Calibration and Fault Analysis of Diaphragm Pressure Gauge

Calibration of diaphragm pressure gauge

Before installing the membrane pressure gauge, carefully check the model, diaphragm material, and measuring range, and check whether the diaphragm is damaged or not. When there is no pressure, check whether the pressure gauge indication is at the zero position and identify the cause. Readjust the calibration after inspection. Use only after passing the inspection. The steps for calibrating diaphragm pressure gauges are the same as those for calibrating conventional pressure gauges, but the following points should be noted:

1. Before calibration, prepare a matching joint according to the membrane device model to be calibrated for use with a general pressure calibration table. The membrane device of the diaphragm pressure gauge is generally flange-connected. A matching pressure joint can be prepared according to the size and model of the flange. Corresponding flanges and universal pressure gauge fittings can be found at the site for processing. This is also the most direct and convenient method.

   
   

2. When fixing the diaphragm pressure gauge to be calibrated on the standard calibration platform, pay attention to handle it with care and do not damage the diaphragm. When turning the calibrated diaphragm pressure gauge with a wrench, the nut that connects the diaphragm device must not be stuck on the universal pressure gauge, because the diaphragm device on the universal pressure gauge and the instrument is a sealed system. Do not disassemble or replace other types of pressure gauges at will to prevent the filling working liquid in the system from leaking. This will affect the performance or even lead to failure, especially for newcomers who just started working, and must explain clearly before calibrating the diaphragm pressure gauge.

   
   

3. Result processing: During the pressurization process, if it exceeds the standard gauge measurement, first check if there is oil leakage or sealing problems. If there is leakage, the sealing is not good, and it can only be returned to the factory for processing or scrapped. If it is not the above situation, the indicator pointer can be removed and reset. The long-term experience is that when the needle is fixed, it is generally reasonable to reset the needle to about 1/2 of the measuring range. If it still exceeds the allowable range, it can only be downgraded or scrapped.
   

Analysis of fault causes of diaphragm pressure gauge

When there is pressure, the pointer does not indicate.

The cause of this failure is generally due to the connection between the pointer and the central gear shaft becoming loose due to strong vibration, and the displacement of the compressed spring tube cannot drive the pointer to deflect. Additionally, too much silicon oil in the spring tube leaks and cannot transmit pressure.

The pressure measurement is inaccurate. The pressure indication changes at the low end and the pointer does not change as the pressure rises.

The cause of this fault is that a small amount of silicon oil in the spring tube leaks, allowing air to enter. Because gas can be compressed, when the pressure rises, the pressure indicated by the pointer is inaccurate or does not move.

During the pressure measurement process, the pointer suddenly jumps.

This fault often occurs in situations where the diaphragm pressure gauge vibrates strongly (such as the pump's outlet pressure). Due to pressure fluctuations, the pointer also swings back and forth, causing severe wear of the center gear of the pressure gauge core and the fan gear. Inappropriate gear selection causes the pointer to suddenly change. To handle pointer jumping faults, the worn center gear can be repaired with a small file and scrapped steel saw blade. When the shaft hole of the pointer becomes larger, a small hammer can be used to knock it back to shrink it until the pointer tightly fits onto the central gear shaft.