GB2506838A

GB2506838A - A method of identifying leaks in a fluid carrying conduit using a pig

Info

Publication number: GB2506838A
Application number: GB1214108.1A
Authority: GB
Inventors: Andrew Hoffman
Original assignee: Atmos Wave Ltd
Current assignee: Atmos Wave Ltd
Priority date: 2012-08-07
Filing date: 2012-08-07
Publication date: 2014-04-16
Anticipated expiration: 2032-08-07
Also published as: GB2506838B; GB201214108D0

Abstract

A method of determining whether there is a leak in a pipeline for carrying fluids. The method comprises the steps of: at least partially sealing off one or both ends of the pipeline 100; introducing an object 200 (such as a pig) into the pipeline; monitoring a position of the object for a time period; determining a distribution 300 of a velocity of the object as a function of its position; identifying any regions 301 of the distribution where the velocity vanishes; and determining that there is a leak 130 in the pipeline if the magnitude of a gradient of the distribution is greater than a predetermined threshold value in any region where the velocity vanishes. With this method, the presence of a leak in a pipeline can be located significantly faster than with prior art methods, limiting the disruption and expense of leak tests. This method also yields information relating to the location of any leaks detected. There is also disclosed an apparatus for carrying out the method.

Description

A method of identifying leaks in a fluid carrvinci conduit The present invention relates to a method of determining whether or not there is a leak in a pipeline for carrying fluids. In particular, but not exclusively, it relates to a method that distinguishes leaks in a sealed pipeline from sections of the pipeline which differ in temperature to the sections of pipeline adjoining them.

It is often necessary to convey fluids such as water and oil over large distances and one method of doing this involves pumping the fluid through a dedicated system of pipes. Such pipes are susceptible to leaks where the pipes are breached or corroded, either accidentally or purposely by a third party. It is important that such leaks or thefts be identified and located as quickly as possible so as to reduce the amount of fluid lost. Furthermore, in the case of an accidental leak of a fluid such as oil, early detection can help minimise the environmental impact of the leak. On the other hand, it is also important to avoid false alarms since the process of shutting down a pipeline for a length of time to investigate a suspected leak is time consuming and expensive.

At least part of these systems of pipes may be inaccessible, for example it may be disposed underground, Therefore there is a need for a method of accurately and reliably determining and locating leaks or thefts in pipelines.

When a leakdevelops in a pipeline the line fluidpressure in asection of the pipeline near to the leak will drop. The initial pressure drop is a dynamic effect caused by the inability of the fluid to respond instantly to the leak. After this initial pressure drop, the pressure continues to drop at a slower rate due to unpacking of the pipeline. Such a pressure drop gives rise to a rarefaction wave. The rarefaction wave starts as a spherical wave centred on the location of the leak. As the rarefaction wave propagates away from the location of the leak it interacts with the pipe wall and changes shape, eventually giving rise to two plane waves each of which propagates down the pipe, in opposite directions, at the speed of sound. By measuring the pressure of the fluid at two positions which are on opposite sides of the leak, these pressure waves can be detected and used to infer the presence of a leak and the position thereof. Two such methods are disclosed in US 5,388,455 and WO 2011/070343.

The pressure of a fluid in a pipeline which is sealed at both ends is dependent upon the temperature of that fluid. Therefore if a section of a pipeline differs in temperature from the sections adjoining it on either side, fluid in that section of the pipeline will be at a different pressure to its adjoining sections. For example, consider a section of an oil pipeline which passes near to or through a river. Said section may be cooled by the river and therefore at a lower temperature, and lower pressure, than the surrounding sections of pipeline. Such a local area of lower pressure can give rise to two rarefaction pressure waves propagating along the pipeline in a manner similar to a leak and therefore may lead to false identification of leaks in the pipeline when using the above mentioned prior art leak detection methods.

