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We have storage tanks for all products and lines connected to Getty for tankers loading/off loading and the distance about 7 km all lines 14/16 inches and ended in terminal by movs (motor operating valves only). My question is can we install gate valves upstream of movs for maintenanc ? ( the terminal still under construction)
 
Answers
25/05/2015 A: Jayaraj Jayam, Chennai Petroleum Corporation Limited, njayaraj@gmail.com
Most of the MOVs are gate valve only. To make the operation easier, motor is fixed and the motor does the work. Even the motor fails or the gear fails, the valve can be taken into manual mode and the same can be operated using the wheel provided on the gear of the valve. So in MOV, other than the motor, it is nothing but a gear operated gate valve.
When facility is available to operate the valve on manual mode without the interference of the motor, providing additional valve will be a sophistication but does not serve any purpose. It is nothing but adding an additional gate valve which will incur additional burden on the project cost.
It can become a nuisance also due to increased number of weak points by having additional flanges, additional point for creating leak such as valve glands, increase the probability of valve gate drop seating. It is not at all advisable to add unwanted valves.
13/05/2015 A: Dhiren Rindani, Reliance Industries Ltd, dhiren.rindani@ril.com
Certainly, you should have manual isolation valve before MOV. It will remain normally open. Incase of MOV problem like MOV gear failure, motor failure etc... manual valve shall help you attending the MOV.