Used Compressors for Sale

It raises gas pressure for storage, fueling or process supply, and its design sets what it can do. Reciprocating (piston) machines reach the highest pressures. Rotary screw machines give smooth, steady flow at lower pressure. Diaphragm machines keep the gas very clean but move less volume.

Sources: Atlas Copco — reciprocating vs rotary · Atlas Copco — diaphragm · PDC hydrogen compressors

Each gas makes different demands. Oxygen compressors need oxygen-compatible materials, parts cleaned for oxygen, and a distance piece that keeps crankcase oil out of the gas. Oil in hydrogen can foul the process, and lighter gases run hotter discharge temperatures. Whether a machine can move to another gas depends on the manufacturer, so contact them before buying for a different service.

Sources: AIGA 048/18 · RIX — why oil-free · Detechtion

In a lubricated machine, oil can carry over into the gas. Oil-free designs avoid that contamination, the risk of dangerous reactions with oxygen, and hydrogen contamination that can harm catalysts. API 618 covers both lubricated and non-lubricated cylinders, so know which you have before a rebuild is scoped.

Sources: RIX — why oil-free · API 618

A diaphragm compressor compresses the gas behind metal diaphragms, so the gas never touches oil or moving seals. That's why it's used where purity and leak-tightness matter, such as hydrogen fueling at up to about 1,000 bar. The trade-offs are lower flow than screw machines and diaphragms that wear and need periodic replacement. Many units include leak detection that trips the machine if a diaphragm fails.

Sources: PDC diaphragm compressors · PDC hydrogen compressors · Atlas Copco — diaphragm

On a piston machine, check the valves, the piston and rider rings, the rod packing, the crosshead and the bearings. Valves are the most common failure point. Cylinder pressure analysis, rod-drop readings, vibration and oil analysis show condition without a teardown. Where the gas must stay oil-free, look for oil carryover. On a diaphragm machine, ask for the diaphragm and leak-detection history.

Sources: Forge Reliability · AIGA 048/18 · PDC diaphragm compressors

Ask for the frame serial number, the gas, the suction and discharge pressures, the running hours and the number of starts. Ask for the overhaul history with what was replaced, why the unit came out of service, and how it was stored. Idle machines collect moisture and corrosion in bearing housings and oil sumps and need inspection before restart.

Sources: Ariel Response Center · AIGA 048/18 · Machinery Lubrication — equipment storage

Look for lost capacity, higher-than-normal discharge temperature, and suction and discharge pressures sitting too close together. On multistage machines, rising interstage pressure with falling capacity usually points to worn rings. A failing valve left in service can damage other parts, so fixing it early beats running it to failure.

Sources: Quincy Compressor · Forge Reliability

Plan for valves, the most frequent wear item, and for foundation and installation work. Reciprocating machines need a solid, anchored and often grouted base, or they shake and break anchor bolts. If your gas or pressures differ from the original duty, the rod load, discharge temperature and pressure ratings must be rechecked first, so contact the manufacturer for that review.

Sources: Forge Reliability · Corken foundation guide · Detechtion