Calibration steps and precautions of diaphragm pressure gauge

Before installation, the diaphragm pressure gauge must carefully check the model, diaphragm material and measuring range, and check whether the diaphragm is damaged; When there is no pressure, the pressure instrument indicates whether it is at zero position, and at the same time, find out the reason, readjust it, and use it only after it is qualified.

The steps of calibrating diaphragm pressure gauges are the same as those of calibrating conventional pressure gauges, and will not be repeated again. The following points should be noted:

(1) Before calibration, firstly, according to the diaphragm device model of the calibrated diaphragm pressure gauge, prepare the matching joint for use in the general pressure calibration platform. The diaphragm device of diaphragm pressure gauge is generally flange-type, and prepare the matching compression joint according to the size and model of the flange. It is also a direct and convenient way to find the corresponding flange and universal pressure gauge joint for processing at the scene.

(2) In the process of fixing the calibrated diaphragm pressure gauge on the standard calibration table, we should pay attention to: handle it with care, and don't hurt the diaphragm. When rotating the calibrated diaphragm pressure gauge with a wrench, the wrench must be stuck on the connecting nut of the diaphragm device, not on the universal pressure gauge, because the universal pressure gauge and diaphragm device on the instrument are a sealed system, and it is not allowed to disassemble or replace other pressure gauges at will, so as to avoid the leakage of working fluid filled in the system, which will affect the use performance or even be scrapped, especially when you just join the work.

(3) Result treatment: in the process of boosting, if it is out of tolerance compared with the standard meter, first check whether there are problems such as oil leakage and sealing. If there is oil leakage or poor sealing, it can only be returned to the factory for treatment or scrapped; If this is not the case, you can remove the indicating needle and reset it. Long-term experience is that it is more reasonable to reset the needle at 1/2 of the range. If it is still out of tolerance, it can only be degraded or scrapped.

What is the difference between diaphragm pressure gauge and ordinary pressure gauge?

1. When measuring the pressure with a common pressure gauge, the measured working medium directly enters the spring tube, while when measuring with a diaphragm pressure gauge, the measured working medium cannot enter the spring tube.

2. Diaphragm pressure gauges are not in direct contact with the measured medium, while ordinary pressure gauges are in direct contact with the medium. Therefore, the diaphragm pressure gauge can be used to measure some corrosive media.

A. What are the advantages of using a diaphragm pressure gauge?

1. Brass tube, tin bronze, 1Cr18Ni9 stainless steel tube and SUS316 stainless steel tube are commonly used for making spring tubes. As other corrosion-resistant materials, such as 304, 316, titanium, tantalum, Hastelloy, Monel, tetrafluoroethylene and other pipes, it is not easy to purchase because of limited use, but the tape used to make the diaphragm is much easier to purchase.

2. As a pressure measuring medium with high viscosity, easy crystallization and solidification, the normal requirements of the instrument can be guaranteed due to the isolation function of the diaphragm.

B, ordinary pressure gauge is used to measure the pressure of non-corrosive liquid gas instrument, diaphragm pressure gauge can generally be used in the following two aspects:

① Measure the pressure when there is a requirement for corrosion-resistant liquid gas (the medium to be measured is corrosive, and different diaphragm materials such as 304, 316, titanium, tantalum, Hastelloy, Monel, tetrafluoroethylene, etc. should be used for different corrosive media).

(2) food hygiene requirements, because the measured medium does not flow inside the pressure gauge when the pressure is measured by the ordinary pressure gauge, it is easy to repeat pollution.

Diaphragm pressure gauge adopts indirect measuring structure. Diaphragm is deformed under the pressure of the measured medium, and the sealing liquid is compressed to form a pressure equivalent to P, which is transmitted to the pressure instrument to display the pressure value of the measured medium. It is suitable for measuring the pressure of liquid, gas or granular solid medium with high viscosity, easy crystallization, high corrosiveness and high temperature. The isolation diaphragm has many materials to adapt to various corrosive media.

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