If the air inlet valve is open and closed normally, but the exhaust valve stem is not open when it should be opened, then the air in the cylinder cannot be discharged, and the air of time and space when the piston moves upward is compressed again, which forces the pressure of high pressure air to rise. At this time, the pressure inside the cylinder will greatly exceed the original air inlet pressure, causing the motor to be overloaded, and the leather belt may slip, or the motor rotor will make a sound of banging, or the fuse will be blown out due to the excessive current, in severe cases, the machine running parts are overloaded and the top of the cylinder will fall off. Therefore, this kind of situation is very harmful, and we should try our best to avoid it.
This phenomenon rarely appears in the process of normal operation, mainly when parking or restarting after overhaul. Because the plunger oil pump is lack of oil or has poor sealing, air enters into the oil tube, causing the exhaust valve to fail to open. In order to avoid the above phenomenon, during the test run, the expansion machine should be operated without load, check whether the exhaust valve stem is normal, and then send compressed air to the expansion machine after it is normal. During normal operation, it should be noted that the oil level in the oil storage box is not less than 2/3 of the oil level gauge.
Once the above phenomenon occurs in the operation, the dryer blow-off valve should be opened immediately to release the pressure. And open the exhaust oiling needle, and then close it after the bubbles are discharged. After the exhaust valve works normally, turn off the drier blow-off valve to boost the pressure.
