GB2532095A

GB2532095A - Gas flue safety valve

Info

Publication number: GB2532095A
Application number: GB1504501.6A
Authority: GB
Inventors: Guscott Daniel; Alexander Breen Paul; Paul Oglesby John
Original assignee: 1ST GREEN DEAL Ltd
Current assignee: 1ST GREEN DEAL Ltd
Priority date: 2014-11-05
Filing date: 2015-03-17
Publication date: 2016-05-11
Anticipated expiration: 2035-03-17
Also published as: GB201504501D0; GB2532095B

Abstract

A safety valve 2 for insertion into a gas flue test point (100, Fig. 9) having an inlet (102, Fig. 9) comprises an elongate body 4 having a first end 6 dimensioned to engage with the inlet, and a second end 8 dimensioned to engage with a gas analysis probe adaptor 20. The body 4 comprises a sleeve 10 within which is located a sliding spool 12, the spool having a fluid aperture 36 therethrough. The spool 12 is moveable between a first closed state where the fluid aperture 36 is sealed relative to the inlet and a second open state where the fluid aperture 36 is in fluid communication with the inlet. A gas flue safety valve testing system and a method of testing gas emissions at a gas flue test point inlet are also provided.

Description

GAS FLUE SAFETY VALVE

The present invention relates to a gas flue safety valve.

it is important to regularly monitor the combustion exhaust gasses from a gas water heater or central heating boiler and to maintain the system to ensure that no combustion exhaust gasses are released into the living environment or other enclosed space used by people. The exhaust gas sampling point commonly, but not exclusively, takes the form of a threaded inlet with a screw-on cap which, when in place, seals the system and prevents gasses escaping into the immediate environment. On removal of the cap, the system can be tested by attaching (sometimes via an adaptor) a gas analysis probe. The probe is in fluid communication with the gasses in the system and a sample of the exhaust gases can be tested, before removal of the probe and replacement of the cap. Failure to replace the cap, or correctly screw the cap back in place can result in a leaky system where gasses can escape into the immediate vicinity. This can have serious and sometimes fatal consequences for people living and working in the immediate vicinity as the exhaust gasses contain carbon monoxide (CO) which is potentially lethal to humans when ingested in sufficient quantities. Normally, Co is carried vented to the atmosphere via a sealed flue. However, where the flue is not sealed i.e. where the cap is incorrectly replaced or absent altogether, CO vents to the immediate environment where it is injurious to humans in concentrations as low as 35 ppm.

Carbon monoxide (CO) is a colourless, odourless, tasteless, poisonous gas produced by incomplete burning of carbon-based fuels, including gas, oil, wood and coal. When CO enters the body, it acts quickly to prevent the blood from efficiently transporting oxygen to cells, tissues and organs.

Further, even if the levels of CO in the immediate environment are not sufficient to kill, these lower levels can still cause serious harm to health if breathed in over a long period of time. In extreme cases, paralysis and brain damage can be caused as a result of prolonged exposure to 30 CO.

Therefore, it is extremely important to minimise exposure to CO, particularly in domestic settings, but also in work environments and other public areas. In order to improve public safety, there is a need to overcome the issue of CO leaking from systems as a result of the omission or incorrect replacement of screw-caps at exhaust gas sampling points. The valve can also be used for any carbon based fuel that is used in boilers and central heating systems.

The present invention seeks to address the problems of the prior art.

Accordingly, a first aspect of the present invention provides a safety valve for insertion into a gas flue test point, the gas flue test point comprising an inlet in fluid communication with an interior of a pipe, the safety valve comprising an elongate body having a first end dimensioned to engage with such an inlet, and a second end located distal to the first end and dimensioned to engage with a gas analysis probe adaptor, the body comprising a sleeve within which is located a sliding spool, the spool having a fluid aperture therethrough, the spool being moveable between a first closed configuration wherein the fluid aperture is sealed relative to the interior of the pipe and a second open configuration wherein the fluid aperture is in fluid communication with the interior of the pipe.