Another known method of determining whether or not there is a leak in a pipeline is to close off both ends of the pipeline and to monitor the pressure over a period of time, The pressure may drop over time if either there is a leak or if the temperature of the fluid in the pipeline differs from that of the ambient temperature surrounding the pipeline. The shape of the pressure curve as a function of time is different for each of these two scenarios and can therefore be used to distinguish between them. However, the pipeline must be closed off for a significant time period, typically several hours, before one can distinguish between the two scenarios and determine whether or not there is a leak. This is inconvenient and can be costly. Furthermore, even if this method concludes that there is a leak in the pipeline does not yield any information regarding its location.

It is an object of embodiments of the present invention to at least partially address the above problems.

According to a first aspect of the present invention there is provided a method of determining whether or not there is a leak in a pipeline for carrying fluids, the method comprising the steps of: at least partially sealing off one or both ends of the pipeline; introducing an object into the pipeline; monitoring a position of the object for a time period; determining a distribution of a velocity of the object as a function of its position; identifying any regions of the distribution where the velocity vanishes; and determining that there is a leak in the pipeline if the magnitude of a gradient of the distribution is greater than a predetermined threshold value in any region where the velocity vanishes.

S According to a second aspect of the present invention there is provided a method of determining the location of one or more leaks in a pipeline for carrying fluids, the method comprising the steps of determining whether or not there are any leaks in a pipeline using the method according to the first aspect of the present invention and, if so, identifying the position of the object where the distribution of the velocity vanishes with the location of a leak.

Advantageously, by introducing the object into the sealed pipeline any movement of the object will essentially show the local flow of fluid due to any pressure differences along the pip&ine. Therefore, the object acts as a probe to monitor this local, micro movement of the fluid.

Advantageously, the methods according to the present invention allow the presence of a leak in a pipeline to be located significantly faster than with prior art methods involving iso!ated or shut in' pipelines. This limits the disruption and expense of leak tests. Furthermore, the method according to the present invention yields information relating to the location of any leaks detected.

A leak will allow the fluid to flow outof the pipeline, creating a region of low pressure. For a true leak, this region of low pressure will be highly localised and point-like'. On either side of the leak the pressure is higher and therefore the direction of the local fluid flow will be different on opposite sides of the leak. Furthermore, one might expect the rate of fluid flow near to the leak to be significant. Therefore, for a true point like leak one would expect there to be a discontinuity in the distribution of the local fluid velocity as a function of displacement along the pipeline at the location of the leak. In a more realistic scenario, due to the finitesize of a real leak and the finite resolution of the method, one would expect the distribution of the velocity of the object as a function of its position to vary sharply from a positive value to a negative value with a large gradient at a region centred on the leak.

In contrast, consider the local fluid flow in a region of the pipeline whose surrounding ambient temperature is lower than that of the sections adjoining it on either side. For example, consider a section of an oil pipeline which passes near to or through a heat sink, such as a river.

One would expect this to also give rise to a local minimum of fluid pressure and, therefore, for the S distribution of the velocity of the object to change sign. However, for a region of pipeline of finite extent, one would expect the magnitude of the gradient of the velocity distribution in the region where the velocity changes sign to be less than that in the vicinity of a true leak.

The predetermined threshold value is preferably chosen so as to eliminate or substantially eliminate any false leak identifications from regions of low temperature. The predetermined threshold value is preferably chosen with regard to the finite size of a typical real leak and/or the finite resolution of the method. The predetermined threshold value may be a parameter of the method and may be optimised by a user of the method.

The method may further comprise the step of rejecting any leak candidates where the velocity of fluid vanishes but where the velocity is such that the flow of fluid is away from the point where it vanishes on either of both sides of that point. This can reject any points where the velocity vanishes as a result of a local maximum in fluid pressure.

Preferably, the object has an outer dimension which substantially matches an inner dimension of the pipeline. Furthermore, the object may be provided with a means for forming a seal between its outer dimension and an inner dimension of the pipeline, The seal may allow a pressure difference to build up across the object. The pressure difference will tend to drive the object towards an area of low pressure and the friction from the seal will tend to resist this. Once the pressure difference becomes sufficiently large, the object will move forward by a finite distance until the seal brings it to a stop. As the object surges forward, it will cause two pressure waves to propagate along the pipeline: a positive wave in the direction of lower pressure and a negative wave in the direction of higher pressure.

