Subsea control system diagnosis

• US 7,895,001 B2
• Filed: 12/23/2008
• Issued: 02/22/2011
• Est. Priority Date: 12/23/2008
• Status: Active Grant

• Current Assignee: Chevron USA Incorporated (Chevron Corp.)
• Original Assignee: Chevron USA Incorporated (Chevron Corp.)
• Inventors: Karamchandani, Ashish, Tanju, Baha Tulu, An, Hailing
• Primary Examiner(s): Lau; Tung S
• Application Number:
  US12/342,951
• Publication Number:
  US 20100161250A1
• Time in Patent Office: 791 Days
• Field of Search: 702/34
• US Class Current: 702/34
• CPC Class Codes: F15B 19/005 Fault detection or monitoring
• CPC Class Codes: G01M 3/26 by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors

Abstract

Accurate, dependable methods for analyzing operational parameters of subsea control systems and diagnosis/prediction of failures are provided, in particular, methods for detection of leaking and/or clogging in hydraulic control system using recorded pressure signals and evaluating response communication strength (signal amplitude) of field equipment from, for example, subsea control systems. Prediction of failure(s) allows an opportunity to prepare for intervention to minimize the impact of failure before failure occurs, for example, by ordering equipment, tools and/or scheduling an intervention vessel. Similarly, diagnosing a failure drastically shortens the intervention time.

Claims

1. A method for monitoring the health of a hydraulic control system comprising:

a) capturing a layout and parameters of the hydraulic control system;

b) capturing a valve signature during a System Integration Test;

c) generating a simulated valve signature to match the valve signature captured during the System Integration Test by using a simulation algorithm and adjusting parameters of the hydraulic control system;

d) recording the parameters of the hydraulic control system used to generate the simulated valve signature that matches the valve signature captured during the System Integration Test;

subsequent to steps c to d;

e) capturing a valve signature for a subsea valve opening/closing;

f) generating a simulated subsea valve signature to match the subsea valve signature captured for the subsea valve opening/closing by using the simulation algorithm and adjusting parameters of the hydraulic control system;

g) recording the parameters of the hydraulic control system used to generate the simulated subsea valve signature that matches the valve signature captured for the subsea valve opening/closing;

h) repeating steps e), f) and g); and

i) tracking changes in the parameters of the hydraulic control system over time.

2. The method of claim 1, further comprising detecting problems with the hydraulic control system based on the changes in the parameters of the hydraulic control system over time.

3. The method of claim 1, wherein the parameters of the hydraulic control system include data on tubing, hydraulic fluid properties, supply pressure, accumulator, actuator and flow restrictions imposed by different equipment in the system.

4. The method of claim 1, wherein the parameters of the hydraulic control system are selected from the group consisting of line length, line inside diameter, line wall thickness, line wall roughness, source pump pressure, accumulator volume, accumulator pre-charge, actuator volume, spring force, flow resistance imposed by equipment, hydraulic fluid properties, and directional control valve drop-out pressure.

5. The method of claim 1, wherein the system comprises a subsea directional control valve, and further wherein the valve signature comprises pressure readings recorded during opening or closing of the actuator.

6. A method for maintaining performance of a hydraulic control system comprising:

a) monitoring the health of the system according to the method of claim 1; and

b) performing preventative maintenance on the system based on analyzed performance of the system.

7. The method of claim 1, wherein steps (b) and (e) comprise recording valve signatures comprising pressure readings recorded during accumulator recharge from pressure sensors;

and further comprising comparing the valve signatures, wherein;

an increased pressure differential of the valve signatures with increased pressure indicates a leak; and

the valve signatures being parallel indicates sensor drift.

8. The method of claim 1, wherein step (b) comprises recording valve signatures from pressure sensors in the system during system integration testing, and further comprising:

calculating an initial flow resistance, Cν

₀, using the recorded valve signatures during system integration testing and actuator volume, V_act;

recording valve signatures from the pressure sensors during operation of the system; and

calculating a value for

9. A method for maintaining performance of a hydraulic control system comprising:

a) determining performance of the system according to the method of claim 7; and

b) performing maintenance on the system if a comparison of the valve signatures indicates a leak or sensor drift.

10. The method of claim 8, wherein calculating Cν

₀ comprises using the equation;

11. A method for monitoring the health of a hydraulic control system comprising:

determining whether a leak and/or clog exists in a hydraulic control system according to the method of claim 8; and

performing maintenance on the system if calculating a value for

12. The method of claim 8, wherein there is not a filter located between the pressure sensors.

13. The method of claim 8, further comprising calculating a leak volume in the system using the equation:

14. The method of claim 8, further comprising calculating a margin of error for the leak volume based on accuracy of the pressure sensors.

15. The method of claim 8, wherein a calculated value for

16. A method for maintaining performance of a hydraulic control system comprising:

determining whether a leak exists in a hydraulic control system according to the method of claim 14; and

performing maintenance on the system if the leak volume exceeds a predetermined amount.