Typical faults of stainless steel diaphragm pressure gauge under negative pressure condition

Stainless steel diaphragm pressure gauge is a commonly used instrument, which contains a sealed diaphragm to prevent the medium in the pipeline from directly entering the pressure sensor assembly in the differential pressure transmitter.

When the diaphragm of stainless steel diaphragm pressure gauge works under negative pressure (that is, the pressure of the measured medium contacted by the diaphragm is lower than the atmospheric pressure). On the contrary, after a period of use, the transmitter is prone to failure. When checking the faulty transmitter, it is often found that there is gas under the diaphragm, and the diaphragm expands to the limit, so the medium pressure can no longer be carried out. This kind of problem exists in distillation, refining and regeneration of gas desulfurization liquid in coal chemical plant. In contrast, similar stainless steel diaphragm pressure gauges have not found such faults under positive pressure.

Error analysis of stainless steel diaphragm pressure gauge

A closed space is composed of diaphragm, diaphragm chamber, capillary tube and part of transmitter body (referred to as pressure guiding chamber). The pressure guiding chamber is filled with pressure guiding fluid (usually silicone oil). The pressure of the measured process medium is transmitted to the transmission body through the diaphragm and the pressure conducting fluid. On the diaphragm, the pressure of the pressure conducting fluid on both sides of the diaphragm, the pressure conducting fluid on both sides of the diaphragm, and the pressure of the process medium form a balanced relationship with the stress when the diaphragm is elastically deformed.

Stainless steel shock-resistant pressure gauge shell and internal components are made of stainless steel. The valve body is filled with silicone oil, so that the pressure gauge pointer plays a role in shock absorption and earthquake resistance.

The stainless steel shock-resistant pressure gauge has both the impact resistance and the corrosion resistance of the stainless steel pressure gauge. Stainless steel shockproof pressure gauge is suitable for industrial and mining places with large vibration and corrosive medium.

1. The ambient temperature of this instrument is-40 ~ 70℃, and the relative humidity does not exceed 80%. If it deviates from the normal temperature by 205℃, additional temperature error should be included.

2. The instrument must be installed vertically and try to keep level with the measuring point. If the difference is too large, the additional error caused by the liquid column will be included, so it is not necessary to consider it when measuring gas. When installing, the explosion-proof port on the back of the box should be blocked to avoid affecting the explosion-proof performance.

3. The measuring range of the instrument in normal use: 3/4 of the upper measuring limit under static pressure and 2/3 of the upper measuring limit under fluctuation. Under the above two pressure conditions, the minimum measured value of the large pressure gauge should not be less than 1/3 of the lower limit, and all vacuum components should be used when measuring vacuum.

4. If the instrument pointer fails or the internal parts are loose or can't work normally, it should be repaired or contacted with the manufacturer for repair.

Replacement and maintenance method of stainless steel seismic table

Release date: September 22, 2021 Author: Click: 44

Replacement and maintenance method of stainless steel seismic table

The stainless steel seismic resistance meter shall be maintained once every three months;

1, check the three-way cock and trap pipe joint, eliminate leakage.

2. Check whether the pressure gauge can return to zero.

3. Check and flush the trap pipe to ensure smooth flow.

After one year's operation, the seismic pressure gauge should be kept at the second level:

1. Remove the pressure gauge and send it to the metering department for calibration and sealing.

2. Dismantle and check the trap pipe, and the thread shall be in good condition.

3. Dismantle and check the three-way cock, polish the sealing surface to ensure no leakage, and its connecting thread should be in good condition.

4, trap pipe, three-way cock derusting, besmear brushs paint.

Replace the seismic pressure gauge in use;

If the pressure gauge is found to be inaccurate during operation, it must be replaced in time. The operation steps are as follows:

1. The pressure gauge to be replaced must be sealed after calibration by the metrological department, and the pressure gauge within the validity period of calibration or a bright new meter with factory certificate.

2. Before replacing the instrument, the three-way cock must be rotated to flush the position of the pressure gauge, and the dirt in the trap pipe must be washed clean.

3. Turn the three-way cock to store water in the trap, remove the old watch with a wrench and replace it with a new pressure gauge.

Turn the three-way cock to its normal working position so that the new watch can be put into operation.

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