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Safety Alert

​Application of radiography to measure the remaining wall thickness of external corrosion

Summary of issue

Tangential (profile) radiography is commonly used for in-service inspection of externally corroded components in the oil and gas industry. Recently it has become apparent that for some forms of localised corrosion, significant underestimates of severity can be obtained. In extreme cases, almost through-wall corrosion can be missed completely, unless the radiation source and film/detector are aligned optimally so that the tangent position is at the point of greatest wall loss. Even then, the measurements of minimum remaining wall thickness may be significantly higher than the actual value. The magnitude of this under-sizing however depends on the morphology of the corrosion, and more extended areas of corrosion can be less affected and hence may be more accurately sized.

Click here to download the full version of the Safety Notice Issue 6

Members Area

​To view information on the members area site you must both work for a HOIS member organisation and be registered with ESR Technology to obtain a username and password.

Contacts and how to join

The HOIS membership includes oil and gas multi-nationals, NDT service companies, equipment vendors and a regulatory authority.  Applications are always welcomed by prospective new members who share the HOIS vision of improving the effectiveness of in-service inspection for the oil and gas industry.

Annual membership runs from 1 April to 31 March. There are two distinct membership levels and associated current subscription fees:

  • Category 1 members (oil and gas producers and major asset managers) - £33k annually.
  • Category 2 members (NDT service providers, equipment vendors and notified/appointed bodies) - £11k annually.

New members are required to commit to a minimum of three years membership.

For full details of membership, or any other enquiries, please contact Steve Burch.

Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

Telephone: +44 (0)1235 213402


Confidential HOIS documents

Most HOIS reports and recommended practice (RPs) or guidance documents are confidential to HOIS members. For a complete list of current confidential HOIS RPs, click here.
Publicly available documents
A number of documents produced by HOIS are publicly available and not restricted to members.
Documents currently available are:
  • HOIS Guidance for UAV based external Remote Visual Inspection (RVI), 2018
  • HOIS Guidance on in-service inspection and integrity management of caissons, 2014
  • HOIS Recommended Practice for the In-Service Inspection of Wall Loss in Pipes by Digital Radiography, 2015
  • HOIS recommended practice on weld corrosion inspection, 2012
  • HOIS good practice for ISI of offshore composite components, 2012
  • Recommended practice for non-intrusive inspection DNV-RP-G103 (based on HOIS NII decision guidance project), 2011


To download these documents please complete the form below.

Note, your email address must be your company email address.


I'm interested in:
Guidance for UAV based external Remote Visual Inspection (RVI)
Caisson in-service inspection and integrity management
Computed Radiography Inspection
Weld Corrosion Inspection
Offshore Composite Components Inspection
Non-intrusive examination of pressure vessels
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HOIS Highlights

ESR Technology produces an annual highlights document which is freely downloadable and contains information on HOIS projects worked on in the most recently completed HOIS year (1 April – 31 March).

HOIS general presentation

This presentation contains information about HOIS which is unrestricted and freely downloadable.

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