System and methods for controlling rotary screw compressors
First Claim
1. An electronic control apparatus for maintaining desired pressures in an air pressure system fed by at least one rotary screw compressor having an inlet valve, comprising:
- inlet valve closing means for selectively closing the inlet valve of the compressor;
inlet valve modulation means for selectively partially closing the inlet valve of the compressor;
processing means connected to the inlet valve closing means and the inlet valve modulation means for selectively reducing output capacity of the compressor by selectively actuating the inlet valve closing means and inlet valve modulation means, the processing means selectively operable in at least two modes, including a first mode wherein the inlet valve closing means is periodically actuated and deactuated to provide an inlet valve duty cycle appropriate to a desired compressor output level, and a second mode wherein the inlet valve modulation means is actuated to partially close the inlet valve; and
mode switching means associated with the processing means for monitoring the number of actuations of the inlet valve closing means during a defined time period in the first mode, and if the number of actuations in the defined time period is greater than a defined value, causing the processing means to switch to the second mode of operation.
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Accused Products
Abstract
An electronic control system dynamically varies the output capacity of a compressor by controlling plural valves associated with the compressor to provide pressurized air to a distribution system at an appropriate rate. The control system operates in any of three modes for standalone operation, including continuous run, auto/dual pressure band, and target pressure modes. In the first two modes, pressure bands are dynamically calculated based on load and unload values entered by an operator. These electronic control systems can also be connected in a peer-to-peer network to coordinate control of up to 16 compressors feeding the same distribution system, so as to maintain a desired target pressure in the system. A modem connected to the system supports remote diagnostics, monitoring, and control. Specialized startup, operating, and shutdown diagnostic algorithms prevent damage to the compressor and avert unsafe operating conditions.
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Citations
17 Claims
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1. An electronic control apparatus for maintaining desired pressures in an air pressure system fed by at least one rotary screw compressor having an inlet valve, comprising:
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inlet valve closing means for selectively closing the inlet valve of the compressor; inlet valve modulation means for selectively partially closing the inlet valve of the compressor; processing means connected to the inlet valve closing means and the inlet valve modulation means for selectively reducing output capacity of the compressor by selectively actuating the inlet valve closing means and inlet valve modulation means, the processing means selectively operable in at least two modes, including a first mode wherein the inlet valve closing means is periodically actuated and deactuated to provide an inlet valve duty cycle appropriate to a desired compressor output level, and a second mode wherein the inlet valve modulation means is actuated to partially close the inlet valve; and mode switching means associated with the processing means for monitoring the number of actuations of the inlet valve closing means during a defined time period in the first mode, and if the number of actuations in the defined time period is greater than a defined value, causing the processing means to switch to the second mode of operation. - View Dependent Claims (2, 3)
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4. A method for electronically maintaining desired pressures in an air pressure system fed by at least one rotary screw compressor having an inlet valve, the method comprising the steps of:
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providing the inlet valve with both means for closing the inlet valve and means for partially closing the inlet valve; determining when an output capacity of the compressor should be reduced to maintain desired pressure in the pressure system, and automatically periodically actuating and deactuating the means for closing the inlet valve to provide an inlet valve duty cycle appropriate to a desired compressor output level; automatically monitoring the number of actuations of the inlet valve closing means during a defined time period, and if the number of actuations in the defined time period is greater than a defined value, actuating the means for partially closing the inlet valve, whereby the operating mode of the compressor is changed to prevent rapid cycling of the inlet valve. - View Dependent Claims (5, 6)
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7. A method for automated shutdown of a rotary screw air compressor having an inlet valve and an output connected to a sump with a blowdown valve, comprising the steps of:
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storing a defined maximum shutdown sump pressure value; detecting an instruction for implementing an orderly shutdown of the compressor; automatically closing the inlet valve to unload the compressor; after closing the inlet valve, automatically opening the blowdown valve to release pressure in the sump; electronically monitoring pressure in the sump until sump pressure is less than said defined maximum shutdown sump pressure value, then stopping compressor rotation, whereby oil foaming is reduced. - View Dependent Claims (8, 9, 10)
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11. A system for electronically maintaining desired pressures in an air pressure system fed by at least one rotary screw compressor comprising:
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at least one inlet valve having both means for closing the inlet valve and means for partially closing the inlet valve; means for determining when an output capacity of the compressor should be reduced to maintain desired pressure in the pressure system, and automatically periodically actuating and deactuating the means for closing the inlet valve to provide an inlet valve duty cycle appropriate to a desired compressor output level; and means for automatically monitoring the number of actuations of the inlet valve closing means during a defined time period, and if the number of actuations in the defined time period is greater than a defined value, actuating the means for partially closing the inlet valve, whereby the operating mode of the compressor is changed to prevent rapid cycling of the inlet valve. - View Dependent Claims (12, 13)
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14. A system for automated shutdown of a rotary screw air compressor having an inlet valve and an output connected to a sump with a blowdown valve, the system comprising:
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a stored defined maximum shutdown sump pressure value; means for detecting an instruction for implementing an orderly shutdown of the compressor; means for automatically closing the inlet valve to unload the compressor; means for, after closing the inlet valve, automatically opening the blowdown valve to release pressure in the sump; and means for electronically monitoring pressure in the sump until sump pressure is less than the defined maximum shutdown sump pressure value;
means for stopping compressor rotation, such that oil foaming is reduced. - View Dependent Claims (15, 16, 17)
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Specification