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Recognised Third Party Organisation (RTPO)

TWI Certification Ltd (TWI CL) is a Recognised Third Party Organisation (RTPO) for the approval of operators, procedures and NDT inspectors for permanent joints in accordance with the Pressure Equipment (Safety) Regulation 2016 (PESR). CSWIP certification enables welders, brazers and NDT inspectors to comply with the PESR.

The PESR applies to the design, manufacture and conformity assessment of pressure equipment with a maximum allowable pressure greater than 0.5 bar (

As the RTPO, TWI Certification Ltd carries overall responsibility for ensuring that the requirements for competence of permanent joining personnel are satisfied and that appropriate approval documentation is issued on the basis of successful evaluation.

Prior to the UK’s withdrawal from the EU, TWI CL was an RTPO for the EU Pressure Equipment Directive (2014/68/EU) (PED), which enabled TWI CL to offer CSWIP certification in compliance with the EU PED, since the withdrawal, this is no longer possible. However, TWI CL has entered into multiple mutual recognition agreements with EU RTPOs to provide certification in compliance with the EU PED. Relevant certificate holders who wish to gain certification in compliance with the EU PED should contact TWI CL for details.

Full details of routes to approval can be found within the Scheme documents below.

Qualification of Welding and Brazing Procedures

CSWIP-PER-1-99-WP, 1st Edition, May 2022 

Qualification of Welders Welding Operators and Brazers

CSWIP-PER-1-99-W, 1st Edition, May 2022

NDT Personnel

CSWIP-PER-2-01, 1st Edition, May 2022

It is the manufacturer’s responsibility to choose the appropriate route and to ensure that the recognition and acceptance of approval documentation is appropriate to their requirements. Whilst TWI Certification Ltd makes every effort to ensure that its approval documentation carries appropriate accreditation, and that evaluation and certification activities are carried out in accordance with best practice, it cannot guarantee acceptance by any particular customer or client.

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