A major UK water utility site was suffering significant problems with pumps repeatedly failing causing significant damage, pressure surges and slam.
The site had installed 4 x 400mm (16”) typical weight and lever style, PN 16 flanged swing check valve. The weight & lever swing check valves were mounted immediately after pumps before a 10-12m rising main. The carbon steel pipework then follows a local river before crossing it with a 200m stretch in uPVC.
The pumps that were installed were failing regularly, were expensive to repair and inefficient compared to modern day pumps. One of the pumps, complete with fly wheel, designed to provide stored energy to assist in reducing media velocities during a power outage, was replaced due to failure. The replacement pump was a typical variable speed drive Pump (VSD pump), without flywheel.
Soon after installation, storm conditions and an electrical failure caused the pump to stop causing a surge – this resulted in significant slam, surge pressures and damage.
How did MGA Controls solve the problem?
A transient analysis was implemented in order to specify the valve type required for the application.
The following data was identified by the transient analysis:
- Recommendation: ‘rapid acting spring assisted type check valves are required on all pumps.
- Flow decay: 2.45 m/s in 0.21 s
- Flow Deceleration: 11.60 m/s*2 (38 fps*2) (based on 400mm id ductile iron pipework)*
Using this data, MGA Controls were able to perform the following calculations for the Val-Matic Surgebuster Check Valve.
- Flow Deceleration at 38 fps*2 Ξ Reverse Velocity of 0.6 fps (slightly into ‘mild slam’)
- Time to closure: 0.6 fps / 38 fps*2 + 0.21s = 0.23 s
- Pressure Surge: 0.6 fps x 50psi = 30 psi = 2.1 Bar + line pressure of approx. 2Bar. (Calculations based on an approximated speed of pressure wave for steel and the Joukowski equation)
*The results of the Transient Analysis carried out at this site are confidential, however to see a hypothetical example of check valve slam predictions, click here.
As a result of the calculations the Val-Matic Surgebuster check valve was installed to prevent surge pressures from damaging the pumps and provide long term reliable performance.
Why was the Surgebuster swing check valve the optimum solution to the site’s problems?
The unique design of resilient hinge and disc accelerator of the Surgebuster swing check valve allows the valve to respond quickly enough to prevent reverse velocities from reaching damaging levels.
The lack of hinges with any wearing parts and non-stick fusion bonded epoxy coating prevents snagging and offers a virtually maintenance free proven performance with a 25 year warranty on the only moving part.
Since the valves were installed they have performed without fault, giving silent closure and effectively preventing slam and pressure surges.
If you have a similar application, and would like to talk to our engineers, please call our technical team on +44 870 803 2001. Alternatively, email us at firstname.lastname@example.org.