The Humble Check Valve

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The selection of check valves for puped systems

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  • Geoff can be contacted at geoffrey.stone@yahoo.co.uk or 0402 35 2313
  • This book comes highly recommended for further study of check valve performance in a pumped system. The publisher is Wiley.
  • These graphs show typical losses for various types of check valves. Reference should be made to the valve manufacturers for more precise data however these data can be used for preliminary designs. This is often necessary as the valve supplier has not been selected when the design is underway.These graphs have been taken from Fluid Transients in Pipeline Systems By ARD Thorley published by Wiley
  • Waterhammer software is readily available from a number of sources. The more common products in Australia are Hytran, AFT’s Impulse, Bentley’s Hammer, Watham and Flowmaster.
  • Delft laboratories undertake dynamic testing of check valves. A search of their website will reveal a selection of technical research papers that provide insight into the dynamic performance of check valves.
  • This graph has been taken from Fluid Transients in Pipeline Systems By ARD Thorley published by Wiley. It illustrates the different values of maximum reverse velocity versus deceleration for common check valves. These values represent actual results of a valve of a particular size. To compare the systems and their check valves dimensionless characteristics are used.
  • This graph shows typical non dimensional maximum reverse velocity versus deceleration for various types of check valves. Reference should be made to the valve manufacturers for more precise data however these data can be used for preliminary designs. This is often necessary as the valve supplier has not been selected when the design is underway.The graphs illustrate the benefits of using the nozzle type check valves where the system exhibits high deceleration.This graph has been taken from Fluid Transients in Pipeline Systems By ARD Thorley published by Wiley
  • These graphs have been taken from Fluid Transients in Pipeline Systems By ARD Thorley published by Wiley. The graphs illustrate the transient response for the same system when different check valves are used. Each system is different and should be independently analysed for transient response.
  • Illustrations from Crane Energy Flow Solutions - High Performance Check Valves
  • Swing check valves come ina variety of forms to meet temperature and pressure conditions. This illustration is one used in the petro-chem industry
  • The valve illustrated here is commonly used in the water industry for transmission pipelines. It is a legacy design that is challenged these days by non slam varieties.
  • The valve illustrated here is commonly used in the water industry for transmission pipelines. It is a legacy design that is challenged these days by non slam varieties.
  • A low cost valve that is commonly used in all industries from nuclear through process to building services. It is manufactured by many companies. Some are better than others in providing technical information required for dynamic analysis.
  • These valves provide a solution for potential surge situations where the fluid contains solids such as in sewage and slurries. For corrosive situations the inserted probes and overrides are usually not specified. Also these valves are available with rubber or epoxy lining. They have found a market in the highly corrosive desalination pipe work market where sea water is highly corrosive..
  • This valve type of valve is manufactured by Mokveld, Noreva, Crane and Ventomat. The valve is the premium valve as far as check valves are concerned. It has the low head loss and very good quick closing characteristics.
  • The hydraulic check valve opens and closes at controlled, adjustable speeds to provide for smoothoperation and reduce pressure surges associated with conventional check valves.When the upstream (inlet) pressure is greater than the downstream (outlet)pressure, the valve moves to the open position at a controlled speed by exhaustingcontrol water from above the diaphragm to the downstream side through an adjustable needlevalve.When the upstream pressure becomes less than the downstream pressure, the valve closes toprevent reverse flow at a controlled speed by introducing control water above the diaphragmfrom the downstream side through a second needle valve.
  • The hydraulic check valve opens and closes at controlled, adjustable speeds to provide for smoothoperation and reduce pressure surges associated with conventional check valves.When the upstream (inlet) pressure is greater than the downstream (outlet)pressure, the valve moves to the open position at a controlled speed by exhaustingcontrol water from above the diaphragm to the downstream side through an adjustable needlevalve.When the upstream pressure becomes less than the downstream pressure, the valve closes toprevent reverse flow at a controlled speed by introducing control water above the diaphragmfrom the downstream side through a second needle valve.
  • A simple check valve used in the building services industry
  • A type of valve used primarily for solids bearing and tidal flow of low pressure corrosive fluids. Valves up to DN2000 are manufactured by red valve. The valves are manufactured by mainly by hand lay up techniques. Head losses is quite high. The valve needs to be orientated as shown in the vertical in order to close on rising head in free service applications. The valve will close around sticks and twigs.
  • This type of valve provides a loss cost unit suitable for large diameters. The design allows for construction in corrosion resistant materials.
