Gas pipeline construction in Bangladesh

Bangladesh is a small country with plenty of natural resources. Among them, the main is natural gas. Approximately 1800 to 2000 million cubic feet of natural gas are produced in a day from all the gas fields in Bangladesh. Gas produced in the gas fields are carried through gas pipelines to the doors of customers.
The gas pipelines are classified into some categories. Transmission pipelines carries natural gas from the gas fields to the City Gate Stations (CGS). Gas pressures in these pipelines are maximum 1000 psig (pounds per square inch gauge). Fittings those are used in these pipelines are typically ANSI class 600. Then there are pipelines which carries gas from CGS to TBS (Town Bordering Station). Gas pressures in these pipelines are maximum 300 psig and fittings used in these pipelines are of 300 ANSI Class. Then gas carried from TBS to District Regulating Station (DRS) or RMS (Regulating and Metering Stations) by distribution main pipeline which has maximum pressure of 150 psig and fittings are used of ANSI 150 Class. Pipeline construction procedures of different category pipelines are also different.
Bangladesh gas pipelines are constructed with API 5L grade A/B seamless pipes. For high pressure (above 150 psig) use schedule 80 pipes are used and for low pressure use schedule 40 pipes are used. Pipelines are connected by means of welding. For various type of pipeline the welding procedures are different. For pipelines of gas pressure higher than 150 psig the pipeline is protected by right of way. Right of way is the acquisition of the land on which the pipeline is laid. The protection of the gas pipelines are done by Gas Safety Rules, 1991. The pipeline construction procedure is almost same for all kind of pipelines.
For low pressure pipelines first, a trench is cut to lay the pipeline. Then outer surface of the pipe to be laid is cleaned and then coated with epoxy coating. After that, a special kind of tape is wrapped around the pipe to prevent contact of outside water or soil contacting with the steel pipes. Then the pipe is lowered to the trench and ends of two adjacent pipes are welded together by a certified welder. After welding works, Non Destructive Test such as X-ray is carried out to be certain of the welding quality. If any welding error is found, then the joint is cut and re-welded until all the welding joints are of acceptable quality. After welding the joint area are epoxy coated and wrapped with tape. If there is any river crossing in the path of the pipeline then HDD (Horizontal Directional Drilling) is carried out. In Bangladesh, all sorts of pipeline construction works are carried out as per American standard ASME B 31.8. The standard is strictly maintained to ensure the quality construction work.