I think the Double Block and Bleed term is more like a feature instead of a kind of valve
2.- This is correct, if you have a DIB valve you can test this feature increasing pressure thru the body vent and check leakage on both seats, no self-relieving in this case.
If you increase pressure on...
1.- I think in this case Block and Isolation means the different characteristic of these valves which will be explained in the next question
2.- For a Double block and bleed valve I think the most common is a Trunnion ball valve (also we can have some other kind of valves like Slab and Expanding...
Those valves are also designed to work in vertical position (the spring needs to be that way) It’s a rule!!!, Because the set point of the PRV must be depending only on the force of the spring, if you install it horizontally, also side forces, sliding and friction affects the setpoint (and you...
Those valves are also designed to work in vertical position (the spring needs to be that way) It’s a rule!!!, Because the set point of the PRV must be depending only on the force of the spring, if you install it horizontally, also side forces, sliding and friction affects the setpoint (and you...