Atlas Copco Oil Stop Valve C111 Replacement – 2901203800

Atlas Copco 2901203800 – Oil Stop Valve C111

The Atlas Copco 2901203800 (2901-2038-00) Oil Stop Valve C111 is a service and replacement component 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 continuous supply of lubricating oil for cooling, lubrication, sealing, and efficient compression. Oil circulates through the compressor oil circuit under controlled pressure.

The Oil Stop Valve C111 regulates the oil passage between the oil circuit and the compressor air-end. When the compressor is running, the operating pressure acts on the internal valve mechanism and moves the valve into its operating position.

This allows the required compressor oil to reach the air-end. The circulating oil lubricates the rotating screw components, removes heat generated during compression, and assists in sealing the clearances between the screw rotors.

When the compressor unloads or stops, the pressure conditions in the oil circuit change. The valve mechanism responds to the reduced operating pressure and moves toward the closed position.

The Oil Stop Valve then restricts the oil passage. This prevents excessive oil from continuing to drain or migrate into the air-end while the compressor is stopped.

This shutdown function is important because uncontrolled oil migration can cause excessive oil accumulation inside the air-end. This may lead to difficult starting, increased oil consumption, oil carryover, abnormal compressor operation, or excessive load during restart.

The 2901203800 is listed in Atlas Copco-related parts references as “OIL STOP VALVE C111” and as “Oil Stop Valve C111 MB.” Other parts references list the same part number as a Kit, Oil Stop/Check Valve, indicating that application descriptions can vary by catalog or compressor configuration.

The valve works through pressure-operated movement and spring-assisted closing. The internal valve mechanism responds to compressor operating pressure, while the spring force assists in returning the valve toward the closed position when the compressor unloads or stops.

The sealing components around the valve prevent oil leakage and maintain the required pressure conditions for proper operation.

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

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

A defective Oil Stop Valve may remain partially open after compressor shutdown. This can allow oil to migrate into the air-end and may cause excessive oil accumulation, increased oil carryover, increased oil consumption, 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 rotor sealing.

Maintenance Procedure:

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

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

The defective valve and associated service components should be replaced using the 2901203800 Oil Stop Valve C111.

All sealing components must be installed correctly and must not be twisted, cut, or damaged. The valve and spring must be installed in the correct position and orientation.

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

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

During testing, the Oil Stop Valve should permit 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 2901203800 Oil Stop Valve C111 during appropriate maintenance helps restore oil-flow control, reduce oil migration, improve shutdown behavior, protect the compressor air-end, and maintain dependable compressor performance.

Part Number: 2901203800
Alternative Number: 2901-2038-00 / 2901 2038 00
Brand: Atlas Copco
Part Description: Oil Stop Valve C111
Component Type: Oil-stop valve
Application: Compatible oil-injected rotary screw compressors
Known Designation: C111
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, and dependable compressor operation.

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