  • Where would we be without these check valves? With modern materials there have been several attempts to introduce the design into industrial applications. The closest clone is the duckbill check valve.
  • Although mainly concerned with pumps ANSI/HI 9.8 standard can be used for pipe lengths design to avoid the effects of vortexing on check valve internals.
  • The Humble Check Valve

    1. 1. THE HUMBLE CHECK VALVE<br />Selection of Check Valves for Pumped Systems<br />By Geoffrey D Stone C.Eng FIMechE; CP Eng FIEAust RPEQ<br />Design Detail & Development<br />http://waterhammer.hopout.com.au/                 Skype address geoffrey.stone@yahoo.co.uk<br />
    2. 2. Why do we need check valves?<br />To prevent reverse flow<br />To stop a pipe or tank emptying when a pump stops<br />To prevent pressure transients damaging the pump<br />To prevent parallel pumps rotating in reverse<br />To prevent contamination in complex networks or in the home<br />To hold pressure in the line<br />For positive displacement pump operation<br />To provide waterhammer mitigation<br />To prevent flooding<br />
    3. 3. Avoiding Check Valve Slam<br />“ Check valves are sometimes selected without proper thought to their response under transient flow conditions.” <br />“In reality , check valve slam is caused by valves that are not matched to the system of which they are an integral part.”<br />Fluid Transients in Pipeline Systems Prof. ARD Thorley<br />
    4. 4. A Check Valve’s Selection and Performance<br />Most check valves are selected based on industry practice & lowest cost<br /> A low level of engineering effort is made in selecting a check valve<br />Unless a surge analysis is done little is known of the behaviour of a check valve in a pumped system<br />A check valve can be as important as a safety relief valve if it mitigates surge<br />Many manufacturers cannot provide technical data such as:-<br />Head loss vs. flow<br />Reverse velocity vs. deceleration<br />Closing time<br />Velocity to close<br />Pressure to fully re-open after closure<br />
    5. 5. Loss Coefficients for Different ValvesA common way of selecting a valve<br />
    6. 6. Systems Most at Risk of Check Valve Slam<br />Parallel pump systems<br />A pump trip in a rising main protected by an air vessel<br />Systems with an initial vertical lift followed by a long horizontal pipeline<br />Networks with varying conditions<br />High head systems<br />Systems fitted with check valves with long travel distance and a high mass of component parts<br />Systems that have not had a dynamic analysis. (Murphy’s Law)<br />NB A resilient seated valve can make as much noise in check valve slam as a metal seated one!<br />
    7. 7. Why avoid check valve slam?<br />Reduce damage to seats, discs and springs<br />Eliminate vibration in adjacent piping<br />Reduce damage to pipe supports and trust blocks<br />Eliminate noise<br />Reduce fear amongst operators and asset owners<br />
    8. 8. How should we select a check valve?<br />Undertake system dynamic modelling to determine:<br />Reverse velocity<br />Fluid deceleration on pump stop<br />Establish the acceptable head rise based upon the pipe rating, design code and/or thrust block design criteria. <br />Determine the maximum allowable reverse velocity using the Joukowsky equation below <br />H = c x ∆V<br /> g<br />where c =celerity m/s; ∆V =change in velocity m/s & g = acceleration due to gravity m/s2<br />Establish which valves have data available<br />
    9. 9. Delft Laboratories Studies<br />Studies at Delft Labs concluded that valve geometry affected the magnitude of pressure surges and reverse velocities. <br />The conclusions were:-<br />Reverse velocities and pressure surges are greater for valves with a larger mass of valve components.<br />(2) Reverse velocities are greater for valves with larger strokes or travel of components to close.<br />(3) Reverse velocities are less for valves that were spring assisted to close.<br />These conclusions are justified because of the increased time necessary to accelerate and overcome the inertia of valve internals and the distance they must travel.<br />
    10. 10. Compare Maximum Reverse Velocity & Deceleration for Different Valves<br />Draw a line from the left of the graph of the computed maximum reverse velocity from the acceptable head rise<br />Draw a line up from the computed deceleration<br />Select any valve who’s plot falls below the intersection of these two lines. <br />A reverse velocity of 0.15 to 0.3m/s will unlikely result in check valve slam<br />
