Atlas Copco Oil Stop Valve Kit Replacement – 2901203900

Atlas Copco 2901203900 – Oil Stop Valve Kit

The Atlas Copco 2901203900 (2901-2039-00) Oil Stop Valve Kit is a service and replacement kit used in compatible oil-injected rotary screw compressor systems. Its primary function is to control the flow of compressor oil to the air end and prevent unwanted oil migration when the compressor unloads or stops.

Working Process:

During normal compressor operation, the screw air end requires a controlled supply of compressor oil for lubrication, cooling, sealing, and efficient compression. Oil circulates through the compressor oil circuit under pressure.

The Oil Stop Valve regulates the oil passage to the compressor air end. When the compressor is operating, the pressure conditions in the oil circuit act on the valve mechanism and move it into the operating position, allowing the required oil flow.

The circulating oil reaches the air end and performs several important functions. It lubricates the moving screw components, removes heat generated during compression, and helps seal the internal clearances between the screw rotors.

When the compressor unloads or stops, the operating pressure in the oil circuit changes. The spring-loaded valve mechanism moves toward its closed position.

The Oil Stop Valve restricts the oil passage and prevents excessive oil from draining or migrating into the air end while the compressor is stopped.

This shutdown function is important because uncontrolled oil migration can cause excessive oil accumulation in the air end. Such a condition may result in difficult starting, increased oil consumption, oil carryover, abnormal compressor operation, or excessive load during restart.

Parts references identify 2901203900 as an Oil Stop Valve Kit, with the equivalent number 2901-2039-00. A specific parts reference identifies it as Oil Stop Valve C90 MB, while another identifies it as an OEM oil-stop valve kit used on a range of Atlas Copco and Chicago Pneumatic rotary screw compressors, commonly with the C96 air end.

The valve assembly operates through pressure-assisted movement and spring-assisted closing. During operation, compressor pressure moves the valve toward the open position. When operating pressure decreases during unloading or shutdown, the spring force returns the valve toward the closed position.

The sealing components maintain a leak-resistant connection between the valve and compressor housing and help maintain the required oil pressure for correct valve operation.

During continuous compressor service, the Oil Stop Valve is exposed to hot compressor oil, pressure fluctuations, vibration, temperature variations, contamination, and repeated loading/unloading cycles.

Over time, the valve mechanism may become contaminated or worn. Springs can lose their required closing force, while sealing components can harden, deteriorate, or become damaged.

A defective Oil Stop Valve may remain partially open after shutdown. This can allow oil to migrate into the air end and may cause excessive oil accumulation, increased oil consumption, oil carryover, difficult starting, or abnormal compressor behavior.

If the valve becomes restricted or fails to open correctly during operation, the oil supply to the air end may be reduced. Insufficient oil circulation can negatively affect lubrication, cooling, and sealing of the compressor element.

Maintenance Procedure:

Before servicing the Oil Stop Valve, the compressor must be stopped, electrically isolated, completely depressurized, and allowed to cool.

The existing valve assembly should be removed according to the applicable Atlas Copco maintenance procedure. The valve mechanism, spring, sealing surfaces, and oil passages should be inspected for wear, contamination, corrosion, deformation, and leakage.

The defective valve and associated service components should be replaced using the 2901203900 Oil Stop Valve Kit.

All sealing components must be installed correctly and without twisting, cutting, or damaging the sealing surfaces. The valve and spring must be installed in their correct positions and orientations.

After reassembly, the compressor should be checked for oil leakage and correct valve movement.

The compressor should then be operated through its start-up, loaded, unloaded, and shutdown cycles.

During testing, the Oil Stop Valve should allow the required oil flow during normal operation and close effectively when the compressor unloads or stops.

Correct operation of the Oil Stop Valve maintains the required oil supply during compressor operation while preventing unwanted oil migration during shutdown.

Using the Atlas Copco 2901203900 Oil Stop Valve Kit during scheduled maintenance helps restore oil-flow control, reduce oil migration, improve shutdown behavior, protect the compressor air end, and maintain dependable compressor performance.

Part Number: 2901203900
Alternative Number: 2901-2039-00 / 2901 2039 00
Brand: Atlas Copco
Part Description: Oil Stop Valve Kit
Related Description: Oil Stop Check Valve Kit
Known Designation: Oil Stop Valve C90 MB
Known Application: Compatible oil-injected rotary screw compressors; references also associate it with C96 air-end applications
Component Type: Oil-stop valve service/repair kit
Primary Function: Controls oil flow to the compressor air end
Secondary Function: Prevents excessive oil migration during unloading and shutdown
Operating Function: Allows controlled oil circulation during operation and restricts oil flow when the compressor stops
Main Benefits: Proper lubrication, cooling, sealing, reduced oil migration, improved starting reliability, reduced oil carryover, and dependable compressor operation.

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