GB2453800A

GB2453800A - Characterising fluid flow through a pipe

Info

Publication number: GB2453800A
Application number: GB0720801A
Authority: GB
Inventors: Philip John Campbell
Original assignee: MARTIN JOESEPH KEANES; PAUL GEORGE MCELHONE
Current assignee: MARTIN JOESEPH KEANES; PAUL GEORGE MCELHONE
Priority date: 2007-10-20
Filing date: 2007-10-20
Publication date: 2009-04-22
Also published as: GB0720801D0; GB0802894D0

Abstract

A flow characterising meter 2, eg a flow meter, may be inserted into and withdrawn from a saddle member 1 placed around a pipe 7 without shutting off the fluid flow through the pipe. The saddle member 1 has a central linear passage 9 which may be sealed by a closure means 8, eg a shut-off gate, part-way along its length. The flow characterising meter 2 comprises a shaft 11 that is initially only partially inserted into the passage 9 in which it is sealed by sealing means 19 on the shaft 11 and/or in the passage 9. The closure means 8 is then opened allowing the shaft 11 to be inserted fully. The meter 2 can then be locked to the saddle member 1 eg by locking nut 17. In a modification (fig.2), the shaft 2 of the meter is elongated and a housing (27) is connected between the meter 2 and the saddle member 1 to prevent the meter 2 being forcibly expelled from the saddle member 1 when it is not locked in position and the pipe is pressurised.

Description

TITLE

Apparatus and Method for Characterising Fluid Flow through a Pipe

DESCRIPTION

Field of Invention

The present invention provides a method and apparatus for characterising fluid flow through a pipe. The invention is particularly suited for use on high pressure pipelines as it provides a method and apparatus that allows a flow characterising meter, such as a flow-rate meter, to be inserted and removed from such pipelines without the need to interrupt the flow of fluid through the pipe.

Background to Invention

Characterising the flow of fluid through pipelines by measuring the flow-rate, pressure or other physical characteristics of the fluid flow is often desirable but may also be difficult. It is usually necessary to install in a pipe one or more flow characterising meters that extend at least partially into the pipe in order to measure the properties of the fluid flow. A particular example of flow characterising meters are flow-rate meters. It is usually necessary that flow-rate meters are installed in a pipe and extend into the fluid flowing through the pipe in order to measure the rate of flow.

This is because many flow-rate meters rely on the fluid flow physically acting upon a sensor placed within the fluid. For example the sensors of flow-rate meters often include one or more vanes that are pushed or otherwise propelled by the fluid and that drive a rotary potentiometer or other similar flow measuring device. Alternatively, the sensor may substantially comprise of a displacement piston that is biased against the action of a spring by the fluid flow. Flow-rate meters are typically designed to be installed through a side-wall of a pipeline.

Current methods of installing flow-rate meters and other flow characterising meters within pipelines involve the interruption of the flow of fluid through the pipeline.

Most commonly, the fluid flow will be shut off causing interruption to the supply.

Then a U-shaped additional section of the pipeline will be joined in fluid communication with the pipeline at each end. The U-shaped additional section of pipeline will include a flow-rate meter and will be fixed to the pipeline in a position such that the meter is easily read and serviceable. A valve is then fixed in the main pipeline between the two ends of the U-shaped additional section so that the main pipeline may be sealed and such that any fluid flowing through the main pipeline will be diverted through the U-shaped additional section and past the meter. Finally, the fluid flow will be restarted and the fluid flow can be measured. If fluid is allowed to flow through the pipe during the process of fixing the U-shaped additional section to the main pipeline and before it is sealed in positionthe fluid may leak out of the pipe.

As will be appreciated, this is a particular problem if the fluid in the pipe is under high pressure.

Irtllig mctcr; wt1 pid uiains water pipes in order to measure the flow of water there-through is particularly troublesome. This is because shutting off mains water pipes is particularly undesirable as it will interrupt the supply of water to customers.

In light of the above there is a need for a new apparatus and method for characterising the flow of fluid through a pipe that allow a flow characterising meter (for example, a flow-rate meter) to be installed in and removed from the pipeline without the need to shut-off the fluid flow through the pipe. Preferably the apparatus and method will be able to be used on high pressure pipelines such as water mains and will enable a meter to be directly inserted into the mains pipeline without the need to attach additional sections of pipeline. It is also preferable that any such apparatus and method will enable the installed meter to be easily read.

