Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
1999-01-29
2001-06-12
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S04050A
Reexamination Certificate
active
06244100
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to leak detection in pipe based on deviation of pressure from an expected pressure-temperature relationship of the fluid in the pipe.
BACKGROUND OF THE INVENTION
To protect the environment, regulations are being enacted to ensure that leaks of hazardous materials from underground pipelines are detected in a timely way to limit spill sizes. One such procedure is the Environmental Protection Agency procedure, “EPA—Standard Test Procedures for Evaluating Leak Detection Methods: Pipeline Leak Detection Systems”. This procedure requires that leaks as small as 3 gph at a 10-psi line pressure must be detected.
In some cases, the only practical method of leak detection is to pressurize the pipeline under static conditions (that is, with valves closed at each end, thereby preventing flow through the pipeline) and then monitor the line pressure for a suitable period to detect a leak. This approach may be referred to as the “pressure decay” method. Given the accurate pressure sensors available today, it is possible to detect leaks as small as 3 gph at 10 psi by monitoring the decay of pressure caused by the leak. The pressure decay method requires that the pipeline temperature be held constant or that changes in temperature over the length of the pipeline be accounted for. Temperature stability or compensation is required since a slight decrease in temperature can also cause pressure decay, a pressure decay which can be mistaken for a leak.
Because maintaining temperature stability is difficult in some situations, the pressure decay method is limited in its use. In many instances, the time required for temperature to equilibrate or stabilize is so long that it imposes unacceptably long downtimes on an operational pipeline. In others instances, sufficient temperature equilibrium may not be attainable.
Compensating for the effects of temperature on buried pipelines can also be too complex or expensive to be practical. Rarely has an array of suitable temperature sensors been installed at the time of pipeline construction.
SUMMARY OF THE INVENTION
The present invention pertains to an apparatus for compensating for changes in fluid temperature to be used in detecting a leak in an isolated segment of a pipe with a known fluid and does so uniquely by compensating for temperature effects on pressure without requiring any direct measurement of temperature.
The apparatus comprises a mechanism for producing pressure pulses in the pipe in order to measure changes in the average propagation velocity of the fluid in the pipeline. The producing mechanism is adapted for connection to the pipe. The apparatus comprises a pressure sensor for sensing the reflection of the pulse in the pipe. The pressure sensor is adapted for connection to the pipe. The apparatus comprises a mechanism for determining whether the pressure of the fluid in the pipe has negatively deviated from that expected from the pressure-temperature relationship of the fluid in the pipe.
The present invention is based on a method for detecting a fluid leak in an isolated segment of a pipe. The method comprises five steps: Step 1, Measure propagation velocity by measuring pressure pulse transit time in an isolated pipe at time t
1
: Step 2, measure the pressure of the fluid in the isolated segment of the pipe at time t
1
. Step 3, measure the pressure of the fluid in the isolated segment of the pipe at time t
2
and calculate the change in pressure occurring between t
2
and t
1
. Step 4, measure the propagation velocity by measuring pressure pulse transit time in the isolated segment of the pipe at time t
2
and determine the corresponding change in propagation velocity and from it determine the change in average temperature. Step 5, calculate the amount of pressure change due to temperature changes and the amount due to probable leaks.
The physical principle used is the relationship between fluid propagation velocity and temperature. (Propagation velocity is the speed at which pressure disturbances move in the fluid in the pipeline.) Consequently, if changes in the propagation velocity are measured, a change in temperature can be determined. Moreover, if the change in propagation velocity over the length of the pipeline can be measured, the effective change in the average temperature over the entire pipeline can be accounted for.
REFERENCES:
patent: 4608857 (1986-09-01), Mertens et al.
patent: 4646560 (1987-03-01), Maresca, Jr. et al.
patent: 4709577 (1987-12-01), Thompson
patent: 4725551 (1988-02-01), Thompson
patent: 4796466 (1989-01-01), Farmer
patent: 5046353 (1991-09-01), Thompson
patent: 5048324 (1991-09-01), Thompson
patent: 5076728 (1991-12-01), Golding
patent: 5078006 (1992-01-01), Maresca, Jr. et al.
patent: 5090234 (1992-02-01), Maresca, Jr. et al.
patent: 5127266 (1992-07-01), Maresca et al.
patent: 5163314 (1992-11-01), Maresca, Jr. et al.
patent: 5170657 (1992-12-01), Maresca, Jr. et al.
patent: 5189904 (1993-03-01), Maresca, Jr. et al.
patent: 5272646 (1993-12-01), Farmer
patent: 5315529 (1994-05-01), Farmer
patent: 5375455 (1994-12-01), Maresca, Jr. et al.
patent: 5415033 (1995-05-01), Maresca, Jr. et al.
patent: 5447055 (1995-09-01), Thompson et al.
patent: 5948969 (1999-09-01), Fierro et al.
Augenstein Donald R.
Estrada Herbert
Hastings Calvin R.
Caldon, Inc.
Politzer Jay L
Schwartz Ansel M.
Williams Hezron
LandOfFree
Temperature compensation for automated leak detection does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Temperature compensation for automated leak detection, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Temperature compensation for automated leak detection will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2503255