Atlas Copco Unloading Valve Kit Replacement – 2906009700

Atlas Copco 2906009700 – Unloading Valve Kit

The Atlas Copco 2906009700 (2906-0097-00) is an Unloading Valve Kit, also referred to as an Unloader Valve Service/Repair Kit, used in compatible Atlas Copco screw air compressors.

The unloading valve is an important part of the compressor control system. It helps place the compressor into a loaded or unloaded operating condition according to the compressed-air demand and system pressure.

Working Process:

During normal loaded operation, the compressor control system allows the compressor to draw atmospheric air through the inlet system. The screw compressor element compresses this air and supplies compressed air to the downstream system.

As the system pressure reaches the specified unload pressure, the compressor controller activates the unloading circuit.

The unloading valve changes position and reduces or interrupts the effective compression process. Depending on the compressor design, this is achieved by controlling the compressor inlet or associated control/pressure circuit.

When the compressor is unloaded, the compressor produces little or no useful compressed-air output while reducing the power required for continuous full-load compression.

As downstream equipment consumes compressed air, system pressure falls.

When the pressure reaches the specified load point, the control system changes the valve position again. The compressor returns to loaded operation and resumes normal compressed-air production.

This automatic load/unload cycle allows the compressor to match air production with demand.

Main Functions:

• Controls compressor unloading.
• Supports automatic load/unload operation.
• Regulates the compressor control/inlet circuit.
• Helps maintain stable system pressure.
• Reduces unnecessary compression during low-demand periods.
• Helps reduce unloaded operating power.
• Restores valve sealing and mechanical performance during maintenance.

Operating Cycle:

1. Start-up: The unloading system places the compressor in the required starting condition.
2. Loading: The control system allows normal compressor operation.
3. Compression: Atmospheric air is compressed by the screw element.
4. Pressure Build-up: System pressure increases.
5. Unload Command: The controller activates the unloading valve when the unload condition is reached.
6. Unloading: The valve changes position and reduces compressor output.
7. Pressure Reduction: Downstream air consumption lowers system pressure.
8. Load Command: The controller returns the valve toward the loaded position.
9. Normal Operation: The compressor resumes compressed-air production.

Valve Function:

The unloading valve operates in response to the compressor’s control signal.

Its internal components must move smoothly and maintain proper sealing so that the control pressure can act correctly.

Sealing elements prevent unwanted leakage through the valve assembly.

When the valve is commanded to unload, the mechanism changes the compressor’s operating condition.

When a load command is received, the valve returns to the normal operating position.

The 2906009700 kit is used when serviceable components of the unloading valve become worn, contaminated or damaged.

Possible Failure Conditions:

With prolonged operation, the unloading valve can experience seal deterioration, contamination, mechanical wear or sticking.

If the valve fails to unload, the compressor may remain loaded after reaching the required pressure. This can increase power consumption and cause unnecessary compressor operation.

If the valve fails to load correctly, the compressor may not produce the required amount of compressed air.

A damaged sealing component can cause control-air leakage and unreliable valve response.

Typical symptoms may include:

• Compressor fails to unload.
• Compressor fails to load.
• Slow pressure build-up.
• Reduced air delivery.
• Compressor remains continuously loaded.
• Excessive power consumption.
• Unstable system pressure.
• Delayed load/unload response.
• Control-air leakage.
• Valve sticking or restricted movement.

Maintenance Procedure:

Before servicing the unloading valve, the compressor must be stopped, electrically isolated and completely depressurized according to the applicable Atlas Copco safety procedure.

The unloading valve assembly should be inspected for:

• Damaged seals
• Worn internal components
• Contamination
• Valve sticking
• Damaged mating surfaces
• Control-air leakage
• Restricted movement
• Abnormal load/unload response

Remove the worn service components carefully without damaging the valve body or associated control components.

Install the 2906009700 Unloading Valve Kit according to the applicable Atlas Copco service instructions.

Clean all sealing and mating surfaces before assembly.

Install the replacement sealing components correctly and ensure that they are not twisted, cut or damaged.

Check the valve mechanism for smooth movement before returning the compressor to service.

After assembly, restart the compressor and observe several complete load/unload cycles.

Verify that:

• The compressor loads correctly.
• The compressor unloads at the appropriate pressure condition.
• The unloading valve responds smoothly.
• System pressure remains stable.
• No abnormal control-air leakage is present.
• The compressor does not remain unnecessarily loaded.

A correctly functioning unloading valve allows the compressor to respond efficiently to changing compressed-air demand.

Using the Atlas Copco 2906009700 Unloading Valve Kit during appropriate maintenance helps restore valve movement, sealing, load/unload response and reliable compressor operation.

Part Number: 2906009700
Alternative Number: 2906-0097-00 / 2906 0097 00
Brand: Atlas Copco
Part Description: Unloading Valve Kit
Also Referenced As: Unloader Valve Kit / Unloading Valve Repair Kit
Component Type: Compressor unloading/control valve service kit
Primary Function: Controls compressor loading and unloading
Secondary Function: Regulates the compressor control/inlet circuit
Operating Function: Changes the compressor operating condition according to the control signal and system pressure
Main Benefits: Stable pressure control, efficient load/unload operation, reduced unnecessary power consumption, improved valve sealing and dependable compressor performance.

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