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Reasons for Pigging ■ Removal of the natural build up of deposits on
the internal bore of the pipeline.
■ Removal of sediment on any low spots
■ To improve pipeline performance (reducing head loss, increasing hydro power output)
■ Need for pigging is massively dependant of pipe diameter/roughness/length in respect to flow –undersized pipelines need lots of pigging
■ Peat – watercourses with high peat contact –classic for building up on inside of pipe
Corrugation Effect
■ Corrugation effect from the build up of peat or other debris within the pipe.
■ Increased resistance.
■ Increases head loss, that would be greater then the loss due to pure reduction in diameter alone.
How to Pig
• Selection of the best suited pig for the penstock
• Soft Pig
• Hard Pig
• Inserting the pig into the penstock pipe via a pig trap; bell-mouth or opening with a greater diameter then the penstock.
• Appling pressure to the pig, via water
• Removal of the pig through a pigging valve or removable pressure vessel; located at the bottom of the penstock pipe
Checks
■ Bends in penstock are known and pig is sized appropriately.
■ Pipe diameter is know for the entire length of penstock.
� Pipe diameter varies with different pressurise ratings (check SDR number).
� Pipes of different materials have different ID.
� Pipe internal shape has not been misshaped external forces i.e. wrong material used when burying the pipe.
Pig insertion
■ Bar and straps
■ Pig launcher
■ Brute force
■ Working below ground – gas meter and certification
Scheme Design
■ Design parameters
– Allow the controlled realise of water, hence controlling the pig position.
– Sealable chamber for the pig that can be depressurised
– Safe and easy removal of the pig.