These two waves can be used to determine the position of the object using, for example, the method disclosed in WO 2011/070343. That is to say, the methods may further comprise the step of monitoring the fluid pressure at two or more positions on the pipeline. Preferably, the two or more positions are located at, or proximate to, opposite ends of the pipeline. This ensures that the pressure is monitored on either side of the object. The method disclosed in WO 20111070343 essentially combines the monitored fluid pressure at two points on the pipeline to form a two S dimensional probability distribution. This two dimensional probability distribution can be used to locate any sources of pressure waves such as leaks in the pipeline or, in this case, the position of the object as it surges forward along the pipeline.

Since one of the two pressure waves that propagate along the pipeline is a positive wave and the other is a negative wave, when using the method disclosed in WO 2011/070343 to identify the object, one of the pressure signals is inverted before the method is applied.

In more detail, the method disclosed in WO 2011/070343 comprises the steps of: mànitoring a fluid characteristic at a first point and second point along the conduit substantially continuously; determining a modified fluid characteristic at the first point and the second point by inverting either the fluid characteristic at the first point or the fluid characteristic at the second point; determining first and second quantities, being related to a differential with respect to time of the value of the modified fluid characteristic at the first and second points respectively; combining the first and second quantities to produce a two dimensional intensity function of time and a position variable, and analysing the magnitude of the intensity function to derive information relating to the fluid. The fluid characteristic may be proportional to fluid pressure and first and second quantities may be related to the second time derivative of modified fluid pressure at the first and second points.

Additionally or alternatively, any other method of monitoring the position of the object for the time period may be employed. For example, the method disclosed in US 5,388,455 may be employed. As a further alternative,, the object may be provided with a transmitter and may be operable to transmit a signal indicative of its position. The object may, for example, be provided with a radio frequency (RF) tag andlor a global positioning service (GPS) device.

S

For embodiments wherein the object is provided with a means for forming a seal between its outer dimension and an inner dimension of the pipeline, the sealing means may be adjustable.

This may allow the quality of the seal or the stickiness' of the object to be varied by a user.

For embodiments wherein the object is provided with a means for forming a seal between S its outer dimension and an inner dimension of the pipeline the quality of the seal or the stickiness' of the object may be optimised by a user. This optimisation may be achieved my adjusting the seal of the object or, alternatively, by selecting the object from a set of objects with different levels of stickiness.

The object may comprise a known type of pipeline inspection gauge (PIG). The object may be generally cylindrical in shape. The object may comprise a plurality disk or cup like members mounted on a shaft. The object disk or cup like members may be substantially circular in section and an outer radius of thereof may be substantially the same as an inner radius of the pipeline.

_iL- .4i....4..4ll4A,.,li+ha,'l e.+r.+r+k Ire iiuetirou nay rurtir, .ui.ipiiSc Li IC tCIJ.11 OO.jUCl iLlI' lilt. JALI'Jll l3 LII'-#I.'JC'.I. lIluaLlsC pipeline at a plurality of positions. Additionally or alternatively, the method may comprise the step of introducing one or more additional objects into the pipeline. Each such object may have substantially similar characteristics and each object may be introduced at a different one of a plurality of positions. The positions may be distributed along the pipeline at substantially regular intervals. The introduction of a single object or a group of objects at different positions is particularly useful since once an object reaches a point where the fluid pressure forms a local minimum, its velocity will tend to zero and it will stop. Therefore, introducing the object into the pipeline at a plurality of positions may allow the distribution of the velocity of the object as a function of its position to be mapped out for substantially the entire length of the pipeline. In particular, it can allow one to map out the distribution on both sides of a local pressure minimum.

Preferably both ends of the pipeline are fully sealed off. This may be achieved by any type of isolation valve or pump as desired or required.

