Refrigeration Plant

What sets a provisions refrigeration plant apart

Unlike a single cold store, a ship's provisions plant runs at least two separate temperature duties from the same compressor package: a chill room held close to 0 to +4 degrees Celsius for dairy, vegetables and short-life goods, and a freeze room held around -18 to -20 degrees Celsius for meat and long-storage items. The two duties are usually served by the same compressors switched between evaporator loads by solenoid valves, or by dedicated compressors per duty on larger vessels, with a common condenser cooled by seawater. The plant has no redundancy of use — there is no shore cold store to fall back on mid-voyage — so its reliability is judged over weeks, not hours.

Main components

Compressors

Typically reciprocating, semi-hermetic units running on R404A, R507A or increasingly R448A/R449A as older HFCs are phased down under refrigerant regulations; duplicated so one duty can be served if a compressor is down for repair.

Condenser

Shell-and-tube, seawater-cooled, rejecting heat from both circuits; fouling here is one of the most common causes of high head pressure trips.

Evaporators

Air-cooling units inside each room, fitted with electric or hot-gas defrost to clear ice buildup that would otherwise choke airflow over time.

Expansion valves and solenoids

Meter refrigerant into each evaporator and switch flow between chill and freeze duty depending on the compressor arrangement.

Control and alarm panel

Monitors room temperature, suction and discharge pressure, and raises an alarm on high temperature drift before spoilage begins, not after.

Selection and sizing

• Total insulated volume of chill and freeze rooms combined with expected provisions load for the vessel's endurance between ports.
• Compressor capacity margin above calculated heat load, allowing for tropical seawater temperatures reducing condenser efficiency.
• Refrigerant choice against current phase-down schedules for high-GWP HFCs, which affects long-term parts and top-up availability.
• Defrost method suited to ambient humidity in the trading area, since heavy icing in humid routes needs more frequent defrost cycles.

Regulations and class requirements

Refrigerant handling and leak reporting fall under MARPOL Annex VI provisions on ozone-depleting substances and controlled greenhouse gases, with a mandatory logbook of any refrigerant added or removed. Class societies require periodic survey of pressure vessels and piping in the refrigeration system, and food storage temperature is checked against flag state or port health requirements during inspections, particularly on passenger and crew-heavy vessels.

Typical faults

What to look for in a supplier

• Parts and refrigerant compatible with the vessel's current charge, not requiring a full retrofit for a single component swap.
• Compressor models with a documented service history on similar tonnage, since provisions plants run near-continuously.
• Alarm and monitoring package that reports to the bridge or engine control room, not only locally at the panel.
• Support for refrigerant recovery and logging that matches Annex VI documentation requirements.

Check the defrost log, not just the room thermometer — a freeze room can read within range for days while the evaporator quietly ices over, and by the time the temperature actually moves the defrost cycle is often too far behind to catch up before spoilage starts.