Fault tolerant analog outputs for turbo compressors

• US 8,805,593 B2
• Filed: 11/18/2010
• Issued: 08/12/2014
• Est. Priority Date: 11/18/2009
• Status: Active Grant

• Current Assignee: Energy Control Technologies, Inc.
• Original Assignee: Energy Control Technologies, Inc.
• Inventors: Johnson, Gregory D.
• Primary Examiner(s): Bahta, Kidest
• Application Number:
  US12/949,304
• Publication Number:
  US 20110113788A1
• Time in Patent Office: 1,363 Days
• Field of Search: 700/282, 700/23, 700/20, 700/42, 607/93, 415/17.2
• US Class Current: 700/286
• CPC Class Codes: G05B 19/058 Safety, monitoring
• CPC Class Codes: G05B 2219/14015 Dual plc's, processors and dual I-O
• CPC Class Codes: G05B 2219/14019 Dual IN, crosscoupled relay, dual AND, dual OUT

Abstract

A control system for operating a device in a turbo machine system. The system includes a first programmable logic control device producing an analog output signal and a relay circuit electrically connected to the first programmable logic control device to receive the analog output signal. A field device is electrically connected to the relay circuit to receive the analog output signal to operate based on the analog output signal to provide a load. In addition, the relay circuit is electrically connected to a second programmable logic control device to communicate the analog output signal to the second programmable logic control device to monitor the analog output signal.

Claims

1. A control system for operating a device in a turbo machine system comprising:

a first programmable logic control device producing an analog output signal;

a relay circuit electrically connected to the first programmable logic control device to receive the analog output signal;

a field device electrically connected to the relay circuit to receive the analog output signal to operate based on the analog output signal;

wherein the relay circuit is electrically connected to a second programmable logic control device to monitor the analog output signal; and

wherein after the analog output signal passes through a load on the field device the analog output signal is received by the relay circuit to send to the second programmable logic control device.

2. The control system of claim 1 further comprising:

a first backup programmable logic control device electrically connected to the relay circuit and producing an analog output signal; and

a second backup programmable logic control device electrically connected to the relay circuit to receive the analog output signal of the first backup programmable logic control device.

3. The control system of claim 1 wherein the field device is a recycle valve in a compressor.

4. The control system of claim 1 wherein the second programmable logic control device detects wire failures.

5. The control system of claim 1 wherein the analog output signal is a highway addressable remote transducer signal.

6. The control system of claim 1 wherein the output signal passing through the field device is the exact signal that is monitored by the second programmable logic control device.

7. The control system of claim 1 wherein the analog output signal from the first programmable logic control device drives the field device unless a failure is detected and then the analog output signal from the first backup programmable control device drives the field device.

8. The control system of claim 1 wherein the output signal from the first programmable logic control device and the first backup programmable control device are sent to the relay circuit simultaneously.

9. The control system of claim 1 wherein the second programmable logic control device is testing the exact same output signal used to drive the field device.

10. The control system of claim 2 wherein the second backup programmable logic control device is testing the output signal from the first backup programmable logic control device while the output signal from the first backup programmable drive is not being used to drive the control device to ensure that the backup signal is accurate and ready to drive the control device when required.

11. A control system for operating a device in a turbo machine system comprising:

a first programmable logic control device producing an analog output signal;

a relay circuit electrically connected to the first programmable logic control device to receive the analog output signal;

a field device electrically connected to the relay circuit to receive the analog output signal to operate based on the analog output signal;

wherein the relay circuit is electrically connected to a second programmable logic control device to monitor the analog output signal; and

wherein the field device produces a highway addressable remote transducer signal over the analog output for additional verification.

12. A control system for operating a device in a turbo machine system comprising:

a first programmable logic control device producing an analog output signal;

a relay circuit electrically connected to the first programmable logic control device to receive the analog output signal;

a second programmable logic control device to monitor the analog output signal

a first backup programmable logic control device electrically connected to the relay circuit and producing an analog output signal;

a second backup programmable logic control device electrically connected to the relay circuit to receive the analog output signal of the first backup programmable logic control device;

a field device electrically connected to the relay circuit to receive the analog output signal;

a control system electrically connected to the relay circuit to send a control signal to the relay circuit; and

wherein the relay circuit receives the control signal from the control system and based on the output signal from the first programmable logic control device and first backup programmable logic control device sends the analog output signal to the field device to operate based on the analog output signal.