Sabroe CMO 28 Reciprocating Compressor

The Sabroe CMO 28 is an 8-cylinder, open-type reciprocating refrigeration compressor engineered for heavy-duty marine provisions, cargo hold refrigeration, marine HVAC, and compact industrial process chilling. Designed to operate under demanding sea conditions, the CMO 28 features an exceptionally rigid nodular cast iron crankcase, replaceable wet cylinder liners, and a dynamically balanced crankshaft supported by heavy-duty sleeve bearings designed to withstand continuous pitch and roll.

Operating across a speed window of 700 to 1,800 RPM, the CMO 28 delivers a swept volume of 194 m³/h at 1,500 RPM (50 Hz) and 233 m³/h at 1,800 RPM (60 Hz / VSD direct-coupled). The unit accommodates natural ammonia (R717) and common HFC/HFO synthetic blends (R404A, R507A, R134a, R448A, R449A) with appropriate synthetic or mineral lubricating oil charges. Integrated hydraulic cylinder unloader mechanisms provide smooth 4-step capacity control (25%, 50%, 75%, 100%) and completely unloaded soft-starting, minimizing electrical peak inrush current on marine generator switchboards.

Model Details

• Series: Sabroe CMO Mk2 / Mk3 Series
• Base Model: CMO 28
• Manufacturer: Johnson Controls Denmark ApS / Sabroe Factory
• Design Type: Single-Stage, Open-Drive, Multi-Cylinder Reciprocating Piston Compressor
• Configuration: V-block 8-cylinder layout (4 cylinder banks of 2)
• Displacement / Swept Volume: 194.4 m³/h @ 1500 RPM | 233.3 m³/h @ 1800 RPM

Primary Assembly Numbers

• Complete Bare-Shaft Compressor: Sabroe MPN 0171-351 / 0171-370 / 3122.028
• UniSAB III System Package: 3722-028-MK2

Critical Sub-Assembly Cross-References

• Mechanical Shaft Seal Assembly: 0241-255 / 531B0086H01 (Slide-ring carbon/cast-iron balanced interface)
• Connecting Rod Assembly: 3122-140 / 0253-128
• Main Bearing Shell Set (Standard): 3122-108 / 0253-112
• Cylinder Liner (70 mm Bore): 3122-115 / 0253-104
• Piston & Pin Assembly (70 mm Stroke): 3122-120
• Suction & Discharge Valve Plate Assembly: 3122-160 / 0253-210
• Internal Reversible Gear Oil Pump: 3122-210 / 0253-315
• Capacity Regulation Unloader Solenoid Valve (24V DC / 230V AC): 0253-812 / Danfoss EVR-3 equivalent

Technical Details:

Equipment Compatibility

• Sabroe Package Units: CMO Unit 28, TCMO 28 two-stage skids, PAC Chiller systems, and ComPact Chillers.
• Marine Prime Movers: Direct-drive flexible coupling arrangements via AMR / Thomas flexible disc couplings, or multi-groove SPC/SPB V-belt drives connected to marine-rated induction motors (Siemens, ABB, WEG).
• Control Platforms: UniSAB II, UniSAB III, Danfoss MCX, or external vessel automation/AMS (MODBUS RTU / Profibus DP communication).
• Direct Drop-in Replacement for Legacy Units: Replaces older Sabroe CMO 18, CMO 26 (with manifold modification), and comparable York / Frick / Carrier 5F/5H 8-cylinder reciprocating units.

Applications

• Marine Provision Refrigeration Plants: Multi-room refrigerated food stores (Meat Room at -25°C, Fish Room at -25°C, Veg Room at +4°C).
• Refrigerated Cargo Holds & Reefers: Direct expansion or secondary brine cooling circuits on fruit, fish, and general refrigerated cargo vessels.
• Fishing Vessel Brine Freezing & RSW: Rapid Sea Water (RSW) immersion tanks and plate freezers on trawlers and purse seiners.
• Offshore Accommodation HVAC Chillers: Compact chilled-water packages for accommodation modules on oil rigs and FPSO platforms.
• Industrial Cold Storage & Process Cooling: Standalone food processing freezers, secondary brew-kettle glycol cooling, and industrial chemical condensations.

Frequently Asked Questions

What is the swept volume of the Sabroe CMO 28 compressor?

The Sabroe CMO 28 has a swept volume of 194.4 m³/h at 1,500 RPM (50 Hz power grid) and 233.3 m³/h at 1,800 RPM (60 Hz marine auxiliary power or Variable Speed Drive operation).

Which refrigerants can be used in the Sabroe CMO 28?

The CMO 28 is fully compatible with natural ammonia (R717) as well as common synthetic fluorinated refrigerants including R404A, R507A, R134a, R22 (legacy), and newer lower-GWP blends such as R448A and R449A. Gasket and seal elastomer kits must be matched to the selected refrigerant and oil base (mineral, alkylbenzene, or polyolester).

How does the capacity regulation work on the CMO 28?

The CMO 28 utilizes an internal oil-pressure-activated hydraulic unloader system. Solenoid valves mounted on the compressor cover channel oil to mechanical lift pins, holding the suction valve plates open in pairs of cylinders. This allows staged capacity operation at 25%, 50%, 75%, and 100% load.

Can a Sabroe CMO 28 operate in either rotation direction?

Yes. The CMO 28 is equipped with an internal, fully reversible eccentric gear oil pump. It provides correct forced lubrication whether the crankshaft rotates clockwise or counter-clockwise, making drive-motor alignment straightforward.

What is the recommended oil change interval on marine installations?

Under normal marine operating conditions, the initial oil charge and cleanable magnetic oil strainer should be serviced after the first 100 hours of run-in. Subsequent oil changes should occur every 2,500 to 3,000 running hours, or at least once every 12 months, supported by regular oil condition testing for moisture and acid formation.

What is the maximum discharge pressure rating for the CMO 28?

The compressor design pressure is rated at 28.0 bar g (406 psig) on the high-pressure side and 21.0 bar g (305 psig) on the low-pressure suction side, with a maximum allowable differential pressure of 21.0 bar.