Sabroe CMO 26 Reciprocating Marine Compressor

Sabroe CMO 26 Open-Type Reciprocating Compressor

The Sabroe CMO 26 is a 6-cylinder reciprocating compressor engineered specifically for demanding marine refrigeration, cargo hold chilling, provision plants, and industrial HVAC applications. Designed to deliver maximum volumetric efficiency and durability under harsh maritime conditions, the CMO 26 features a compact nodular cast iron crankcase capable of handling standard synthetic and natural refrigerants, including R717 (Ammonia), R22, R134a, R404A, R507A, and R407C.

Operating across a variable speed range from 900 RPM to 1800 RPM, the CMO 26 provides a nominal swept volume of 174 m³/h at 1800 RPM (145 m³/h at 1500 RPM). It is equipped with an integrated reversible oil pump, suction gas-cooled or water-cooled cylinder heads, internal mechanical capacity regulation (unloading steps at 33%, 67%, and 100%), and a balanced mechanical shaft seal designed for positive and sub-atmospheric suction pressures.

Whether replacing an active unit or overhauling an existing marine provision system, this compressor provides low-vibration operation, standard IEC/NEMA electric motor coupling, and full rebuildability in situ.

Model Details

• Manufacturer: Sabroe
• Series: CMO Series (Mk 1 / Mk 2)
• Model: CMO 26
• Design Type: Single-Stage, Open-Drive Reciprocating Piston Compressor
• Manufacturer Part Number (MPN): CMO26-MK2 / CMO-26-RECIP
• Cross-Reference OEM Codes: 0171-478, 0662-215, 3132-005, 3132-154

Key Features

1. 6-Cylinder High-Displacement Architecture: Features a 70 mm bore and 70 mm stroke delivering up to 174 m³/h swept volume at 1800 RPM, balancing high refrigeration capacity with low mean piston speed to extend ring and liner life.
2. Step-Controlled Hydraulic Unloading: Factory-fitted with hydraulic cylinder unloading mechanisms allowing operation at 33%, 67%, and 100% capacity steps, enabling reduced inrush current on start-up and precise staging under fluctuating thermal loads.
3. Independent Reversible Lubrication System: Internal trochoid/gear oil pump operates independently of rotation direction, ensuring continuous positive pressure lubrication to big-end bearings, wrist pins, and the shaft seal during steady-state and transient speeds.
4. Versatile Marine Refrigerant Compatibility: Built with internal metallurgy suited for dry expansion halocarbons (HFCs/HCFCs) as well as anhydrous ammonia (R717) without necessitating crankcase or piston metallurgic changes.
5. Balanced Slide-Ring Shaft Seal: Heavy-duty carbon-against-cast-iron dynamic face seal with oil flushing, rated to maintain vacuum integrity during pump-down and prevent refrigerant egress up to maximum static design pressures.

Technical Details:

Compatibility

• Direct Compressor Bedplate Replacements: Drop-in dimensional interchangeability with Sabroe CMO 16, CMO 26 Mk 1, and CMO 26 Mk 2 units.
• Control Systems Compatibility: Fully compatible with Sabroe UNISAB II, UNISAB III, PLC-based compressor monitoring panels, Danfoss MCX, and standard electro-mechanical high/low pressure safety cut-outs.
• Driver Compatibility: IEC Frame 160M/L, 180M/L, 200L electric motors (4-pole 1450 RPM / 60 Hz 1750 RPM) via flexible pin/bush or tyre couplings, and V-belt pulley arrangements.

Frequently Asked Questions

What is the swept volume and cooling capacity of the Sabroe CMO 26?

The Sabroe CMO 26 delivers a swept volume of 145 m³/h at 1500 RPM (50 Hz motor direct drive) and 174 m³/h at 1800 RPM (60 Hz motor direct drive). Exact cooling capacity varies with evaporating and condensing temperatures; for instance, operating on R404A at -10°C evaporating and +40°C condensing, the compressor typically delivers between 70 kW and 85 kW of refrigeration capacity.

Can the Sabroe CMO 26 run on both Ammonia (R717) and Freon refrigerants?

Yes. The CMO 26 is engineered for open-drive operation without copper internal windings, making it naturally compatible with anhydrous ammonia (R717) as well as conventional fluorinated hydrocarbons (R22, R134a, R404A, R507A). Always ensure that the lubricating oil viscosity and elastomer seal rings (O-rings and shaft seal elastomers) are correctly matched to the target refrigerant charge.

How does the capacity control system function on the CMO 26?

The compressor uses a hydraulic suction-valve-lifting mechanism operated by internal lubrication oil pressure via external solenoid valves. It unloads pairs of cylinders sequentially, allowing steps of 33% (2 cylinders loaded), 67% (4 cylinders loaded), and 100% (all 6 cylinders loaded), facilitating reduced starting loads and balanced continuous chilling.

How is the correct oil pressure verified on the CMO 26?

The compressor features an integrated internal gear pump. Operating oil pressure must be measured as differential pressure: read the oil manifold pressure and subtract the crankcase suction pressure. The resulting net oil pressure should consistently measure between 1.5 bar and 2.5 bar above crankcase pressure during steady-state run periods.

What is the recommended overhaul interval for a marine CMO 26?

Under normal continuous operating conditions, routine valve ring and suction/discharge plate inspection is recommended every 5,000 running hours. A major overhaul—involving replacement of main and connecting rod bearings, piston rings, shaft seal, and thorough inspection of crankshaft journals—should be conducted every 15,000 to 20,000 operational hours.