Quinny 65040-AB manual Capacity Control System

Section II - Description

Capacity Control System

The standard method of capacity control for the QSD™ oil-free compressor is Continuous Run with load/no-load.

The Continuous Run Mode of operation is ideal for a compressed air system that will operate at full load conditions most of the time, with minimal unloaded time.

The QSD™ allows very consistent and tight control of air system pressure by constantly monitoring package discharge pressure and operating within a deadband of as low as 5 PSI. This means the system pressure never needs to fall below the normal required pressure.

The recommended receiver size for a QSD™ oil-free compressor is a minimum of three (3) gallons per rated compressor CFM; the more the better. If there is more than one compressor, the receiver must be sized based on the total CFM of all compressors. This should be increased to a minimum of five (5) gallons per total compressor CFM for systems with sharp changes in demand. The receiver must be located immediately adjacent to the compressor and before any additional system components such as dryers and filters. This allows the Power$ync II™ controller to operate the compressor coincident to system demand changes without dramatic episodes of rapid loading and unloading (cycling) of the machine.

NOTE

Continuous operation with rapid load/no-load cycles will reduce component life. Cycle rates should never exceed six (6) per minute. Proper receiver sizing is essential for reliable operation.

The QSD™ does not use an inlet valve, but rather the patented Power$ync® lift valve technology to unload the machine. With this type of control, the unit is operating either at full capacity or 0% capacity, depending on system pressure.

Suction or inlet valves on competitor designs act to close the inlet to the compressor and induce a vacuum in both compressor stages as it continues to try to compress air.

This vacuum creates a reverse pressure differential across the bearing seals, causing the bearing fluid to migrate toward the compression chamber when the machine is unloaded.

The QSD™ incorporates patented Power$ync® lift valves on both stages of compression. The valves, one per stage, actually relieve the compressor stages ability to compress air. Because the unloading is positive, and no vacuum is created, unloaded horsepower is minimized. Also, since the compressor stages are not creating a vacuum in the unloaded state, there is no tendency for the bearing fluid to migrate toward the compression chambers, reducing the likelihood of fluid contamination of the air.

The QSD™ loads and unloads in response to the air system pressure. The Power$ync II™ controller monitors package discharge pressure into the compressed air system and either opens or closes the lift valves to load or unload the compressor, based on preset pressure values. Upon start-up, the QSD™ will operate at full capacity up to a predetermined maximum value, usually 5 PSI above the normal plant air system operating level. The blowdown valve and both lift valves are closed at this time. When the preset pressure value is reached, the Power$ync II™ controller opens both lift valves and the blowdown valve simultaneously, reducing the compressor output to 0%. The QSD™ will continue to operate in the unloaded condition, with the lift valves and the blowdown valve in the open position, until the Power$ync II™ controller detects a reduction in pressure indicating a reset condition. This pressure, like the unload, is determined by the customer, based on the air system operating requirements. The Power$ync II™ controller reacts to the signal by closing the lift valves and the blowdown valve, thus reloading the compressor and returning to 100% output to complete the cycle.

NOTE

If the stage two discharge blowdown valve fails to open an excessive pressure differential across stage two will occur. The unit will shut down automatically to prevent excessive temperature build-up in the stage two airend.

Quincy Compressor® - QSD™ 11