Atlas Copco Inlet Valve Service Kit Replacement – 2906065900

Atlas Copco 2906065900 – Inlet Valve Service Kit

The Atlas Copco 2906065900 (2906-0659-00) is an Inlet Valve Service Kit designed for compatible ZR and ZT oil-free screw compressors. Atlas Copco specifically references the kit for the ZR/T 55–90 range. The official catalog lists a kit weight of approximately 180.076 g.

The inlet valve is an important part of the compressor air-intake and control system. It regulates the flow of atmospheric air entering the compressor element and helps control the compressor between its operating and unloaded conditions.

Working Process:

During normal compressor operation, atmospheric air enters through the compressor inlet system.

The inlet valve controls this airflow before the air reaches the compressor element. When the compressor needs to produce compressed air, the valve moves to its operating position and permits the required quantity of air to enter.

The compressor element then compresses the incoming air and delivers it through the subsequent compressor stages and air-treatment system.

When the compressor reaches the required operating condition or the control system commands unloading, the inlet valve changes position.

The valve restricts the incoming airflow, reducing the amount of air supplied to the compression element. This places the compressor into its unloaded or reduced-capacity condition.

When compressed-air demand increases again, the control system commands the inlet valve to return toward its operating position.

The valve opens sufficiently to restore the required air intake, allowing the compressor to resume normal air production.

This automatic control of inlet airflow helps the compressor respond to changing air demand while maintaining efficient operation.

Main Functions:

• Controls compressor inlet-air flow.
• Supports compressor loading and unloading.
• Regulates the amount of air entering the compression system.
• Helps maintain stable compressor operation.
• Supports efficient compressor capacity control.
• Helps prevent unwanted air leakage through the inlet-valve assembly.
• Restores sealing and valve-control performance during maintenance.

Official Kit Components:

Atlas Copco’s official catalog lists the following components for 2906065900:

• O-ring – 1 pc
• Pin Spring – 1 pc
• O-ring 49.2 × 5.7 – 1 pc
• O-ring – 1 pc
• Diaphragm – 1 pc
• O-ring – 1 pc
• O-ring – 1 pc
• O-ring – 1 pc
• Membrane – 1 pc

These components are used to restore the sealing and control characteristics of the inlet-valve assembly.

The O-rings provide sealing between the valve and associated components, preventing unwanted air leakage.

The diaphragm and membrane form part of the valve’s pneumatic control mechanism. Changes in control pressure act on these flexible components to produce the required valve movement.

The pin spring provides the required mechanical force for the valve mechanism and supports correct component positioning.

Operating Cycle:

1. Start-up: The inlet-valve control system places the valve in its required starting position.
2. Air Intake: Atmospheric air enters through the compressor inlet.
3. Loading: The valve permits the required airflow into the compressor element.
4. Compression: The compressor element compresses the incoming air.
5. Control Command: When the required operating condition is reached, the control system changes the inlet-valve position.
6. Unloading/Capacity Reduction: The valve restricts the incoming airflow.
7. Reduced Air Intake: Less air enters the compressor element.
8. Demand Increase: System demand causes the control system to request increased compressor output.
9. Valve Reopening: The inlet valve returns toward its operating position.
10. Normal Compression: The compressor resumes the required air intake and compression.

The cycle is controlled automatically by the compressor’s pneumatic/electrical control system.

Role of the Diaphragm and Membrane:

The diaphragm and membrane are important for pneumatic valve actuation.

Control pressure acts on the flexible membrane/diaphragm and produces movement in the valve mechanism.

If these components become damaged, hardened or degraded, the valve may not respond correctly to control-pressure changes.

This can result in incomplete opening, incomplete closing or delayed valve response.

Importance of O-Rings:

The O-rings supplied in the 2906065900 service kit maintain airtight sealing between the valve’s mating components.

Over time, O-rings can become hardened, flattened, cracked or damaged because of operating conditions and repeated movement.

A leaking O-ring can reduce control pressure and interfere with correct inlet-valve operation.

Replacing the O-rings during service restores the sealing performance of the assembly.

Possible Failure Conditions:

Long-term operation can cause the inlet-valve service components to deteriorate.

Possible failure conditions include:

• Damaged O-rings
• Hardened seals
• Damaged diaphragm
• Damaged membrane
• Weak or damaged spring
• Valve sticking
• Pneumatic leakage
• Contamination
• Restricted valve movement
• Incorrect inlet-air control

Typical compressor symptoms may include:

• Compressor fails to load correctly.
• Compressor fails to unload correctly.
• Reduced air delivery.
• Slow pressure build-up.
• Unstable compressor operation.
• Excessive air leakage.
• Delayed inlet-valve response.
• Inlet valve remains partially open.
• Inlet valve remains restricted.
• Abnormal compressor cycling.

If the inlet valve does not open sufficiently, the compressor may receive inadequate air and its output can decrease.

If the valve does not restrict airflow correctly during unloading, the compressor may continue drawing unnecessary air.

Maintenance Procedure:

Before servicing the inlet valve, the compressor must be stopped, isolated from its electrical supply and depressurized according to the applicable Atlas Copco safety procedure.

Inspect the valve assembly for:

• Damaged O-rings
• Hardened or cracked seals
• Damaged diaphragm
• Damaged membrane
• Weak or damaged spring
• Contamination
• Restricted movement
• Pneumatic leakage
• Abnormal control response

Remove the old service components carefully without damaging the valve housing or sealing surfaces.

Install the replacement components supplied with the 2906065900 Inlet Valve Service Kit according to the applicable Atlas Copco service instructions.

Clean all mating and sealing surfaces before assembly.

O-rings must be installed correctly without twisting, cutting, overstretching or pinching.

The diaphragm and membrane must be correctly positioned and free from folds or damage.

The spring must be installed in its specified location.

After assembly, verify that the valve mechanism moves correctly and that the control circuit does not have abnormal leakage.

Restart the compressor and monitor several operating cycles.

Verify that:

• The inlet valve responds correctly to control commands.
• The compressor loads correctly.
• The compressor unloads correctly.
• Air delivery is normal.
• Pressure remains stable.
• No abnormal pneumatic leakage is present.
• Valve movement is smooth and unrestricted.

A correctly serviced inlet valve ensures reliable control of compressor air intake and supports stable and efficient operation of the ZR/ ZT compressor.

Using the Atlas Copco 2906065900 Inlet Valve Service Kit during appropriate maintenance restores the valve’s sealing, pneumatic-control and airflow-regulation performance.

Part Number: 2906065900
Alternative Number: 2906-0659-00 / 2906 0659 00
Brand: Atlas Copco
Official Description: Inlet Valve Service Kit
Application: ZR / ZT oil-free screw compressors
Known Application: ZR/T 55–90
Official Listed Weight: 180.076 g
Component Type: Inlet valve pneumatic service/repair kit
Main Components: O-rings, pin spring, diaphragm and membrane
Primary Function: Controls compressor inlet-air flow
Secondary Function: Supports compressor loading, unloading and capacity control
Operating Function: Regulates airflow entering the compressor element according to the control signal
Main Benefits: Reliable inlet-air control, improved sealing, stable compressor operation, proper load/unload response and efficient compressor performance.

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