This allows exhaust gasses to be selectively leaked from the pipe at the flue test point on demand i.e. when the spool is in the first closed configuration, no exhaust gasses (and therefore no CO) is released from the pipe at the flue test point. When the exhaust gasses are to be sampled, the spool is moved from the first closed configuration to a second open configuration where the exhaust gasses are released from the pipe via the flue test point inlet.

In one embodiment, the sleeve has a first cross-sectional dimension corresponding to an external dimension of the spool and a second cross-sectional dimension greater than the external dimension of the spool, such that movement of the spool from the first closed configuration to the second open configuration results in movement of the fluid aperture from a sealed to an open configuration relative to the pipe interior.

Thus, when the spool is in the second open configuration, there is fluid communication from the pipe interior via the space between the spool and the portion of the sleeve having the second cross-sectional dimension and through the fluid aperture and out of the valve via the interior of the sleeve.

Preferably, the spool further comprises a resilient biasing means, the resiliently biasing means biasing the spool in the first closed configuration. The resiliently biasing means preferably comprises a coiled spring. However, it is to be appreciated that the resilient biasing means may comprise any other suitable alternative known to the skilled person and capable of functioning to achieve a similar outcome.

In a further embodiment, compression of the resiliently biasing means slidably moves the spool within the sleeve from the first closed configuration to a second open configuration.

In one embodiment, movement of the spool into the second open configuration opens up fluid communication between the interior of the pipe and the second end of the elongate body.

For example, where the resilient biasing means is located between the spool and the flue test point, application of force to the spool will cause the spool to slide within the elongate body in a direction towards the flue test point, thereby compressing the resilient biasing means and moving the spool into the second open configuration and bringing the fluid aperture into fluid communication with the pipe.

Preferably, engagement with the gas analysis probe adaptor results in the application of force by the gas analysis probe adaptor on the resiliently biasing means, compressing the resiliently biasing means and moving the spool from the first closed configuration to the second open configuration. Where the spool is located between the gas analysis probe adaptor and the resilient biasing means, application of force by the gas analysis probe adaptor on the spool would cause the spool to apply force to the biasing means, compressing the resilient biasing means and moving the fluid aperture into fluid communication with the pipe.

Preferably, the second end 8 of the elongate body is provided with screw thread engagement means to engage with complementary screw thread engagement means provided at the inlet.

Most flue test points are provided with a thread for complementary inter-engagement with a screw cap. The safety valve of the present invention can be retro-fitted to such arrangement by providing screw head engagement means at the second end 8 of the elongate body to allow attachment of the valve to the flue test point. On attachment of the valve at the flue test point, the exhaust gasses can be tested by attaching a conventional gas analysis probe adaptor (and gas analyser) to the second end of the elongate body to compress the resilient means and open the pipe to fluid communication with the adaptor (and attached gas analyser). Removal of the gas analysis probe adaptor will result in the biasing means returning the spool from a second open configuration back to a first closed configuration where the pipe is sealed with respect to the external environment. There is therefore no need to replace a screw-cap, or plug on the flue test point as is the conventional arrangement in the prior art. This overcomes the danger posed by failure to replace the screw-cap or failure to correctly replace the screw-cap.

Preferably, the valve is installed using a tamper-proof nut such that once it is installed in place, the valve is not removable except by destroying the tamper-proof nut, or by use of a special tool which engages the nut in such a way as to lock the two nut components together thus enabling the nut to be removed. This has the advantage that the valve cannot be accidentally removed. Purposeful force would be required to destroy the tamper-proof nut. In addition, it would be obvious during an authorised inspection of the test point if the valve has been subjected to any unauthorised tampering as there would be damage to the tamper-proof nut.

