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How to interpret the principle of the differential pressure level gauge

Author:QINSUN Released in:2023-05 Click:46

Differential pressure liquid level gauge (also known as differential pressure liquid level transmitter) is a kind of measuring instrument used to measure the liquid level of the oil tank, and its working performance is relatively stable.

Factors affecting the long-term stability of the liquid level gauge are not only the structure of the sensor itself, but also the environment in which the liquid level gauge liquid is used.

Therefore, for the liquid level gauge to have good stability, the liquid level gauge must have a better working environment.

Working Principle and Existing Problems of Differential Pressure Level Gauge

1 Working Principle of Differential Pressure Level Gauge

A liquid level transmitter is a terrain directly installed on a pipeline or container, and its internal isolation membrane is directly in contact with the liquid medium;

By measuring the liquid The pressure at the lower part is converted into the height of the liquid level according to the density of the medium, and the output is 4~20mA, which is convenient for the control system to monitor and control.

2 There are problems with the differential pressure level gauge

(1) The single flange differential pressure level gauge is installed in the open air, where crude oil The freezing point is about 12°C, which is affected by temperature;

If the heat preservation work does not can not keep up, the liquid level value of the liquid level gauge transfer tank drifts up and down, or the value will stand still, and the display The liquid level coming out is not the valuereal.

(2) It is difficult to check and maintain the fluid level gauge in winter, and it is difficult to disassemble it.

Oil in the flange nipple connecting the liquid level gauge is at the rear end, associated with the poor insulation effect and failure of the electric belt, it is easy to condense the crude oil in the nipple, which requires Using a steam car for processing is difficult and time-consuming, and the problem of the liquid level gauge cannot be solved on time.

(3) In order to avoid the deviation of the value displayed by the liquid level gauge, the heat preservation work of the electric heating band wrapped around the gauge liquid level has been added.

Every spring and fall tank cleaning job, plus the usual inspection and maintenance of the oil level gauge.quide, need to disassemble the insulation layer and the electric heating belt back and forth, so that the electric heating belt is damaged, and the electric heating belt often occurs Short circuit or tripping phenomenon, the outer insulation of the disassembled fluid level gauge cannot be restored to its original appearance.

2 solutions to the problem

The liquid level gauge is one of the three main safety accessories of crude oil storage tanks. The internal level quid is like the eyes of the surveillance room.

Once there is an error in the display of the liquid level gauge, it will directly cause the error of judgment by the monitoring personnel and cause a risk important for safety. Based on the above mentioned problems of the liquid level gauge, the installation position of the liquid level gaugeof is changed.

Depending on the working conditions and combined with the site conditions, the return line turned off in each single-tank collection room is used, so that the liquid level gauge can be moved from outside to inside.

1) In order not to affect the normal operation of the liquid level gauge, the wiring work should be done in advance, and the signal line connected to the liquid level gauge. liquid level should be connected to the pipe through the pipe. Enter the Collector\'s Room.

Remove the metal pipe from the return line into the manifold room, prefabricate the flange gasket with the same size as the liquid level gauge, and let the gauge flush head liquid level.

2) Use the tank cleaning period to clean the sludge in the bottom of each tank and the sludge in the return nipple connected to the jaliquid level gauge, connect the flange joint of the liquid level gauge, and It is docked with the differential pressure liquid level gauge.

3) Connect the signal line to the DCS system, open the inlet valve, check for leaks, check the liquid level transmitter and adjust DCS system settings.

4) Unscrew the protective cover of the new calibration parameter, then adjust it by connecting a standard 24VDC external power supply and an ammeter (accuracy better than 0.2% is required ).

5) When there is no liquid in the submersible liquid level transmitter, adjust the zero point resistance so that the output current is 4mA.

6) Add liquid to the full scale of the input liquid level transmitter and adjust the full scale resistor to make the output current 20mA. Repeat the above steps two or three fois until the signal is normal.