Eliminate Water Slam in Water Applications with Innovative Swing Check Valves
Check Valves are commonly used in water applications. Water slam is a common problem associated with check valves in pumping systems. Water slam occurs after pump stoppage, when flow reverses back towards the pump before the check valve is fully closed. The closing of the valve results in a sudden stoppage in the column of water which causes a water hammer, which can cause serious damage to the whole pumping system. This action is associated with a large noise, which is due to the impact of the disc hitting the seat and the pipe stretching under the force of water hammer.
Water slam is extremely difficult to predict and therefore hard to prepare for. One solution is to use valves that are less likely to slam. In severe pumping applications nearly all basic check valves will slam, however in mild applications, hardly any check valves will slam. Between the two extremes is a vast and uncertain middle ground, this makes predicting check valve slam very difficult. The solution to the problem is not how to predict water slam, but perhaps how to prevent it!
Solutions for Preventing Water Slam
Check Valve's Closing Too Quickly
If the check valve closes extremely quickly slam can be prevented. The check valve closes before a large amount of reverse flow is built up. In order for the check valve to close quickly the disc should have low inertia and friction, motion of the disc should be assisted with springs and travel of the disc should be short.
Check Valve's Closing Too Slowly
Closing slowly prevents slam as the check valve closes once reverse flow has started and so water hammer is reduced. In order for the check valve to close slowly the check valve must have external devices, such as oil dashpots.
However, one problem with this method is oil dashpots significantly add to cost of a check valve, increase maintenance requirements and may cause valve clogging in wastewater applications.
Val-Matic's Solution to Water-Slam
The most popular and successful solution to this problem is the Surgebuster Check Valve, which utilised assisted spring technology to ensure rapid closure of the valve.
Val-Matic maintains matching the non-slam characteristics of the check valve to the pumping system is important. So before selecting a non-slam check valve, the pumping system must be analysed and the deceleration after stoppage for the liquid column must be calculated. Designers can make informed decisions using characteristics such as head loss, laying length, waterway design for fluids containing solids and cost etc.
There are advantages of using the Surgebuster Check Valves in your application such as reduced cost, low head loss and special flow characteristics. These benefits can be delivered due to the following design features of the check valves:
- Expanding bodies and smooth flow paths to ensure low head loss
- Closing characteristics which minimise slamming potential
- Valve discs which are stabilised under flow conditions to maximise performance and minimise wear
Read more about how the SurgeBuster check valve was used in a wastewater treatment plant in North Texas: SurgeBuster Check Valve In Wastewater Treatment Plant.
Val-Matic Valve and Manufacturing Corporation
Val-Matic Valve & Manufacturing Corp. is a leading designer, manufacturer and marketer of check valves, quarter turn shut-off valves, air valves and foot valves for water/wastewater, industrial and building markets.
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