1. Deluge Water Spray System
2. Factors determining the requirement of Deluge Water Spray System
3. Type of Deluge Valves
4. Deluge valve – Principle of Operation
5. Deluge Valve & By-Pass Valves & Location
6. Deluge Skid Specifications/ Requirements
7. Water Spray Nozzles
8. Piping Requirements for Deluge System
1. Deluge Water Spray System:
- An automated water spray system where the water distribution piping is equipped with open spray nozzles for discharging over a protection area or equipment.
- Deluge water Spray systems designed according to NFPA 15, API 2030, IP 19 guidelines and local regulations.
- The main objectives are any one or combination of the following :
- Extinguishment of fire
- Control of burning
- Exposure protection
- Prevention of fire
Typical Application rates for Deluge Water Spray System: (API 2030):
2. Factors determining the requirement of Deluge Water Spray System:
- Spray System for Process Pumps:
- When pumps handle hydrocarbon liquids (flammable or combustible) at temperatures above its flash point.
- Located Close to equipment that can be quickly damaged by pump fire.
- Where protection of pumps is impractical by monitors/hydrants and potential of fire escalation is possible.
- Spray System for Pipe racks:
- To be evaluated based on potential of pool fires or severe exposures below the pipe rack.
- Spray System for Vessels & Columns :
- High pressure vessels (>10 barg) handling flammable / combustible liquids with inventory above 5 tons and also based on project philosophy.
- Vessels handling flammable / combustible liquids and located in a congested area.
- Spray System (cooling) for Atmospheric Storage Tanks:
- API 2001 recommends protection of the portion of shell and roof not in contact with the liquid content of tank. (@4.1 lpm/m2)
- Sectionalization of the spray rings should be done for optimization of water quantity.
Fig: Example of a Water Spray System Installation
3. Type of Deluge Valves:
- Type of Deluge Valves (based on operation):
- Complete On/off deluge Valve: These are deluge valves which open fully upon activation and closed fully upon resetting.
- Variable Pressure Control Deluge Valve: Preset constant Valve downstream side pressure is maintained irrespective of the upstream pressure.
- Type of Activation of Deluge Valves :
- Hydraulic Activation : By means of hydraulic Quartzoid bulb detection
- Electrical Activation : By means of F&G detection system
- Electro-Pneumatic Activation : By means of pneumatic Quartzoid bulb and/or F&G detection system
4. Deluge valve – Principle of Operation:
- Area of upper chamber of DV is twice that of the lower chamber
- Force in Upper Chamber = Pressure x 2 Area
- Force in Lower Chamber = Pressure x Area
- Pressure is same on both sides.
- Force in upper chamber is more than that of the lower chamber
5. Deluge Valve & By-Pass Valves & Location:
- Deluge valves are always 15 meter away from the protected equipment and any other process equipment. (from pipe racks at least 6 m preferred where 15 not possible)
- Manual by-pass valves shall be located opposite side or tapped from another part of the ring main.
- Manual valve shall be 30 meter from the protected equipment.
- Both valves shall be upstream of the wind direction preferably.
6. Deluge Skid Specifications/ Requirements:
- The type of Deluge Valve mounting (ie vertical or horizontal).
- Vertical mounting are more space saving
- Where ambient temperature is of concern, the skids shall be inside enclosures and shall be provided with a heater to maintain the temperature at above 5 deg.C
- All components should be within the enclosure
- Space for deluge Skids to be indicated in the plot plan for the required size at early stages of the plot plan development.
- Deluge Skids shall be at least 2 meter away from the road edges.
- Electrical Heat Tracing of water filled pipe lines up to the deluge valve is required in freezing climatic conditions.
- All components shall be listed/ approved type.
- Specify vendor limits clearly in the P&I Ds.
7. Water Spray Nozzles:
- An open water discharge device that, when discharging water under pressure, will distribute the water in a specific, directional pattern.
- Types of water spray Nozzles :
- Medium Velocity – Used for vessels, pumps, cable galleries, etc.
- High Velocity – Used for Transformer spray system.
- Pressure required for MV Nozzles 1.4 bar(g) and for HV nozzles about 3.4 barg for optimum performance.
- Minimum Pipe Sizes in Deluge Systems (as per NFPA 15) is 1”.
8. Piping Requirements for Deluge System:
- Piping Requirements as per NFPA :
- 40, Carbon Steel (Galvanized) up to 8”
- 30, Carbon Steel (Galvanized) 8” & above
- Piping Installation requirements :
- Suitable slope in the dry section of pipe
- Provide Low point drain at suitable location
- Pipe Velocity considerations: NFPA 15 allows up to 7.94 m/sec of water velocity for the deluge downstream side. However, please check project piping design philosophy where velocity may be limited to 5 m/sec downstream of the deluge valve and 3 m/sec upstream.
- Design of the system should be such that the water spray fully covers the equipment in within 30secs upon activation.