Valve packing gland pressure sensing by capacitance measurement

• US 6,752,024 B2
• Filed: 07/09/2002
• Issued: 06/22/2004
• Est. Priority Date: 08/16/2001
• Status: Expired due to Fees

• Current Assignee: Davie/Coffey Technologies, LLC
• Original Assignee: Davie/Coffey Technologies, LLC
• Inventors: Coffey, E. Michael, Davie, Neil R.
• Primary Examiner(s): NOORI, MAX H
• Application Number:
  US10/191,090
• Publication Number:
  US 20030033886A1
• Time in Patent Office: 714 Days
• Field of Search: 737/80, 738/623.37, 738/626.8
• US Class Current: 73/780
• CPC Class Codes: F16K 37/0041 for measuring valve parameters F16K37/0033 takes precedence
• CPC Class Codes: F16K 41/02 with stuffing-box ; Sealing rings
• CPC Class Codes: G01L 1/142 using capacitors
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence

Abstract

A thin flat disk-like capacitive load sensor of layered sandwich construction having a central opening and a circular outer periphery for installation above a packing follower or beneath the packing follower or packing gland. The load sensor has a thin first and second insulating outer layer between which an inner layer is secured. The inner layer is formed of dielectric material having a known dielectric constant, a first face having at least one thin electrically conductive circular ring surrounding the central opening in coaxial radially spaced relation, and a second face having a thin electrically conductive circular ring surrounding said central opening in coaxial radially spaced relation. The inner and outer layers contain electrical conductors engaged with respective electrically conductive circular rings on the opposed faces that are adapted to be connected with an electrical measurement apparatus. As the inner layer is compressed the spacing between the electrically conductive rings on the opposed faces is decreased such that compressive force on the packing can be measured as a function of the change in capacitance of the sensor. Proper compression of the padding can be achieved by monitoring during installation. Follow-up sampling or continuous measurement of packing compression provides early detection prior to packing failure to allow corrective action.

Claims

1. A system for determining the compressive loading of a packing gland providing a seal around an elongate member inserted through a stuffing box, the packing gland being compressed by a source of applied force, comprising:

a load sensor for disposition between the packing gland and the source of applied force comprising;

a compressible inner layer having opposed generally flat faces on opposite sides and a central opening, said inner layer formed of dielectric material having a known dielectric constant;

an electrically conductive ring on a first one of the faces and surrounding the central opening;

an electrically conductive ring on the second, opposite face and surrounding the central opening;

a first outer layer of dielectric material having a central opening in registration with the central opening in the inner layer;

a second outer layer of dielectric material having a central opening in registration with the central opening in the inner layer; and

a pair of conductors coupled to the electrically conductive rings on the faces of the inner layer; and

a capacitance measuring instrument connectable to the load sensor conductors and producing a signal indicative of the measured capacitance between the electrically conductive rings as a function of the spacing between the rings; and

a display coupled to the capacitance measuring instrument to receive the measured capacitance signal and provide a readout of the compressive loading on the packing gland.

2. The system of claim 1 wherein the load sensor further includes a connector comprising a tab at a peripheral edge of the inner layer and carrying the load sensor conductors.

3. The system of claim 1 wherein the electrically conductive ring on the first face of the inner layer of the load sensor is of a predetermined width so as to reside within an area of compression loading of the packing gland.

4. The system of claim 1 wherein the first face of the inner layer of the load sensor includes a second, outer electrically conductive ring surrounding the first ring.

5. The system of claim 1 wherein the inner ring has a width to reside within an area of compression loading of the packing gland and wherein the outer ring is radially spaced a distance from the inner ring to reside outside the area of compression loading of the packing gland.

6. The system of claim 5 wherein the ring on the second face is of a width that extends from a location proximate the central opening to a location proximate the peripheral edge, and wherein the outer ring on the first face together with the ring on the second face form a reference capacitance.

7. The system of claim 6 wherein the reference capacitance is electrically coupled in series with the capacitance formed between the inner ring on the first face and the second ring on the opposite second face.

8. The system of claim 1 wherein the display comprises a personal computer coupled to the capacitance measuring instrument using a universal serial bus interface.

9. The system of claim 8 wherein the personal computer is connectable to a data communication link.

10. The system of claim 1 wherein the display comprises a personal computer connectable to a data communications link for the transmission of valve packing gland integrity data.

11. The system of claim 10 further comprising a remote data center coupled to the data communications link for receiving data from the personal computer.

