Pressure Relief Valves/Surge relief Valve: Click here to know more about Surge relief valves. 
There are several passive protection equipment available in the market that operates without the need for additional power. 5: Passive Equipments for Surge Protection Extending the closure times attenuates pressure surge possibility.īe informed that these devices require power and during load shedding or power-failure cannot be of use.įig.
Slow closing and opening valves: A common form of pressure surge initiation is due to the rapid closing of a valve. Soft starters: The primary purpose of Soft starters are to reduce the electrical load on the power supply to a facility. Variable speed pumping: Variable speed drives provide a reliable means of prevention of damage from pressure surge events. Piping/Pipeline systems can be protected against Surge impact by using devices during pipeline normal operation like: Also, providing supports near concentrated mass will reduce high local stresses. Providing Additional Pipe supports: By adding more supports in the piping system, the natural frequency of the system in increased. Increase of pump inertia by incorporating a flywheel. Increase of the pipe diameter, thereby reducing the velocity. Changing of piping material, thus altering the wave speed. Rerouting of the pipeline avoiding high/low points. Use of pipework with a higher pressure rating i.e to make the pipework stronger to withstand the effects of surge pressure (Normally followed for radioactive, highly corrosive or lethal fluids, where no fluid is allowed to escape.). Protection of systems against water hammer can be parted into three groups: To avoid pressure surge system must be protected. Column separation can often result in surge pressures exceeding those predicted by the Joukowsky equation and therefore the Joukowsky equation should not be applied when analyzing system in which the pipeline pressure can rapidly drop below the fluid vapor pressure. 
Joukowsky equation does not consider column separation in its analysis of fluid hammer. System frictional losses are similar to that of a water transport system. Valve closure time is significantly shorter than the pressure wave communication time. there are no branches by which pressure waves can be reflected back and cause constructive interference in the main line. It’s application should be limited to situations matching the following criteria:. Joukowsky formula is applicable to a limited set of fluid systems. The acoustic wave speed formula depends on the fluid and the pipe characteristics expressed as: The most important parameters to estimate the magnitude of transient pressures is: This can be used as a rule of thumb at the initial assessment phases. In relation to Total Valve Closure Time, this is typically the last 15% opening for butterfly valves, 25% opening for ball valves and 30% opening for plug valves. Effective Valve closure Time: The period over which a Valve reduces the flow from 90% of its steady state to zero. Pressure Head:– Pressure measured as the height of fluid (10 m head of water is roughly 1 atmosphere). Pipeline Period:– Time required for a pressure wave to traverse the pipe/pipeline length and come back. Joukowsky equation:– Relationship relating head change to velocity change and acoustic velocity. 
Wave speed or acoustic velocity:– The velocity at which pressure waves travel through the liquid/fluid. Pressure Surge:– It is basically a pressure wave caused due to a sudden change in flow velocity. 2: Consequences of Pressure Surge Basic Definitions concerning Pressure Surge: Pressure Surge of Significant nature creates high pressure and velocity rise that can lead to:įig. 2 to understand what a pressure surge can cause to a Piping System. Surge pressure is created during the last 20% of valve closure. When a surge relief valve opens, it vents the pressure to a safety system. A pressure surge normally consists of multiple events, resulting in up to ten times the normal pipeline pressure. Pressure Surge (pressure rise) increases as the pipeline straight length increases since the contained momentum within two direction changes (elbows/Tee) will be higher (more volume). Some pipelines are in transient operations over 75% of the time. Pressure Surges can occur in open channels and partly liquid-filled pipes, as wellĪll of the above causes will generate high pressure waves that can travel both upstream and downstream from point of origin. Presence of Air pockets inside piping/ pipeline systems, especially during pump start. Quick operation of Valve (Sudden closure/opening). Pump start & stop, specifically due to load shedding or sudden power failure.
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