Deluge Water Spray 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.