Air compressors have different valves, and each valve has a different function. If you can thoroughly understand the design function and working principle of each valve, it will play a vital role in the later inspection and maintenance of the air compressor.
Because the valve has a certain service life, when the use time reaches the limit that the valve can withstand, it is inevitable that the valve will fail, so how should we avoid the occurrence of failure! This article will give some support and help to the solution of common valve faults!

The five major valve parts of the fuel injection air compressor are: Unloatding valve, Min pressure valve, Oil stop valve, Check valve, Thermostatic valve, the following is an explanation of the function and troubleshooting of each valve part one by one.

A. Unloatding Valve

Function: When the air consumption changes, the intake valve adjusts the opening degree of the valve body through the control system to match the air consumption. It is a valve that controls the air compressor to produce and not produce gas.

Common corresponding faults:
1.The air compressor does not load. This fault control panel displays (no alarm; operating status ‘loading’; fuel injection pressure is very small or ‘0’; head outlet temperature<70C°) to conclude that the unit is not loaded. The problem lies in the unloading valve body, control circuit, loading and unloading solenoid valve, etc., which need to be checked and eliminated one by one.
2. The air compressor is not unloaded. This failure control panel displays (no alarm; operating status ‘unloading’; fuel injection pressure rise> 4; head outlet temperature> 80°C), and it can be concluded that the unit is not unloaded. The problem lies in the unloading valve body, control circuit, loading and unloading solenoid valve, etc., which need to be checked and eliminated one by one.

B. Min pressure valve

Function:
1. The opening pressure of the minimum pressure valve is about 4bar, to ensure that the pressure in the cylinder is not lower than this minimum pressure when the air is output, so as to prevent the air flow rate from being too fast to reduce the separation effect of the oil and gas separator.
2.When the machine starts, a certain pressure is established in the oil cylinder to ensure lubricating oil circulation and provide initial control pressure to the control loop. 3. It has the function of a one-way valve to prevent the compressed air from the pipe network from returning to the inside of the machine.

Common corresponding faults:
1. The safety valve of the oil cylinder blows air during operation. This failure is because the minimum pressure valve is not opened, which causes the pressure in the cylinder to be too high, and the safety valve is pressure-relief protection.
2. The computer has motor overload protection during operation. This fault is that the minimum pressure valve is not opened, causing the pressure in the cylinder to be too high, the main motor load increases, the current increases, and the thermal relay protects and stops.
3. The air compressor failed to start. This fault is that the minimum pressure valve is not closed tightly, causing the compressed air of the pipe network to return, causing a certain pressure in the oil cylinder, causing the unit to fail to start. When the air compressor is started, when the control computer detects a certain pressure in the cylinder, the unit will not be able to start.
 4. The oil pressure is too high when the air compressor is unloaded. This fault is that the minimum pressure valve is not closed tightly. When the unit is unloaded, the compressed air of the pipe network returns, which causes the pressure in the oil cylinder to rise, which causes the oil pressure to rise, and the energy consumption of the unit increases.

C. Oil Stop Valve

Function:
After the air compressor is turned on, the oil cut-off valve is opened, and the lubricating oil that has passed through the oil filter is injected into the main engine. After the compressor is shut down, the oil cut-off valve is closed to cut off the oil supply.

Common corresponding faults:
1. The machine will trip at high temperature quickly after starting up. This fault is that the oil cut-off valve is not opened and the lubricating oil cannot be sprayed into the machine head. The oil cut-off valve needs to be checked and maintained.
2. Air compressor high temperature alarm. This fault is that the oil cut-off valve is not fully opened, and the amount of lubricating oil sprayed into the machine head is insufficient, and the oil cut-off valve needs to be cleaned and maintained.
3. Lubricant will be sprayed back into the air filter when the machine stops suddenly. This fault is caused by the lagging or lax closing of the shutoff valve when the unit suddenly shuts down. The shutoff valve needs to be cleaned and maintained.

D. Check valve

Function:
The oil and gas mixture compressed by the main engine is transported to the oil cylinder in one direction to prevent the oil and gas mixture in the cylinder from being sprayed back into the machine head when the machine is shut down due to a sudden failure, causing the rotor to reverse rotation.

Common corresponding faults:
The oil and gas mixture is sprayed back into the air filter during shutdown. This fault is caused by the one-way valve stuck or damaged when the unit suddenly shuts down, and the one-way valve needs to be cleaned and maintained.

E. Thermostatic valve

Function:
1. The temperature control spool uses the principle of thermal expansion and contraction, extending and contracting to adjust the change of the oil passage formed between the valve body and the housing, control the proportion of lubricating oil entering the oil cooler, and ensure that the rotor temperature is within the control range.
2. The temperature control valve is an original part that controls the outlet temperature of the machine head not less than 68℃. When the oil temperature is low, the temperature control valve is closed, and the lubricating oil is directly sprayed into the machine head without passing through the cooler to quickly heat up, so that the machine head outlet temperature rises rapidly. High to prevent condensed water in the compressed air from being generated in the cylinder.

Note:
1. The opening temperature of the thermostatic valve is generally indicated on the valve core.
2. The maximum opening temperature of the thermostatic valve is the marked temperature + 15°C.