Pressure control for calibrating process control devices

Patent metadata

Field	Value
Publication number	US-2016273676-A1
Application number	US-201615074715-A
Country	US
Kind code	A1
Filing date	Mar 18, 2016
Priority date	Mar 19, 2015
Publication date	Sep 22, 2016
Grant date	—

Abstract

A method of calibrating a positioner includes determining a pressure value corresponding to a particular state of an actuator, wherein the actuator is controlled by the positioner, and controlling a pressure within the actuator according to a set point pressure, wherein the set point pressure is based on the pressure value such that the particular state of the actuator is maintained. The method further includes receiving a measured value indicating an actual pressure within the actuator, and determining a bias of the positioner based on the measured value and the set point pressure.

First claim

What is claimed is:

1 . A method of calibrating a positioner, the method comprising:
determining a pressure value corresponding to a particular state of an actuator, wherein the actuator is controlled by the positioner; controlling, with the positioner, a pressure within the actuator according to a set point pressure, wherein the set point pressure is based on the pressure value such that the particular state of the actuator is maintained; receiving a measured value indicating an actual pressure within the actuator; and determining a bias of the positioner based on the measured value and the set point pressure.

2 . The method of claim 1 , further comprising controlling, with the positioner, the actuator to perform one or more process control functions, wherein controlling the actuator to perform the one or more process control functions includes executing control logic that accounts for the determined bias of the positioner.

3 . The method of claim 1 , wherein the particular state of the actuator is defined by a constant volume of the actuator, and wherein determining the pressure value corresponding to the constant volume of the actuator includes determining an upper pressure limit of a bench set of the actuator.

4 . The method of claim 3 , wherein the set point pressure based on the pressure value is greater than the upper pressure limit.

5 . The method of claim 1 , wherein the particular state of the actuator is defined by a constant volume of the actuator, and wherein determining the pressure value corresponding to the constant volume of the actuator includes determining a lower pressure limit of a bench set of the actuator.

6 . The method of claim 5 , wherein the set point pressure based on the pressure value is lower than the lower pressure limit.

7 . The method of claim 1 , wherein the particular state of the actuator is defined by a range of pressure values within or supplied to the actuator, and wherein determining the pressure value includes determining the pressure value to be in the range of pressure values.

8 . The method of claim 1 , wherein the particular state of the actuator occurs when the actuator is under end-point pressure control, and wherein determining the pressure value includes determining the pressure value to be in utilized in the end-point pressure control.

9 . The method of claim 1 , wherein the actuator is part of a safety instrumented system.

10 . The method of claim 1 , further comprising:
receiving an internal measured value indicating a travel of a spool valve or pneumatic relay within the positioner; and determining a minor loop feedback bias of the spool valve or pneumatic realy based on the internal measured value.

11 . A process control system comprising:
an actuator; and a positioner coupled to the actuator, and wherein the positioner is configured to control the actuator while accounting for a bias of the positioner, wherein the positioner determines the bias by: controlling a pressure within the actuator according to a set point pressure, wherein a particular state of the actuator is maintained while the pressure is controlled within the actuator, receiving a measured value indicating an actual pressure within the actuator, and determining a bias of the positioner based on the measured value and the set point pressure.

12 . The process control system of claim 11 , wherein controlling the pressure within the actuator includes:
generating current signals based on the set point pressure, and converting the current signals to an output pressure that is supplied to the actuator, wherein the bias of the positioner is a current to pressure bias.

13 . The process control system of claim 11 , wherein determining the bias of the positioner based on the measured value and the set point pressure includes accumulating a measure of an offset of the measured value in relation to the set point pressure.

14 . The process control system of claim 13 , wherein accounting for the bias of the positioner includes utilizing control logic of the positioner that accounts for the bias of the positioner by adding the measure of the offset to a default bias of the positioner.

15 . The process control system of claim 13 , wherein the positioner includes control logic that implements at least a portion of a pressure control loop, and wherein the measure of the offset is an pressure integrator term utilized by the pressure control loop.

16 . A computer device comprising:
one or more processors; and one or more non-transitory memories having computer executable instructions stored thereon that, when executed by the one or more processors, cause the computer device to:
determine a pressure value corresponding to a particular state of an actuator,
control a pressure within the actuator according to a set point pressure, wherein the set point pressure is based on the pressure value such that the particular state of the actuator is maintained,
receive a measured value indicating an actual pressure within the actuator, and
determine a bias of the positioner based on the measured value and the set point pressure.

17 . The computer device of claim 16 , wherein the computer executable instructions further cause the computer device to control the actuator to perform one or more process control functions, wherein controlling the actuator to perform the one or more process control functions includes executing control logic that accounts for the determined bias of the positioner.

18 . The computer device of claim 17 , wherein the control logic accounts for the bias of the positioner by adding the bias of the positioner to a default bias of the positioner within a control loop implemented in the control logic.

19 . The computer device of claim 16 , wherein the actuator is a piston of an emergency shutdown valve, and wherein the pressure value corresponds to a hard stop of the piston.

20 . The computer device of claim 16 , wherein the actuator actuates a valve configured to prevent surges at a compressor.

Assignees

• Fisher Controls Int Llc

Inventors

• Junk Kenneth W

Classifications

• F15B19/007

  Simulation or modelling · CPC title

• F15B19/002 Primary

  Calibrating · CPC title

• F16K37/0091 Primary

  by measuring fluid parameters · CPC title

• G05B2219/31334

  Database with devices, configuration, of plant · CPC title

• G05B19/4186 Primary

  by protocol, e.g. MAP, TOP · CPC title