Summary of Invention

The present invention provides an apparatus for characterising fluid flow through a pipe provided with a saddle member having a first sub-passage formed therethrough extending between a radially inner end and a radially outer end and closure means which may seal the first-sub passage part-way along its length; wherein the apparatus comprises: a flow characterising meter that may be inserted into the outer end of the passage and extend through the length of the passage; and sealing means disposed on the meter and/or the passage, which may sealingly engage the meter with the passage when the meter extends part-way through the passage and the closure means seal the passage and when the meter extends through the length of the passage.

The apparatus of the present invention may be used in the following way. First the saddle member will be fitted to a pipe, for example a mains water pipe, using an under pressure collar in a conventional manner as will be understood by those skilled in the art. The saddle member will be attached such that the radially inner end of the passage i:....., __._fl _.(...1 , vvau.n uic pIpc.

The saddle member may be a conventional saddle member such as those used to attach new supply sections to mains water pipes, as will be known to a person skilled in the art. Alternatively, the saddle member may be specially formed and form part of the apparatus of the present invention.

A hole is thenprovided in the wall of the pipe in correspondence with the passage of the saddle member. This may be achieved by drilling a hole in the pipe through the passage of the saddle member. In order to avoid damage to the closure means it is necessary that the closure means is not sealing the passage when a hole is being drilled through the passage. After the hole has been provided the passage of the saddle member will be sealed with the closure means in order to prevent fluid escaping from the pipe through the passage. In this manner a sealed access point to the hole in the pipe is provided by the closure means and the saddle member.

A flow characterising meter will then be partially inserted into the passage whilst the closure means keeps the passage sealed. The meter will be inserted such that it is sealing engagement with the passage. The closure means is then removed and the meter is fully inserted such that it extends through the passage and an inner end, where a sensor is mounted, extends into the pipe. During this insertion the meter will maintain its sealing engagement with the passage. The meter may then be locked to the saddle member to prevent it being forcibly expelled from the passage by the action of any pressurised fluid within the pipe. The fluid flow within the pipe may then be monitored using the meter.

In order to withdraw the meter from the pipe the process is reversed. First, if the meter has been locked to the saddle member it is unlocked. Then the meter is partially withdrawn from the passage whilst maintaining its sealing engagement with the passage. The closure means is then used to seal the passage and finally the meter is fully withdrawn from the passage.

Prefer�y thc �iic rcmbcr wii ciist f twu pcub. itdiiily iirncr part and a removable radially outer part. The inner part may substantially consist of a conventional saddle member. Furthermore, the inner part may be permanently attached to the under pressure collar such that it may be permanently mounted on a pipe to allow repeated investigation of a pipeline. As will be appreciated, in order to allow a pipeline to be repeatedly examined it is necessary that the closure means closes the passage within the inner part of the saddle member such that if and when the outer part of the saddle member is removed the passage and therefore the pipeline may still be sealed. The removable outer part of a saddle must be able to be sealingly attached to the inner part. For example, the outer part may be able to be screwed into and out of the inner part by means of complementary screw threads formed on the two parts.

Having a removable outer part of the saddle member may be preferable as any specific outer part may serve as an adaptor for a specific flow characterising meter. In this manner different meters may be used to examine a single pipeline merely by changing the outer part of the saddle member. Thereby removing the need to fix and remove different under pressure collars and without the need to unseal the pipe or interrupt the flow of fluid through the pipe.

The closure means may be a simple shut off plate that may be slid into and out of position within the passage of the saddle member. However, it is to be understood that any suitable closure means that may be used to open and seal the passage through the saddle member. If the saddle is formed in two parts, as set out above, the closure means may be in either part. However, it is currently preferable that the closure means is formed in a radially inner part of the saddle member.

Advantageously the passage through the saddle member will be substantially cylindrical. A cylindrical passage is particularly preferred if, as set out above, the saddle member consists of two parts that are screwed into sealing engagement.

1 Thp flaw hru'tp.rcnri rreter cf the ppart of thc prc.cit ij,11 i, iiapcd iu sealingly engage the passage of the saddle member. Preferably the meter will substantially consist of an elongated shaft that is shaped to sealingly engage and extend through the passage of the saddle member and that has an inner end and an outer end. A flow sensor, for example a flow-rate sensor, will be attached to and may extend from the inner end of the shaft such that when the meter is mounted within the saddle member the sensor may protrude into a pipe to which the saddle member is attached. The meter may have a locking means at the outer end of the shaft which enables the meter to be removably locked to the saddle member when it is mounted within the saddle member. The meter may be asymmetrical at its outer end or have some other indicator that will indicate to a user what orientation the sensor is in with respect to the fluid flow within a pipe. This may enable a flow-rate meter to be correctly positioned within the fluid flow.

