Method for measuring water pressure behind the water pump
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Pressure measurement after the water pump; the value is displayed on the DCS. The first idea was to use a pressure transmitter, with a range that is twice that of the actual pressure, slightly higher to prevent damage due to fluctuations. The pressure after the pump experiences considerable vibrations and fluctuations； Another idea is to use a pressure gauge with a standard signal output of 4–20 ma; due to the low temperatures in the northeast during winter, digital gauges are prone to problems, while analog gauges are likely to get damaged. It’s quite confusing! There are also water pressure transmitters available online, but I’m not sure which brand is the best. Does anyone have any experience to share? The first option seems to be the most reliable.
The EJA is of the differential pressure type; it is not prone to damage when frozen, and can still be used once the ice melts. If the pressure transmitter is sensitive to vibrations, use flanged wire tubes to lead the transmitter out, or use pressure transfer tubes instead; at the same time, ensure proper heating and insulation for the pressure tapping tubes as well as the instruments.
It is recommended to use capillary pressure transducers, with the gauge installed indoors; at such low temperatures in the northeast, without proper insulation, no gauge will function well. A reminder: don’t trust advertisements. There’s another thing I’ve only seen but never used. It is a remote-operated pressure transmitter capable of measuring the temperature of liquid nitrogen, and it functions properly at temperatures below -200 degrees. It’s just not displayed on-site. If you only need long-distance transmission, you can give it a try.
A regular pressure transmitter will suffice; just ensure proper insulation. It’s not possible to prevent vibration in the transmitter located at the pump outlet, so it has to be placed at a distance from the outlet. This has nothing to do with temperature. The device used for measuring liquid nitrogen temperature upstairs measures the temperature of that medium, and it’s unrelated to the outdoor temperature. For liquid nitrogen at around -174 degrees Celsius, as used in air separation processes, special ultra-low temperature transmitters are employed
It can definitely be measured using a pressure transmitter
EJA438 diaphragm-sealed pressure transmitter
I agree with what was said on the fifth floor: a regular pressure transducer will suffice. Of course, a non-contact type (one with diaphragms) is also excellent, but it’s more expensive than a regular pressure transducer, so there’s no need for that. For the operating conditions you described, a single pressure transducer mounted on the pump head is sufficient; as long as proper insulation and heating are provided (either through steam or electric heating), it’s fine to use the most basic type of transducer available. My recommendation is to use a standard pressure transformer, with a pressure tapping pipe arrangement and a two-valve assembly for connection; the pressure tapping pipe should be insulated with heat tracing. For the maximum range, 1.5 times the pump’s head value can be used as the upper limit; there is no need to use a value that is twice as large.