More preferably, the valve is removably engaged with the inlet. This allows retro-fitting of the valve to existing flue pipe systems. Alternatively, it will be appreciated that the valve may be provided as an integral fitting to the flue test point on the pipe on installation of the pipe system.

In one embodiment, the gas analysis probe adaptor engages with the elongate body by bayonet fitting. However, it is to be appreciated that any other suitable engagement arrangement may be used including, but not limited to male-female complementary inter-engagement means, threaded fit, frictional fit and twist fit. The fitting of the gas analysis probe adaptor to the gas flue safety valve in this way allows the gas analysis probe (and gas analyser) to be held in fluid engagement with one another in a hands-free manner. In addition, there is no fluid communication between the gas test point and the immediate environment. Therefore there is no emission of exhaust gases into the immediate environment during the gas sampling and analysis process, which is safer for the operator. This is a significant advantage over conventional prior art arrangements. Furthermore, there is no possibility of contamination of the gas sample being analysed as there is no ingress of gasses from the immediate environment into the sample being analysed by the gas analyser.

A valve as claimed in any preceding claim, further comprising a dust cap for sealable engagement with the second end. Although a screw-cap is not required to seal the exhaust gasses within the pipework relative to the immediate environment, a dust cap may be applied, particularly, but not exclusively in locations where dust may be a problem and cause blockage of the passages within the valve.

A second aspect of the present invention provides a gas flue safety valve testing system comprising a safety valve according to a first aspect of the present invention and a gas analysis probe adaptor, the gas analysis probe adaptor having a first end adapted for engagement with the second end of the elongate body and a second end adapted for engagement with a gas analyser.

A third aspect of the present invention provides a method of testing gas emissions at a gas flue test point inlet, the method comprising the steps of: a. Providing a safety valve according to a first aspect of the present invention; b. Engaging the first end of the safety valve with the gas flue test point inlet; c. Engaging a gas analysis probe adaptor with the second end of the safety valve so as to move the spool from the first closed configuration to a second open configuration so as to bring the gas analysis probe adaptor into fluid communication with the gas flue test point inlet.

It will be appreciated that the present invention allows hands-free fully sealed sampling of exhaust gases from a test point. Traditional gas sampling methods involve the removal of a cap from an exhaust test point and manual attachment of the gas analyser to the gas test point. At all times during removal of the cap from the gas test point, exhaust gas is free to flow through the gas test point from the interior of the system being tested to the immediate external environment.

In the present invention, the gas flue safety valve is engaged with the gas test point and prevents emission of exhaust gasses into the immediate environment until the valve is operated by means of attaching the gas analysis probe adaptor to the valve. Where the gas analysis probe adaptor is connected to the gas analyser prior to engaging with the gas safety valve, opening of the valve by attachment of the gas analyser probe adaptor allows exhaust gases to flow from the gas test point through the gas analysis probe adaptor and into the gas analyser, without any flow of exhaust gases into the immediate environment. Thus, unlike conventional gas exhaust analysis systems, fully sealed gas sampling is possible with the present invention.

Fully sealed gas sampling is very important and failure to sample flue gasses without contamination of the sample from the immediate environment can result in sampled gasses that are not truly representative of the actual flue gas concentration. As a consequence of the incorrect analysis results, the combustion setting of the boiler/heater in the system may be re-set to give an incorrect burn of the carbon-based fuel used in the boiler/heater. In turn, an incorrect set burn of the boiler/heater combustion settings could lead to increased levels of carbon dioxide being produced by the system and released into the atmosphere. This has undesirable consequences with respect to global warming.

Another consequence of incorrect combustion settings of the boiler/heater in the system is potentially reduced efficiency of the boiler/heater and therefore increased costs of operating the system. There is also no certainty that the boiler/heater is working within the manufacturer's combustion setting parameters.

