Calibration of Diaphragm Pressure Gauge
In order to solve the maintenance problem of the diaphragm pressure gauge, the company has made a set of equipment for filling the spring tube with silicone oil by using the existing device after many tests, and summarized the oil filling method. The specific method is as follows:
1. Make a special calibration tool for diaphragm pressure gauges
The connecting thread of the diaphragm pressure gauge head used is a standard thread. In addition, each diaphragm pressure gauge is equipped with a connecting flange. Therefore, the calibration of the diaphragm pressure gauge needs to make a special support flange for calibration.
2. Calibration process of diaphragm pressure gauge
1) First remove the head of the diaphragm pressure gauge from the flange. Then connect the pressure gauge and the calibrator together, and use the pressure calibrator for calibration and adjustment according to the calibration method of ordinary pressure gauges. Clean the diaphragm flange and fill with oil through the funnel;
2) At this time, the transformer oil may enter the spring tube. Hold the gauge in your hand and shake it a few times to clean the transformer oil in the spring tube. Place the pressure gauge with spring tube head down on the vacuum gauge calibration table;
3) The two-way valve is set to the "open" position, and the three-way switching valves A, B, and C are not connected. Use the air pump to draw air, the vacuum degree indicated by the standard vacuum gauge is greater than 0.93pa, the bigger the better. If the vacuum degree is less than 0.93pa, the air extraction system is not well sealed, and small air bubbles will appear after oiling the spring tube, which will affect the accuracy. First turn the two-way valve to the "off" position, and then flip the three-way switching valve, so that A and C are connected except for B, and silicone oil is injected into the table. In order to let the tiny air bubbles left in the spring tube escape when the oil filling and pumping are not completed, it is best to stop for 10 minutes and then remove the pressure gauge;
4) Place the head of the spring tube pressure gauge vertically upwards to prevent oil leakage. After filling, wrap teflon sealing tape around the joint, fast-tighten, connect the pressure gauge head and flange capsule together and tighten. Since the silicone oil sealed in the pressure gauge is under pressure when tightening, the zero point of the pressure gauge rises. Use an Allen key to open the air vent on the capsule to release the residual pressure in the capsule, and observe that the pointer of the instrument indicates the zero scale. During the pressurization process, when the pointer of the gauge under test points to the first large scale line and is exactly the same as the standard gauge pressure, tighten the thread;
5) Finally, verify the zero point and range. Connect the diaphragm pressure gauge and make the calibration with the flange, and install the assembled pressure gauge on the pressure calibrator for calibration to make it qualified.
In the above steps, the most important thing is to exhaust the air, and there should be no small bubbles in the oil, otherwise the instrument error will be large, the pointer will not return to zero, and the accuracy will be greatly reduced. Check the accuracy of the original gauge in the manual, and the accuracy of the gauge repaired by the above method qualified.
