Compressor system and method and control for same

• US 6,102,665 A
• Filed: 10/27/1998
• Issued: 08/15/2000
• Est. Priority Date: 10/28/1997
• Status: Expired due to Term

• Current Assignee: Quincy Compressor LLC (Atlas Copco AB)
• Original Assignee: Coltec Industries Incorporated (Enpro Industries Incorporated)
• Inventors: Centers, Steven D., Moffat, Paul G.
• Primary Examiner(s): Freay, Charles G.
• Assistant Examiner(s): Evora, Robert Z.
• Application Number:
  US09/179,523
• Time in Patent Office: 658 Days
• Field of Search: 417/53, 417/15, 417/17, 417/18, 417/19, 417/20, 417/32, 417/44.2, 417/44.3, 417/44.4, 417/286, 417/279
• US Class Current: 417/18
• CPC Class Codes: F04B 2205/05 Pressure after the pump outlet
• CPC Class Codes: F04B 2205/07 Pressure difference over the pump
• CPC Class Codes: F04B 2205/11 Outlet temperature
• CPC Class Codes: F04B 2207/703 Stopping
• CPC Class Codes: F04B 49/10 Other safety measures

Abstract

An electronic control system is disclosed to control and to prevent damage to a standalone or a network of oil free, two stage compressor packages. The electronic control system uses pressure and temperature sensors to detect actual shutdown conditions or predict shutdown conditions based on the operating state of the compressor package and the current temperatures or pressures of the air at strategic locations in the compressor package. It has been determined through experimentation that, if the pressure at the inlet of the stage two compressor is less than the discharge pressure of the stage two compressor by more than an allowable value, then a high temperature condition will occur in the stage two compressor and cause the compressor to seize. It has also been determined the pressure differential occurs first in this situation and that the electronic control system can predict the failure based on the pressure differential data and to shut the compressors down before the stage two compressor failure occurs. The electronic control system then records the shutdown event in an area of nonvolatile memory and displays the reason for the shutdown on a LCD display visible to the compressor operator. A plurality of electronic control systems can be connected in a peer-to-peer network to coordinate control of a plurality of compressors connected to the same air distribution system. A modem connected to the electronic control system supports remote diagnostics, monitoring, and control. Methods for controlling the operation of the compressor packages using the electronic control system are also disclosed.

Claims

1. An electronic control system for controlling the operation of at least one or a network of compressor packages, the system comprising:

at least one or a network of oil less, two stage screw compressor packages, operatively connected to a pressure system in which pressure is to be maintained within a predetermined range of possible pressures;

measuring means, operatively connected to the first and the second screw compressor stages, for determining the pressure exiting the first and the second compressor stages;

processing means, operatively connected to the measuring means for receiving signals from the measuring means, for comparing the determined pressure exiting the first screw compressor and the second screw compressor stages with the predetermined range of possible pressures; and

means, operatively connected to the oil free, two stage screw compressor package and the processing means, for shutting down the screw compressor package before the screw compressor package is damaged.

2. The system of claim 1 wherein, if the air pressure exiting the first and the second compressor stages goes above the predetermined range of possible pressures, the control system will shut down the screw compressor package.

3. The system of claim 2 wherein, the air pressure exiting the first and the second screw compressor stages is established by computing a value by measuring the second stage screw compressor discharge pressure and the first stage screw compressor discharge pressure, such that when the second stage screw compressor discharge pressure is greater than about eighty psi (>

80 psi) and the first stage screw compressor discharge pressure is less than about ten psi (<

10 psi), for a period of about ten (10) seconds, an alarm is flagged and the control system shuts down the screw compressor package.

4. The system of claim 1 further comprising:

measuring means, operatively connected to the first and the second screw compressor stages, for determining the temperature of the gas exiting the first and the second screw compressor stages, wherein the processing means compares the determined temperature exiting the first screw compressor and the second screw compressor stages with a predetermined temperature limit; and

means, operatively connected to the oil free, two stage screw compressor package and the processor means, for shutting the screw compressor package down before the package is damaged, if the exiting temperatures exceed such predetermined temperature.

5. The system of claim 4 wherein, the predetermined temperature limit of the air exiting the first screw compressor and the second screw compressor stages is set at about four hundred thirty five degrees Fahrenheit (435°

F.).

6. The system of claim 4 wherein, the predetermined temperature limit of the air entering the second stage screw compressor and the screw compressor package discharge temperatures is set at about one hundred twenty degrees Fahrenheit (120°

F.).

7. The system of claim 4 wherein, after shutting down the screw compressor package, the control system records which of the four measured temperatures was responsible for shutting down the screw compressor package, and at what time and date the shutdown occurred.

8. The system of claim 1 further comprising:

at least one cooling means, operatively positioned between the stage one screw compressor and the stage two screw compressor, for cooling the air prior to the air entering the second stage screw compressor;

at least a second cooling means, operatively positioned between the stage two screw compressor exit and the screw compressor package exit, for cooling the air prior to the air entering the end user air system;

means, operatively connected to each cooling means, for establishing a high predetermined temperature limit for the temperature of the air exiting each cooling means; and

measuring means, operatively connected to each cooling means for measuring the temperature of the air exiting each cooling means; and

means, operatively connected to each measuring means and the processor means, for shutting the screw compressor package down before the package is damaged, if either of the exiting temperatures exceed the predetermined high temperature limit.

