Surge Analysis Forum

Can variable speed drives (VSDs) replace surge vessels on pumping systems?

There is a temptation to avoid the use of air vessels on pumping systems and a plethora of options that are proposed to avoid their use, from surge anticipation valves, through triple acting air valves to variable speed drives.  Maintaining poorly designed surge vessels can make life difficult for those responsible for ensuring they are compliant and working correctly. In view of financial pressures in the water industry,  poor decisions

Major burst in Finsbury Park

A modern drive to reduce network pressures can increase the risk of cavitation and so bursting. This event is yet to be investigated but it will be interesting to see if they identify pressure surge as a major contributor. Details of the lates burst news is available at https://peterglover.co.uk/pressure-surge-burst-investigations/ There are also some dramatic videos of major pipe bursts that are worth a look.

Imbalanced Air Vessels

The nature of copy and paste engineering is that fundamental design errors are reproduced many times. One fundamental error in banks of surge vessels is to forget to ensure multiple vessels are connected by inertially equivalent connections. This leads to an instability that undermines the vessel performance and can nullify the protection provided. This paper was published at the 11th International BHR Pressure Surge conference in Lisbon 2012 but sadly

Check Valve Slam

Check valve slam is a major contributor to pressure surges in pipeline systems and one which is poorly understood. The major damage caused by check valves is related to delayed closure of the check valve and not rapid closure as many would presume. Delayed closure will allow a reverse velocity to develop before the valve closes. When the valve closes on a moving column of fluid, it sets up a

Surge Anticipation Valve

The surge anticipation valve is a pilot operated plug valve. When there is a sudden drop in pressure (associated with a pump failure), the valve automatically opens rapidly, and then closes gradually.  The time for opening and closure is configurable by the designers.The philosophy of the valve’s operation is to ensure there is discharge to atmosphere when recoil pressures are at a maximum.In reality it has very limited potential application.

Cavitation

A particularly dramatic pressure surge effect is vapour cavity formation and collapse which occurs when pressures surges allow the fluid to reach vapour pressure. This causes “cold boiling” which creates vapour cavities through the fluid. When pressures recover, the collapse of these cavities is extremely rapid, and can cause very high localised pressures that can burst pipes, accelerate fatigue and damage linings. While many 1D software packages attempt to model this

Air Valves and Vacuum Breakers; a modelling nightmare

We published this paper at the 13 International Pressure Surge Conference (BHRGroup) in Dublin 2015. The findings are still significant and modellers ought to be aware of these issues. The BHR conferences are important for sharing this kind of knowledge.

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