Welding of pipelines

American Petroleum Institute. Welding of Pipelines and Related Facilities, 19th API Standard 1104 American Petroleum Institute Washington, DC, 1999. 

Weld failure is the most severe problem in offshore and refinery pipelines. Figure 9.7 shows a random leak in the weld of pipelines. This problem is more concerned with the proper welding, followed by a quality check and postcoating over that. 

OK Pipeweld electrodes have always been a safe and productive solution in the welding of pipelines. 

This can be avoided by using basic electrodes developed specially for welding of pipelines in the vertical-down position. These electrodes contain iron powder in the coating and therefore have higher productivity than cellulose electrodes since they also can be welded at higher currents than cellulose electrodes. 

In the field of radiation methods of control, development work was performed in order to create the X-ray detectors with a low content of silver. X-ray TV systems with improved performance for automatic interpretation of the X-ray TV images, portable radiometers and dosimeters, creation of portable equipment for radioscopy of the welded joints of pipelines, etc. 

Slides Covering pipelines with polymeric films cathodic protection of pipelines, ships, etc.. With zinc bracelets use of inert polymers in chemical plant galvanic corrosion in architecture (e.g. A1 window frames held with Cu bolts) weld decay. 

Distribution networks in towns have been built over periods of deeades with various phases of pipeline teehnology. Networks ean eonsist of welded steel pipes, steel pipes with lead soekets, different types of east iron and plastie pipes. 

In pipelining, the trend is towards all-welded steel for long lines, and since the wall thickness is less than that of cast iron, protection is the more important. Many types of coating are used, from thick concrete to thin paint films, and each has its own particular suitability, but the majority of pipelines throughout the world today are coated with hot-applied coal tar or petroleum asphalt-base-filled pipeline enamels, into which reinforcing wraps, such as glass fibre are applied. 

In the case of long continuously-welded steel pipelines the above pipecoating methods present the disadvantage that the joints have to be coated in the field after welding. To overcome this difficulty equipment which travels along the welded pipeline has been developed. 

Line Wrapping the technique of wrapping a pipeline over the pipeline trench applied only to welded steel pipelines. It is carried out by a linewrapping machine which travels along the pipe, cleaning it, priming it. 

From the preceding discussion, it is seen that characterization of hydrogen uptake and embrittlement of pipeline steels in high hydrogen pressure environment is at its initial stage. In particular, there is little data on weld and heat-affected zone. Much more work needs to be done in the forthcoming years. 

Precautionary Considerations Alternative Rules for Evaluating Stress Range Recommended Practices for Proof Testing of Pipelines in Place Estimating Strain in Dents Sample Calculations for Branch Reinforcement in Piping Welded Branch Connections and Extruded Headers in Pipeline Systems... 

Pipeline systems shall be tested after construction to the requirements of this Code except for pretested fabricated assemblies, pretested tie-in sections, and tie-in connections. The circumferential welds of welded tie-in connections not pressure tested after construction shall be examined by radiographic, ultrasonic, or other nondestructive methods in accordance with para. PL-3.19.2. 

Used to test integrity of pipeline welds, boilers, and aircraft... 

The most frequent application of gamma radiography is checking the welds in pipelines. This is done most conveniently by putting the source inside the centre of the pipe and attaching the film to the outside of the weld. For checking long pipelines, sophisticated, self-propelled crawlers which travel in the pipe are used. These devices can be positioned exactly at the desired position from the outside. At a command the exposure is made. Then the crawler is instructed to move on to the next weld. Practically all new gas- or oil-pipeline systems are checked with this type of equipment. 

NACE Technical Committee, Task Group T-lF-23, Stress corrosion cracking resistance of pipeline welds a special report on sulfide stress cracking resistance of pipeline welds. Mater. Perform. 32 (1993) 58-64. 

G. A. Zhang, Y.F. Cheng, Micro-electrochemical characterization of corrosion of welded X70 pipeline steel in near-neutral pH solution, Corros. Sci. 51 (2009) 1714—1724. 

Repair of pipelines. Problems emerging diuing pipeline operation include failure of rust-preventing coatings on the internal and external parts of a pipe, decrease in pipe strength due to corrosion failure, appearance of flute cracks in the pipe body, and diffusion of gas through leaks in welds. 

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