9. The system of claim 1 further comprising:

lubricating oil containing means, operatively positioned in the stage one screw compressor and the stage two screw compressor, for lubricating parts isolated from each screw compressor compression chamber;

measuring means, operatively connected to the each lubricating oil containing means, for measuring the oil pressure thereof;

means, operatively connected to each lubricating oil containing means measuring means and to the processing means for establishing a range of operating oil pressures; and

means, operatively connected to each measuring means and the processor means, for shutting the screw compressor package down before the package is damaged, if the oil pressure deviates from the predetermined oil pressure range.

10. The system of claim 1 further comprising:

means, operatively connected to the processing means, for measuring the pressure of the air exiting the screw compressor package after the second stage cooling means;

means, operatively connected to the processing means, for measuring the temperature of the air exiting the screw compressor package after the second stage cooling means;

means, operatively connected to the processing means, for establishing a range of screw compressor package discharge temperatures and pressures; and

means, operatively connected to the package exiting temperature and pressure measuring means, for shutting down the screw compressor package if either the temperature or the pressure exceeds a predetermined limit.

11. The system of claim 10 wherein, the package discharge pressure is used to determine when to unload and load the two screw compressor stages.

12. A method for controlling a single or a network of oil less, two stage screw compressor packages, the method comprising the steps of:

providing at least one or a network of oil less, two stage screw compressor packages;

operatively connecting the at least one or a network of oil less, two stage screw compressor packages to a pressure system in which pressure is to be maintained within a predetermined range of possible pressures;

operatively connecting an electronic control system to at least one two stage screw compressor package;

controlling the operation of the at least one or the network of screw compressor packages by;

determining the pressure exiting the first and the second screw compressor stages;

comparing the determined pressure exiting the first screw compressor and the second screw compressor stages with the predetermined range of possible pressures; and

if the determined pressure exiting either the first or the second screw compressor stages equals or exceeds the predetermined range of possible pressures, shutting down the screw compressor package before the screw compressor package is damaged.

13. The method of claim 12 wherein, the air pressure exiting the first and the second screw compressor stages is established by computing a value by measuring the second stage screw compressor discharge pressure and the first stage screw compressor discharge pressure, such that when the second stage screw compressor discharge pressure is greater than about eighty psi (>

80 psi) and the first stage screw compressor discharge pressure is less than about ten psi (<

10 psi) for a period of about ten (10) seconds, an alarm is activated and the control system shuts down the screw compressor package.

14. The method of claim 12 further comprising the steps of:

determining the temperature of the gas exiting the first and the second screw compressor stages;

comparing the determined temperature exiting the first screw compressor and the second screw compressor stages with a predetermined temperature limit; and

shutting the screw compressor package down before the package is damaged, if the exiting temperatures exceed such predetermined temperature.

15. The method of claim 14 wherein, the predetermined temperature limit of the air exiting the first screw compressor and the second screw compressor stages is about four hundred thirty five degrees Fahrenheit (435°

F.).

16. The method of claim 14 wherein the predetermined temperature limit of the air entering the second stage screw compressor and the screw compressor package discharge temperatures is about one hundred twenty degrees Fahrenheit (120°

F.).

17. The method of claim 14 wherein, after shutting down the screw compressor package, the control system records which of the four measured temperatures was responsible for shutting down the screw compressor package, and at what time and date the shutdown occurred.

18. The method of claim 12 further comprising the steps of:

cooling the air prior to the air entering the second stage screw compressor by operatively positioning at least one cooling means between the stage one screw compressor and the stage two screw compressor;

cooling the air prior to the air entering the end user air system by operatively positioning at least a second cooling means between the stage two screw compressor exit and the screw compressor package exit;

establishing a high predetermined temperature limit for the temperature of the air exiting each cooling means;

measuring the temperature of the air exiting each cooling means by operatively connecting measuring means to each cooling means; and

if the exiting temperatures exceed a predetermined temperature limit, shutting the screw compressor package down before the package is damaged.

19. The method of claim 12 further comprising the steps of:

operatively positioning lubricating oil containing means in the stage one screw compressor and the stage two screw compressor for lubricating parts isolated from each screw compressor compression chamber;

measuring the oil pressure of both the stage one screw compressor and the stage two screw compressors by operatively connecting measuring means to the each lubricating oil containing means;

establishing a range of predetermined operating oil pressures; and

if the oil pressure deviates from the predetermined oil pressure range, shutting the screw compressor package down before the package is damaged.

20. The method of claim 12 further comprising the steps of:

measuring the pressure of the air exiting the screw compressor package after the second stage cooling means;

measuring the temperature of the air exiting the screw compressor package after the second stage cooling means;

establishing a range of screw compressor package discharge temperatures and pressures; and

if either the temperature or the pressure exceeds a predetermined limit, shutting down the screw compressor package.