Reciprocating Compressors

Overview

recip_comp_packReciprocating Compressors Overview

M&M Refrigeration’s reciprocating compressor packages use heavy-duty compressors designed for use in all types of industrial refrigeration. Suitable for most refrigerants—including HCFC, HFC, hydrocarbons, ammonia, and carbon dioxide—they are proven, safe and reliable.

Our basic reciprocating compressor package design was introduced in 1954, and all subsequent design improvements are compatible with earlier compressor models—a feature that ensures older compressors can be upgraded to the latest design with improved efficiency.

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

Applications

recip_comp_graphM&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

Features

Features

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
    • oversized connecting rod bearings and piston pin bearing
    • efficient oil filtering
    • internal gear–type oil pump for pressure lubrications of bearings
  • Reduced cylinder and piston wear
    • cylinder liners with nitrited hardening of surface (Ni–temper)
    • hard chromium piston rings
    • lightweight pistons of special design and material
  • 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:
    • suction and discharge stop valves
    • electric immersion heater
    • oil charging valve
    • evacuating valve
    • valve for prelubricating of bearings after a long standstill period
    • oil level sight glass
    • high, low, and oil pressure gauges
  • 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:
    • high and low pressure switch
    • oil pressure differential switch
    • discharge and oil temperature switch
  • Asbestos free gaskets
  • Balanced refrigerant tight shaft seal
  • Low demand for spares
  • Easy maintenance due to good accessibility
  • Totally field repairable

Cooling

Cooling

V-belt driven SMC 104 compressor

V-belt driven SMC 104 compressor

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:

  • Water cooled top cover
  • Water cooled side cover including oil cooling
  • Refrigerant cooled oil cooler

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.

Four different intermediate cooling systems are available:

recip_cooling07Injection 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.

recip_cooling08Injection 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.

recip_cooling09Open 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
recip_cooling10

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.

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