However, fully sealed gas sampling is not always easy to achieve as there are many different sizes and styles of gas flue sample test points configurations, including some with and some without threads. This is due at least in part to the large number of manufacturers, each with their own boil en/heaters and flue designs. It is therefore very difficult if not impossible for an operator working alone to adequately achieve a gas tight seal when taking flue gas samples. The gas flue safety valve and gas analysis probe adaptor combination of the present invention serve to provide a new, standard geometry at the test point for attachment of a gas analyser. This allows a hands-free, guaranteed sealed sampling procedure.

Those components exposed to the exhaust gases need to be composed of materials that are suitably durable in such environments. The material for other components may require careful selection to ensure reliability over time with respect to durability and function. For example, a suitable material for the spring may be 316 stainless steel; the remaining valve components may comprise polypropylene (PP) which is suitable for resisting degradation by flue gasses over time; the gas analysis probe adaptor may comprise any suitable material selected from a diverse selection extending from acetyl polymer to 303 free cutting stainless steel. However, it is to be appreciated that the materials mentioned above are provided as non-limiting examples only and any suitable materials may be used that are appropriate to achieve the desired function over time without compromise. Suitable selection is important to avoid premature failure of the valve arrangement and subsequent endangerment of the lives of people within the immediate vicinity.

An embodiment of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 illustrates a gas flue safety valve in accordance with an embodiment of the present invention in the closed position, thus preventing flue gasses escaping to the environment; Figure 2 illustrates the gas flue safety valve of figure 1 engaged with a gas analyser probe adaptor such the valve is in the open position (the dust cap has been omitted for the purposes of illustrative clarity only); Figure 3 is a cross-sectional view of a further gas flue safety valve engaged with a gas analyser probe adaptor in accordance with a further embodiment of the present invention, with the value in the open position; Figure 4 is a cross sectional view of the gas analyser probe adaptor of figures 2 and 3; Figure 5 is a cross-sectional view of the gas flue safety valve and gas analyser probe adaptor of figure 3 with the valve in the closed position; Figure 6 is a perspective cut away view of the gas flue safety valve of figure 3 with the valve in the closed position; Figure 7 is a perspective cut away view of the gas flue safety valve of figure 6 with the valve in the open position; Figure 8 is a perspective view from the side of the embodiment of figure 6; and Figure 9 is a cross-sectional view of a gas flue safety valve engaged at a gas flue test point.

The present invention will now be described with reference to figures 1 to 9 in which the same reference numerals have been used to designate the various features of the invention.

Figure 1 shows an embodiment of a gas flue safety valve 2 in accordance with a first aspect of the present invention. Body 4 has a first end 6 dimensioned for engagement with a gas flue test point 100 and a second end 8 dimensioned for engagement with a gas analyser probe adaptor (shown in figure 2).

Gas flue test point 100 comprises an aperture 102 in gas pipe 104 to which first end 6 of body 4 of gas flue safety valve 2 is engaged, in use (see figure 9). Once engaged with the gas flue test point, seal 106 seals the gas flue safety valve 2 to the gas pipe 104.

Figures 5 to 8 show a further embodiment of the present invention where the end cap and sleeve 25 components are threaded.

Body 4 comprises a sleeve 10 within which is located a spool 12, spool 12 being slidable within sleeve 10. Spool 12 is retained in a first closed position (as shown in figure 1) within sleeve 10 by means of a resilient biasing means in the form of a spring 14 located at the first end 6 of sleeve 10, and is sealed relative to sleeve 10 by virtue of flue seal Z which takes the form of an 0-ring. Spring 14 biases the spool 12 towards the second end 8 of body 4, the extension of spring 14, and therefore the travel of spool 12 in this direction being limited by a shoulder stop. The internal dimension of sleeve 10a is dimensioned to correspond to the external dimension of spool 12 such that spool 12 is held is close fit with sleeve 10 when spool 12 is in a first closed configuration, as shown in figure 1. Sleeve 10 is also provided with an internal dimension lob which is larger than that of internal dimension 10a such that movement of spool 12 within sleeve results in a fluid gap 18 between sleeve 10 and spool 12, as shown in figure 2. Spool 12 is provided with a spool guide XX (see figures 5, 6 and 7, which slides in end cap YY. The cross section of spool guide XX is such that it allows flue gas to communicate with spool 12. The cross section feature of spool guide which allows the flue gasses from end 6 to communicate with the spool 12 is the same or similar to the cross sectional area of the bore in spool 12, which in turn is the same or similar to the cross sectional area of some gas analyser instrument sample intakes. Thus the flow of flue gasses to the gas analyser is not impeded. The spool guide also stabilises the spool 12 under the influence of the spring 14 such that the spool 12 is not misaligned at any stage.

