Advantages
This process of continuous research and development has produced a product line that is superior to any on the market with regard to:
- Compressor range
- Flexibility
- Reliability
- Operating efficiency
- Environmental safety
- Operating safety
- Maintenance
Applications
M&M Refrigeration reciprocating compressor packages can be used in all kinds of industrial refrigeration. In the application examples listed below, particular benefits can be obtained regarding installation and operating cost:
- All small to medium size plants as booster and high stage compressors
- High stage compressors in large plants
- Peak load and “weekend” compressors in large plants with load variations during day/week/year
- All chiller units, especially with load variations during day/week/year
- Chiller units and other applications where immediate capacity cut off is required
- CO2 cascade systems
Quality and Reliability in Each Step
- Casing, covers, crankshaft, connecting rods, and cylinder liners manufactured at Meehanite foundries to ensure full process control
- Casing in grey cast iron quality GG25 (nodular ductile cast iron quality GGG50 for 580 psi high pressure compressors)
- Crankshaft in nodular ductile cast iron quality GGG70
- Design pressure: 370 psi for standard single and two stage compressors / 580 and 725 psi for high pressure compressors
- Compact modern industrial design with integrated suction and discharge manifolds
- Resistant to minor slugs of oil and refrigerants due to robust construction including spring loaded safety heads
- Oversized suction filters for protection of vital parts in the compressor
- Reliable lubrication ensured at all conditions through
- Reduced cylinder and piston wear
- Gas dampened discharge valves ensure long life
- Stop valves with non–rising spindle in stainless steel for long life and trouble–free operation
- External oil filter
- Water cooled heads removable without opening the refrigerant side of the compressor
Operating Efficiency and Safety
- Easy operation due to the comprehensive standard equipment such as:
- High COP and excellent part load characteristics for reduced operating costs
- Automatic capacity regulation
- Fully unloaded start
- Guaranteed ratings according to ISO 916
- Low oil carry over due to highly efficient oil separation
- Oil separators are constructed according to current ASME codes
- Low noise and vibration level
- Internal by-pass valve to avoid excessive pressure
- Safety switches to stop compressor in cases of excessive pressure and temperature, including:
- Asbestos free gaskets
- Balanced refrigerant tight shaft seal
- Low demand for spares
- Easy maintenance due to good accessibility
- Totally field repairable
Cooling
Depending on refrigerant and operating conditions, it might be necessary to supplement the basic convection air cooling with one of the following to obtain adequate cooling of the compressor:
Direct drive CMO 26 compressor unit
Refrigerant-cooled oil cooling
Water-cooled side and top covers
Two-stage Compressor Systems
The M&M Refrigeration two–stage compressor integrates a low pressure (LP) and a high pressure (HP) compressor in one housing. The LP cylinders compress the refrigerant gas from evaporator pressure to intermediate pressure. In an intermediate cooling system, the LP discharge gas is cooled to near saturation temperature and then drawn into the HP cylinders, where it is compressed to condensing pressure. In connection with the intermediate gas cooling, a subcooling of liquid refrigerant from the condenser can be obtained.
Two–stage compression combined with intermediate gas cooling lowers discharge temperature and the pressure ratio in the cylinders. Consequently, wear and oil carry–over are reduced and the overall efficiency is improved.
Intermediate Cooling Systems
Injection Interstage Gas Cooling
System A is a simple, inexpensive system which cools the gas by injecting liquid refrigerant into a special intermediate pipe connecting the LP discharge and the HP suction. This system does not contain liquid subcooling and efficiency improvements are limited.
Injection Interstage Gas and Liquid Cooling
System B is similar to System A, but extended with a shell and tube heat exchanger, DX feed, for liquid subcooling down to approximately 15°F above intermediate temperature. Efficiency and unit capacity are considerably improved. Liquid pressure remains at condensing pressure after subcooling. This system is mainly used for HCFC and HFC refrigerants.
Open Flash Interstage Cooling
System C is an open flash intermediate cooling system creating the maximum efficiency and unit capacity improvement. The liquid from the condenser is subcooled down to intermediate temperature. Liquid pressure also equals intermediate pressure, which in some applications can be a disadvantage.
Closed Flash Interstage Cooling
System D is a closed flash intermediate cooling system creating considerable efficiency and unit capacity improvement. The liquid from the condenser is subcooled down to approximately 10°F above intermediate temperature. Liquid pressure remains at condensing pressure after subcooling. This system can be used as an alternative to System C, and is mainly used for R717.