Water Corporation has 12 DN600 control valves in service in the metro region. Water Corporation has purchased these valves with non-standard stainless steel clamping plates in place of ductile iron components.
Seven have failed, so far with relatively minor consequences but there is the potential for high pressures to impact the reticulation network that may cause widespread damage. The likely root cause is a non-standard clamping plate specified for Water Corporation in Stainless Steel rather than standard ductile cast iron. A better understanding of the failure mechanism is needed in order to best manage the problem and avoid reoccurrences.
An understanding of the bending stresses in-service is needed to move forward. This might be developed from numerical techniques such as finite element analysis, from stress measurement by strain gauge or both.
What stresses are experienced by the clamping plates in all operating mode? Is the design and material selection appropriate for the valves in their specified application? What changes are needed to ensure safe operation and maintenance of the valves in the future?