The or each object may be introduced into the pipeline via a suitable access point.

The or each object may be provided with a propulsion means. The propulsion means may allow the object to move along the pipeline even up a pressure gradient. The obiect may be provided with an energy source which may provide power for the propulsion means. The propulsion means may be provided with a control means. This may allow a user to control S movement of the object in the pipeline. The object may be provided with a receiver and the control means may be operable remotely.

The distribution of the velocity of the object as a function of its position may be determined using any suitable method. The distribution of the velocity of the object as a function of its position may be smoothed out by performing a local time averaging. This is particularly advantageous for embodiments wherein the mption of the object is rather jerky. For example, embodiments wherein the object forms a seal with an inner surface of the pipeline, so that the object remains static until a pressure difference across is causes it to surge forward.

The identification of any regions of the distribution where of the velocity vanishes may comprise any analytical or numerical method, or a combination thereof.

The position of the object may be monitored intermittently or substantially continuously for the time period. The time period may be any suitable length as desired or required. The time period may be of the order of minutes.

In order that the invention may be more clearly understood an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: Fig. 1 shows a section of pipeline, which is suitable for carrying a fluid, and which comprises two ends; Fig. 2 shows a pipeline inspection gauge (PIG) as employed by the present invention; Fig. 3 shows, schematically, the PIG of Fig. 2 and how it will move in the pipeline of Fig. 1 due to local pressure differences; Fig. 4 is a plot of the fluid pressure as measured by two pressure sensors, each of which is disposed at a different end of the pipeline of Fig. 1; and Fig. 5 shows, schematically, a section of pipeline with a true leak and a cool region and the associated local fluid velocity as a function of displacement along the pipeline.

Referring to Fig. 1, a section of pipeline loot which is suitable for carrying a fluid, and which comprises two ends 101, 102, is shown. At each end 101, 102 the pipeline 100 is provided with a means for isolating the pipeline 100. In particular, a first end 101 is provided with a first valve 111 and a second end 102 is provided with a second valve 112. The pipeline is further provided with two pressure sensors 121, 124. A first of the pressure sensors 121 is disposed at, or proximate to, a first end 101 of the pipeline 100 and a second of the pressure sensors 124 is disposed at, or proximate to, a second end 102 of the pipeline 100. Although one pressure sensor is disposed at, or proximate to, each of the two opposing ends 101, 102 of the pipeline 100, optionally, a second pressure sensor (not shown) may be provided at each end of the pipeline 100. Furthermore, the two pressure sensors 121, 124 need not necesèarily be disposed at, or proximate to, each of the two opposing ends 101, 102 of the pipeline 100 and may be disposed at any two points along the pipeline 100.

A method of determining whether or not there is a leak in a pipeline 100 and, if so, locating the leak according to the present invention comprises the step of introducing an object into the pipeline 100. This may be achieved using one or more access points (not shown), as is well known in the art. Either before or after the object is introduced into the pipeline, the method further comprises the step of shutting in' the pipeline 100 by sealing off both ends 101, 102 using the isolation valves 111 112.

With reference to Fig. 2, the object 200 is a known type of pipeline inspection gauge (PIG). The PIG 200 is generally cylindrical in shape, comprising a plurality of disks 201 and cup like members 202 mounted on a shaft 204. A central section of the PIG comprises a substantially cylindrical brush 203. The disks 201, cup like members 202 and brush 203 are substantially circular in section and an outer radius of thereof substantially matches an inner radius of the pipeline 100.

S

Furthermore, the disks 201 and cup like members 202 form a means for forming a seal between an outer dimension of the PIG 200 and an inner dimension of the pipeline 100.

As shown schematically in Fig. 3, the PIG 200 will move in the shut in pipeline 100 due to local pressure differences therein. The PIG 200 therefore acts as a probe to monitor any local flow of fluid due to any pressure differences along the pipeline 100.

