3 Important Types of Pipe Joining Methods
Pipework is extensively used
throughout an offshore installation to move fluids and gases from one location
to another. Usually large diameter pipelines as used to carry the production
products from installation to installation or from the field to the onshore
terminal.
Pumps and compressors are used to drive fluids and gases along pipes and valves
to route and control the various substances and ensure that they are correctly
segregated from each other. The contents of the pipework are carried at widely
varying temperatures, pressures and flow rates and, therefore, different types
of pipework and associated equipment are required.
There are three common methods of joining piping, each with its own advantages and disadvantages.
·
Butt Welded Piping Systems
·
Screwed Piping Systems.
·
Socket-Welded Piping Systems
Butt Welded Piping Systems are used for most process, utility or
service piping. Butt welding is the most practicable way of obtaining strong,
leak-proof joints; especially on larger piping. The pipe and fitting used have,
or are prepared with, standard weld preparation. They require high levels of
workmanship in their assembly and welding.
Screwed Piping
Systems are used for small lines, usually of 50 mm
diameter and are easily assembled using standard fittings. The removal of metal
to create the thread is a disadvantage and fatigue strength is poor. There is
no need for coded welders when a screwed pipe system is used except where seal
welding is undertaken.
Socket-Welded
Piping Systems: are used for lines of small diameter which carry flammable,
toxic or expensive materials where no leakage is permitted. They are easier to
assemble and weld than butt welds and no weld metal can enter the bore. The
pipe end is finished square and fitted into the fittings, usually with a 1.5 mm
gap. This gap sometimes pockets liquids and is not recommended if severe
erosion of crevice corrosion is anticipated.
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