Water Hammer Calculation

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What is the simplest way of calculating the maximum water hammer for an HDPE pipe?

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10 Answers

  1.  ​Calculating the ​maximum water ​hammer for an ​HDPE pipe water may differ from our Oil and Gas work, you may find the attached useful: 

  4. Caroline  the SDR value of the HDPE pipe will give you the nominal pressure rating of the pipe, Further the HDPE pipe as per AWWA C901 the allowable total pressure during recurring surge is 1.5 X times of the Nominal Pressure and occasional  Surge (Water Hammer) is 2 Times of  the Nominal Pressure. SAY SDR 9 Pipe of say nominal pressure rating of 100 psi then recurring surge would be 150 and occasional surge will be 200 psi. You need to check if your system generate more surge pressure as compared to the stated rated rating of Pipe. As Reuben defined the formula's will be used for calculating the surge pressure. 

  5. You may use bentleys hammer software. I previously applied this program and i got very good meaningful results. U should integrate other related  structures within your conveyance or etc system including your pipe. 

  6. This was a problem in the UK in the early 1970s and solved through research at WRc. Though calculations were carried out I recall them only being part of the solution as the problem was identified based on case histories and the solutions based on eliminating the risk factors. The main area of concern was where pumps shut down too quickly combined with using the lower grade of PVC which is not able to withstand negative pressure. Pipe failures tended to occur at points of stress in the pipeline especially where there were large solids in the trench backfill. As mentioned earlier, the main measure to reduce surge pressure is to ensure that pumps do not shut down suddenly and the installation of surge vessels. Since the advent of PE, which absorbs shock loading better than PVC it has become the preferred material for smaller diameters.

  8. I'd suggest you refer to "Fluid Mechanics for Civil Engineers" by Weber pp133 onwards to fully appreciate this. Basically you are arresting suddenly a column of water in a pipe. Many of the network modelling packages have facility to calculate water hammer but I'd suggest an understanding is essential rather than believing a number from a black box. I've seen field measurements using elaborate sensors and loggers and some truly alarming forces can be generated. The transient wave is followed immediately by an equal negative vacuum wave and this could be catastrophic for a PE pipe. Once you have a better understanding of the forces you may consider other materials or provide surge vessels  on the line to reduce the effect. Operationally you should ensure that valves are open and closed slowly and if pumps are present that they cannot fail suddenly. 

    Hope this helps. It's a good question and a topic that is often not given sufficient thought. 

  9. Try this: 

    T [N] = 2PAsinΔ/2

    Where: T - resulting force

    P - Hydrostatic pressure in the pipe

    A - Crossection of pipe

    Δ - Angle of bend in pipe

     

    This is the formula for the water hammer in pipe bends, for reductions or other such please contact me.

  10. Dear Caroline Cheptoo，

    Normally, the DN of PE pipe is equal and below DN300. No need water hammer calculation in design.

    And, as we known that PE pipe has flexible pipe material. The transient pressure will not damage PE pipe.

    BR,

    Wu Hao