Methods and apparatus to apply multiple trip limits to a device in a process control system

Patent metadata

Field	Value
Publication number	US-9239576-B2
Application number	US-201213399251-A
Country	US
Kind code	B2
Filing date	Feb 17, 2012
Priority date	Feb 17, 2012
Publication date	Jan 19, 2016
Grant date	Jan 19, 2016

Abstract

Methods and apparatus to apply multiple trip limits to a device in a process control system are disclosed. An example method involves monitoring a value of a parameter associated with the operation of the device and receiving an input indicative of an operational state of the device, where a first input indicates a first operational state and a second input indicates a second operational state. If the first input is received, comparing via a function block the value of the parameter to a first trip limit, and if the second input is received, comparing via the function block the value of the parameter to a second trip limit, and implementing a response based on the comparison.

First claim

What is claimed is:

1. A method to apply multiple trip limits to a device in a process control system comprising:
monitoring a value of a parameter associated with operation of the device;
receiving via a function block an input that is either a first input or a second input, the first input indicating the device is in a first operational state and the second input indicating the device is in a second operational state;
when the first input is received at a first time period:
(a) comparing via the function block the value of the parameter to a first trip limit; and
(b) implementing a response based on the comparison of the value of the parameter to the first trip limit;
when the second input is received at a second time period:
(a) comparing via the function block the value of the parameter to a second trip limit; and
(b) implementing the response based on the comparison of the value of the parameter to the second trip limit; and
wherein the value of the parameter is compared to the first trip limit and not the second trip limit at the first time period associated with the first input, and wherein the value of the parameter is compared to the second trip limit and not the first trip limit at the second time period associated with the second input, wherein the first trip limit and the second trip limit are independently input into the function block by at least one of an operator or an engineer.

2. A method as described in claim 1 , wherein the response comprises at least one of sending an alarm to an operator, tripping the device into a third operational state different than the first and second operational states, or shutting down the device.

3. A method as described in claim 2 , wherein the value of the parameter in the third operational state is within the first trip limit and within the second trip limit.

4. A method as described in claim 1 , further comprising:
when the input changes to the second input, activating a timer to run a duration of a time limit; and
after the time limit has elapsed, comparing via the function block the value of the parameter to the first trip limit regardless of the input.

5. A method as described in claim 4 , wherein the time limit is independently input into the function block by at least one of an operator or an engineer independently of the first trip limit and the second trip limit.

6. A method as described in claim 1 , wherein the first operational state of the device corresponds to a normal operational state of the device, and wherein the second operational state of the device corresponds to an abnormal operational state of the device.

7. A method as described in claim 1 , wherein the first trip limit corresponds to a low limit for the parameter and the second trip limit corresponds to a high limit for the parameter.

8. A method as described in claim 1 , wherein the first trip limit corresponds to a first low limit for the parameter and the second trip limit corresponds to a second low limit for the parameter lower than the first low limit, or the first trip limit corresponds to a first high limit for the parameter and the second trip limit corresponds to a second high limit for the parameter higher than the first high limit.

9. A method as described in claim 1 , wherein the input is received via at least one of a key switch or a push button.

10. A processor which, when operated, implements a function block to:
receive an input indicating a process control system device is in either a first operational state or a second operational state;
receive first and second trip limits for a parameter associated with the operation of the device, wherein the first and second trip limits are associated with the respective first and second operational states of the device;
when the input indicates the process control system device is in the first operational state at a first time period:
(a) enable the first trip limit to compare with a value of the parameter and disable the second trip limit; and
(b) implement a first response when a value of the parameter passes the first trip limit; and
when the input indicates the process control system device is in the second operational state at a second time period:
(a) enable the second trip limit to compare with the value of the parameter and disable the first trip limit; and
(b) implement a second response when the value of the parameter passes the second trip limit; and
wherein the value of the parameter is compared to the first trip limit and not the second trip limit at the first time period associated with the first operational state, and wherein the value of the parameter is compared to the second trip limit and not the first trip limit at the second time period associated with the second operational state, wherein the first trip limit and the second trip limit are independently input into the function block by at least one of an operator or an engineer.

11. A processor as described in claim 10 , wherein at least one of first or second operational states corresponds to an unsafe condition.

12. A processor as described in claim 10 , wherein the first and second responses comprise at least one of sending an alarm to an operator, tripping the device into a third operational state different than the first and second operational states, or shutting down the device.

13. A processor as described in claim 12 , wherein a value of the parameter in the third operational state is within the first trip limit and within the second trip limit.

14. A processor as described in claim 10 which, when operated, implements the function block to further:
activate a timer when the second trip limit is first enabled to run a duration of a time limit; and
after the time limit has elapsed, implementing the first response when the parameter passes the first trip limit regardless of which trip limit is enabled.

15. A processor as described in claim 10 , wherein the first operational state of the device corresponds to a normal operational state of the device, and wherein the second operational state of the device corresponds to an operational state other than the normal operational state.

16. A processor as described in claim 10 , wherein the first trip limit corresponds to a high limit for the parameter and the second trip limit corresponds to a low limit for the parameter.

17. A processor as described in claim 10 , wherein the first trip limit corresponds to a first low limit for the parameter and the second trip limit corresponds to a second low limit for the parameter lower than the first low limit, or the first trip limit corresponds to a first high limit for the parameter and the second trip limit corresponds to a second high limit for the parameter higher than the first high limit.

18. A processor as described in claim 10 , wherein the input is received via at least one of a key switch or a push button.

19. A tangible article of manufacture storing machine readable instructions which, when executed, cause a machine to at least:
monitor a value of a parameter associated with operation of a process control system device;
receive an input that is either a first input or a second input, the first input indicating the device is in a first operational state and the second input indicating the device is in a second operational state;
when the first input is received at a first time period:
(a) compare the value of the parameter to a first trip limit; and
(b) implement a first response based on the comparison of the value of the parameter to the first trip limit; a

Assignees

• Bellville Keith Richard
• Law Gary Keith
• Sherriff Godfrey R
• Smith David Mark
• Fisher Rosemount Systems Inc

Inventors

• Bellville Keith Richard
• Law Gary Keith
• Sherriff Godfrey R
• Smith David Mark

Classifications

• G05B23/0235 Primary

  based on a comparison with predetermined threshold or range, e.g. "classical methods", carried out during normal operation; threshold adaptation or choice; when or how to compare with the threshold · CPC title