How to migrate a differential pressure level gauge

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Simply put, when the level of the medium to be measured is at the zero position, if the negative chamber is under pressure, it will shift downward. For example: if the measured medium level is at the zero position, the pressure in the negative chamber is 20 KPa, and the measurement range for the medium is 10 KPa, then the measurement range of the instrument needs to be shifted downward by -20 to -10 KPa.

The capillaries allow for good migration. First, place the two diaphragm boxes in the same plane, use a calibrator to zero the differential pressure gauge, then install it on the equipment and check what the pressure difference indicated is on the gauge. (This pressure difference is negative; if a positive value is shown, it means the positive and negative sides of the diaphragms are installed in the wrong order.) Enter the pressure value displayed by the gauge into the gauge’s settings – with 0 as the upper limit value

Whether it is a capillary tube or a pressure tapping tube, the principle to follow for calibration is that the difference between P_positive and P_negative gives the actual differential pressure of the differential gauge; this value must be adjusted out at zero position. When calibrating during pump relocation, it is best to do so when the liquid level is at 0. You can imagine the liquid level to be at zero in your mind, and then consider that the differential pressure between the positive pressure side and the negative pressure side represents the amount that needs to be adjusted. If this value is positive, the pump should be moved forward by that amount; if it’s negative, it should be moved backward by that amount. In other words, the goal is to make the differential pressure between the positive and negative pressures equal to 0 at this point. For those with a condensation-filled pressure guiding tube, only the pressure of the water filled in that tube needs to be taken into account; the principle is no different from that of the others.

First, you need to know how the amount of migration is calculated: the pressure difference between positive and negative pressures at the highest or lowest liquid level is the amount of migration. In a double-flange capillary level gauge, the installation location does not affect the migration amount; the design drawings indicate the maximum and minimum liquid levels, as well as the positions for taking pressure readings under positive and negative pressures, the length of the pressure sensing tubes, and the density of the medium. You can then calculate the amount of migration. The pressure tapping tubes are the same as those for condensation.

Their calibration principles are all the same. I have a little tip to share with you: calibrating double-flange level gauges is the most troublesome task. As you all know, I won’t go into the reasons for that. I usually carry out calibration while the device is in operation, setting the liquid level at around 50%, and then using a BT200 or HAER375 to adjust the readings according to the 50% level within the range of measurement – it’s a very practical method. I’m not sure if what I said is correct; I’d like to hear everyone’s opinions as well.

First, place them on the same horizontal plane for zero-point calibration; then place them at different heights relative to the installation position, and perform zero-point adjustment again

It is recommended that you look up information on your own; reference books and similar materials provide explanations on this. This is the most basic aspect of instruments, with many applications in measuring levels and boundaries. Find information by yourself so that it stays better engraved in your memory.

How are the pressures on the positive and negative sides calculated? And how is the pressure of the water column in the pressure guide tube taken into account in the calculations?