How to put differential pressure transmitters and pressure transmitters into operation?

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It is necessary to check the zero points of pressure transmitters and differential pressure transmitters; regular cleaning of these transmitters also involves turning them on and off. Therefore, knowing how to properly start and stop pressure transmitters and differential pressure transmitters is also one of the skills that need to be mastered. Changhui Instruments explains in this post the shutdown and startup of pressure transmitters and differential pressure transmitters. Commissioning of differential pressure transmitters: yunrun.com.cn/tech/1196.html 1. Steps for shutting down and commissioning locally installed pressure transmitters. The installation method for locally installed pressure transmitters is basically the same as that for spring pressure gauges; there is only one sampling valve, and some models also have a drain valve. Note: The pressure transmitters that can be installed in place as mentioned in this post refer mainly to those with threaded connections, such as the monocrystalline silicon gauge pressure transmitter YR-ER102. ① Method for shutting down a locally installed pressure transmitter: To shut it down, close the sampling valve of the locally installed pressure transmitter, then slowly open the discharge valve to release the pressure being measured. In the absence of a release valve, pressure can only be relieved by slowly loosening the threads of the pressure transmitter’s connection; care must be taken to avoid injury from the medium pressure during this process. ② Method for putting into operation a locally installed pressure transmitter: To bring it into operation, it is sufficient to open the sampling valve of the locally installed pressure transmitter. 2. Steps for shutting down and starting up a pressure transmitter installed remotely: A pressure transmitter installed remotely is connected to at least three valves and pressure guiding pipes. The sampling valve is used for sampling and shutting off the process medium, while the drain valve is used to flush the pressure guiding pipes and remove any condensate or gas from within them. The stop valve used to connect the pressure guiding pipes to the pressure transmitter is also known as a secondary valve. ① Method for shutting down a pressure transmitter installed at a remote location: To shut it down, close the secondary valve of the pressure transmitter, and then relieve the pressure by using the drain and vent valves on the measurement chamber of the pressure transmitter, or the drain valve of the pressure guiding tube. If necessary, the sampling valve should also be closed. For transmitters with isolation fluid, the drain valve cannot be opened arbitrarily to relieve pressure. ② Operation method for remotely installed pressure transmitters: For transmitters used for measuring ordinary media, simply opening the secondary valve is sufficient to put them into operation. For steam pressure measurement with the pressure guide tube already emptied, first close the secondary valve and the drain valve, then open the sampling valve. Next, open the drain valve to flush the pressure guide tube; after closing the drain valve, wait for more than half an hour until the pressure guide tube is filled with steam condensate before opening the secondary valve. And use a transmitter to measure the exhaust valve in the chamber to remove air. When performing the above operations, the associated control system should be switched to manual mode, and the process operators should be informed. Technical library: yunrun.com.cn/tech/ 3. Steps for shutting down and starting up a differential pressure transmitter. A differential pressure transmitter is connected to at least five valves; two of these are sampling valves used for taking samples and shutting off the process fluid ； The two drain valves are used to flush the pressure guide tube, or to remove condensate or gas from it ； The connection between the pressure guiding pipe and the differential pressure transmitter is achieved using either a three-valve assembly or a five-valve assembly, and the shutdown and startup of the differential pressure transmitter involve operations on this three-valve assembly. http://yunrun.com.cn/upload/201612/18/201612181643580016.jpg ① Method of shutting down a differential pressure transmitter: When shutting down a differential pressure transmitter, the steps for closing the three-valve assembly are as follows: first, close the negative pressure valve ； Open the balance valve again ； Finally, close the positive pressure valve. When a differential pressure transmitter is not in use for an extended period of time, the primary valve and the positive and negative pressure valves of the three-valve assembly should be closed, while the balance valve should be opened to ensure that the pressures on both sides of the transmitter’s measurement chamber are equal, maintaining a state of balance. ② Method of putting a differential pressure transmitter into operation: When commissioning a differential pressure transmitter, the steps for opening the three-valve assembly are as follows: first, open the positive pressure valve ； Close the balance valve again ； Finally, open the negative pressure valve. When using differential pressure transmitters for measuring steam flow during start-up and shutdown, differential pressure transmitters equipped with isolators, or level differential pressure transmitters that utilize balance vessels, it is not allowed for the positive pressure valve, negative pressure valve, and balance valve to be open at the same time when switching the three-valve assembly. Even if they are opened for a short period of time, it is possible for the condensate water in the balance vessel or the isolation fluid in the isolator to be lost, which can result in incorrect readings from the instruments; in severe cases, it may even be impossible to operate the differential pressure transmitter. It is necessary to use a differential pressure transmitter to measure the drain and vent valves on the chamber, in order to remove any air or condensed water from them.