Before a pressure vessel, piping spool, valve manifold or compressed-air receiver goes into service it is often proof-tested or leak-tested with air or an inert gas at a pressure well above the operating point. That work cannot be done straight from a 7 to 10 bar factory header. A high-pressure booster compressor takes feed air from an existing compressor and raises it to the 30, 40 or 60 bar the test procedure requires, under close control and usually for short, intermittent runs. This guide explains how to size a booster for pneumatic pressure testing and compares real KOTECH KVW, KVM and KVF frames against feed and target pressure.
Why a booster instead of one high-pressure compressor
Most facilities already produce large volumes of air at 7 to 10 bar for general use. Pressure testing needs only a small flow but at much higher pressure, and only occasionally. Buying a single machine that both makes the base air and reaches 60 bar would be expensive and inefficient for everyday duty. The economical arrangement is a booster: a second compression stage that draws from the ordinary compressed-air network and lifts that feed air to the test pressure.
Because a booster works on top of an existing pressure, its compression ratio is lower than compressing from atmosphere, which improves its efficiency for the high-pressure step. The trade-off is that the booster’s delivered flow and final pressure depend on the feed pressure, so both sides of the machine must be specified together rather than in isolation.
The air load in a pressure test
Pneumatic testing is defined by three numbers: the internal volume of the item under test, the target pressure, and the time allowed to reach and hold that pressure. Filling a large vessel to 30 or 60 bar needs a calculable mass of air; the booster’s free-air delivery at the stated inlet pressure sets how long the fill takes. Once target pressure is reached, flow falls to only what leaks out, so the duty is a high fill rate followed by a long, near-zero hold, which is why boosters for test work are usually sized on fill time rather than continuous output.
Safety dominates the specification. Pneumatic tests store a great deal of energy, so pressure must rise in controlled stages with pressure relief, isolation, certified gauges and a written procedure. The booster needs reliable pressure regulation and over-pressure protection, and dry, clean feed air prevents water and oil from being pushed into the test piece, where contamination or corrosion could be a problem.
- Size the booster from test volume, target pressure and required fill time at the available feed pressure.
- Specify regulation and relief protection for staged, controlled pressurisation of the test piece.
- Provide dry, clean feed air so moisture and oil are not forced into vessels or piping.
- Remember the duty is intermittent: a high fill flow followed by a long low-flow hold, not continuous production.
Real KOTECH high-pressure booster specifications
Current factory figures from the KOTECH product page. Model figures indicate flow, inlet pressure and outlet pressure; the KVF frame is a high-ratio final stage.
Read the inlet and outlet columns together. A booster that reaches 60 bar does so from a 20 to 34 bar feed, not from the atmosphere, so a complete 60 bar test rig includes the lower-pressure machines that produce that intermediate air. Matching the whole chain is what makes the fill-time calculation correct.
Building a test air system
A practical test station combines feed compression, buffering, drying and the booster. A receiver on the feed side keeps inlet pressure stable while the booster fills the test piece, because a sagging feed pressure reduces booster output and lengthens the fill. A dryer and filtration on the feed deliver clean, dry air, and a high-pressure buffer or accumulator after the booster can smooth delivery and allow a smaller booster to serve repeated tests if the schedule allows recharge time.
Controls and documentation matter in test work. Logging the pressure curve during the hold gives evidence of leakage and of compliance with the test standard, and positive isolation and venting protect personnel. Choosing a booster with stable regulation keeps the pressure from overshooting during the sensitive final approach to target, which both protects the test piece and gives a cleaner leak reading.
Other high-pressure duties that share the equipment
The same boosters that support pressure testing frequently serve other intermittent high-pressure loads in industry, which can improve utilisation for a rental fleet or test contractor. PET preform blowing, high-pressure scavenging, certain leak-test rigs and charging of high-pressure systems all sit in the 30 to 40 bar region, while specialised applications go higher. Selecting a frame with the right inlet and outlet band lets one machine cover testing and a secondary duty without being forced into an oversized rating.
Where the work is mostly continuous PET blowing rather than intermittent testing, the duty and cooling specification differ, and a machine optimised for that running pattern should be chosen. For mixed hire and test work, frames around the KVW-1.8/5-31 to KVW-3/5-34 offer a useful balance of outlet pressure and flow.
Buying tips
- Define test volume, target pressure and acceptable fill time before choosing the booster frame.
- Check the available feed pressure; 60 bar frames need a 20 to 34 bar intermediate supply.
- Include a feed receiver, dryer and filtration for stable, clean, dry test air.
- Specify staged pressurisation, pressure relief and certified gauges as part of the rig, not add-ons.
- If the machine will also do PET blowing or other duty, confirm the frame suits that running pattern.
Frequently asked questions
What is a high-pressure booster compressor used for in pressure testing?
How do I calculate what size test booster I need?
Can a 60 bar booster draw air straight from the factory line?
Why does feed air need to be dry and clean for testing?
Is pneumatic pressure testing dangerous?
Can the same booster do PET bottle blowing as well as testing?
Tell us your test volume, target pressure, feed pressure and required fill time, and our engineers will size the right KOTECH high-pressure booster package for your test station.