FIRE WATER HYDRAULIC CALCULATIONS Contents ⚫ ⚫ ⚫ ⚫ ⚫ What is fire water ? Objective of fire water hydraulic calculation. Various steps involved in performing Fire Water Hydraulic Calculation. Codes and Standards Material of Construction / Calculation constraints. What is Fire Water ? ⚫ ⚫ ⚫ An exposure protection for the equipment in the form of water spray through nozzles. For fighting of fire that may occur in localized areas through hydrant hose reels. For fighting of fire in elevated structures or areas that are inaccessible from grades through firewater monitors. Objective of fire water hydraulic calculations ⚫ ⚫ ⚫ ⚫ To find the total fire water requirement. To calculate the discharge pressure of fire water pump. To check whether the required pressure is available at the fire water consumer point. To find the pipe sizes to meet the allowable velocity with respect to the MOC of pipe. Various steps involved in performing Fire Water Hydraulic Calculation ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ Making the list of fire water consumer’s. Identifying the Design cases. Making the nozzles arrangement sketches. Making the firewater network P & ID. Making the network diagram. Tools for Performing the Calculations. Making the final report. Making the list of fire water consumers In general fire water consumers are ⚫ Equipment both static and rotating including specifically Oil and Gas manifolds ,Pig launchers and receivers. ⚫ Structures supporting the plant ⚫ Protective structures.( fire walls & floors/ceilings) ⚫ Fire water / foam monitors. ⚫ Fire water / foam hose reels. Identifying the Design Cases ⚫ ⚫ ⚫ ⚫ In offshore platforms, fire on two decks simultaneously need not be considered. If two or more platforms are connected by bridge ,fire need to be considered on any one platform only. In general, fire needs to be considered up to a height of 9m above the source of fire. In onshore installations, fire needs to be considered in one building unit of the plant only, unless otherwise specified. Making the nozzle arrangement sketches ⚫ Nozzle arrangement sketches shows 1.Approximate location of nozzles. 2.Type and number of nozzles required for that particular consumer. 3.Dimensions for making a detailed layout drawing by piping. Cont…. Types of nozzles and its application. Medium velocity full cone spray nozzles - Deluging of equipment, machinery and Structures. Water curtain nozzles– Deluging of vertical surfaces. Oblong nozzles – For structural members. Criteria for selection of nozzles. Types of nozzles based on application. K- factor. ( bore size) Spray angle.(600,750,900,1200, etc) Cont…. Methodology for calculating the number of nozzles. 1.Calculate the area to be deluged. 2. Calculate the fire water demand for each consumer. Water density required for deluging. (NFPA-15,2001 Edition.) For surface area of vessels , heat exchangers, vertical structural members and tanks – 10.2 lpm/m2. For large size tanks - 4.1 lpm/m2. For rotating equipment and wellheads – 20.4 lpm/m2. Projected areas for horizontal structural members – 4.1 lpm/m2. 3. Calculating the number of nozzles required by selecting K factor. 4. Finalizing the number of nozzles based on spray pattern to ensure coverage with some overlap. Minimum spacing between the nozzle and surface to be deluged – 0.65 m . Maximum spacing between the nozzles (both vertical and horizontal ) – 3 m . Making the network P & ID Requirements ⚫ Approved equipment layout . ⚫ Tentative routing of fire water piping. P & ID must show the schematics of all fire water piping, including branches, fittings like deluge valves, manual isolation valve, and all the fire water nozzles from the source of fire water to the equipment to be deluged. Final sizes of fire water piping are shown in this P & ID. Making the network diagram Network diagram ⚫ The diagram shows the schematic interconnection of nodes through segments. ⚫ Also fittings like strainers deluge valves, other valves, hose reels, orifice etc should be shown on the network drawing. Table- Aid to prepare the network diagram. ⚫ The table would show following details as applicable for each node / segments : allowable operating pressure range, flow rate , approximate distance from node to node, the number of fittings, mainly elbows and reducers , and changes in elevation. Tool for Performing the Fire Water Hydraulic Calculation PIPENET software for the green field jobs. For brown field jobs the calculations are limited to finding the firewater requirement and number of nozzles for the new facilities using in-house excel spread sheet. Making the final report ⚫ ⚫ ⚫ A summary, stating the background, work done, cases considered, governing case if applicable, limits or limitations and results in brief. The calculations themselves ,whether done manually or using spreadsheet/software . Conclusions and recommendations. Codes and Standards ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ ⚫ NFPA 15 –Water Spray fixed Systems for Fire Protection. NFPA 13 – Installation of Sprinkler Systems. NFPA 14 – Installation of Standpipe and Hose Systems. NFPA 20 – Installation of Centrifugal Fire Water pumps. API RP 14G – Recommended practice for fire prevention and control on open type Offshore production platform. API 2030 – Application of Fixed Water Spray Systems for Fire Protection in the Petroleum Industry. API 2001 – Fire Protection in Refineries. API 2510 – Design and construction of LPG installations. API 2510A – Fire protection consideration for the Design and operation of LPG storage facilities. OISD 116 – Fire protection facilities of petroleum refineries and Oil & Gas installations. OISD 117 – Fire protection facilities for petroleum depots and terminals. OISD 118 – Layout for Oil & Gas installations. OISD 156 - Fire protection facilities for port oil terminals. Material of Construction / Calculation constraints ⚫ Pipe Sizes. ⚫ Fluid Velocity. Piping material ⚫ Max Velocity (m/s) Carbon steel 3 Galvanized CS 3 Cupro-Nickel 1.6 for 2” and below,3.3 for 3” & 3.5 for 4” and above. Available type and sizes of nozzles. ⚫ Pressure range For spray nozzle– (1.4 to 3.5 barg). For hydrants and monitors – 7 barg. (normal)
