Fire Pumps and Hydrants

How the firewater supply works

The fire pumps lift seawater into a ring main that runs around the unit with isolation valves between sections. A small jockey pump holds the main at pressure. When pressure drops, or the fire and gas system calls for water, the main pumps start automatically. An emergency fire pump in a separate space, with its own power and suction, keeps water available if a fire takes out the main pump room.

Jack-ups and semisubmersibles usually draw from deep below the hull. Typical arrangements are vertical turbine pumps with long lineshafts in a caisson, electric submersible pumps, or submerged pumps driven hydraulically from a deck power pack.

Configurations

Key specifications

Standards and what they ask of a used pump

SOLAS chapter II-2 regulation 10.2 sets minimum hydrant pressures, hose lengths and dual-purpose jet and spray nozzles. Chapter 12 of the FSS Code covers the emergency fire pump. Its capacity must be at least 40 percent of the total required capacity of the main fire pumps, and on cargo ships of 2,000 gross tonnage and above never less than 25 m3/h (110 US gpm). A diesel driver needs a service tank for at least 3 hours at full load, with reserves outside the category A machinery spaces for another 15 hours. MSC.1/Circ.1314 adds that where the emergency pump also feeds a fixed water-based system protecting the machinery space, it must supply that system plus two jets at the required pressure. MSC.1/Circ.1388 asks that available suction head exceed the required head across the normal range of drafts.

Units built to NFPA 20 use listed pumps with a flat curve. An NFPA 20 pump must deliver at least 150 percent of rated flow at no less than 65 percent of rated pressure, and its churn pressure must not exceed 140 percent of rated. NFPA 25 sets weekly or monthly churn runs and an annual flow test.

Failure modes and inspection

• Impeller erosion and cavitation damage, measured against OEM wear ring clearances
• Lineshaft bearings, couplings and alignment on long caisson pumps
• Column pipe and bowl corrosion where the caisson splash zone meets air
• Mechanical seals and packing leaking seawater into bearings
• Diesel starting batteries, air or hydraulic start and the charger
• Right-angle gearbox oil, backlash and bearing noise
• Controller auto-start on pressure drop and on remote command

A performance test with a calibrated flowmeter and pressure gauges, plotted against the certified curve, is the core check. Add vibration readings and an oil analysis for the diesel.

Hydrants, hoses and nozzles

Check the hydrant coupling type against your hoses. Instantaneous, Storz and NST threads do not mix without adapters. Hoses are a wear item, so check their pressure test dates and buy new ones if records are missing. SOLAS asks for dual-purpose nozzles in 12 mm, 16 mm or 19 mm sizes, matched to the space.

Documentation

• Certified factory test curve and the latest field performance test
• Class or listing certificate, such as UL or FM to NFPA 20
• Diesel running hours and overhaul history
• Controller test records and wiring diagrams
• Materials certificates for the pump and column

Integration and recertification

Match flange ratings, column length and suction depth to your caisson and drafts. Check the emergency pump's power source and that it starts from the emergency switchboard or its own diesel. Wire the controller into your fire and gas logic. Recertifying a used pump set usually means an overhaul with new wear rings, seals and bearings, a driver service and a witnessed performance test for class. An unused surplus pump set from a cancelled project is often the best buy if its rating fits. Naventr can arrange a witnessed pump test as part of an inspection. Framo and Sulzer are well-known firewater pump makers offshore. For the systems the pumps feed, see deluge and sprinkler systems.