The recommendations contained in this document were aimed specifically to improve the inspection of conventional pressurised equipment. However, the drafting committee considers that these measures can also apply to any application of manual ultrasonic inspection including fairground or railway components, offshore equipment, and conventional plant in nuclear installations.

H Bainbridge
Gas and Process Safety Technology Division
Health and Safety Executive

Introduction

It is widely recognised that NDT can be less effective than anticipated by those applying it or by those using the results to determine component integrity. This has been confirmed in a number of trials and most recently, for manual ultrasonic in-service inspection¹ , by the PANI project [Ref. 1]. Consequently, the Health and Safety Executive (HSE) has judged it appropriate to issue the recommendations of the PANI committee, which identify when problems can arise in the application of NDT and what solutions might be adopted. The measures contained in this document are recommended by the HSE for the conduct of manual ultrasonic inspection. They are intended to promote the adoption of good practice and apply to in-service inspection of existing plant or to repairs. The measures could also be applicable to the inspections carried out during the manufacture of new or replacement plant. They apply both to inspections carried out by the NDT department of the company owning or manufacturing the plant and to those carried out by external NDT organisations under contract. In the latter case, they are intended to assist in the procurement process by highlighting the issues that need attention.

This document has been drawn up by a committee of experts assembled by the HSE for this purpose. Their names and affiliations are given in Appendix 1, from which it will be apparent that they represent a very wide range of those parts of UK industry using the relevant NDT methods. In addition, they have considerable expertise in and responsibility for the application of NDT to industrial plant. The recommendations contained in this document are based on two main sources. The first is the recently completed PANI exercise mentioned above. This was an HSE-funded project involving the application of manual ultrasonic methods used for in-service inspection to test-pieces, containing defects, representing a range of typical industrial plant items. The inspections were carried out as they would be in practice and the results have great significance in assessing the performance to be expected of current methods as well as in identifying areas and means for improvement. These measures represent an immediate application of the results of the PANI project pending a more protracted investigation of the issues raised. The second basis for the recommendations is the collective experience and expertise of the committee mentioned earlier. Many of the members were also members of the PANI Management Committee.

Section 2 contains a review of the current way in which most manual ultrasonic inspections are designed and carried out and the way in which the quality of the inspection is assured. The inspection methods examined in the PANI project were developed using this approach. Section 3 continues with an analysis of potential problems together with a list of the measures which can be adopted in response. In doing this, it is recognised that the extent to which it is reasonable to include additional features in the inspection, and incur additional costs as a result, depends on the role of the inspection in assuring plant safety, the economics of the inspection activity and the consequences of the inspection failing to achieve its objectives. Accordingly, Section 4 contains recommendations on how the effectiveness required of the inspection can be assessed and on how this then affects the adoption of the additional inspection measures identified in Section 3.

Full-Text

¹ The term “inspection” is commonly used to mean both NDT and inspection in its wider sense. Throughout this document, it is used to mean NDT.

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