How to Clean Compressor Spare Parts

1. Cleaning of Load Relief Safety Valve (Intake Valve)

If the intake valve is heavily contaminated, switch to a different type of cleaning agent during cleaning. Clean cleaner components first, 

followed by heavily soiled parts to avoid corrosion and premature service life reduction of components. Parts rinsed with clean water shall be placed in a clean area for air drying to prevent rusting of iron-containing components.

When cleaning the valve plate and the valve body contacting the valve plate, pay attention to the flatness of the contact surfaces. Clean or replace the components if necessary. 

Otherwise, the air compressor will face heavy startup load (failure to start under loaded conditions for large screw air compressor units).

2. Cleaning of Minimum Pressure Valve (Pressure Maintaining Valve)

Although the minimum pressure valve of a screw air compressor looks compact, it governs the operation of the whole unit. 

The maintenance methods for the minimum pressure valve of screw air compressors are introduced below to ensure stable operation under normal working conditions.

The minimum pressure valve consists of valve body, valve spool, adjusting nut, spring and sealing elements. Its main functions are establishing internal unit pressure, 

facilitating lubricating oil circulation and meeting the operating pressure requirements of pressure reducing valves. In addition, 

the minimum pressure valve acts as a check valve to prevent backflow of compressed air from the air receiver tank to the air compressor during unit unloading.

The minimum pressure valve features a simple structure. Unscrew the nut between the valve spool and valve body to remove internal components. 

The valve spool of small-size minimum pressure valves can be fitted inside the valve body; all internal parts can be disassembled after removing the valve cover.

The minimum pressure valve can be cleaned following the cleaning procedure for load relief safety valves. Its assembly process will not be described item by item due to the simple structure. However, 

attention must be paid to the orientation of the U-ring if equipped internally. After completing the full cleaning procedure of the screw air compressor minimum pressure valve, reinstall it onto the air compressor.

3. Cleaning of Oil Return Check Valve

The check valve is composed of valve body, steel ball, steel ball seat, spring and other components. The oil-air mixture compressed by the air compressor air end is firstly separated by centrifugal force inside the oil tank. 

Since oil is heavier than air, most oil in the oil-air mixture falls into the oil tank under centrifugal force. Driven by internal pressure, oil flows back to the air end of the screw air compressor for lubrication circulation. 

Compressed air carrying trace oil is further separated by the oil-air separator.

The lubricating oil separated by the oil-air separator accumulates at the bottom of the separator. To prevent this oil from being carried away by compressed air, 

an oil pipe is designed to extend to the separator bottom. Internal pressure delivers the recovered oil directly to the air end for lubrication. 

A check valve is installed on the oil pipe, known as the oil return check valve for screw air compressors.

It enables smooth oil recovery from the separator to the air end and prevents reverse flow of oil from the air end into the oil-air separator. The single-circuit valve is mounted on the valve body. Loosen the valve body, then remove the spring, 

steel ball and steel ball seat.

Cleaning procedures for oil return check valve: Use cleaning agent to flush the valve body, spring, steel ball and steel ball seat. Some check valves are equipped with built-in filters, which shall be cleaned together if present.
4. Cleaning of Thermostatic Valve
The thermostatic valve used in central air conditioning systems consists of valve body, valve spool, temperature sensing element and spring. It realizes constant temperature control.

When the oil temperature detected by the temperature sensing element of the thermostatic valve is lower than the actuation value (typically 71°C for temperature sensing elements), 

lubricating oil flows directly back to the air end from the oil-air tank.

When the measured oil temperature exceeds the actuation value, the temperature sensing element actuates to open the built-in bypass valve, 

diverting lubricating oil into the cooler for cooling. The higher the detected temperature, the larger the opening of the bypass valve. Cooled lubricating oil then flows back to the air end.

The thermostatic valve of screw air compressors is fitted with a cover equipped with threaded holes. Select a suitable nut and screw it into the cover. Use a spring clip to remove the retaining spring for the cover, 

pull out the nut installed previously, and then remove the cover and all internal components. Clean all parts of the thermostatic valve according to the cleaning method for pressure reducing valves.

After all the above components are cleaned and dried, they can be installed back onto the air compressor. Once all components are reassembled, double-check for missing parts, and clear away tools and sundries left during installation.