Failure Reasons and Treatments of Electric Contact Pressure Gauges

Ⅰ. Failure inspection and judgment before repairing electric contact pressure gauges

Before repairing the pressure gauge, check the appearance, such as the appearance of damage, whether the parts are complete, and whether the joint screws are in good condition, etc. Then install the pressure gauge that needs to be repaired on the pressure gauge calibrator, slowly increase the pressure from small to large, and increase to full scale; then gradually reduce pressure from large to small, and reduce to zero. The pressure gauge should be free of needle jamming, obvious non-linearity, and obvious over-tolerance. If there is an abnormal phenomenon, find out the fault location and cause, and then determine the repair method and replacement parts.

Ⅱ. Preliminary verification of electric contact pressure gauges

1. Install the pressure gauge on the calibrator, and use the needle selector to set the two electrical signal pointers outside the upper and lower limits to verify the pressure part. The specific steps are as follows:

(1) Selection of the verification point of the electric contact pressure gauge: select the numbered scale line of the meter to be tested as the verification point. Note: According to the verification point determined by the calibration meter, it is the indication point of the standard meter and is used as the experimental point.

(2) Gradually increase the pressure of the electric contact pressure gauge in the upward stroke direction (from small to large), so that the standard indication value reaches each verification point, check it point by point, and record each verification point before tapping the case and tapping the case. After the indication.

(3) Press the stroke direction (from large to small) to gradually reduce pressure, so that the standard indication value reaches each verification point, check point by point, and record the value of each verification point before and after tapping the case.

(4) Repeat 5 times of "up stroke + down stroke" and record the data in the experimental data record table.

2. The following situations generally occur during the initial inspection:

(1) When the applied pressure reaches the upper limit of the measured value of the pressure gauge, the pointer does not move or moves very little, indicating that the pressure is not transmitted to the spring tube. At this time, check whether the passage and spring tube at the joint of the pressure gauge calibrator are blocked.

(2) When the pressure is increased to a certain value, the pointer gradually drops back. At this time, check whether there is any leakage in the connecting pipeline and spring tube.

(3) When the electric contact pressure gauge is in the process of pressurization, the pointer of the calibration meter will be bounced, sluggish or deteriorated, indicating that the transmission mechanism has friction, and its meshing and wear should be checked.

(4) After the pressure of the electric contact pressure gauge is removed, the pointer of the calibrated gauge does not return to zero and exceeds the allowable error of the instrument. After adjustment, the indication error is still uneven, indicating that the spring tube has been deformed and needs to be replaced.

Ⅲ. The main failures and causes of electric contact pressure gauges

1. The pressure gauge of electric contact has a great change. Cause: There is friction between the mechanisms or the upper and lower splints are misaligned, causing the shaft to tilt; the pin is loose, the shaft hole is worn, and the connecting screw is loose; the transmission mechanism is not clean; the balance spring torque is insufficient; the spring tube has a large elastic aftereffect.

2. The indication error of the electric contact pressure gauge is large. Reason: The pointer is loose from the central axis or the copper sleeve; the pointer collides with the dial or glass surface; the scale is not concentric with the axis.

3. The pointer of the pressure gauge with electric contact jumps and rotates. Reason: the free end of the spring tube and the connecting rod connecting screw are not moving; the connecting rod and the sector gear connecting block are too tight; the joint surface of the sector gear, the central gear and the splint is not parallel or damaged, and the meshing is too tight; the two shafts of the gear The end journals are not concentric and are bent.

4. The sector gear and central gear of the electric contact pressure gauge cannot rotate flexibly. Reasons: The gear mesh is too tight; there is dirt at the gear mesh; the shaft hole is too small; the plane of the sector gear and the central gear are not perpendicular to each other.

5. The pointer of the electric contact pressure gauge does not move or moves very little. Reason: Leakage of spring tube needs repair welding.