VIBRATION AND NOISE

  No matter how well the compressor is isolated, some noise and vibration will be transmitted through the piping, but both can be minimized by proper design and support of the piping.

  On small units a coil of tubing at the compressor may provide adequate protection against vibration. On larger units, flexible metallic hose is supported by vibration absorbing mounts allowing compressor movement, refrigerant lines should not be anchored solidly at the unit, but at a point beyond the vibration absorber, so the vibration can be isolated and not transmitted into the piping system.

  The noise characteristics of a large refrigeration or air conditioning system, particularly when installed with long refrigerant lines and remote condensers, are not predictable. Variation in piping configuration, the pattern of gas flow, line sizes, operating, all can affect the noise generated by the system. Occasionnlly a particular combination of gas flow and piping will result in a resonant frequency to an undesirable level. Gas pulsation from the compressor may also be amplified in a similar manner.

  If gas pulsation or resonant frequencies are encountered on a particular application, a discharge line muffler may be helpful in correcting the problem. The purpose of a muffler is to damper the pulses of gas in the discharge line and to change the frequency to a level which is not objectionable. A muffler normally depends on multiple internal baffles and/or pressure drop to obtain an even flow of gas. In general, the application range of a muffler depends on the volume and density of the refrigerant gas discharged from the compressor are both factor in muffler performance.

  A given muffler may work satisfactorily on a fairly wide range of compressor sizes, but it is also quite possible that a given system may require a muffler with a particular pressure drop to effectively dampen pulsations. On problem applications, trial and error may be the only final guide. While large muffler are often more efficient in reducing the overall level of compressor discharge noise, in order to satisfactorily dampen pulsations, smaller muffles with  a greater pressure drop are usually more effective. Adjustable mufflers are often helpful since they allow tuning of the muffler pressure characteristics to the exact system requirement.

  Occasionally, a combination of operating conditions, mounting and piping arrangement may result in a resonant condition, which tends to magnify compressor pulsation and cause a sharp vibration, although noise may not be a problem. For large Copelametic compressors, discharge muffler plates haven been developed for use when necessary to dampen excessive pulsation. The muffler plate fits between the discharge valve and the compressor body and has a number of muffling holes break up the pattern of gas flow  and create sufficient restriction to reduce the gas pulsation to a minimum.

  When piping passes through walls or floors, precaution should be taken to see that the piping does not touch any structural members and is properly supported by hangers in order o prevent the transmission of vibration into the building. Failure to do so may result in the building structure becoming a sounding board.