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Hydraulically activated pipeline pigging (HAPP) is a pigging technology applied for pipeline cleaning. The basic principle is that a pressure drop is created over a by-passable pig held back against a pipeline's fluid flow. The pipeline fluid passing through the pig's cleaning head is accelerated by this pressure drop, forming strong cleaning jets.
If the barrel is not completely depressurized, the pig can be ejected from the barrel and operators have been severely injured when standing in front of an open pig door. A pig was once accidentally shot out of the end of a pipeline without a proper pig receiver and went through the side of a house 150 metres (500 ft) away. [11]
The pig is designed to push all or most of the liquids contents of the pipeline to the outlet. This intentionally creates a liquid slug. Slugs formed by terrain slugging, hydrodynamic slugging or riser-based slugging are periodical in nature.
A trapdoor or hatch is a sliding or hinged door that is flush with the surface of a floor, ceiling, or roof. [1] It is traditionally small in size. [ 2 ] It was invented to facilitate the hoisting of grain up through mills, however, its list of uses has grown over time. [ 3 ]
October 15 – A natural gas pipeline under construction in Grand Prairie, Texas was running a cleaning pig without a pig "trap" at the end of the pipe. The 150 pound pig was expelled from the pipeline with enough force to fly 500 feet (150 m), and crash through the side of a house. No one was injured. [44]
A sewer pipe is normally at neutral air pressure compared to the surrounding atmosphere.When a column of waste water flows through a pipe, it compresses air ahead of it in the system, creating a positive pressure that must be released so it does not push back on the waste stream and downstream traps, slow drainage, and induce potential clogs.
Water enters at right, fills the trap, and continues left. Inverted siphoning occurs below the line "A". Examples of traps. In plumbing, a trap is a U-shaped portion of pipe designed to trap liquid or gas to prevent unwanted flow; most notably sewer gases from entering buildings while allowing waste materials to pass through. In oil refineries ...
Bursting discs, restriction orifices, strainers and filters, steam traps, moisture traps, sight-glasses, silencers, flares and vents, flame arrestors, vortex breakers, eductors; Process piping, sizes and identification, including: Pipe classes and piping line numbers; Flow directions; Interconnections references; Permanent start-up, flush and ...