Based on the past experience on detailed examination of cracks and other damages observed in storage tanks and pressure vessels, the following points in regard to inspection techniques must be considered. 1. Use improved techniques to detect sub-surface flaws, dimensions, locations, depth and number of cracks. 2. Improved technique should be able to : (а) […]

Govt. bodies and jurisdictional agencies get involved in FFS and RLA if the welded structure concerned is critical and its failure may cause hazard to life and heath of the people living around. The trend is towards their increased interest in performance-inspection frequency, acceptance standards, repair procedures, and record keeping. In some countries it is […]

12.1 INTRODUCTION 1. All welded structures are expected to have an estimated service life. The actual service life may be more or less than the estimated period. 2. To ensure safe service and avoid unexpected failure, it is customary to inspect the welded components/structures at regular intervals. 3. Welded structures suffer from defects/discontinuities leading to […]

Most pipeline welding involves girth welding from external side only, because the diameters are too small to permit welding from the inside. The commonly used joint design is shown in Fig. 11.9. It is well suited for the stovepipe technique described below. In special cases, the angle of bevel is increased from 30° to 37.5°. […]

This section deals with cross-country transmission pipelines which conduct natural gas or liquid products such as crude oil. Pipes of reasonably long lengths are produced in a tube mill. They are either seamless or electric-resistance welded, or submerged-arc welded. Laying of pipelines involves only circumferential welding in the field. Seamless pipes are made from solid […]

A company in the Netherlands fabricates exacting offshore pipework using several automatic TIG and MIG welding installations, each having a turntable with two sets of adjustable roller beds. For 100 mm diameter pipes, manual TIG is used for the root pass and automatic TIG with wire feed for filling and capping passes. For 300 mm […]

Preheating, concurrent heating and postweld heating are important steps in the welding of pipings; and their successful performance in service often depends upon correct heat treat­ment. The heat treatment procedure includes consideration of the maximum temperature to be attained, time at maximum temperature, rates of heating and cooling, and the width of the heating band. […]

Backing rings are commonly employed for welding carbon steel and low-alloy steel piping by the MMA process in steam power plants and other applications. While split rings are some­times used for non-critical applications, solid flat or taper-machined backing rings are pre­ferred for critical applications. Some designs of backing rings and the manner in which they […]

As stated earlier, the usual joint to be welded in pipings is the circumferential butt joint. To weld such a joint by the MMA process, the pipe edge can be square or slightly chamfered when the wall thickness is below 5 mm for carbon steel, and below 3.2 mm for stainless steel. Thick­nesses greater than […]

In the industrial world, the term piping is usually understood to cover pipe; tubing; fittings such as tees, elbows, flanges and reducers; valves and hearders used in oil refineries, power stations, nuclear plants, chemical and petrochemical plants and other industrial plants. The term pipelines usually applies to long transmission pipelines designed to conduct liquids such […]