All pipeline systems are susceptible to water hammer that can cripple critical infrastructure. One effective method to relieve excessive waterhammer pressures in pipelines is to use air chambers....
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water hammer
All pipeline systems are susceptible to water hammer that can cripple critical infrastructure. One effective method to relieve excessive waterhammer pressures in pipelines is to use air chambers....
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Water Hammer Surge Dr. Lay Tiong LIM Total Indonesia (Balik Papan) – 9th to 12th May 2011
Water Hammer • Water hammer is a pressure surge due to forcing a fluid (normally liquid) to stop or change direction suddenly such due to closing an ESD valve • Other causes of water hammer are pump trip/failure, check valve slam etc • Build up of high pressure and result in shock wave • Also, the water downstream of the valve will attempt to continue flowing, creating a vacuum that may cause the pipe to collapse . • In general, pressure surges results in noise, pipeline vibration, damages to plant's equipment such as valves, pumps and pipe
Mitigation Method • • • • • • •
Reduce flow Higher pipeline design pressure Reduce valve closing time Change operating procedure Shorter pipe length Pumping station bypass Liquid surge relief valve, surge drum, air vessel, non return valve and specialized surge arrestors onshore • Air and vacuum relief valves can be installed close to the valve
Joukowsky equation • For a valve closing instantaneously • ∆Hmax = ∆v. a. / g where – – – –
(a)
H - head in meters a – wave speed g - acceleration of gravity ∆v - change in velocity
• In terms of the pressure, this equation becomes: – ∆Pmax = ∆v.a.ρ (b) – where ∆P is the change in pressure and ρ is the fluid density
• For longer closing times, effects such as packing of pipeline before the valve is fully closed may give rise to an additional increase
Accounting for pipe wall elasticity • Pipe wall elasticity reduces the magnitude of the pressure surge and causes more rapid decay. • a = (K/l )1/2 / (1+D/e.K/E)1/2
K = l / (dl / dp) Bulk modulus
Pipe wall elasticity correction: D = inner diameter e = wall thickness E = modulus of elasticity
Olga Model-Tips • Boundary Condition – pressure boundary should be used at the inlet of the pipeline
• Elastic Wall Option – OLGA 6.3 and onwards allows for elastic pipe wall materials –