Figure 4 shows a gas analysis probe adaptor 20 and figure 2 shows the gas analysis probe adaptor 20 engaged with the gas flue safety valve 2 of figure 1. Gas analysis probe adaptor 20 has a first end 22 frictionally engagable with the second end 8 of body 4 of the gas flue safety valve and is retained in engagement with body 4 by means of bayonet fitting 25. Bayonet fitting 25 can be seen more clearly in the embodiment shown in figure 8. This frictional engagement is via two 0 ring seals 23, 25, which also act to prevent contamination by environmental gasses of the flue gasses being sampled. Seals 23, 25 are separated by spacer 27. Gas analysis probe adaptor 20 has a second end 24 which is dimensioned for engagement with a gas analyser (not shown) for analysis of exhaust gases from the flue (not shown).

It is to be appreciated that rotation of the bayonet fitting 25 of the gas analysis probe adaptor 20 holds the gas analysis probe adaptor in sealed engagement with gas flue safety valve 2. When a gas analyser is connected to end 24 of the gas analysis probe adaptor 20, the sampling operation can then be carried out in a hands-free manner without risk of release of flue gasses into the immediate environment or risk of influx of environmental gasses into the flue gas sample being analysed.

The external dimensions of first end 22 of gas analyser probe adaptor 20 correspond to the internal dimensions of the second end 8 of body 4 such that the first end 22 of gas analyser probe adaptor 20 can be slidably received within body 4 of the gas flue safety valve 2 (see figure 2).

Body 4 is provide with abutments 26 which butt against corresponding abutments 28 on gas analyser probe adaptor 20, when gas analyser probe adaptor 20 is inserted into body 4 of the gas flue safety valve 2 to limit the degree of insertion that can occur. (The gas analyser probe adaptor 20 is attached to the gas analyser either directly by sliding the gas analyser sampling hollow tube into the gas analyser probe adaptor 20 and rotating the screw 50 thus causing the 0-rings, or other compressible components 52, 52', separated by a spacer 53 (see figure 2) to form a seal with the hollow tube, thereby securing the hollow tube to the gas analyser probe adaptor 20, or by means of a flexible tube from the gas analyser attached around the exterior of ferrule 25 (serated by a spacerat second end 24 of gas analysis probe adaptor 20 (see figure 2).

Gas analyser probe adaptor 20 is provided with further abutments 30 which, when the gas analyser probe adaptor 20 is partially inserted into body 4 of the gas flue safety valve 2, abut with corresponding abutments 32 of spool 12. Application of further force to the second end 8 by the gas analyser probe adaptor 20 pushes gas analyser probe adaptor 20 further into body 4 of the gas flue safety valve 2, thereby sliding spool 12 in a direction towards the first end 6 of body 4. This force applied to spool 12 via gas analysis probe adaptor 20 results in spool 12 compressing spring 14 (as shown in figure 2), thereby allowing spool 12 to further slide within body 4 towards the first end 6 of body 4. Travel of spool 12 in this direction brings fluid apertures 36 of spool 12 into contact with fluid gap 18. The spool 12 is now in the open configuration (as shown in figure 2). This allows exhaust gasses from the gas flue test point (not shown) at the first end 6 of gas flue safety valve 2 to flow through the gas flue safety valve 2 and into the gas analysis probe adaptor 20, and subsequently into a gas analyser (not shown) attached to the second end 24 of gas analysis probe adaptor 20. Travel of spool 12 within body 4 ceases when abutments 28 of the gas analyser probe adaptor 20 abut against corresponding abutments 26 of the gas flue safety valve 2.

