The compressor stands on spring or rubber mounts, and its body moves by a few millimetres, especially at start and stop. The pipes, however, are fixed to the frame. This movement loads the brazed joint and the elbows at every run; the copper fatigues and months later a hairline crack opens. Vibration cracks are the source of a significant share of the refrigerant leaks on condensing units. The vibration eliminator damps this movement within itself. By the time a leak is noticed a significant part of the refrigerant has long gone.
The part consists of a thin-walled stainless steel bellows, the wire braid that holds it against the pressure, and the copper braze ends at either end. Its diameter is chosen equal to the line diameter; the working pressure must suit the refrigerant used, and high-pressure types are needed for R410A and CO₂. In small hermetic compressors the same job is done by a loop formed in the pipe (vibration loop); no separate part is used. Its length usually varies between 20 and 40 cm depending on its diameter, and it cannot be shortened.
The installation rule is clear: the vibration eliminator is placed as close to the compressor as possible and parallel to the crankshaft; in this way it meets the rocking movement of the body at right angles to its axis. The bellows does not work in compression or tension, it only flexes sideways. It must not be fitted stretched, compressed or twisted; the other end must be fixed to the frame with a sturdy clamp. If the movement is in two axes, two parts at right angles to each other are used. An eliminator fitted in the wrong direction does not damp the vibration; it fatigues itself and becomes the first part to crack. The transport bolts of the compressor mounts are also slackened before commissioning.
During brazing the bellows is cooled with a wet cloth and nitrogen is passed through it; a bellows that overheats hardens and cracks in a short time. On eliminators working below zero in the suction line, if water fills the convolutions of the bellows and freezes, the bellows is crushed; so it is insulated or a sheathed type is chosen. A vibration eliminator is not used to correct misalignment in the pipework; the pipes are aligned correctly first. If a trace of oil is seen on the bellows or a broken wire in the braid, the part is replaced without waiting.