Advantageously the locking means may be a captive nut that is formed integrally with and extends from the shaft of the meter. In order to lock the meter to the saddle member the captive nut may be screwed onto a complementary threaded portion of a radially outer end of the saddle member.

Alternatively, the meter may have at least one protrusion extending outwards from the outer end of the shaft. For example, there may be an annularly protruding ring formed at the outer end of the shaft. A separate locking nut may then be used to lock the meter to the saddle member by means of the protrusion or protrusions. For example, the nut may fit over and cooperate with any protrusion formed on the outer end of the shaft of the member and be screwed onto a complementary threaded portion of a radially outer end of the saddle member to thereby hold the meter in position.

The sensor of the flow characterising meter may be any sensor that may be used to characterise the fluid flow within a pipe. In one embodiment the sensor may be a rotary paddle wheel that protrudes from the inner end of the shaft of the meter and is used to monitOr the fluid flow-rate. However, it is to be appreciated that the apparatus and method of the present invention are equally suitable for introducing other flow charactrising nors into the fid f!cv.' cf thc fui cAdizipie a pressure sensor.

Wires may lead from any sensor through the centre of the shaft of the meter to a suitable electrical attachment formed at the exterior of the outer end of the shaft. In this manner the readings from the sensor may be communicated to a suitable external electronic device as will be understood by the person skilled in the art. The sensor may be electronically connected to a transmitting device that may transmit the readings from the sensor to a remote receiving device. This may be particularly preferable if the pipeline being examined is usually underground or otherwise difficult to access as it enables the readings of the sensor to be gathered without the need to access the pipeline after the initial installation of the sensor. The transmitting device may also be remotely activatable in order to transmit the data such that it is only activated when necessary.

As will be appreciated by a person skilled in the art the sealing means of the present invention may be any means that provide a sealing engagement between the meter and the saddle member. The sealing means must be capable of maintaining the sealing engagement whilst the meter is inserted and removed from the saddle member. In an embodiment of the present invention the sealing means may be a simple annular rubber ring mounted within the inner surface of the passage within the saddle member. Alternatively or additionally an annular rubber sealing means may be mounted on or in the external surface of the shaft of the flow characterising meter.

Preferably the apparatus of the present invention will include a safety mechanism to prevent the flow meter being forcibly expelled from the saddle member when it is not locked to the saddle member and there is a pressurised fluid flowing through any attached pipe. The safety apparatus may be an external housing.

In an embodiment of the present invention the apparatus further comprises an external housing that is connectable to the radially outer end of the saddle member at a first end, for example by means of complementary screw threads formed thereon. The hccing ay bc btaitay a ti'ai 0d u'fiiiiig wi internai passage through which a cooperating meter may be passed. The internal passage will have at least one inwardly protruding member formed at a radially outer end. This member may be and an inwardly projecting annular flange. The cooperating meter will have at least one cooperating protruding member formed part-way along its length. Advantageously this will be an annular protruding flange formed part-way along its length such that, due to the inwardly projecting annular flange formed at the radially outer end of the housing, it can only be inserted into the internal passage of the housing from a radially inner end of the housing and it cannot pass through the tubular passage beyond the point where the annular flanges come into contact. Preferably, the meter will have a substantial length either side of the annular flange that enables the meter to be pushed and pulled into and out of position within the saddle member when the meter is positioned within the housing and the housing is connected to the saddle member If a housing, as described above is used it is necessary to first insert the meter within the housing from the radially inner end of the housing until the flanges of the housing and meter are brought into contact. Then the housing may be connected to the saddle member. Preferably, in this position the meter will only extend into the housing a distance whereby the closure means may seal the passage of the saddle member but will extend far enough into the passage such that the meter and passage are in sealing engagement. If the passage is sealed, it will then be opened. The meter may then be fully inserted into the saddle member using a portion of the meter extending out of the housing. Finally, the meter may be locked in position, either by being locked to the housing or by being locked directly to the saddle member.

In this manner, as long as the housing remains connected to the saddle member the meter is maintained in a sealing engagement with the passage of the saddle member.

