/Sprinkler Module.

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6.1.1 Pressure Model The two main options for the pressure model are the Darcy Equation and the Hazen-Williams Equation. The Hazen-Williams Equation must be used for water and foam solution systems, and the Darcy Equation must be used for foam concentrate systems.

6.1.2 Design Rules The fire protection systems follow norms including: NFPA NFPA 96 FOC OLDFOC

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These norms are in-built into the Spray/Sprinkler Module.

6.1.3 Spray or Sprinkler Mode There are two modes provided in this module. In the spray mode, all the nozzles input is open by default; and in the sprinkler mode, all the nozzles input are closed by default.

6.2

Pipe Types

In the Spray Module, all pipes in a network must be of a specified type. A pipe type is associated with a pipe schedule, and this schedule must already exist before the pipe type can be created. There is an optional lining definition, which may be provided by specifying the material and the lining thickness. Please note that, if no pipe type is defined, the Pipe Drawing Tool on the toolbar is disabled, and the message “No Pipe Type” appears in the status bar at the bottom of the screen. This message will disappear when a pipe type is defined, in which case, the Pipe Button will be enabled.

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6.2.1 Creating a New Pipe Type Use the following procedure to create a new pipe type. 1. Click on the New Button. 2. Select the associated schedule from the drop-down list provided. Note that a name and a description are supplied automatically. 3. Provide a C-factor for the pipe schedule. The C-factor value will be taken into consideration when the Hazen-Williams Formula is selected for performing the calculation. 4. Supply velocities for all bores that are to be provided by the schedule. Bores can be marked as available or unavailable by selecting the bore in the bottom right-hand corner of the window and clicking on the “Use in design” Button or “Avoid in design” Button as appropriate (and the default is for all valid bores to be marked as available).

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5. Linings can also be provided using the drop-down menu (in which case, the thickness of the lining must be given). 6. Click on the Apply Button to complete the creation of the pipe type.

6.2.2 Editing an Existing Pipe Type 1. Select the pipe type from the top left-hand corner of the window. 2. Make the required changes to the pipe-type parameters. 3. Click on the Apply Button to commit the changes.

6.2.3 Deleting a Pipe Type 1. Select the pipe type from the top left-hand corner of the window. 2. Click on the Delete Button. Note that a pipe type cannot be deleted if it is in use.

6.3

Libraries

Libraries are used for storing items that are to be used either (a) several times in the same network or (b) in different networks. The library is associated with the data file, and is opened when the data file is open. For the Spray/Sprinkler Module, a library can contain the following items. 1. 2. 3. 4. 5.

Pipe schedules, Nozzles, Pumps (Coefficients Known and Coefficients Unknown), Linings, Deluge valves.

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There is only one local user library, which has the file extension “.SLF”, and replaces all of the separate library files from previous modules. While a data file is open, entries can be added, deleted or edited using the Library Editor Dialog. PIPENET VISION automatically saves the library file when the “Sunrise Data File” or “.SDF” file is stored. The name of the library file is derived from the name of the “Sunrise Data File”.

6.4

Pipe Schedules

Pipe schedules can be viewed using Libraries | Schedules. There are about eight built-in pipe schedules in PIPENET VISION. The user is also able to define other pipe schedules.

On the left-hand side of the window is a list of available schedules, both built-in and userdefined. If you select any item in this list, the properties of the schedule are displayed on the right-hand side of the window. At the top right-hand corner, there are three fields common to all library editors:

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1. The name of the schedule as it appears in pop-up menus (the length of this name being limited to 20 characters). 2. An optional longer description. 3. The source of the schedule, which may be one of the following: • Built-in schedule provided with the Spray/Sprinkler Module - built-in schedules cannot be edited. • Local user library - these items may be edited whilst a network is open. • System library - these items can only be edited using the External System Library Editor. Below these three fields is a field that contains the roughness; and, below that field, is a grid showing the standard nominal sizes and the corresponding internal diameters. If the nominal diameter is "unset" then the corresponding nominal diameter is not included in the schedule. Nominal diameters are greyed-out, indicating that their value is fixed; however, if you scroll down to the end of the grid, you can see 10 user-defined sizes (for which both the nominal and internal bores can be edited). The roughness value and the diameters are displayed in the user-specified units.

