Pressure tapping inside and outside the self-acting control valve
Thread Content
There are differences between self-acting control valves with internal pressure tapping and those with external pressure tapping; what are the differences in their applications?
Internal pressure tapping is convenient, but the adjustment accuracy is somewhat lower; therefore, the maintenance costs for systems with internal pressure tapping will likely be higher
I was too ignorant! I only knew about pressure sampling before and after the valve, without paying attention to internal and external pressure sampling. When the pressure measurement point is located before the valve, it is used to maintain a constant pressure before the valve ； When the pressure measurement point is located behind the valve, it is used to maintain a constant pressure behind the valve.
Taking pressure readings from the external connections before and after the valve, as well as from inside the valve body on both sides, has little impact on accuracy. Taking pressure readings externally is more cumbersome, but accessories such as filters can be used.
In terms of process control parameters, I think it’s better to take pressure readings from outside the valve, before and after it; there is a slight difference between the pressure inside the valve and the pressure in the outer pipe.
It depends on the process design; for example, some equipment has a PCV installed on the outlet pipeline at the top, while the pressure measurement point is located on the equipment itself.
Some valves are selected with internal area pressure, and it’s not entirely clear