The inspection interval comes from the operating country, not from the code – why ASME parts have no shorter interval

Rule of thumb

Whether a plant is built to EN or ASME says nothing about how often it is inspected – that is said by the operating law of the country it stands in.

Where does the rule come from?

In the trade the assumption “EN plants every two years, ASME annually” – or the reverse – persists. It is wrong because it confuses two things: the construction code to which a component was designed and made, and the operating law that regulates in-service inspection. EN 13445 and ASME VIII Division 1 say how a vessel is built; when it is inspected is in neither. The rule was confirmed on 1 October 2026 after our own research and released as a rule of thumb.

What is technically correct?

In Germany the Betriebssicherheitsverordnung (Annex 2 Section 4) sets maximum intervals for pressure systems – external, internal and strength test – and the operator fixes the interval in the risk assessment within these maxima; the approved inspection body may shorten it (TRBS 1201 Part 2). To which code the component was made plays no role. In the USA API 510 (vessels) and API 570 (piping) together with the jurisdiction of the state regulate in-service inspection – again operating law, not construction code. The inspection concept follows the risk (medium, pressure, corrosion), not the standards world.

Where does the rule end?

• Operator company standards may demand shorter intervals or their own inspection programmes – they take precedence but are contract, not code.
• At the initial inspection before commissioning the origin of the component may matter (proof of conformity, material appraisal) – that is placing on the market, not in-service inspection.
• Other countries have other operating laws (Switzerland, Austria, France with their own regulations) – the rule says where the interval comes from, not how long it is.
• This rule replaces no legal information; the legal text is binding.

What does the standard say?

The construction standards are silent: EN 13445, EN 13480 and ASME VIII/B31 regulate design, manufacture and acceptance, not operation. The Pressure Equipment Directive 2014/68/EU ends with placing on the market. The Betriebssicherheitsverordnung names maximum intervals and the procedure for fixing them; TRBS 1201 Part 2 details the inspection of pressure systems. API 510 and API 570 describe inspection intervals as operator inspection practice in the USA.

DIN/EN versus ASME/ASTM

Both worlds separate construction and operation alike: in Europe in-service inspection belongs to national operating law under the operator’s risk assessment, in the USA to API standards and the jurisdiction. A component to ASME in a German plant is inspected under the Betriebssicherheitsverordnung; a component to EN in a plant in Texas under API 570 and state law. The standards world of the component is just one line in the inspector’s documentation.

Worked example

A customer asks whether an extension with ASME flanges and ASTM materials means “more frequent visits from the inspection body”. No: the inspection interval of his plant is in his risk assessment and follows the maximum intervals of the Betriebssicherheitsverordnung; the extension changes nothing. What he needs is the material evidence for the ASTM parts at placing on the market – material appraisal under the Pressure Equipment Directive – not a shorter interval.

Zickwolff reference

No company lore for this rule.

Checked today

Verdict: applies (class A). The responsibility (operating law instead of construction code) is unambiguous; the rule deliberately names no intervals.

Further reading

• EN and ASME compared: eight axes on which the standards worlds differ – EN and ASME in eight axes – inspection intervals as a question
• Standards worlds by region: where EN applies, where ASME, where both – and how we know – which country demands which world
• How binding standards are: contract, law, recognised rules of engineering – contract, law, rules of engineering
• ASME and ASTM standards in piping: the 13 standards we supply to – ASME and ASTM profiles
• Materials between the worlds: material number to UNS and ASTM grade – and the limits of comparison – ASTM materials under the Pressure Equipment Directive