Are valve assemblies required in front of differential pressure instruments? ? ?

Valve assemblies are installed for ease of maintenance; transmitters such as EJA and 3051 do not require a three-valve assembly.

For differential pressure transmitters, it depends on the environment in which they will be used – a valve assembly is not always necessary. For example, when measuring gases, there is no need for a valve assembly; merely installing a root valve is sufficient. Of course, there are corresponding standards for all these situations

Indeed, there is usually a three-valve manifold in front of the differential pressure gauge; this is done for ease of maintenance as well as for safety reasons. For example, in the event of a malfunction, you can determine whether the transmitter is functioning properly by operating the three-valve assembly, without having to close the valves each time and then loosen the connections to allow technicians to troubleshoot the issue – this also helps to avoid unsafe procedures. But not all differential pressure transmitters have a three-valve assembly. For example, basically all the double-flange differential pressure transmitters in our installations do not have three-way valve assemblies or vent valves. Because some media cannot be placed randomly.

I would like to ask the experts: Is a orifice plate flow meter the same as a differential pressure flow meter? Is it difficult to install? Is maintenance required? How is the range selected?

The main purpose of the three-valve assembly is to protect the differential pressure instruments from damage; it is not designed for ease of maintenance. Initially, this assembly was introduced because differential pressure instruments had poor resistance to pressure on one side only, and its aim was to prevent the instruments from being damaged due to excessive pressure on a single side during operation. There are also strict requirements regarding the operation of this assembly. Therefore, it must be used when the operating pressure exceeds the maximum pressure that the differential pressure instrument can withstand

The three-valve assembly consists of a valve body, two stop valves, and a balance valve. Operation procedure for putting the differential pressure transmitter into operation: First, open the two drain valves on the differential pressure transmitter, then open the balance valve. Next, slowly open the two stop valves to remove any air or debris from within the pressure guiding tubes. After that, close the two drain valves and then close the balance valve; the transmitter is now ready for use. Operation procedure for online zero-point calibration of differential pressure transmitters: First, open the balance valve and close the two stop valves, then the transmitter can be calibrated for its zero point. The three-valve manifold can be connected to transmitters such as 3051, 3095, 1151, EJA, FX-2, FCX-A/C, and Honeywell ST3000 series.

Before putting the differential pressure gauge into use, the balance valve on the three-valve assembly should be opened first, followed by the valve on the low-pressure side, and then the one on the high-pressure side. Once all three valves are open, the balance valve should be closed; only then can the gauge be considered to be in operation. When it is necessary to shut down or remove the differential pressure gauge, the balance valve should be opened first, after which the valve on the high-pressure side and the one on the low-pressure side should be closed in sequence, before the gauge can be removed

The friends upstairs have covered everything quite thoroughly; I’ll add just a few points. If a regular differential pressure transmitter is used to measure the liquid level and there is moisture migration, then a three-valve assembly is necessary. This is because the low-pressure isolation tank must be filled with the medium. By closing the high- and low-pressure primary valves, unscrewing the plug on the low-pressure isolation tank, opening the balance valve, and then opening the high-pressure primary valve, the medium flows from the high-pressure primary valve → the high-pressure valve of the three-valve assembly → the balance valve → the low-pressure valve of the three-valve assembly, entering the low-pressure isolation tank. Once the tank is filled, the high-pressure primary valve is closed and the plug is screwed back in. After that, the high-pressure primary valve is opened again, the low-pressure valve is opened, and the balance valve is closed – thereby completing one cycle of filling the tank.

I think it’s simple – it depends on whether you’re using a capillary tube or a pressure guiding tube

I’ve learned it! ! ! ! ! ! ! !