1. The length of the pressure guiding tube between the differential pressure transmitter and the differential pressure source is generally within 3-50m, and the diameter should not be less than 8mm; the pressure guiding tube should have a slope of not less than 1:10, that is, horizontally laid. At 10m, the height difference between the two ends is 1m. The slope of the pressure guiding pipe should meet:
(1) When the measured medium is a gas, the cold gel in the gas should be automatically flowed back to the process pipeline or equipment along the pressure guiding tube, so the installation position of the differential pressure transmitter is preferably higher than the pressure source. If this is not possible in the actual installation, the liquid collector and drain valve should be installed at the lowest point of the pressure guiding tube.
(2) When the measured medium is liquid, the gas which is precipitated in the liquid should flow back to the process pipeline or equipment along the pressure guiding tube. Otherwise, the gas collector should be installed at the highest point of the pressure guiding line. Gas valve, so the differential pressure transmitter installation position is better than the pressure source. In summary, the slope and aspect of the pilot line are to ensure that only the single-phase medium (gas phase and liquid phase) is present in the pilot line and differential pressure transmitter to ensure measurement stability and prevent additional errors.
(3) When the medium is steam, a condensing container should be installed in the pressure guiding pipeline to prevent the differential pressure transmitter from being damaged due to entering high temperature. The condenser should be installed in such a way that the condensate level in the two pressure guiding tubes is maintained at the same level for a long time. The pressure guiding pipeline from the condensing vessel to the differential pressure transmitter shall be laid according to the requirements when the measured medium is liquid. For corrosive media, isolation equipment shall be installed in the pressure guiding tube to prevent differential pressure transmission. The device is corroded. In the case where the measured medium has a large viscosity, is easy to precipitate or crystallize, has a low gas-phase/liquid phase conversion temperature, and is easily polymerized, a corresponding isolation device should also be adopted to prevent the pressure-conducting tube from being clogged.
Second, the intelligent differential pressure transmitter should pay attention to the following three points:
(1) The measurement range, zero point, drift amount, accuracy, static pressure error, etc. must be reviewed before use;
(2) After the installation of the intelligent differential pressure transmitter, it is necessary to check the working pressure, working temperature, measuring range and drift of various transmitters before driving. See if it matches the actual situation. If there is any discrepancy, you must find out the cause and correct it before driving.
(3) When opening and deactivating, the differential pressure transmitter should be protected from one-way compression. For each differential pressure transmitter, a set of three sets of valve parts should be attached. Usually, three sets of valves are installed in differential pressure transmission. Above the device, valve 1 and valve 3 are high pressure and low pressure shut-off valves respectively, and valve 2 is a balancing valve. Balance valve 2 is used to protect the differential pressure transmitter and facilitate the zero position when opening and stopping the meter. When opening the differential pressure transmitter, first open the balancing valve 2, then open the valve 1 and the valve 3, and when the valve 1 and the valve 3 are all open, close the valve 2. When the differential pressure transmitter is deactivated, the balancing valve 2 should also be opened before valve 1 and valve 3 are closed. Turning on and off the differential pressure transmitter in the above order can prevent the differential pressure transmitter from being subjected to one-way static pressure and overload. For differential pressure transmitters with cold gel or spacer fluid, cold gel or spacer fluid can also be avoided.
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