Proper Filtration First Priority

You wouldn’t run your car without an air filter, so you certainly wouldn’t want to operate a compressor without proper filtration. Sounds simple enough, but some important precautions concerning filtration often go overlooked.

Click here for a PDF of the above booster compressor P&ID setup

The number one problem with new installations of air and gas boosters is debris from the piping system damaging the new compressor. Hycomp service technicians have found weld slag, mill scale, Teflon tape, pipe dope, filter element fibers, rust and even carbon dust contaminating newly installed air boosters and gas compressors.

This debris can become embedded in the polymer piston rings, causing scoring of the cylinder wall, or get lodged in the valves, causing valve damage and valve leakage. Perhaps the worst case was an air booster attached to 1,000 ft. of old, underground iron pipe. The owner started the air booster for the first time, went to lunch, and upon return found the connecting rod had punched out the side of the crosshead cylinder because the compressor had literally filled with rust particles and other debris, seizing the entire compression end.

When installing a Hycomp air or gas booster into your system, setup is not complicated. But if the proper installation method is not followed, it can lead to a variety of problems. Simply put, the inlet air/gas absolutely must be filtered. However, due to the pulsations caused by a reciprocating compressor, it is not acceptable to simply put a filter directly in front of the Hycomp booster. The pulsing air/gas can tear the filter element apart, causing it to be sucked into the booster, leading to the same damage the filter was designed to prevent.
The solution is to place a receiver directly upstream of the booster compressor, with a properly sized filter at the inlet of the receiver. In addition to providing a local capacitance for the booster, the receiver acts as a pulsation dampener to prevent damage to the inlet filter. It then becomes a question of sizing the filter properly, and ensuring the receiver and piping from the receiver to the booster, are clean of debris.

The inlet filter should be rated at one (1) micron to remove any contaminant introduced by the original plant piping. To properly size the inlet filter, remember that the booster doesn’t flow smoothly, but takes in gasps at 600 RPM, an air booster takes gasps of air 10 times per second. Since filter elements are rated for smooth continuous flow, and the inlet stream to the compressor is pulsing, consideration must be made to accommodate the difference. Hycomp recommends sizing the inlet filter for twice the nominal flow of the booster, to ensure pressure drop is minimized and damage to the filter element does not occur. Install the filter directly at the inlet to the receiver.

Next, the inlet receiver must be clean of any foreign contaminant. During manufacturing, air and gas receivers are welded, hydro-tested, and then shipped to the customer, leaving mill scale, slag, rust, water and oil inside the ‘new’ receiver. This must be removed, or the debris from the ‘new’ inlet receiver will cause problems. Hycomp recommends getting the receiver epoxy lined (when compatible with the gas stream), to ensure the interior is clean and free of debris. The receiver should not restrict the gas flow, so for larger systems, it is often necessary to use a larger receiver. Contact Hycomp for assistance in sizing a standard receiver.

Finally, the piping from the inlet receiver to the booster compressor must be cleaned. Hycomp service technicians have found newly installed piping filled with weld slag, mill scale, Teflon tape and pipe dope. Hycomp strongly recommends against the use of pipe dope, as it is often applied too liberally, causing excessive dope to be pushed inside the pipe during the assembly process.

Teflon tape with a proper sealant such as a few drops of Loctite 545, is an excellent method of sealing pipe threads. Just remember that the tape should be placed at least one full thread back, to ensure no tape can make its way into the pipe during assembly – and at no time should the Teflon tape overhang the end of the thread. If the pipe is welded or soldered, cleaning before welding/soldering, and especially after, will prevent oxidized particulates from breaking free during operation and entering the booster.

Remember these key points during installation:
• Install the inlet filter directly at the inlet to the receiver, sized for twice the nominal flow, and rated at one (1) micron.
• Use a clean or epoxy lined receiver.
• Keep the piping between the receiver and the booster as short as possible to prevent unwanted pressure drop. Plus, short piping means less chance of debris.
• Use a flexible metal hose at the booster inlet to isolate vibration.

Hycomp can supply a packaged air/gas booster compressor with inlet filtration and a receiver pre-assembled and either installed on the skid, or shipped loose for local installation. As this is not complicated, we certainly don’t require that a pre-assembled inlet setup is purchased from us. We do, however, require that no debris enter the booster compressor, and this method of installation has proven to be very successful at allowing smooth, worry free startup and operation.