Malfunction of false signal generated by pressure switch itself

The main faults of pressure relays are false signals and failure to send signals. Proper use and adjustment can avoid such faults. Due to poor fit between the plunger and the sleeve, the plunger got stuck and the pressure relay did not operate

 

The clearance between the plunger and the sleeve hole should be ensured to be 0.007-0.15mm. During assembly, it should be cleaned thoroughly and then coated with disulfide keys to enhance lubrication. Users often think that the disulfide keys are dirt and wash them off.

 

The rubber film has ruptured.

 

The working principle of a pressure relay is that when the oil pressure rises, the film bulges and pushes the plunger to work. When the thin film ruptures, the pressure oil directly acts on the plunger, causing oil to leak out from the clearance between the plunger and the sleeve hole, resulting in significant changes in the working value and return area of the pressure relay, leading to instability and resulting in misoperation. At this point, a new film can be replaced.

 

Micro switch positioning is not secure

 

The micro switch of DP-63 pressure relay used to rely solely on a screw for compression and positioning, which prevented it from moving forward. A small screw still felt insufficient rigidity. Therefore, during wiring and disconnection, the force applied by the screwdriver to the micro switch and the force of twisting the wire when removing the cover during maintenance both cause the micro switch to be misaligned, resulting in a change in the action value, altering the previously adjusted action pressure, and mistakenly sending the action signal.

 

Micro switches are not sensitive and have poor resetting performance

 

The spring spring inside the micro switch is not elastic enough, and the contact cannot bounce up after being pressed, or due to dust sticking to the contact, the electrical signal of the micro switch is abnormal and the action signal is mistakenly sent. At this time, the micro switch should be repaired or replaced.

 

Poor manufacturing accuracy of pressure pressure switch

 

The lever rotation is not flexible, the clearance between the lower seat and upper body of the spring is too small, the plunger size is not accurate, and the main and auxiliary adjustment screws of the pressure relay are loosely adjusted. The lever cannot function as a pressure micro switch, and the pressure relay fails.

 

PF type pressure switch

 

If the oil drain chamber is not directly connected to the oil tank, it may cause false signals due to high back pressure at the oil drain port.

 

Differential pressure switch

 

Due to the separation of the microswitch and the oil discharge chamber by a rubber membrane, when the inlet and outlet chambers are reversed, the pressure oil will break through the rubber diaphragm and enter the microswitch, causing damage to the microswitch and resulting in misoperation or failure to operate. In addition, due to the communication between the pressure regulating spring chamber and the oil discharge chamber, there is no sealing device at the adjusting screw. Therefore, there may be leakage at the adjustment screw, so the drain port and the inlet port cannot be reversed, and the drain port L must be separately connected back to the oil tank.

The above:Structure and working principle of spur gear pump