12. The system of claim 10 wherein the remote data center comprises:

a network server interfaced to the communications link to receive a set of collected measures from the personal computer, the collected measures set comprising individual measures related to a particular valve packing gland and recorded by the personal computer;

a database server coupled to the network server and storing the collected measures set into a valve packing gland integrity record for an individual valve packing gland;

an application server coupled to the database server and analyzing the collected measures sets in the valve packing gland integrity record for the individual valve packing gland relative to one or more other collected measures sets stored in the database server for the individual valve packing gland to determine a valve packing status indicator.

13. The system of claim 12 wherein the application server includes a feedback module providing tiered feedback over a feedback communications link to field maintenance personnel concerning individual valve packing gland integrity comprising:

at a first level of feedback, communicating an interpretation of the valve packing status indicator;

at a second level of feedback, communicating a notification of a potential valve packing defect concern based on the valve packing status indicator to on-site field maintenance personnel;

at a third level of feedback, communicating a notification of a potential valve packing defect concern based on the valve packing status indicator to maintenance personnel in local proximity to the individual valve packing; and

at a fourth level of feedback, communicating a set of valve packing installation modification instructions based on the valve packing status indicator.

14. The system of claim 1 wherein the display comprises a personal computer that processes the measured capacitance signal to provide valve packing compression information.

15. The system of claim 14 wherein the personal computer includes software comprising:

a software module providing a set of collected measures comprising individual measures related to a particular valve packing and recorded by the personal computer;

a database storing the collected measures set into a valve packing integrity record for an individual valve packing;

a software module analyzing the collected measures sets in the valve packing integrity record for the individual valve packing relative to one or more other collected measures sets stored in the database for the individual valve packing to determine a valve packing status indicator; and

a feedback module providing feedback to field maintenance personnel concerning individual valve packing integrity, said feedback including communicating an interpretation of the valve packing status indicator, communicating a notification of a potential valve packing defect concern based on the valve packing status indicator; and

communicating valve packing installation modification instructions based on the valve packing status indicator.

16. A compression load sensor for disposition between a packing gland providing a seal around an elongate member inserted through a stuffing box and a source of applied force compressing the packing gland, comprising:

a compressible inner layer having opposed generally flat faces on opposite sides and a central opening, said inner layer formed of dielectric material having a known dielectric constant;

an electrically conductive ring on a first one of the faces and surrounding the central opening;

an electrically conductive ring on the second, opposite face and surrounding the central opening;

a first outer layer of dielectric material having a central opening in registration with the central opening in the inner layer;

a second outer layer of dielectric material having a central opening in registration with the central opening in the inner layer; and

a pair of conductors coupled to the electrically conductive rings on the faces of the inner layer.

17. A system for determining the compressive loading of a packing gland providing a seal around an elongate member inserted through a stuffing box, the packing gland being compressed by a source of applied force, comprising:

a load sensor for disposition between the packing gland and the source of applied force in the area of packing gland compression comprising a capacitor having;

a compressible inner layer having opposed generally flat faces on opposite sides and a central opening, said inner layer formed of a dielectric material having a known dielectric constant;

a first plate comprising an electrically conductive ring on a first one of the faces and surrounding the central opening;

a second plate comprising an electrically conductive surface on the second, opposite face;

a first outer layer of dielectric material having a central opening in registration with the central opening in the inner layer; and

a second outer layer of dielectric material having a central opening in registration with the central opening in the inner layer;

a reference sensor disposed outside the area of packing gland compression comprising a capacitor having;

a first plate comprising an electrically conductive ring on the first one of the faces of the inner layer of the load sensor, the ring being radially displaced from the electrically conductive ring on the first one of the faces of the inner layer of the load sensor; and

a second plate comprising the electrically conductive surface on the second, opposite face of the inner layer of the load sensor;

a first conductor coupled to the electrically conductive ring plate of the load sensor;

a second conductor coupled to the electrically conductive ring plate of the reference sensor;

a third conductor coupled to the electrically conductive surface plate on the second, opposite face of the inner layer;

a capacitance measuring instrument individually connectable to the load sensor and to the reference sensor, said capacitance measuring instrument producing an output indicative of the measured capacitance of the load sensor and of the measured capacitance of the reference sensor; and

a circuit coupled to the capacitance measuring instrument to receive the measurement output for the load sensor and the measurement output for the reference sensor, the circuit combining the outputs to produce corrected load sensor outputs.