Oil-Free Oxygen Cylinder Filling Compressor

ZW series reciprocating compressors for boosting PSA or vaporised liquid oxygen to 150 bar (15.0 MPa) or 165 bar (16.5 MPa) for cylinder filling — with zero oil contamination in the compression zone.

An oxygen cylinder filling compressor is a high-pressure reciprocating machine that raises the pressure of oxygen from a low-pressure source — typically the output of a PSA (Pressure Swing Adsorption) oxygen generator or a liquid oxygen vaporiser — to the pressure required to fill gas cylinders. The standard fill pressure for oxygen cylinders is 150 bar (15.0 MPa) or, for higher-density filling, 165 bar (16.5 MPa).

Our ZW series covers the full range of cylinder filling station capacities — from a small hospital PSA station filling 50 cylinders per day with the ZW-1/150, up to a high-throughput commercial filling station running around the clock with the ZW-5/150 at 300 Nm³/h.

Every model in the ZW series is engineered to API 618 standard with an oil-free compression zone, inter-stage cooling between every stage, and a comprehensive set of automatic safety protections for unattended operation.

• ✓ Meets ISO 11513 for standard medical oxygen cylinder filling
• ✓ Standard fill pressure across Asia, Africa and Middle East markets
• ✓ Recommended: hospital PSA stations, medical gas distributors
• ✓ 4-stage (ZW-1 to ZW-1.82) or 5-stage (ZW-3 to ZW-5)

• ✓ Higher fill density — approx. 10% more gas per cylinder vs 150 bar
• ✓ Preferred by European markets and high-volume industrial gas distributors
• ✓ Recommended: welding & cutting gas suppliers, commercial filling stations
• ✓ Same frame as /150 series — matching footprint and installation requirements

The ZW-1 series is the entry-level configuration of the ZW platform — a two-column, four-stage reciprocating machine delivering 60 Nm³/h at 150 bar on just 30 kW. It is specifically sized for hospital PSA stations and small-to-medium medical gas filling operations where footprint and noise level are as important as throughput.

Oil-Free Cylinder Design

PTFE-compound piston rings run without lubrication inside the cylinder bore. External bearing points require only one grease application per year. Output oxygen meets ISO 8573-1 Class 0 oil content — no downstream coalescer filter needed.

Low-Speed, Long Service Life

Operating speed 260–350 RPM — far lower than oil-injected screw compressors at 3,000+ RPM. Reduced mechanical stress extends the mean time between overhauls to 25,000+ hours, significantly lowering downtime risk.

4 to 5 Compression Stages with Inter-Cooling

Each compression stage is followed by a tube-and-shell inter-cooler and moisture separator. Discharge temperature stays close to ambient, keeping moisture content in the filled cylinder minimal and protecting valve life.

Comprehensive Safety Protections

Standard safety package includes: inlet low-pressure automatic shutdown, outlet over-pressure relief valve, inter-stage temperature alarm and automatic stop. Designed for 24-hour unattended operation with PLC control panel as standard.

Minimal Maintenance Requirements

No oil changes. No oil filter elements. No oil separator cartridges. Consumables are limited to piston rings, valve plates and packing rings. Grease points require servicing once per year — a fraction of the maintenance burden of oil-injected alternatives.

API 618 Compliant Design

Designed and manufactured to API 618 (Reciprocating Compressors for Petroleum, Chemical and Gas Industry Services). CE marking available for European markets. ISO 9001 certified manufacturing facility. Every unit factory-tested before shipment.

Hospital PSA generators deliver oxygen at 4–6 bar for ward pipeline supply. Reserve cylinders and emergency stocks are filled to 150 bar for when the main supply is offline. Oil-free compression is a mandatory compliance requirement for medical gas service.

Commercial gas distributors run filling stations around the clock. High throughput, low downtime and minimal maintenance overhead are the operating priorities. The ZW-3/150 to ZW-5/150 handles 180–300 Nm³/h on continuous 24-hour duty with just one grease service per year.

Oxy-fuel cutting and gas welding operations need reliable 150 bar or 165 bar oxygen cylinder supply. The 165 bar series gives approximately 10% more gas per cylinder — a meaningful efficiency gain at distributor scale. Available in flow rates from 100 to 300 Nm³/h.

