Answer: There are two adjustment screws on the pressure switch. One is the pressure adjustment screw, which is used to
adjust the empty starting pressure. The counterclockwise direction increases the empty pressure. The other is to adjust the pressure difference, that is, the loaded pressure. The counterclockwise direction increases the pressure difference.
Reasonable empty and loaded pressure can improve the working efficiency of the air compressor, reduce the operating time of the air compressor, and extend the service life of the air compressor. The following issues should be noted when setting the pressure switch:
(1) The empty and loaded pressure settings of the pressure switch are set based on the upper and lower limits of the air compressor joint control cabinet pressure. The upper and lower limits of the air compressor joint control cabinet pressure are set based on the gas-using equipment as a reference.
(2) The empty pressure is set lower than the rated pressure of the air compressor. It is generally 0.02MPa lower than the rated pressure.
(3) Since the pressure points are different, there should be a certain difference between the empty pressure and the upper limit pressure of the air compressor control cabinet. This difference is due to the pressure drop of equipment such as air dryers and air filters. Generally, when the compressed air flow is stable, the maximum pressure drop after passing through the filter and dryer is set to 0.05MPa. If the upper limit pressure of the air compressor control cabinet is set to 0.75MPa, the empty pressure setting of the pressure switch should be lower than 0.7MPa.
(4) The oil fine separator can produce a maximum pressure difference of 0.11MPa. If the empty pressure setting is equal to the rated pressure of the air compressor, the maximum actual working pressure of the air compressor may exceed the rated pressure, thereby causing the air compressor motor to overcurrent. If the air compressor motor capacity does not have a 10% overload margin, the air compressor will fail and shut down due to overcurrent. In this case, the empty pressure of the air compressor should be lower than the rated pressure, and the specific value can be determined based on the on-site equipment.
(5) Once the air compressor stops due to being idle for too long, the joint control cabinet cannot start the machine when the system pressure is lower than the lower limit, and the pressure switch of the machine is used to start the machine.
(6) The difference between the empty pressure and the loaded pressure of the pressure switch should preferably be more than 0.15MPa to facilitate the operation accuracy of the pressure switch.
(7) The loaded pressure setting value of the pressure switch should be higher than the lower limit of the joint control cabinet pressure, and the pressure drop of equipment such as air dryers and air filters should be considered. For example, if the lower limit of the joint control cabinet pressure is 0.55MPa, the loaded pressure setting value should be greater than 0.60MPa.
(8) The empty and loaded pressure settings of the pressure switch should be based on the principle of not causing frequent start and stop of the air compressor. That is, when the system pressure is high, the pressure switch first sends an empty signal, and when the pressure continues to rise, the joint control cabinet sends a stop signal; conversely, when the system pressure is low, the pressure switch first sends a loaded signal, and when the pressure continues to drop, the joint control cabinet sends a start signal.
(9) When multiple air compressors are connected in parallel, the empty and loaded pressure settings of the pressure switch cannot be set to a gradually increasing or decreasing fixed value. If this is set, it will cause a machine to be frequently turned on or off, reducing the service life of the machine. The setting values should be consistent to facilitate the normal switching and operation timing of the host of the joint control cabinet.
