What is a valve manifold?
The valve manifold used to protect the DP transmitter from higher range. This device isolates the transmitter from fluid pressure for calibration and for maintenance purposes.
The manifold is a combination of valves in a single body. Each valve will have separate openings ad controls.
The manifolds commonly use the ball, bleed, needle, and vent valves.
3 Valve manifold:
The 3 valve manifolds consist of 3 valves with two block valve and one equalizing valve. There is an extra “bleed” valve, used to vent trapped fluid pressure to atmosphere.
During operation, equalizing valve is closed and the block valves are opened to connect the process pressure across the DP cell.
To place or remove a transmitter, valves must operate in a sequential way so that, high pressure does not affect DP capsule
Operational sequence for placing valve into service:
- Ensure all valves closed
- Open equalizing valve to ensure same pressure is at the both sides of the transmitter
- Open high-pressure block valve to leak from both high and low-pressure side
- Close equalizing valve to lock pressure from both sides
- Open low-pressure block valve to apply process pressure
Operational sequence for remove valve out of service:
- Close the low-pressure block valve to trap pressure in the lower side
- Open equalizing valve to force dp to zero
- Close the high-pressure block valve to isolate the transmitter
- The transmitter is ready to remove
5 Valve manifold:
It consists of 5 valves, 2 block valve, 2 equalizing valves and one bleeding valve. Bleed valve vent out trapped pressure through a tube to some remote location.
Equalizing valves never be open while both block valves are open.
For normal operation, all the equalizing valves and bleed valve are shut, while blocking valves are open. To isolate transmitter from service, equalizing valves are opened and blocking valves are shut.
Pressure transmitter valve manifolds also come in single block-and-bleed configurations, for gauge pressure applications