AquaMist ULF AM11

Common issues

• Nozzle orifice or upstream strainer blockage from pipe scale or debris, reducing discharge performance
• Thermal (glass bulb) release element painted over or contaminated, delaying or preventing activation
• Incorrect temperature-rated bulb fitted after a nozzle replacement
• Corrosion or pitting of stainless steel/brass nozzle bodies in an aggressive engine room atmosphere
• Missing or damaged protective dust cap allowing pre-activation blockage of the orifice
• Zone/section valve failing to open fully on test, reducing pressure delivered at the nozzle

Inspection checklist

• Visual check of every nozzle for missing/painted bulb, dust cap in place, and no physical damage
• Verify nozzle orientation and spacing have not been altered by adjacent pipework or equipment changes
• Check pipework and strainers for internal corrosion or scale during periodic flushing
• Functional test of the pump unit and zone/section valves to design pressure per the approved test procedure
• Verify pressure gauge readings at test points fall within the design range for this nozzle type
• Check nozzle count and layout against the approved fire control drawing for the protected space
• Confirm automatic and manual release, plus alarm functions, operate correctly
• Inspect the pump skid, accumulator and associated piping for leaks

Service intervals

Typical wear limits

Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.

Critical spares

• Replacement nozzles of the correct type and thermal rating (closed automatic, ultra-low-flow)
• Spare glass bulb release elements of the matching temperature rating
• Nozzle dust caps
• Strainer elements
• Zone/section valve seals and actuator components

Safety

• System piping operates at 7-12 bar - isolate and depressurize before maintenance
• An incorrect bulb temperature rating can cause nuisance activation or fail to activate in a real fire
• Nozzles are tested devices - fitting a non-approved substitute invalidates the Class A fire test basis for the protected space
• Residual pressure/water hammer risk when reopening an isolated section

Class survey

Water mist (Hi-Fog type) systems are Continuous Survey Machinery items on classed vessels; surveyors typically review maintenance records for periodic pump/valve function tests and nozzle visual condition, and check that any replacement nozzles carry the same type approval as the original installation.