PRESSURE VESSEL INSPECTION

What Pressure Vessel Inspection Involves

Pressure vessel inspection establishes whether a vessel is fit to remain in service, and produces the documented evidence that it is. It combines external and internal visual examination with non-destructive testing to measure wall thickness, detect cracking and corrosion, and assess the condition of welds, nozzles, supports and protective coatings.

The scope of any individual inspection is set by the vessel's hazard level, its service history and the applicable standard, and the outcome is a report that supports the owner's continued-operation decision and satisfies regulatory and insurer requirements.

Pressure Vessel Certification and AICIP

Certification is the formal confirmation that a pressure vessel complies with the standards governing its design, manufacture and in-service inspection, and that the records supporting it are complete. In Australia, in-service inspection of pressure equipment is carried out by personnel certified under the Australian Institute for the Certification of Inspection Personnel (AICIP) scheme, which is the credential regulators and insurers look for on a pressure equipment inspection report.

APEC's inspection personnel hold AICIP certification, and APEC Inspection Services is certified to ISO/IEC 17025:2017 by NATA. Where a vessel's records are incomplete — a common situation with older equipment that has changed ownership — the practical first step is a documentation review alongside the physical inspection, so that gaps in the history are identified before they become a barrier at audit.

In-Service Inspection vs Design and Commissioning Inspection

Design and commissioning inspection confirms that a new vessel has been built and installed to its design, covering design verification, material and weld records, hydrostatic testing and the completeness of the manufacturer's data report before the vessel enters service.

In-service inspection is a different task: it establishes what has changed since the vessel was last examined. Wall thickness is compared against previous readings to calculate corrosion rates, and those rates set the remaining life and the next inspection interval. This is why the value of an inspection compounds — a single set of readings gives a condition snapshot, while a consistent series gives a trend that can be used to plan.

Australian Standards and Owner Duties

In-service inspection of pressure equipment in Australia is governed by AS/NZS 3788, which sets out inspection types, intervals and the competencies required to perform them. Design and manufacture fall under AS 1210, and both sit within the duties that work health and safety legislation places on the owner or person with management or control of the plant.

Those duties do not transfer to the inspection body. What an inspection provides is the evidence the owner needs to discharge them — which is why the completeness and defensibility of the report matters as much as the testing behind it. Our plain-English guide to AS/NZS 3788 sets out how the standard structures those obligations.

Inspection Intervals and Hazard Levels

AS/NZS 3788 assigns pressure equipment a hazard level based on contents, pressure, temperature and location, and that hazard level drives the maximum interval between inspections. Higher hazard equipment is inspected more often and more thoroughly; lower hazard equipment may be examined externally with internal inspection at longer intervals.

Intervals are not fixed for life. Measured corrosion rates, a change of service, a modification or repair, or an operating incident can all shorten them, and a vessel with a stable, well-documented history may qualify for extension where the standard permits it. Setting the interval is an engineering judgement supported by data, not a calendar rule.

NDT Methods Used in Pressure Vessel Inspection

A pressure vessel inspection draws on several methods, selected for the vessel and the degradation mechanisms expected. Ultrasonic testing measures remaining wall thickness and detects internal flaws. Magnetic particle inspection and dye penetrant inspection find surface cracking in welds and nozzles. Phased array ultrasonic testing provides detailed imaging of critical welds.

Positive material identification confirms alloy composition where material substitution is a risk, hardness testing assesses the effect of heat treatment or in-service damage, and hydrostatic testing verifies pressure integrity where the standard or the repair requires it.

Ultrasonic Testing of Pressure Vessels

Ultrasonic thickness measurement is the backbone of in-service pressure vessel inspection. Readings are taken at defined grid locations on shells, heads, nozzles and any area where corrosion or erosion is expected, and repeated at the same locations at each inspection so that loss can be trended rather than merely observed.

Where a flaw needs to be characterised rather than simply detected, shear wave or phased array techniques are used to size it and determine its orientation, which is what allows a fitness-for-service assessment to decide whether the vessel can continue to operate. Insulated vessels present the additional problem of corrosion under insulation, where damage is hidden beneath cladding and inspection planning has to account for access.

Common Failure Modes and What Inspection Catches

Most pressure vessel failures develop slowly and are detectable well before they become dangerous. General and localised corrosion thin the wall; pitting concentrates that loss into small areas that a coarse thickness grid can miss; erosion attacks inlets and areas of high velocity. Cracking develops at welds, nozzle attachments and support points where stress concentrates, and can be driven by fatigue, environmental cracking or residual stress from fabrication or repair.

Coating and lining breakdown, corrosion under insulation, and damage to supports and foundations are also part of the picture. An inspection is planned around the mechanisms a particular vessel is actually exposed to, which is why service history matters as much as the vessel drawings. Our article on the risks associated with pressure vessels covers how these mechanisms develop.

What You Receive

A pressure vessel inspection is issued as a written report recording the equipment identification and design data reviewed, the inspection type and standard applied, the methods used and where, wall thickness readings against previous data with calculated corrosion rates, findings and their significance, any non-conformances or defects with photographs, and a clear statement on fitness for continued service together with the recommended next inspection date.

Where remaining life is assessed, the assumptions behind that assessment are stated so the result can be reviewed as conditions change.

Where We Work

APEC is based in Newcastle and inspects pressure equipment throughout the Hunter, the Central Coast and Sydney, with inspectors mobilising to sites across New South Wales and interstate. Inspection is carried out on site during shutdowns and outages, or in workshops where equipment can be brought in.

Coverage outside New South Wales is set out on our Queensland, Victoria, Western Australia and South Australia pages. We also inspect storage tanks and air receivers.

Why Choose APEC Inspection for Pressure Vessel Inspection

APEC Inspection is a NATA-accredited inspection body with AICIP-certified inspection personnel and AINDT-certified NDT technicians, which means the inspection and the testing behind it are covered by the same accredited system. We mobilise from Newcastle across Australia and report in a form that supports your continued-operation decision. To discuss a pressure vessel inspection, request a quote or call our team.