Power plants ASME N-stamp
Shut-off valves from the professionals – it pays off
Pumps, valves and their actuators control the flow of coolant in the cooling circuits and ensure constant power plant operation. But what happens if a pump in the cooling water circuit fails?
The failure of a pump has consequences for the directly and indirectly connected plant systems, such as pump drives and condensers. Such failures can be avoided through professional planning and calculations. Take the example of a cooling circuit pump: All flows should be stopped by a non-return valve as soon as the return flow of the medium starts to protect the pump and its drive against a reversal of the movement counter to the operational direction of rotation. Protection is provided here by special valves such as check valves or combined non-return valves that prevent a reversal of the running direction based on an automatically switching coupling. Modern pumps are fitted with an automatic blocking system, but unlike check valves this does not prevent the return flow of the medium. The water thus flows through the stationary pump and the pipeline system empties in an uncontrolled manner - possibly even completely - with unpleasant consequences: because of the complex refilling procedure, an empty condenser prevents a fast start-up after the malfunction.
Maximum control, minimum use of force: VAG Butterfly Valves
Complete and thus reliable protection is provided only by valves – ideally with the VAG HYsec Hydraulic Brake and Lift Unit - which control and completely shut off the water and prevent further damage such as pressure surges through individually adapted closing times. Due to the hydraulic interlocking by means of a drop weight, VAG Butterfly Valves require no electrical power for emergency closing and thus notceably improve the energy efficiency of the system. VAG butterfly valves can also be used multi-functionally through clever combination or extension:
- as a check valve for pump drive protection,
- as a controlled butterfly valve for the prevention of pressure surges in the pipeline system,
- as a pump start-up valve for the targeted start-up of pumps within the characteristic curve,
- as a shut-off valve to prevent return flows and
- as a safety valve (with optional accident prevention interlock) for carrying out maintenance work in the pipeline.
Our recommendation: the double-offset VAG EKN® Butterfly Valve combined with the VAG HYsec PRO Hydraulic Brake and Lift Unit and the optional accident prevention interlock.