Air Receiver Inspections

Air receivers are the most common pressure system we examine. Almost every workshop, garage, MOT bay, food production line, paint booth, and small-scale manufacturing facility runs a compressed air system — and where the receiver volume × working pressure exceeds 250 bar-litres, that system falls under the Pressure Systems Safety Regulations 2000. This page covers when PSSR applies, what we examine, and what to expect from the report.

When PSSR applies to your air receiver

PSSR applies to compressed air systems containing a relevant fluid above 0.5 bar. In practice that's nearly every installed compressor — atmospheric pressure is 1 bar absolute, so anything pressurised counts. The threshold question for most sites is whether a full Written Scheme of Examination is required, which depends on the bar-litre product:

The bar-litre calculation applies to each receiver in isolation. A site running three small receivers below the threshold is not automatically exempt — interconnected pressure systems are assessed together where the failure of one part could endanger another. If you're not sure how to draw the line, send us the data-plate details for each receiver and we'll confirm in writing before any work is quoted.

What we examine on an air receiver

A thorough examination under PSSR covers every part of the system the Written Scheme of Examination identifies. For a typical workshop air receiver, that means:

• Pressure relief valve — set pressure, condition, free movement, evidence of leak-by or weeping. We test the relief valve where the WSE specifies, including lift-and-reseat testing if required.
• Pressure gauge — accuracy across the working range, condition of the dial face, and isolation arrangements.
• Vessel walls and end caps — internal examination of the receiver surface for corrosion, pitting, weld defects, and any thinning. External examination of mountings, support structure, and external corrosion.
• Weld integrity — circumferential and longitudinal welds visually examined; ultrasonic testing where the WSE or condition indicates.
• Drain valves and condensate management — automatic and manual drains, including evidence of accumulated condensate that may have promoted internal corrosion.
• Safety fittings and protective devices — pressure switches, fusible plugs (where fitted), bursting discs (on specialist systems), and any electrical interlocks.
• Foundations and supports — vessel mountings, anti-vibration mounts, pipework supports, and the area around the receiver.

Where the examination identifies defects, the report categorises them as either an imminent danger requiring immediate action under Regulation 14, defects requiring action by a specified date, or observations for the duty holder's attention. The categorisation is the basis for what happens next.

Compressors, air receivers, and the wider compressed air system

PSSR is concerned with the air receiver itself and any pipework whose failure could give rise to danger — but in practice the receiver doesn't sit alone. The compressor head, the inter-cooler, after-cooler, separators, pressure regulators, and distribution pipework all interact with the receiver's safe operation. A typical examination will note the condition of the wider system even where specific items aren't formally part of the WSE.

Many of the failures we see on air receivers are actually upstream issues — a worn compressor allowing oil into the receiver and accelerating internal corrosion, a failing inter-cooler causing wet air to accumulate, or an undersized after-cooler allowing condensate to overload the drain. Where we identify those patterns we'll flag them in the report so the duty holder can address root causes alongside the immediate defects.

Examination frequency for air receivers

The Written Scheme of Examination is the legal authority for the interval. Typical intervals seen in practice are:

• 26 months — the most common interval for installed workshop receivers in normal use.
• 14 months — higher-risk applications: paint spray booths, pneumatic conveying, food contact, oxygen-enriched systems, or sites where condensate management is poor.
• 72 months — occasionally seen on very large, well-protected receivers in low-duty service, justified by the WSE.

A common compliance gap is the receiver that was examined 14 or 26 months ago and is now overdue because the duty holder lost track of the recall date. Under PSSR Regulation 9 the legal duty to arrange re-examination at the WSE-specified interval sits with the duty holder, not with the inspection provider. Build the next-examination date into your own compliance diary — treat any provider reminder as a useful backup, not a substitute for the dutyholder's own diary management.

What happens if your air receiver fails examination

Failures fall into three brackets. Each triggers a different action in the report and a different conversation with the duty holder.

• Imminent danger — the receiver must come out of service immediately. We serve a written notice under PSSR Regulation 14, the duty holder isolates and depressurises the system, and the receiver cannot be returned to use until rectified and re-examined. This is uncommon but does occur, typically where corrosion has progressed unnoticed for several inspection cycles.
• Defect requiring action by a specified date — the system can continue in service but the defect must be resolved by a stated deadline. Examples: a pressure relief valve due for replacement, a gauge reading outside tolerance, a drain valve that needs servicing. We re-examine at the next visit or earlier if requested.
• Observation for the duty holder's attention — non-urgent items the duty holder should know about: external corrosion starting on a support frame, condensate accumulation that needs addressing operationally, signs of upstream compressor wear.

The categorisation is deliberate. We've seen sites where every defect was lumped together in a single list, leaving the duty holder unable to tell which items were safety-critical and which were maintenance hygiene. Our reports separate them clearly so action can be prioritised.

Frequently Asked Questions