"We installed three ZW-3/150 units at our medical gas filling station in Riyadh. Running 18 hours a day, we've had zero unplanned stops in 14 months of operation. The oil-free design was a hard requirement for medical compliance, and Ever Power delivered exactly that. The inter-stage cooling keeps the discharge temperature manageable even in 45°C summer heat."

"Very solid machine. We paired the ZW-1.67/150 with our PSA generator and integration was straightforward. Ever Power's engineer helped us size the buffer tank correctly, which made a big difference — no more low-pressure trips. Annual grease service is genuinely all the maintenance it needs. Total cost of ownership is much lower than the oil-injected machine we replaced."

"We went with the ZW-4.2/165 for our welding gas distribution business. The 165 bar option gives us about 10% more gas per cylinder which matters a lot at our volume. The compressor has been running 20+ hours daily for over a year. Documentation for CE and API 618 was provided on time and without issues — important for our import compliance."

"We've been using Ever Power ZW-5/150 in our high-volume oxygen filling centre for 18 months now. Output is consistently 300 Nm³/h. The machine is quieter than I expected for its size. The only minor point is that spare parts documentation could be more detailed initially, but their after-sales team was responsive and sent the full BOM quickly. Overall very happy."

Can this hook up directly to our PSA generator? +

Yeah, it's designed for exactly that. PSA generators typically output at 0.3–0.6 MPa, and the ZW series handles atmospheric inlet just fine with those conditions. The main thing we'd recommend is putting a buffer receiver between the PSA and the compressor — around 10 minutes of flow capacity. This smooths out the pressure swings during the PSA regeneration cycle and stops the compressor tripping on low-pressure alarm every time the PSA switches beds.

What's the real difference between 150 bar and 165 bar? Is it worth the upgrade? +

Mostly it comes down to how much gas you can get into each cylinder. Filling to 165 bar gives you roughly 10% more gas per cylinder than 150 bar — which sounds small, but at high volume that adds up. The machines themselves are built on the same frame, same footprint, same installation requirements. If most of your cylinders are rated for 200 bar working pressure (which most modern ones are), 165 bar is a perfectly valid option. If you're in a market where 150 bar is the local standard, stick with that — otherwise you'll have compatibility questions at the filling manifold.

How much maintenance does this thing actually need? +

Honestly, not much. The biggest thing is grease — external bearing points once a year. After that, you're looking at valve plate and piston ring inspection around 8,000–12,000 hours, and eventual replacement somewhere around 15,000–25,000 hours depending on operating conditions. There's no oil to change, no oil filters, no oil separator cartridges. That's the real advantage of the oil-free design for running costs — the maintenance schedule is much lighter than an oil-injected machine of equivalent output.

Can you supply the complete filling station, not just the compressor? +

Yes. If you want a complete skid-mounted package — compressor, high-pressure buffer vessel, filling manifold, high-pressure flexible hoses, safety relief valves, and a PLC control panel — all pre-assembled and factory-tested before it leaves — we can do that. Just tell us your daily cylinder count, available floor space, PSA output specs, and local power supply. We'll design the package around your setup.

We have unusual requirements — non-standard pressure or flow. Can you handle that? +

Yes, definitely. The standard models in our catalogue cover the most common configurations, but non-standard specifications are something we handle regularly. Whether that's a different inlet pressure, a non-standard outlet pressure, a different voltage or frequency, special materials for corrosive environments, or a specific noise level requirement — bring us your specs and we'll work through the engineering. We're set up for custom orders, not just catalogue sales.

Engineering Oil-Free Oxygen Compression for Global Industry

Ever Power has been manufacturing industrial reciprocating gas compressors for over two decades, supplying hospitals, industrial gas distributors, steel producers and engineering contractors across more than 50 countries. Our production facility — covering 68,000 m² — houses fully integrated casting, machining, assembly and pressure-testing operations. Every compressor we ship has been performance-tested on our own test bench before it leaves the factory.

Our ZW, LW and DW series are designed to API 618, certified to ISO 9001, and CE marked for European markets. We hold over 68 patents in compression technology, and our engineering team has authored several of the national standards for reciprocating gas compressors used in China and recognised internationally.

Beyond our standard catalogue, we specialise in non-standard engineering. Whether you need a custom inlet pressure configuration, a non-standard outlet pressure, ATEX explosion-proof certification, a specific noise level, or a fully integrated skid-mounted package designed around your site constraints — we build to your specification, not just to ours. We welcome enquiries from customers who have drawings, data sheets or non-standard requirements to discuss.