4T-8.2, 4T-12.2, 4P-10.2, 4P-15.2

Common issues

• Valve plate/reed valve wear or leakage causing reduced cooling capacity
• Oil return problems, especially on systems with long or complex refrigerant piping runs
• High discharge temperature from low suction superheat, refrigerant undercharge, or fouled condenser
• Refrigerant leakage at shaft seal (on semi-hermetic open-drive variants), fittings, or service valves
• Motor winding damage from frequent short-cycling or single-phasing
• Capacity control (unloader/solenoid) malfunction
• Moisture/acid contamination of the oil after a motor burnout, if filter-driers were not renewed

Inspection checklist

• Check crankcase oil level and condition (color, clarity) at the sight glass
• Check suction and discharge pressures/temperatures against the normal operating envelope for the refrigerant in use
• Check for abnormal noise or vibration at the compressor and mountings
• Verify crankcase heater is energized and functioning during standstill
• Function-test high-pressure and low-pressure safety cutouts and the oil differential pressure switch
• Check for refrigerant leaks at valves, fittings, and shaft seal using an appropriate leak detector
• Check discharge line temperature and discharge check valve operation
• Inspect mounting isolators/vibration dampers for wear or failure

Service intervals

Critical spares

• Valve plate / reed valve set
• Gasket and O-ring set
• Suction and discharge service valves
• Crankcase heater
• HP/LP pressure switches and oil differential pressure switch
• Filter-drier cores
• Motor contactor/overload protection

Safety

• Refrigerant is stored and circulated under pressure - risk of frostbite or asphyxiation if released in an enclosed compressor/machinery space; ensure the space is ventilated and refrigerant-detection alarms are functional
• Hot surfaces at the discharge line and cylinder head during operation
• Electrical hazard at motor terminals - isolate and lock out before opening the terminal box
• Do not open the refrigerant circuit without first recovering/isolating the charge under a permit-to-work
• If the system uses ammonia (R717) or another toxic/flammable refrigerant, specific PPE and ventilation requirements apply - confirm the refrigerant type before working on the plant

Class survey

Note: the listed type ('Rotary Vane Steering Gear') does not match this item - the manufacturer and model designation (4T/4P series) identify this as a semi-hermetic reciprocating refrigeration compressor, part of the ship's refrigeration/provision or HVAC plant, not steering gear. If surveyed, this equipment normally falls under the refrigerating machinery/provision plant survey scope rather than the steering gear survey scope - confirm the correct class item and notation before applying steering gear inspection routines.