PSSR 2000 · Pressure systems

Air-oil receiver examination under PSSR

Independent examination of your air-oil receiver under a Written Scheme of Examination, by a competent person under PSSR.

On an oil-flooded screw compressor the air-oil receiver is the vessel that separates the oil from the compressed air and holds the pressure, and the oil and water that sit in its base hide the wastage. PSSR treats it as a pressure system, examined to a written scheme by a competent person.

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  • Independent and impartial
  • Competent engineer surveyors
  • Reports issued promptly
Written schemeExamined to a certified written scheme of examination
On the compressorThe separator vessel that holds the system pressure
Certified reportA written report of examination, within 28 days
Internal tooOil and condensate hide corrosion at the base
Pressure equipment we examine

Why your air-oil receiver needs PSSR examination

An air-oil receiver, the separator tank on an oil-flooded screw compressor, does two jobs at once: it separates the lubricating oil from the compressed air and acts as the primary receiver that holds the system pressure. Because it carries both oil and air under pressure, the mixture of oil and condensate that settles in the base is where corrosion and wastage build up out of sight.

Under the Pressure Systems Safety Regulations 2000 the receiver is a pressure system where it is in scope, and Regulation 8 requires a written scheme of examination before it is operated. The oil is drained so the inside can be examined, the safety valve and gauge are tested, and the working examination confirms the system behaves as the compressor builds pressure. We examine it independently and report to the scheme.

Separator vessel
Internal corrosion
Oil and base
Safety relief valve
Pressure gauge
Minimum pressure valve
Discharge pipework
Nameplate and SWP
How it works

How we examine your air-oil receiver

A competent engineer surveyor drains the oil and examines the separator vessel inside and out, looking for the pitting and wastage that the oil and condensate hide. The safety valve is removed and pressure-tested, the gauge is checked for accuracy, and the working examination follows the system as the compressor loads and the pressure cut-out operates.

  • 1

    Get in touch

    Tell us the compressor and its air-oil receiver, the pressure and whether a scheme is in place.

  • 2

    On-site examination

    A competent engineer surveyor drains and examines the vessel inside and out and tests the valve and gauge, to the scheme.

  • 3

    Your report

    You receive a written report of examination, any defects and timescales set out, within the statutory window.

Why businesses choose SEIS

  • Independent and impartial: we examine the receiver, we do not supply or service the compressor
  • Competent engineer surveyors used to screw compressors and PSSR
  • Internal and external examination with the oil drained, not a walk-round
  • Certified reports issued promptly, the next examination date flagged
What we examine

Air-oil receiver: what a thorough examination covers

Internal corrosion and the base

The inside of the separator and the base where oil and condensate settle, examined for pitting and wastage, the corrosion that an external look and a film of oil both hide.

Safety relief valve

The valve removed and pressure-tested so it lifts at the set pressure, the protection that stands between the compressor and an over-pressured vessel.

Pressure gauge

The gauge checked for accuracy across its range, because a gauge fed through an oil-sludged tube can lock at a reading that no longer reflects the vessel.

Minimum pressure valve and connections

The minimum pressure valve and the discharge connections, checked for security and condition where the hot, oily air leaves the vessel.

Shell, welds and supports

The shell, welds and the mountings to the compressor frame, for cracking, distortion and the fretting that vibration brings.

Nameplate and safe working pressure

The plate and marked safe working pressure, so the separator is run within the limits the written scheme is built around.

Scheme and certification

How it works, and what you receive

Where an air-oil receiver is in PSSR scope it is a pressure system, so under Regulation 8 it must have a written scheme of examination, drawn up or certified by a competent person, before the compressor is operated. It is then examined to the intervals the scheme sets, with the oil drained for an internal examination as the scheme requires. After each examination you receive a written report on the condition of the vessel and its protective devices, with any actions and timescales, issued within twenty-eight days.

Step oneA Written Scheme of Examination, certified before use
To schemeExamined to the intervals the scheme sets
28 daysA written report, issued within the statutory window
IndependentWe examine it, we do not supply it

You receive a report on the condition of the system and its safety devices, with any actions and timescales set out clearly.

Full statutory cover

Part of our full PSSR inspection service

Air-oil receiver is one of the many kinds of equipment we cover. We inspect the full range, across every sector, as an independent provider, one item or a whole site, anywhere in the UK.

See our full PSSR inspection service
Other services

Other statutory inspections we carry out

Many sites run more than one regime. We can examine all of it, under one independent provider.

LOLER inspectionThorough examination and certification of lifting equipment and accessories. PUWER inspectionInspection of work equipment against the five PUWER duties, with a written record. LEV testingLEV thorough examination and test of your extraction systems.
PSSR FAQs

Air-oil receiver examination: common questions

Does an air-oil receiver need a PSSR examination?
Yes, where it is in scope. The separator vessel on an oil-flooded screw compressor is a pressure system once it is over 250 bar litres, and it must not be operated without a written scheme of examination. You can read the duty in the HSE guidance on the Pressure Systems Safety Regulations.
Do I need a written scheme of examination, or a certificate?
A written scheme. Regulation 8 requires a written scheme of examination, drawn up or certified by a competent person, before the system is operated, and the examination against it produces a certified written report. Our guide to PSSR explains the scheme and what it must contain.
How often should an air-oil receiver be examined?
To the intervals the written scheme sets, based on the duty and condition. The scheme will set when external and working examinations are due and when the vessel is opened, with the oil drained, for an internal examination.
Is it covered by PSSR or PUWER?
PSSR, where it is over 250 bar litres. Below that the written scheme duty falls away, but the compressor and its vessel remain work equipment under PUWER, and your insurer may still require an examination. A PUWER inspection does not replace a PSSR examination.
What does the examination cover?
The separator vessel inside and out, the base where oil and condensate corrode, the safety relief valve tested to confirm it lifts, the pressure gauge checked for accuracy, the minimum pressure valve and discharge connections, and the nameplate and safe working pressure.
Who is competent to examine it?
A competent person with the training, skills, experience and knowledge for the system, independent of its operation. Our engineer surveyors examine compressor air-oil receivers regularly and report to the written scheme.
Does the oil have to be drained for the examination?
For an internal examination, yes. The oil and the condensate beneath it hide the corrosion in the base, so the vessel is drained and opened to the scheme so the inside can be examined directly rather than guessed at.
Do you examine air-oil receivers across the UK?
Yes. Our engineer surveyors travel to sites with screw compressors nationwide, a single machine or a compressor house. Call 0330 043 8191 to arrange a visit around your shutdown.

Is your air-oil receiver due an examination?

Talk to an engineer surveyor, get a quote and book your inspection anywhere in the UK.

0330 043 8191 Request a quote