The cooperating flanges of the housing and meter prevent the meter being removed from the passage entirely. Thus the housing may prevent the meter being expelled from the passage, for example by the action of high pressure fluid within the pipeline.

The present invention also provides a method of characterising fluid flow through a ic mr%,',,rn c. rr "r

(i) attaching a collar to the pipe, the collar including a saddle member having a linear passage formed there-through extending between an radially outer end and a radially inner end, and closure means which may seal the passage part-way along its length; (ii) providing a hole in the pipe in correspondence with the passage of the saddle member and sealing the passage with the closure means; (iii) partially inserting a flow characterising meter into the sealed passage such that the meter is in sealing engagement with the aperture; (iv) removing the closure means from its sealing engagement with the passage; and (v) fully inserting the flow characterising meter to extend through the passage and into the pipe whilst maintaining the meter's sealing engagement with the passage.

Preferably the meter will be locked to the saddle member after it has been inserted through the passage. As explained above, this may be achieved through the provision of a locking means provided at an outer end of a shaft of the meter. Locking the meter to the saddle member is preferable as it will prevent the meter being expelled from the passage due to the fluid pressure within the pipe.

As explained above it may be preferable that the saddle member consists of at least a radially inner part that has the closure means and that is permanently attached to the collar and a removable radially outer part that may be sealingly attached to the inner part.

If the saddle member does consist of a radially inner part and an outer part it may be preferable that the outer part of the saddle member is only attached to the inner member after step (ii) of the method set out above and before step (iii) Further advantages of the present invention will become apparent from the following description of a preferred embodiment of the invention, as shown in the drawings. ic

Drawings Figure 1 shows cross-section through a first preferred embodiment of the apparatus of the present invention attached to a pipeline; and Figure 2 shows a cross-section through a second preferred embodiment of the apparatus of the present invention attached to a pipeline.

A cross-section of a first preferred embodiment of the present invention is shown in Figure 1. The apparatus substantially consists of a saddle member I and a flow-rate meter 2. The saddle member 2 comprises a radially inner part 3 and a radially outer part 4. The outer part 4 is removably attached to the inner part 3 by means of complementary threaded portions 5 formed on each part. The join between the inner part 3 and the outer part 4 of the saddle member I is sealed by an annular sealing member 6 provided on an inner surface of the inner part 3. The saddle member I is attached to a pipeline 7 in a conventional manner by means of an under pressure collar (not shown). The inner part 3 of the saddle member I includes a shut-off gate 8 that may be used to seal a central passage 9 formed within the saddle member when the flow-rate meter 2 is removed from the portion of the passage adjacent the gate. A hole is provided in the pipeline 7 through which the flow-rate meter 2 protrudes into the fluid 10 within the pipeline.

The flow-rate meter substantially comprises an elongated shaft 11 which extends through the length of the saddle member 1 from an outer end 12 to an inner end 13.

The shaft 11 is sealingly engaged with the saddle member 1 by means of an annular seal 19 mounted in the inner surface of the outer part 4 of the saddle member 2. The seal 19 allows the shaft 11 of the flow- rate meter 2 to be slid up and down the passage 9 without breaking the seal between the shaft 11 and the saddle member 1.

A rotatable paddle wheel 14 is mounted at the inner end 13 of the shaft 11 of the flow-rate meter 2 and is connected by wires 15 running through the centre of the shaft 11 to an electrical connection 16 at the outer end 12 of the shaft 11. Fluid 10 flowing 1 t!iriigh th pipe!e 7.v!I rctatc thc paddk wii 4. Thc iutation of the pacidie wheel 14 provides an electrical signal which is relayed via wires 15 and an electrical connection 16 to a suitable external electronic device (not shown). In this manner the flow-rate of the fluid 10 within the pipeline 7 may be monitored.

The flow-rate meter 2 is removably fixed to the saddle member 1 by means of an integral locking nut 17 formed adjacent to the outer end 12 of the shaft 11. The locking nut 17 is screwed to the cooperative threaded portion of the outer part 4 of the saddle member I. The flow-rate meter 2 additionally has two diametrically opposed radially extending protrusions 18 that extend through the locking nut 17. The protrusions 18 facilitate the screwing and unscrewing of the locking nut 1 7, and hence the flow-rate meter 2, from the saddle member 1. As the locking nut 17 is formed integrally with the shaft 11 of the flow-rate meter 2 it is not possible to insert the flow-rate meter into the passage 11 beyond the locking nut.

