Анализ 5 распространенных неисправностей манометров

The pointer fails to return to zero, Large zero position error

Pressure gauges are commonly used measuring instruments and are widely applied in various fields. During their usage, many problems may happen. One of which is failure to return to zero.

In the absence of external pressure, pressure gauge pointer indicates pressure value reading. If the deviation value is greater than the allowable measurement value, it will cause significant interference with the measurement result. It will affect life or even cause safety hazards. The reasons and troubleshooting methods for pressure gauges fail to return to zero as follows,

1, Pressure gauge is under excessive load pressure, excessive deformation of the bourdon tube beyond to elastic coefficient allowable value. The bourdon tube is permanent deformation.

The solution to this kind of failure: remove the pointer, pointer it to zero, and re install it for test.

If the performance still does not meet the requirements after calibration, the bourdon tube have to be replaced.

2, Pressure gauge is shaking, because the fixing screws of pressure gauge are loose. Use professional tools to secure and install screws.

3, The gear teeth of pressure gauge is missing. Because the quantity of meshing teeth between the pressure gauge sector gear and the gear shaft is too less.

4, The pointer indication end is deformed. Because the load pressure on the pressure gauge is too high. Disassemble the pressure gauge and replace the pointer.

5, After working for a period of time, the internal cavity is blocked and need to clean the channel.

The indicating end of the pointer is behind zero stop pin

After the pressure gauge has been working for a period of time, the pointer indicating end will be located behind the zero stop in the dial occasionally. The distance between the pointer and dial of pressure gauge is too large or pointer is not strong enough. When the pressure gauge vibrates violently, the pointer jumps over the stop pin and cannot reset itself after adjusting to the stop pin. Solving method: Gently remove the protective cover of the pressure gauge, lift the pointer to the zero stop pin, and adjust the distance between the pointer and dial to avoid the same fault happening again.

The displacement exceeds the allowable error when tapping the pressure gauge

During the pressure of pressurization and decompression of some pressure gauges, the pointer of pressure gauge will continue to swing when the outer shell is lightly tapped, or the swing amount exceed the absolute value of the indication error. The causes and solutions for this kind of failure as follows,

1, The initial torque is too small during the assembly process before pressure gauges leave factory. Solutions: Adjusting the tightness of hairspring and increasing the initial torque of the pressure gauge.

2, Pressure gauges work in harsh environment for long time. It causes that the hairspring is be corroded.  Solutions: disassemble pressure gauge and replace the hairspring. After a period of usage, part of pressure gauge gear teeth are worn. The temporary measure is that slight wear can be corrected by adjusting the meshing position between gear. If the wear is server, the worn gears need to be replaced.

3, The hairspring or pin seat in pressure gauge falls off, causing the outer ring or inner ring of pressure gauge hairspring to be out of control. Solution: Reinstall the hairspring holder or pin to the original position.

4,Riveting of pressure gauge pointer to the shaft bushing is not enough strong, pointer and bushing vibration or dial fixing screws loose. Solution: Re-tighten the fixing screws of dial rivet the pointer to shaft sleeve.

5, Pressure gauge spring contact with other parts inside the gauge, or spring disorder is common problem that can affect the accuracy and reliability of the pressure gauge. It causes hairspring movement to be restricted. Solution: Re-adjust the hairspring or eliminate contact between the hairspring and adjacent components.

Pointer deflection is not stable

The phenomenon of unstable pointer deflection on a pressure gauge can be generally divided into two situations; First, pointer jitters when moving. There are 2 reasons as follows,

1, Dust enters the sector gear and pinion in the pressure gauge or the sector gear is skewed. Pointer jitter can be eliminated by cleaning stains or correcting the sector gear.

2, Deformation of the pointer causes the pointer to contact the scale disk. Solution: adjusting the pointer shaft to prevent contact with the graduated disk.

Second, the pointer lags and jumps when rotating. There are 5 reasons as follows,

1, The transmission parts inside the pressure gauge rust or get dusty, causing the transmission mechanism to stick. Solution: Remove rust from rusted areas and clean stained areas. If some parts are severely rusted and cannot be completely rusted, the parts need to be replaced.

2, The movement parts of pressure gauge are too tight to move freely. Solution: Readjust the clearance of transmission parts to the appropriate level and add an appropriate amount of lubricant.

3, Pressure difference between the two groups of bearing holes on the upper and lower clamping plates inside the pressure gauge, causing poor transmission of the mechanism. There are difference in the lengths of different pillars in the pressure gauge or the pillars are skewed during riveting. To solve this kind of matter, you can add spacers at the pillars to make the lengths of the pillars also.

4, The small holes at both ends of the tie rod in the pressure gauge, and their connections are not properly matched, causing the tie rod to become stuck. Solution; Adjusting the fit to restore flexibility to a tie rod.

5, The difference between the wheel diameter of pressure gauge and concentricity of wheel shaft. Solution: Straightening the axle

Pointer indication failure

Bourdon tube манометр under load, pointer failure can generally be divided into 3 situations:

1, Pressure gauge does not rotate under load;

2, The pointer rotates normally within a certain range, but when the load pressure is close to 1/3 -3/4 of upper limit of measurement, the pointer gets stuck and stops at a certain position

3, The pointer’s rotation axis is normal after loading, but when it is close to upper limit of measurement, the pointer cannot return by itself after removing the load.

The causes of abnormal rotation of the pressure gauge pointer and the corresponding solutions are as follows:

1, The working environment of pressure gauge has large vibrations, causing pins or screws between bourdon tube and pull rod to fall off, just reinstall the fallen pins or screws, then connect bourdon tube and pull rod together, and then tighten the screws.

2, The damping between sector gear and center gear in the pressure gauge is too large. Generally, add shim to the column to increase the gap between the gear and lower mounting plate.