scope:

INTRODUCTION

When heavy-wall pipe field welds are radiographed, common practice is to route the radiation source through a hole in a pipe near a weld, and locate it on the centerline using a J-shaped tube. The Jshaped tube is then removed and a plug is screwed into the hole. The plug is then welded to the pipe around the plug's circumference. Initially, the stresses are carried by the plug's threads. However after prolonged service, stresses are increasingly carried by the circumferential plug welds. In addition to thread corrosion, creep stretches the hole in which the plug is located, possibly increasing stress on the circumferential plug weld. Creep failures of radiographic access port plugs have been observed.

Historically, Pipe Fabrication Institute standard ES-16 [1] offered guidance for the design of these plugs. An example of an ES-16 compliant plug geometry is shown in Figure 1. ES-16 plugs are solid, however some high temperature component manufacturers use bored out or thimble-shaped plugs with the intent of offering more compliance with creep.