6.4.1 Adding a New Schedule To add a new schedule, select the New Button in the bottom left-hand corner of the dialog box, enter the desired values (if the Description Field is left empty, the description will become the same as the schedule name). Next, enter the roughness and the diameters, and then select either (a) the Apply Button, to accept the new schedule, or (b) the Cancel button, to abort.

6.4.2 Editing an Existing Schedule From the left-hand side of the window, select the schedule that is to be edited, enter the desired changes, and then select the Apply Button to accept the changes.

6.4.3 Deleting an Existing Schedule Select the schedule to be deleted (on the left-hand side of the window), and then click on the Delete Button.

6.5

Nozzles

The nozzles in PIPENET VISION correspond to the spray or sprinkler nozzles, which are open to the atmosphere. To set the nozzle attributes, the user can either enter the values directly in the schematic or obtain them from the library.

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The nozzle library dialog box can be accessed through Libraries | Nozzles.

To view a library nozzle, select the required nozzle from the left-hand side of the window, and see its properties on the right-hand side. To delete a nozzle, select the nozzle (in the left-hand side of the window) and then click on the Delete Button. To add a new nozzle: 1. Click on the New Button. 2. Provide a unique name for the nozzle and an optional description. 3. Enter the values for the K-factor, minimum pressure, and maximum pressure. 4. Click on the Apply Button to add the nozzle to the library.

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6.6

SPRAY: CHAPTER 1 REVISION 2.1, SEP 2010

Linings

Linings for the pipes are provided to protect the inner surface of the pipe from corrosion, which is caused by the fluid medium. In most fire systems, fluid remains stagnant, resulting in a higher rate of corrosion. The linings can be concrete, epoxy, thermo setting plastic, asbestos, etc.

To view a library lining, select the required lining from the left-hand side of the window (and its properties are displayed on the right-hand side). To delete a lining, select the lining, and then click on the Delete Button. To add a new lining: 1. Click on the New Button. 2. Provide a unique name for the lining and an optional description.

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3. Enter a value for the roughness. 4. Click on the Apply Button to add the lining to the library.

6.7

Deluge Valves

Typically, deluge valves are modelled as equipment items. As mentioned earlier in this chapter, deluge valves still available in PIPENET VISION for historical reasons. Without this model, it might not be possible to open some older data files. For the sake of completeness, the method of inputting deluge valves is described below.

To view a library deluge valve, select the required deluge valve from the left-hand side of the window, and see its properties on the right-hand side. To delete a deluge valve, select the deluge valve, and then click on the Delete Button.

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To add a new deluge valve: 1. Click on the New Button. 2. Provide a unique name for the deluge valve and an optional description. 3. Enter the values for the K-factor, X-factor and bore. 4. Click on the Apply Button to add the deluge valve to the library.

7.

Other Useful Features of PIPENET VISION

Any description of PIPENET VISION would be incomplete without the following features being covered.

7.1

Global and Local Edit

This functionality is applicable to the Data Window. It is best illustrated by an example. (Although the example itself is taken from the Standard Module, exactly the same principle applies in the case of the Spray/Sprinkler Module.) Change the roughness of all pipes from 0.06 mm to 0.08 mm.

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A local edit can be performed in a similar manner. In this case, the user must select the pipes to which the copied value is to be pasted.

7.2

Sorting in Columns in the Data Window

This invaluable feature can be used, for example, to determine the pipe with the maximum velocity or the maximum pressure. This sorting can be performed in the data window.

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Select the Results Tab

Click on the heading to sort the column

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7.3

Copy/Paste to a Spreadsheet

Click here to select the results

Copy the data using Edit/Copy as shown below.

SPRAY: CHAPTER 1 REVISION 2.1, SEP 2010

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SPRAY: CHAPTER 1 REVISION 2.1, SEP 2010

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7.4

SPRAY: CHAPTER 1 REVISION 2.1, SEP 2010

NFPA Style of Output

Some fire engineers prefer to use the style of presentation shown in the NFPA rules. This style is available in PIPENET VISION, and is obtained (after a calculation) by using Calculation | Browse, and then selecting the NFPA Submittal Option.

Extracts from such an output are shown below.