One such source of pressure differences is leaks 130 in the pipeline 100. A leak 130 allows fluid to flow out of the pipeline 100, creating a region of relatively low pressure. The seal formed between the PIG 200 and the pipeline 100 allows a pressure difference to build up across the PIG ?00, with a region 141 of relatively lower pressure on the side of the PIG 200 on which the leak 1301s disposed and a region 142 of relatively higher holding pressure on the opposite side of the PIG 200. This pressure difference exerts a force on the PIG 200 in the direction of the region 142 of low pressure and the friction from the seal of the PIG 200 will tend to resist this.

Once the pressure difference becomes sufficiently large, the PIG 200 will move towards the region 142 of lower pressure by a finite distance until the seal brings it to a stop. As the PIG 200 surges forward, it will cause two pressure waves to propagate along the pipeline 100: a positive wave in the direction of the region 142 of lower pressure and a negative wave in the direction of the region 141 of higher pressure.

The method further comprises the step of monitoring the fluid pressure at the pressure sensors 121, 124. The pressure measured by each of the pressure sensors 121, 124 as a function of time will comprise the periodic waveform of one of the pressure waves that results in from the PIG 200 surging forward, folded with any general trend in the pressure in the pipeline as a whole. Fig. 4 shows the fluid pressure 401 as determined by the pressure sensor 121 at the first end 101 as a function of time and the fluid pressure 402 as determined by the pressure sensor 124 at the second end 102 as a function of time. The two waves that result from the PIG 200 surging forward, as detected by these two pressure sensors, can be used to determine the position of the PIG 200. In the present embodiment, the method disclosed in WO 2011/070343 is used to determine the position of the PIG 200, however, as will be obvious to one skilled in the art, other methods may alternatively be used. The method disclosed in WO 2011/070343 essentially combines the monitored fluid pressure at the two pressure sensors to form a two dimensional probability distribution. This two dimensional probability distribution can be used to locate any sources of pressure waves such as leaks in the pipeline 100 or1 in this case, the position of the PIG 200 as it surges forward along the pipeline 100.

Sinceone of the two pressure waves that propagate along the pipeline 100 is a positive wave and the other is a negative wave, when using the method disclosed in WO 2011/070343 to identify the PIG 200, one of the pressure signals is inverted before the method is applied.

In more detail, the method disclosed in WO 2011/070343 comprises the steps of: monitoring a fluid characteristic at a first point and second point along the conduit substantially continuously; determining a modified fluid characteristic at the first point and the second point by inverting either the fluid characteristic at the first point or the fluid characteristic at the second point; determining first and second quantities, being related to a differential with respect to time of the value of the modified fluid characteristic at the first and second points respectively; combining the first and second quantities to produce a two dimensional intensity function of time and a position variable, and analysing the magnitude of the intensity function to derive information relating to the fluid. The fluid characteristic may be proportional to fluid pressure and first and second quantities may be related to the second time derivative of modified fluid pressure at the first and second points.

The position of the PIG 200 is monitored for a time period and a distribution of the velocity of the PIG 200 is determined as a function of its position. The position of the PIG 200 may be riionitored intermittently or substantially continuously for the time period. If determined intermittently, it is preferably determined once each time it surges along the pipeline 100.

The method according to the present invention further comprises the step of sequentially introducing the PIG 200 into the pipeline 100 at a plurality of positions. The positions are preferably distributed along the pipeline 100 at substantially regular intervals. The introduction of the PIG 200 at different positions is particularly useful since once the PIG 200 reaches a point where the fluid pressure forms a local minimum, its velocity will tend to zero and it will stop.

Therefore, introducing the PIG 200 into the pipeline at a plurality of positions may allow the distribution of the velocity of the PIG 200 as a function of its position to be mapped out for substantially the entire length of the pipeline 100. In particular, it can allow one to map out the distribution on both sides of a local pressure minimum.

