Reasons for Failure of Diaphragm Pressure Gauge and Repair Methods

Diaphragm pressure gauges are widely used to indicate and measure local pressure in contact with strong corrosive media in production. They are easily damaged during use, so many pressure gauges are scrapped. The main reasons for the damage are rust, damage and silicone oil leakage caused by long-term placement of the meter on the chemical site. In order to reduce costs and turn waste into treasure, it is necessary to solve the problem of overhaul of diaphragm pressure gauges. Here the company summarizes a set of maintenance methods for everyone.

Ⅰ. The pressure measurement principle of diaphragm pressure gauge and ordinary pressure gauge and the difference in structure

The principle of pressure measurement of ordinary pressure gauges is: the pressure to be measured is introduced into the pressure measuring spring. After the spring tube is compressed, it produces elastic displacement, driving the connecting rod and the central gear to deflect, and the pointer is mounted on the central gear shaft to display the pressure. Measured value. The so-called diaphragm pressure gauge, in addition to the part with the ordinary pressure gauge, adds a connecting flange and an isolating diaphragm (the isolating diaphragm can be made of different materials in order to adapt to different corrosive media or temperatures). The pressure transmission medium silicone oil is filled between the isolation diaphragm and the pressure measuring spring tube.

The main difference between the diaphragm pressure gauge and ordinary pressure gauges is that the medium to be measured only touches the isolation diaphragm during the pressure measurement process of the diaphragm pressure gauge. In this way, corrosive and crystalline media can be prevented from entering the spring tube, and corrosion and blockage of the spring tube can be avoided.

Ⅱ. The reason analysis of the failure of the diaphragm pressure gauge in use

1. When the diaphragm pressure gauge has pressure, the pointer has no indication. The reason for this kind of failure is generally that the connection between the pointer and the central gear shaft is loosened due to strong vibration, and the displacement of the spring tube after compression cannot drive the pointer to deflect. Secondly, the silicone oil in the spring tube leaks too much, and the pressure cannot be transmitted.

2. If the diaphragm pressure gauge has these failures: the measured pressure is inaccurate, the pressure indicator changes at the low end, and the pointer does not change when the pressure rises, then the reason is that a small part of the silicone oil in the spring tube is lost, allowing air to enter. Because the gas can be compressed, when the pressure increases, the pressure indicated by the pointer is inaccurate or does not move.

3. In the process of pressure measurement, the pointer changes leaps and bounds. This kind of failure of the diaphragm pressure gauge often occurs when the diaphragm pressure gauge is in a large vibration (such as the outlet pressure of the pump). Due to the fluctuation of the pressure, the pointer also oscillated back and forth, causing serious wear on the central gear of the pressure gauge core, and the central gear and the sector gear did not match well, which caused the pointer to change abruptly.

For the treatment of pointer jumping failure, small assorted files and scrap steel saw blades can be used to file and repair the worn center gear. When the shaft hole of the pointer becomes larger, you can tap it with a small hammer to shrink it until the pointer can be closely integrated with the center gear shaft. In addition to proper maintenance, it is also important to choose a reliable pressure gauge supplier when purchasing products.

Ⅲ. The maintenance of the diaphragm pressure gauge

In the maintenance of multiple diaphragm pressure gauges, it was found that most of the failures were caused by the leakage of silicone oil in the spring tube. It can be said that filling the spring tube with silicone oil is the key to solving the maintenance of the diaphragm pressure gauge, but it is not easy to fill the spring tube with silicone oil. Under normal circumstances, manufacturers have special equipment for filling silicone oil, using a vacuum pump to extract the air in the bomb tube. In the case of negative pressure, let the silicone oil automatically flow into the spring tube.