The preferred embodiment of the present invention is used in the following manner.

First the inner part 3 of the saddle member I is attached to the pipeline 7 using the under pressure collar. The pipeline may, for example, be a 6 inch (0.l52m) water mains pipe. The hole is then drilled in the pipeline 7 in correspondence with the passage 9 through the saddle member I by using a drill (not shown) extending through the passage 9. During the drilling the shut-off gage 8 is withdrawn from the passage 9 to allow a drill bit to pass through uninhibited. The drill is then withdrawn from the passage 9 and the passage is sealed using the shut-off gate 8. In this manner a sealable access hole is provided in the pipeline 7.

In order to monitor the fluid flow in the pipeline 7 the outer part 4 of the saddle member 1 is screwed into and thereby attached to the inner part 3 of the saddle member 1. The flow-rate meter 2 is then partially inserted into the passage such that the seal 19 sealingly engages the shaft 11 of the meter 2. The shut-off gate 8 is then removed from the passage 9 and the flow-rate meter 2 is fully inserted through the passage. The flow-rate meter 2 is then locked to the saddle member 1 using the locking nut 17. In this manner the paddle wheel 14 is positioned in the fluid flow ic ui;thi, tk I -j--I--.----In order to remove the flow-rate meter 2 the above process is reversed. First, the locking nut 17 is unscrewed from the saddle member I and the flow-rate meter 2 is partially withdrawn from the passage 9 up to the mark on the shaft. During this withdrawal it is important that the flow-rate meter 2 is not fully withdrawn and that the shaft 11 of the meter remains in sealing engagement with the seal 19.. The shut-off gate 8 is then closed to seal the passage 9. The flow-rate meter 2 may then be fully withdrawn. Finally the outer part 4 of the saddle member 1 may be unscrewed if necessary.

Figure 2 shows a second preferred embodiment of the invention. This embodiment is of similar construction to the first preferred embodiment except that it additionally comprises a housing 27 and the shaft 11 of the meter 2 is consequently elongated.

Therefore, where appropriate the same reference numerals have been used to denote the equivalent features of both embodiments of the invention. -12-

The housing 27 is connectable around the meter 2 and the saddle member 1. The housing 27 serves as a safety mechanism to prevent the meter 2 being forcibly expelled from the saddle member I when it is not locked in position and there is a pressurised fluid 10 flowing through the pipe 7.

The housing 27 is connectable to the radially Outer end of the outer part 4 the saddle member 1 at a first end by means of complementary screw threads formed thereon.

The housing 27 is a substantially a tubular body defining an internal passage 20 through which the meter 2 is passed. The housing has an inwardly projecting annular flange 21 formed at a radially outer end. The meter 2 has a cooperating annular protruding flange 22 formed part- way along its length such that, due to the inwardly projecting annular flange 21 formed at the radially outer end of the housing 27, it can only be inserted into the internal passage 20 of the housing 27 from a radially inner end of the housing 27 and it cannot pass through the internal passage 20 beyond the pcit where the arhr fiangc 21, 22 ciiic itc, cöi1tâj. Tiic iiivi.ci 2 kis substantial length either side of the annular flange 22 that enables the meter 2 to be pushed and pulled into and out of position within the saddle member I whilst the meter 2 is positioned within the housing 27 and the housing 27 is connected to the saddle member 1, as shown in Figure 2. An engaging portion 23 formed at the radially outer end of the meter 2 has a screw thread 24 formed on its outer surface. A corresponding screw thread 25 is formed at the radially outer end of the housing 27.

An operating member 26 is provided to enable the meter 2 to be pulled through the internal passage 20 and to meter 2 to be screwed into the housing 27.

