HallScrew Semi-hermetic Air-Cooled Ammonia Chiller
J&E Hall International HallScrew Semi-hermetic Air-Cooled Ammonia Chiller — Low-charge air-cooled ammonia chiller using HallScrew semi-hermetic single-screw compressors. Designed for cold store cooling, process cooling, and comfort cooling. Available in single or dual compressor configuration. Suitable for industrial and marine refrigeration applications..
Inspector Detail
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Common issues
- Ammonia leakage at the compressor shaft seal, valves, or pipe joints
- Screw compressor slide valve/capacity control sticking
- Oil separator or oil return system fouling causing oil carryover from the compressor
- Condenser fan motor or fan blade failure reducing head pressure control
- Gasket or fitting degradation causing low-level ammonia odor/leaks
- Compressor motor overheating from low refrigerant charge or a fouled condenser
- Suction or discharge valve leakage reducing compressor capacity
Inspection checklist
- Check for ammonia odor or leaks with an appropriate detector at joints, valves, and seals
- Inspect the condenser coil/fins for fouling and clean as needed
- Check oil level and oil pressure differential across the compressor
- Verify high/low pressure and oil safety cutouts trip correctly
- Check slide valve operation and capacity control response
- Check refrigerant charge level via sight glass or level indicator
- Inspect suction line insulation for condensation or ice buildup
- Test the ammonia detection/alarm system
- Check condenser fan motors for vibration or bearing noise
Service intervals
| Oil change/analysis | typically 4000-8000 hours or annually, per maker's schedule |
| Safety cutout (HP/LP/oil) testing | per class requirement, typically annually |
| Condenser coil cleaning | quarterly or per fouling condition |
| Ammonia detection system calibration | per maker/class schedule, typically annually |
Typical wear limits
| Oil moisture/acid level | monitor via oil analysis trend against the maker's limits rather than a fixed onboard reading |
| Refrigerant charge level | maintain per the sight glass/level indicator range specified by the maker - do not top up without first tracing and repairing any leak |
Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Critical spares
- Shaft seal kit for the screw compressor
- Solenoid/expansion valve
- Oil filter element
- Refrigerant filter-drier
- High/low pressure safety switch
- Condenser fan motor
- Refrigerant joint gasket/O-ring set
Safety
- Ammonia is toxic and, in certain concentrations, flammable - full PPE (gas-tight goggles, gloves, escape breathing apparatus) is required for any refrigerant work
- Confirm the ammonia detection and alarm system is operational before entering the compressor/chiller space
- Refrigerant piping and vessels are under pressure - isolate and recover charge before opening
- Screw compressor rotating parts and drive coupling guards must be fitted
- Ensure adequate ventilation of the machinery space per class requirements for ammonia systems
Class survey
Ammonia refrigeration plant is subject to class rules specific to toxic/flammable refrigerants (detection, ventilation, machinery space arrangement) in addition to standard refrigeration machinery survey. Class checks leak detection function, pressure vessel/piping certification, and relief discharge arrangements at survey.
Components & Design
Component data being added…
Technical Data
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Common failures & inspection points
Check and clean refrigerant circuit: inspect for leaks (NH3 or HFC), verify refrigerant charge level, and test ammonia leak detection sensors (if fitted)
Inspect and service compressor: check oil level and oil pressure, replace oil filter, verify bearing temperatures and vibration levels against manufacturer limits
Clean heat exchangers: inspect and clean evaporator and condenser (water-side fouling, shell-and-tube or plate HX scaling; air-side coil cleaning for air-cooled units)
Verify shock-mount and structural integrity: inspect anti-vibration/shock mounts for wear or deterioration, check skid/base-frame fastenings and pipe flex connections (critical for naval shock ratings up to 30g)
Test safety and control systems: verify high-pressure and low-pressure cut-outs, flow switches, thermostatic controls, and SCADA/monitoring connectivity; test ammonia/refrigerant alarms
Inspect electrical components: check terminal connections, contactor condition, motor insulation resistance (megger test), and rating of variable-frequency drives; confirm SOLAS low-smoke wiring integrity
Check glycol/brine secondary circuit: verify glycol concentration (freeze point), inhibitor levels, pH, and absence of corrosion or fouling in the secondary side; inspect pump seals and strainers
Review classification society documentation: confirm pressure vessel inspection records are current (LR or equivalent), update service logbook, and verify compliance with applicable marine standards (SOLAS, class rules)
Type-general inspection and maintenance points for this equipment category — not model-specific.
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