Removal of the gas analysis probe adaptor 20 from the gas flue safety valve 2, results in slidable movement of spool 12 within the body 4 towards second end 8 under bias from spring 14. The return of the spool 12 to a closed configuration (as shown in figure 1) where there is no fluid communication between the gas flue test point and second end of body 4 means that the valve provides an effective and safe seal, preventing exhaust gasses being released into the immediate environment, without the requirement for an operator to remember to apply a sealing cap at second end 8 of gas flue safety valve 2 after completion of the exhaust gas collection and analysis.

In the embodiment shown in figure 1, second end 8 of gas flue safety valve 2 is provided with a dust cap arrangement 38 comprising an engagement ring 40 attached to an end cap 42 via a retention strap 44. Engagement ring 40 fits around body 4 and is retained in place between the gas flue test point and portion 4' of body 4. End cap 42 press fits over second end 8 of body 4 and is held in place via frictional engagement, thereby providing an effective seal to prevent ingress of dust into body 4. The frictional engagement between cap 42 and body 4 is facilitated by the presence of 0-rings 45, 46 located therebetween, 0-rings 45 and 46 being separated by spacer 47. However, it will be appreciated that other engagement means may be employed, including threaded engagement. Finally, retention strap 44 is provided to anchor end cap 42 to the engagement ring 40 such that the end cap cannot be lost when removed from second end 8 of body 4, in use. Further, an operator does not have to either hold the end cap or keep it somewhere safe to hand and remember to replace it at the end of the gas analysis operation. Instead, the end cap 42 will be readily visible as it will be hanging from the gas flue safety valve 2 by retention strap 44. It is a simple operation for a user to then simply replace the end cap over second end 8 of body 4.

As shown in figure 2 spool 12 is provided with seal supports 11, 11' with a seal 16 located therebetween. When spool 12 moves within sleeve 10 between a first closed configuration to a second open configuration, seal 16 moves with spool 12 and exerts a wiping action on the interior walls of sleeve 10. This facilitates the prevention of dust reaching seal Z provided between seal supports 17, 17' when end cap 42 is removed from second end 8 of body 4 to allow attachment of gas analyser probe adaptor 20. Although it would be anticipated that end cap 42 would be replaced after each gas sampling event, should the operator fail to replace the end cap 42, no exhaust gasses would be emitted into the immediate environment as the valve would be closed on removal of the gas analysis probe adaptor 20. Further, even if the immediate environment were dusty, no dust would be able to access the valve and affect the operation of the gas flue safety valve due to the presence of seal 16 preventing any dust present from travelling beyond seal 16 and into spool 12. A Filter in the bore of spool is also required (not shown), to prevent ingress of dust into the spool. Any dust accumulation between sampling of flue gasses would be sucked away by the vacuum pump of the gas analyser during the normal flue sampling procedure.

Seal Z is an 0 ring located between seal supports 17, 17' and provides a fluid seal between the inner wall of sleeve 10 and the outer wall of spool 12 when gas flue safety valve 2 is in the closed position. Seal support 17 floats (0.5mm when the Spool Guide XX attached to Spool 12 is moved in the direction of end 6, compressing Springl4) and acts to constrain the movement of seal Z towards first end 6 of body 4, while seal support 17' acts to constrain the movement of seal Z towards second end 8 of body 4. In the closed position, seal Z is slightly squeezed between support 17 and support 17', thereby causing seal Z to engage the spool 12 and sleeve 10 firmly, forming a gas seal. In addition, seal supports 17, 17' also act as spacers between the inner wall of sleeve 10 and the outer wall of spool 12 to prevent over-compression of seal Z. Prevention of over-compression is important as repeated over-compression could result in gradual loss of original shape of the seal, which may compromise it's function and, over time, allow fluid leakage from the gas test point though the valve. This is in contrast to traditional spool valves, such as those used in tyres and the like, where over-compression of the seals is not considered to be a problem. In the case of the present invention, distortion of the seal due to over-compression could have fatal consequences to anyone in the immediate vicinity if exhaust gasses are emitted into the environment.