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SPRAY: CHAPTER 1 REVISION 2.1, SEP 2010

SUMMARY VALUES Title

Calculation date

29-Sep-2010 14:09

Calculator

PIPENET VISION Spray calculator, version 4.4

Friction loss formula

Hazen-Williams

Design standard

NFPA

Total number of sprinkler heads

3

Number of sprinkler heads on

3

Total sprinkler discharge (l/min)

455.255

Total non-sprinkler output flow (l/min)

0.000

Total input flow (l/min)

455.255

Highest fluid velocity (m/sec)

2.667

Pressure at input nodes

See NODE ANALYSIS table

NODE ANALYSIS Node tag

Elevation (m)

Node Type

Pressure (Bar G)

Discharge (l/min)

1

0.00

Input

1.704

0.000

2

0.00

1.701

0.000

3

0.00

4.709

0.000

4

5.00

4.151

0.000

5

4.50

4.190

153.527

6

5.00

4.053

0.000

7

4.50

4.093

151.728

8

5.00

3.960

0.000

9

4.50

4.000

150.000

Sprinkler

Sprinkler

Sprinkler

Notes

Nozzle label: 201

Nozzle label: 202

Nozzle label: 203

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PIPE INFORMATION Node 1

Elev 1 (m)

K factor

Flow added (q) (l/min)

Nominal ID (milli.m.)

Node 2

Elev 2 (m)

Pipe label Nozzle label

Total flow (Q) (l/min)

Actual ID (mm)

455.255

80

455.255

73.990

1

0.00

2

0.00

Fittings quantity, type, and equivalent length (m)

L (m)

C factor

F (m)

T (m)

0.500

120.0

0.00

4

5.00

80

455.255

5.00

1xE=2.13

10.000

120.0

6

5.00

301.728

0.068

5.000

120.0

5.00

75.00

5

4.50

4 201

40

6

5.00

0.098

0.500

120.0

8

5.00

0.500

150.000

0.010

5.000

120.0

5.00

75.00

7

4.50

6 202

40

8

5.00

75.00

0.093

0.500

120.0

9

4.50

7 203

Vel = 2.233 m/sec

0.019 0.500

0.009

0.500

120.0

0.000 150.000

4.093

0.049

37.973

40

Vel = 2.207 m/sec

0.019

0.000 151.728

3.960

0.000

37.973 5.000

6

Vel = 2.259 m/sec

0.019

0.000 5

4.190

0.049

37.973

40

Vel = 2.667 m/sec

0.020

0.000 153.527

4.053

0.000

48.997 5.000

4

Vel = 1.765 m/sec

0.006

0.000 3

4.151

-0.489

73.990

50

Vel = 1.765 m/sec

0.003

12.134

4

1.701

0.000

2.134 2

Pf (Bar)

0.006 0.500

3

Notes

Pe (Bar) Pf per m (Bar)

0.000 1

Pt (Bar G)

4.000

0.049

37.973

0.019 0.500

0.009

PIPE FITTINGS CODES HE

Standard 45° Elbow

E

Standard 90° Elbow

LE

Long radius 90° Elbow

T

Tee or Cross (Flow turned 90°)

G

Gate Valve

C

Swing Check Valve

NR

Non-return Valve

BV

Ball Valve

B

Butterfly Valve

Vel = 2.207 m/sec

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7.5

SPRAY: CHAPTER 1 REVISION 2.1, SEP 2010

Elevation Error Correction

Elevation mismatch errors in firewater ringmains are some of the most difficult problems to resolve. However, PIPENET VISION has tools to assist the user in resolving such problems. Let us consider the highlighted pipe in the following simple network.

The attributes of this pipe are as shown in the Properties Window below.

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Let us suppose that the user has made an error, and has input an elevation of 1 metre (instead of 0 metres). We now change the elevation value to 1 metre, and then illustrate the tools in PIPENET VISION that can be used to resolve this elevation error.

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If we click on the Check Network Button, a diagnostic appears. However, in some cases, there is little information on the exact location of the error.

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We now double click on an error message (shown in red), which indicates an elevation error. All of the components in the loop in which the elevation error occurs now appear in red. Note that the user must ensure that suitable colouration-display rules are selected; for example, if “None” is selected, it is possible to see the red loop; otherwise, the loop may not be coloured red.

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We now click on the Graphs Tab in a Data Window. The elevation profile along the loop is then shown in the Data Window, starting and ending at Node 1. Note that the node numbers can be displayed on the profile.

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Alternatively, we can click on the Common Height Errors Button on the Diagnostic Window. In this case, only the pipes common to more than one problem loop are shown.

Common Height Errors Button

In some cases, this approach leads to fewer pipes for which the elevations need to be checked.