Fig. 5 shows a scenario wherein a section of pipeline 100 comprises both a leak 130 and a relative!y cool region 130. The relatively cool section 130 is of finite extent, being of the order of meters long, and may be caused by any local heat sink 500, such as a river or a section of ground with different thermal properties to its adjoining sections, which is close to said section 130. A distribution 300 of the velocity of the PIG 200 is determined as a function of its position in the pipeline 100 and any regions 301 of the distribution where of the velocity vanishes are identified.

For the true leak 130, the surrounding region of low pressure will be highly localised and 1point-like'. On either side of the leak 130 the pressure is higher and therefore the direction of the local fluid flow will be different on opposite sides of the leak. Furthermore, one might expect the speed of fluid near to the leak to be significant. Therefore, for a true point like leak 130 one would expect there to be a discontinuity 302 in the distribution 300 of the local fluid velocity as a function of displacement along the pipeline 100 at the location of the leak 130. In a more realistic scenario, due to the finite size of a real leak 130 and the finite resolution of the method, one Would expect the distribution 300 of the velocity of the object as a function of itsposition to vary sharply from a positive value to a negative value with a large gradient at a region centred on the leak 130.

In contrast, consider the local fluid flow in the region 130 of the pipeline 100 whose surrounding ambient temperature is lower than that of the sections adjoining it on either side.

One would expect this to also give rise to a local minimum of fluid pressure and, therefore, for the distribution 300 of the velocity of the PIG 200 to change sign. However, due to the finite extent of the region 130 of the pipeline 100, one would expect the magnitude of the gradient of the velocity distribution to be greater than that in the vicinity of a true leak 130.

Therefore, the method of determining whether or not there is a leak in the pipeline 100 comprises the step of determining that there is a leak in the pipeline if the magnitude of a gradient of the distribution is greater than a predetermined threshold value in any region where the velocity vanishes. Therefore, the method of determining the location of one or more leaks in a pipeline for carrying fluids, the method further comprises the step of identifying the position of the PiG 200 where the distribution of the velocity vanishes, and where the magnitude of the gradient of the distribution is greater than a predetermined threshold value, with the location of a leak.

The predetermined threshold value is preferably chosen so as to eliminate or substantially eliminate any false leak identifications from regions of low temperature. The predetermined threshold value is preferably chosen with regard to the typical size of real leaks andIor the finite resolution of the method. The predetermined threshold value may be a parameter of the method and may be optimised by a user of the method.

