Pay attention to the following matters during on-site online inspection of pressure calibrators and differential pressure transmitters
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ARIPY
Time : 2020-03-03 16:18 Pageviews : 32
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Existing problems in on-site pressure instrument testing and verification
A pharmaceutical company now mainly has three types of pressure measuring instruments: pressure gauges, pressure transmitters and differential pressure transmitters.
The existing installation method makes the disassembly and assembly difficult, many disassembly points, time-consuming, and heavy workload during the verification. The thread slips at the thread and the pressure tube is deformed.
When calibrating the pressure transmitter, due to the small size of the valve body assembly and the small distance between the holes, the space for disassembly and assembly is narrow, which is inconvenient to operate and affects work efficiency.
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Using online inspection method
In view of the current situation, the vent valve of the second valve assembly in the middle of the pipe connected to the pressure gauge can be slightly modified to realize on-site online verification without disassembly.
Modify the end of the vent tube (see the above picture), weld or rive a stainless steel special internal thread adapter at the end of the tube (this avoids the need for a dust cap for external threads, and also affects normal emptying). It can be directly connected to the pressure gauge testing equipment through a dedicated pressure hose, and it can be verified in accordance with the pressure gauge verification regulations.
Pay attention to the following points during verification:
(1) On-site inspection should be selected in spring and autumn. Generally, the inspection temperature can be controlled within (20 ± 5) ℃, which meets the temperature requirements of the verification regulations.
(2) During verification, close the lower valve and slowly adjust the second valve assembly, first empty the natural gas in the pipeline, and then adjust until the pressure gauge is connected to the emptying valve, that is, the pressure gauge is connected to the pressure calibrator
(3) Try to choose a dedicated pressure transfer high-pressure hose. At the same time, the smaller the cavity volume, the easier it is to pressurize.
(4) The manual air pressure pump has a high pressure (the range is usually 0-16 MPa), and it is difficult to pressurize. Using a manual air pressure pump as a pressure source requires pressurizing dozens of times to obtain the required pressure.
In response to this problem, a three-way connection and a bottle of compressed nitrogen can be installed in the middle of the detection hose, which can effectively improve work efficiency and save manpower.
For the on-site detection of pressure transmitters and differential pressure transmitters used on the conveying pipeline, you can refer to the method of pressure gauge detection. Use the two valve assembly in the middle of the pressure pipe to connect the vent interface to the pressure calibrator for verification, reducing Disassembly effectively prolongs the service life of the pressure transmitter and saves costs.
Pay attention to the following matters during the on-site online inspection of pressure transmitters and differential pressure transmitters: (1) When disconnecting the power cord, the positive electrode of the power supply should be removed first, and the exposed part should be wrapped with insulating tape immediately after removal to prevent contact and waves. Surge, causing damage to the control system and misoperation.
Then remove the negative pole of the power supply, and also wrap the exposed part with insulating tape; (2) Use the intelligent digital pressure calibrator, which comes with a 24 V power supply, and the pressure transmitter is simple and convenient to connect. You can power and Measure the current signal; (3) When testing these devices, it is best to choose a testing device with air as the medium to avoid clogging of valve body components, etc.; (4) When testing the differential pressure transmitter, first close the valves at both ends, slowly Open the middle-way valve, and then slowly open the emptying valve to empty the gas inside.
Connect the pressure calibrator to the differential pressure transmitter through the high-pressure side emptying valve, close the middle-way valve, open the low-pressure side emptying valve to communicate with the atmosphere, connect the power supply and signal wires, and then perform on-site inspection according to the verification regulations .
In summary, by improving the existing detection methods, the risk of enterprise safety production and the workload of equipment maintenance personnel and inspection personnel are effectively reduced, and the subsequent maintenance costs are low, the practicability is high, and there is practical value for application promotion.
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