AUMA: Variable speed actuation and calm networks

A practical example at South West Water’s Network Training Centre

Published: 2nd September 2024 | Issue 95

South West Water serves over 1.8 million customers. It is committed to driving improvements in its performance and has collaborated with AUMA Actuators Limited on valve speed actuation and calm networks at its specialist Network Training Centre.

The work carried out between AUMA and South West Water focused on the effects on pipeline pressure transients by applying a simple variable speed actuation profile to the closing of a quarter turn valve.

Clive Dumbleton, Resource & Production team, South West Water explains: “South West Water is invested in ‘Calm Networks’ training, in tandem with our focus on pressure management and the basics of pressure control. The research we conducted with the team at AUMA aimed to determine the effects of variable speed actuation on pipeline pressure transients, and mitigate the risk of water hammer.”

Tests included firstly closing the valve at a constant speed and measuring the pressure transients upstream of the valve. This was the benchmark. A simple speed profile was then set in the variable speed actuator. First, drive full speed to 20% open, then at the slowest variable speed to closed. Next, drive full speed to 20% open, then at half speed to closed. Finally, drive full speed was set to 20% open, then at quarter speed to closed. The results of the four tests were recorded and the upstream pressure transient and the system flow rate for each of the profiles were compared for a conclusion to be reached.

Colin Borrows, Operations Manager, AUMA Actuators Limited: “With a constant speed actuator, an unwanted pressure spike over twice the system pressure was created. With a slow variable speed profile, the pressure transient was removed entirely, but the time taken to close the valve was more than double the fixed speed. The quarter speed variable setting provided the best compromise of speed of response against minimising transient pressure surges, reducing the ‘spike’ from over 100% of the system pressure to a much smaller 17% transient.”

This is a relatively simple test to demonstrate the effectiveness of a variable speed actuator in the mitigation of risk of ‘water hammer’. The actuator can be configured to a more sophisticated speed profile with multiple speed changes through the stroke if needed.

Colin Borrows concludes: “Having the flexibility of variable speed in the actuator, the system designer can introduce tolerance in the system both before and after installation making it perfect for new and retrofit applications.

Variable speed actuators help control aged assets in the field, minimising leaks, damaged valves, and expensive call-outs. This experiment clearly demonstrates the effectiveness of variable speed actuators in calm networks.