The housing 27 is used in the following maimer. First, the meter 2 is inserted within the internal passage 20 of the housing 27 from the radially inner end of the housing 27 until the flanges 21, 22 are brought into contact. Then the housing 27 is connected to the saddle member I. In this position the meter 2 will extend into the passage 9 a distance whereby the closure means 8 may seal the passage 9 without impinging upon the meter 2 and the meter 2 and passage 9 are in sealing engagement. If the passage 9 is sealed by the closure means 8 the closure means may then be opened. The meter 2 may then be fully inserted into the saddle member I using a portion of the meter 2 -13 -extending Out of the housing 27. Finally, the engaging portion 23 of the meter 2 is used to lock the meter 2 to the housing 27 and the sensor 14 in position within the fluid 10 in the pipe 7. In order to remove the meter 2 the above method is reversed. -14-

Claims

1. An apparatus for characterising fluid flow through a pipe provided with a saddle member having a passage formed therethrough extending between a radially inner end and a radially outer end and closure means which may seal the passage part-way along its length; wherein the apparatus comprises: a flow characterising meter that may be inserted into the outer end of the passage and extend through the length of the passage; and sealing means disposed on the meter and/or the passage, which may sealingly engage the meter with the passage when the meter extends part-way through the passage and the closure means seal the passage and when the meter extends through the length of the passage.

2. An apparatus according to claim 1, wherein the meter substantially consists of a shaft that s shad k ciigagc wiiii and extiid Litrough the passage of the saddle member and has an inner end and an outer end, a sensor substantially at the inner end of the shaft and a locking means substantially at the outer end of the shaft and which may be used to removably lock the meter in position within the saddle member.

3. An apparatus according to claim 2, wherein the locking means is a captive nut that is integral with the shaft of the meter and may be locked to the saddle member by means of a screw thread formed at a radially outer end of the saddle member.

4. An apparatus according to claim 2, wherein the locking means is a captive nut that is separate from the shaft of the meter and that may lock the meter to the saddle member by means of a screw thread formed at a radially outer end of the saddle member and at least one protrusion formed at the outer end of the meter that prevents the outer end of the meter being inserted into the passage of the saddle member.

5. An apparatus according to claim 2, further comprising a housing defining an internal passage through which the meter may be passed, that is connectable to a -15-radially outer end of the saddle member at a first end and that has at least one inwardly projecting member formed at a second end of the passage, wherein the meter has at least one outwardly projecting flange formed part-way along its length that may cooperate with the projecting member of the housing when the meter is mounted within the internal passage of the housing to thereby prevent the meter passing completely out of the outer end of the housing and to maintain the meter in sealing engagement with the passage of the saddle member when the housing is connected thereto.

6. An apparatus according to claim 5, wherein the locking means may lock the meter to the housing.

7. An apparatus according to any of claims 2 to 6, wherein the sensor comprises a rotary paddle wheel that protrudes from the inner end of the shaft of the meter.

8. An apparatus according to any preceding claim, wherein the sealing means comprises an annular seal.

9. An apparatus according to any preceding claim, wherein the saddle member consists of a radially inner part and a removable radially outer part that may be sealingly attached to the inner part and the apparatus further comprises the radially outer part of the saddle member.

10. An apparatus according to claim 9, wherein the radially inner part of the saddle member has the closure means.

11. An apparatus according to claim 9 or claim 10, wherein the outer part of the saddle member is removably attachable to the inner part of the saddle member by means of complementary screw threads formed on the outer and inner parts.

12. An apparatus according to any of claims I to 8, further comprising the saddle member. -16-

13. An apparatus according to any preceding claim, wherein the closure means is a shut-off plate.

14. An apparatus according to any preceding claim, wherein the passage is substantially cylindrical.

15. An apparatus for characterising fluid flow through a pipe substantially as described herein and as shown in the Figures.

16. An apparatus further comprising transmitting means connected to the sensor and external to the meter for transmitting readings from the sensor to a remote electronic device.

17 A mtod of characterizing fhid flc;' tugh a pipc Cps thc icjm of (i) attaching a collar to the pipe, the collar including a saddle member having a linear passage formed there-through extending between an radially outer end and a radially inner end, and closure means which may seal the passage part-way along its length; (ii) providing a hole in the pipe in correspondence with the passage of the saddle member and sealing the passage with the closure means; (iii) partially inserting a flow characterising meter into the sealed passage such that the meter is in sealing engagement with the aperture; (iv) removing the closure means from its sealing engagement with the passage; and (v) fully inserting the flow characterising meter to extend through the passage and into the pipe whilst maintaining the meter's sealing engagement with the passage.

18. A method according to claim 14, further comprising the step: (vi) locking the meter to the saddle member.

19. A method according to claim 14 or claim 15, wherein the saddle member consists of a radially inner part having the closure means and a removable radially outer part that may be sealingly attached to the inner part.

20. A method according to claim 14, wherein the outer part of the saddle member is sealingly attached to the inner part of the saddle member after step (ii) and before step (iii).