Many organisations still misunderstand the relationship between butt weld testing and fillet weld approval. This is particularly true when a welder undertakes an H L045 pipe qualification and a supplementary fillet test piece.
Let us deal with it properly and clearly.
BS EN ISO 9606 1 is explicit:
They are separate weld types. However, Clause 5.4 e introduces a controlled mechanism whereby a butt weld can qualify fillet welds. This is achieved through a supplementary fillet weld test piece via a structured qualification route.
Where a butt weld is used to qualify fillet welds, the welder must weld a supplementary fillet test piece that:
Once this supplementary test is completed successfully, the standard states, “The welder shall be qualified for all fillet welds as given for the butt weld qualification variables related to the range of qualification for fillet welds.”
This sentence is critical because it links the fillet weld approval directly to the butt weld qualification variables.
Consider a welder who completes:
The butt weld establishes the qualification variables:
Once the supplementary fillet requirement is satisfied, those same qualification variables apply to fillet welds. The supplementary PB fillet test is the gateway that unlocks fillet approval. It is not the limiting factor.
The supplementary fillet test must be performed in PB as that is a mandatory test condition. However, once Clause 5.4 e is satisfied, the range of approval for fillet welds follows the butt weld qualification variables and the applicable positional tables. In practical certification body interpretation across industry, the fillet weld positional range mirrors the positional range derived from the butt weld qualification.
For example:
An H L045 butt weld is regarded as an all position pipe test. With a compliant supplementary fillet test, fillet weld approval extends in accordance with the butt weld positional coverage. This is how certification bodies apply the clause in practice.
A pipe butt weld demonstrates:
What it does not directly demonstrate is:
The supplementary PB fillet test confirms that the welder can control these specific characteristics. Once that is demonstrated, the butt weld qualification variables govern the range.
The most common errors made by companies operating without deep familiarity with the standard are that they either assume butt welds automatically qualify fillet welds without a supplementary test, or they assume the supplementary PB test restricts fillet approval to PB only. Neither interpretation reflects how Clause 5.4 e is applied within accredited certification bodies. The correct interpretation is structured, conditional, and linked to qualification variables.
If your production includes both butt and fillet welds:
Under ISO 3834 environments, auditors will expect the link between Clause 5.4 e and the range of approval to be technically justified and documented. Failure to apply this correctly can invalidate welder approval in high consequence sectors such as rail, pressure equipment, and structural fabrication.
A welder who completes a butt weld qualification in H L045 and a compliant supplementary fillet weld test piece is qualified for fillet welds within the range of qualification established by the butt weld variables, in accordance with BS EN ISO 9606-1.
The supplementary fillet test activates fillet weld approval, while the butt weld determines the range. Understanding that distinction is critical to compliant certification.
Contact NECIT Services for expert welding inspection services for the UK engineering sector and ensure full safety and compliance within your welding processes.