    11. 11. Using Dimensionless CriteriaThis is used when data is only available for one size of valve from the manufacturer and another is used in the design<br />MRV = Dimensionless maximum reverse velocity<br />Decln= Dimensionless deceleration<br />
    12. 12. Dimensionless Criteria for Different Valves<br />
    13. 13. Comparison Swing vs. Nozzle Check Valve<br />Swing Check Valve<br />Nozzle Check Valve<br />
    14. 14. Types of Check Valves<br />Swing<br />Tilt<br />Dual Plate<br />Flexible Flap<br />Nozzle (Disc)<br />Nozzle (Ring)<br />Diaphragm<br />Hydraulic<br />Ball<br />Piston<br />Lift<br />Duckbill<br />Wafer Plate<br />Heart Type<br />
    15. 15. Different Principles of Operation<br />Swing Check<br />Duo Check<br />
    16. 16. Swing Check<br />Economic<br />Corrosion resistant materials or or coated for same<br />The most common type<br />Metal or Soft Seated<br />Full Bodied or Wafer<br />Gravity or Spring<br />Hinged flap<br />Extended Spindle for:-<br /> Counterweight<br />Hydraulic dampener<br />Limit switches<br />Position indicator<br />
    17. 17. Swing Check (Counterweight)<br />Complicated swing check<br />Fitted with Counterweight <br />Fitted with pneumatic or hydraulic dampener<br />High maintenance to remain effective<br />High mass & inertia<br />Long travel distance to close<br />Counterweights increase head loss<br />High cost<br />
    18. 18. Tilt Type<br />Common in the water industry<br />Large Diameter<br />Full bodied type<br />Soft or metal seats<br />Coated for corrosion resistance<br />High mass<br />Extended spindle for :-<br />Counterweight<br />Hydraulic dampener<br />Limit switches<br />Position indicator<br />
    19. 19. Dual Plate<br />Economic<br />Wafer bodied<br />Variety of spring stiffness's<br />Corrosion resistant materials<br />
    20. 20. Flexible Flap<br />Economic<br />Use in water, sewage & mining industries<br />Coatings for corrosion resistance<br />Full bodied type<br />
    21. 21. Nozzle (Disc)<br />Universal application for clean fluids<br />Original design of non slam valve<br />Low head loss<br />Used for gas and liquids<br />
    22. 22. Nozzle (Ring)<br />Universal application for clean fluids<br />Modern design for surge mitigation<br />Low mass <br />Short travel<br />Tight shut off<br />Low head loss<br />Available in corrosion resistant materials<br />
    23. 23. Diaphragm Type<br />Solids bearing fluids<br />Positive displacement pump operations<br />Corrosion resistant materials<br />Limited life<br />
    24. 24. Hydraulic<br />Economic<br />Used in the water and aviation industry<br />Combination valve with functions such as:-<br />Flow control<br />Altitude control<br />Pressure Control<br />Surge anticipation<br />
    25. 25. Ball Type<br />Economic<br />Simple construction<br />Balls easily damaged<br />
    26. 26. Piston Type<br />Use in steam and petro-chem service<br />
    27. 27. Lift Type<br />Simple <br />Generally small bore<br />Gravity or spring operation<br />Used in steam or water systems<br />
    28. 28. Duckbill Type<br />Used for solids bearing fluids<br />Large diameters<br />Corrosion resistant materials<br />In line or connected to end of pipe<br />High head loss<br />Closes against solids<br />
    29. 29. Wafer Plate Type<br />Economic<br />Large diameter<br />High head loss<br />Low pressure applications<br />Corrosion resistant materials<br />
    30. 30. Heart Valve<br />We all have them<br />Considered the most important of check valves<br />Artificial heart valves developed in Australia<br />These check valves allow the positive displacement heart pump to function with pressure transients<br />Maintains pressure in the system<br />
    31. 31. Installation Criteria<br /><ul><li>Pipe Fittings
    32. 32. Two Elbows
    33. 33. Pumps</li></li></ul><li>Instability at Pipe Fitttings<br />
    34. 34. Instability Near Elbows<br />
    35. 35. Instability at Pump Discharge<br />
    36. 36. Questions<br />Is data available from check valve suppliers?<br />Yes & No, The more technically proficient have undertaken tests<br />Can I assume that there will not be check valve slam?<br />If the system is very similar to an existing system this is possible.<br />
    37. 37. The End<br />Thanks are extended to Prof ARD Thorley for his very informative book Fluid Transients in Pipeline Systems for the valuable graphs & insights in dynamic behaviour of check valves.<br />Also I would like to thank those check valve suppliers who publish data on the internet or provide such to engineers. <br />These include but are not limited to:-<br />Noreva, Mokveld, Tyco, Crane, Red Valve, AVK, Apco, Valmatic, Cla-Val & Valmatic <br />

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