The above embodiment is described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1. A method of determining whether or not there is a leak in a pipeline for carrying fluids, the method comprising the steps of: at least partially sealing off one or both ends of the pipeline; introducing an object into the pipeline; monitoring a position of the object for a time period; determining a distribution of a velocity of the object as a function of its position; identifying any regions of the distribution where the velocity vanishes; and determining that there is a leak in the pipeline if the magnitude of a gradient of the distribution is greater than a predetermined threshold value in any region where the velocity vanishes.
2. A method of determining the location of one or more leaks in a pipeline for carrying fluids, the method comprising the steps of determining whether or not there are any leaks in a pipeline for carrying fluids according to claim 1 and, if so, identifying the position of the object where the distribution of the velocity vanishes with the location of a leak.
3. A method as claimed in either of claims 1 or 2, the method further comprising the step of rejecting any leak candidates where the velocity of fluid vanishes and the velocity is such o that the flow of fluid is away from the point where it vanishes on either of both sides of that point.
4. A method as claimed in any preceding claim, wherein an object, with an adjustable seal between its outer dimension and an inner dimension of the pipeline, is introduced into the pipeline and the method further comprises the step of adjusting that seal.
5. A method as claimed in any preceding claim, the method further comprising the step of providing the object with a means for forming a seal between its outer dimension and an inner dimension of the pipeline.
6. A method as claimed in any preceding claim, the method further comprising the step of monitoring the fluid pressure at two or more positions on the pipeline.
7. A method as claimed in claim 6, the method further comprising the step of combining the monitored fluid pressure at two points on the pipeline to form a two dimensional probability distribution.
8. A method as claimed in any preceding claim, wherein monitoring the position of the object for a time period comprises the steps of: monitoring a fluid characteristic at a first point and second point along the conduit substantially continuously; determining a modified fluid characteristic at the first point and the second point by inverting either the fluid characteristic at the first point or the fluid characteristic at the second point; determining first and second quantities, being related to a differential with respect to time of the value of the modified fluid characteristic at the first and second points respectively; combining the first and second quantities to produce a two dimensional intensity function of time and a position variable, and analysing the magnitude of the intensity function to c) derive information relating to the fluid.
9. A method as claimed in any preceding claim, further comprising the step of fitting the object with a transmitter, operable to transmit a signal indicative of its position.
10. A method as claimed in any preceding claim, wherein the object is provided with an adjustable sealing between its outer dimension and an inner dimension of the pipeline, and the method further comprises the step of adjusting the seal.
11. A method as claimed in any preceding claim, further comprising the step of sequentially introducing the object into the pipeline at a plurality of positions.
12. A method as claimed in any preceding claim, further comprising the step of introducing one or more additional such objects into the pipeline.
13. A method as claimed in claim 12, wherein the objects are introduced into the pipeline at substantially regular intervals.
14. A method as claimed in any preceding claim, wherein the one or more objects are introduced into the pipeline via a suitable access point.
15. A method as claimed in any preceding claim, further comprising the step of substantially completely sealing off the ends of the pipelines.
16. A method as claimed in claim 15, wherein the ends of the pipeline are substantially completely sealed off by the provision of any or both of an isolation valve and/or a pump.
17. A method as claimed in any preceding claim, further comprising the step of smoothing out the distribution of the velocity of the object as a function of its position by performing a local time averaging.
18. A method as claimed in any preceding claim, further comprising the step of performing a numerical or analytical method, or combination thereof, in order to identify regions of the distribution of the velocity of the object as a function of its position where the velocity vanishes.CD
19. A method as claimed in any preceding claim, wherein the position of the object is V" monitored intermittently.o
20. A method as claimed in any of claims ito 18, wherein the position of the object is LI') 15 monitored substantially continuously for the time period.
21. A method as claimed in any preceding claim, wherein the time period may be of the order of minutes.
22. An apparatus for determining whether or not there is a leak in a pipeline for carrying fluids, the apparatus comprising: an object; monitoring means for monitoring the position of the object and means for determining the velocity of the object.
23. An apparatus for determining the location of one or more leaks in a pipeline for carrying fluids, the apparatus comprising the features of claim 22 for determining whether or not there are any leaks in a pipeline for carrying fluids, and a processing means, and if it is determined that a leak is present, the processing means is operable to identify the position of the object where the distribution of the velocity vanishes, with the location of a leak.
24. An apparatus as claimed in either of claims 22 or 23, wherein the object is provided with a means for forming a seal between its outer dimension and an inner dimension of the pipeline.
25. An apparatus as claimed in claim 24, wherein the seal is adjustable.
26. An apparatus as claimed in any of claims 22 to 25, wherein the object is a pipeline inspection gauge (PIG).
27. An apparatus as claimed in any of claims 22 to 26, wherein the object is generally cylindrical is shape.
28. An apparatus as claimed in any of claims 22 to 27, wherein the object comprises a plurality disk or cup like members mounted on a shaft.
29. An apparatus as claimed in claim 28, wherein the object disk or cup like members may be substantially circular in section and an outer radius of thereof may be substantially the same as an inner radius of the pipeline. C')30. An apparatus as claimed in any of claims 22 to 29, wherein the object is provided with propulsion means.0 31. An apparatus as claimed in claim 30, wherein the object is provided with an energy LI') source which may provide power for the propulsion means.32. An apparatus as claimed in either of claims 30 or 31, wherein the propulsion means is provided with a control means.33. An apparatus as claimed in claim 32, wherein the object is provided with a receiver and the control means is operable remotely.34. A method substantially as herein described with reference to any of the accompanying drawings.35. An apparatus substantially as herein described with reference to any of the accompanying drawings.