Check hydraulic oil on sight level gauge on hydraulic tank, pumps would be making noise if oil level is low. Make sure all hoses are connected properly and not damaged. Check couplings and make sure they are plugged in properly.
[pdf] This test is performed to ensure that there are no leaks in the piping, compressor, or other pressure containing parts of the package. All openings in the completed compressor package are plugged and the unit is pressurized with nitrogen to 350 psig.
[pdf] Adding back pressure will reduce over compression by maintaining the internal discharge pressure throughout the entirety of the discharge port. Essentially, vibrations within the compressor are reduced by forcing rapid expansion to occur in the discharge line instead of the discharge port.
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