Thus, it can be appreciated that gas sampling and analysis can take place without either contamination of the gas sample being analysed or emission of exhaust gasses into the immediate external environment.

Valve 2 is preferably attached to the gas test point by means of a one way ratchet (not shown). In other words, the one way ratchet can be tightened, but it cannot be loosened. This ensures that valve 2 is retained in place at the gas test point so that no exhaust gases can be emitted from the gas test point after a gas sampling and analysis event has taken place. However, it is to be appreciated that alternative arrangement may be employed, such as but not limited to a one-way screw thread arrangement i.e. valve 2 is engaged with the gas test point and secured in position using a screw thread arrangement by screwing in one direction. However, once secured in place, valve 2 cannot be released from the gas test point by screwing in the opposite direction.

Although aspects of the invention have been described with reference to the embodiment shown in the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment shown and that various changes and modifications may be effected without further inventive skill and effort, for example, the gas safety flue valve of the present invention is not limited for use in gas powered boilers but may be applied with respect to all types of boilers powered by carbon based fuels where the flue gases need to be sampled. Further, adaptors may be provided to fit between the gas test point and the valve so that different designs and dimensions of gas test points of different makes of boilers etc can be accommodated by the same valve design and dimensions.

Claims

CLAIMS1. A safety valve for insertion into a gas flue test point, the gas flue test point comprising an inlet in fluid communication with an interior of a pipe, the safety valve comprising an elongate body having a first end dimensioned to engage with such an inlet, and a second end located distal to the first end and dimensioned to engage with a gas analysis probe adaptor, the body comprising a sleeve within which is located a sliding spool, the spool having a fluid aperture therethrough, the spool being moveable between a first closed configuration wherein the fluid aperture is sealed relative to the interior of the pipe and a second open configuration wherein the fluid aperture is in fluid communication with the interior of the pipe.
2. A valve as claimed in claim 1, wherein the sleeve has a first cross-sectional dimension corresponding to an external dimension of the spool and a second cross-sectional dimension greater than the external dimension of the spool, such that movement of the spool from the first closed configuration to the second open configuration results in movement of the fluid aperture from a sealed to an open configuration relative to the pipe interior.
3. A valve as claimed in claim 1 or claim 2, wherein the spool further comprises a resilient biasing means, the resiliently biasing means biasing the spool in the first closed configuration.
4. A valve as claimed in any preceding claim, wherein compression of the resiliently biasing means slidably moves the spool within the sleeve from the first closed configuration to a second open configuration.
5. A valve as claimed in any preceding claim, wherein engagement with the gas analysis probe adaptor results in the application of force by the gas analysis probe adaptor on the resiliently biasing means, compressing the resiliently biasing means and moving the spool from the first closed configuration to the second open configuration.
6. A valve as claimed in any preceding claim, wherein movement of the spool into the second open configuration opens up fluid communication between the interior of the pipe and the second end of the elongate body.
7. A valve as claimed in any preceding claim, wherein the first end of the elongate bod), is provided with screw thread engagement means to engage with complementary screw thread engagement means provided at the inlet.
8. A valve as claimed in any preceding claim, wherein the valve is removably engaged with the inlet.
9. A valve as claimed in one of claims 1 to 6 wherein the valve is integral with the gas flue test point.
10. A valve as claimed in any preceding claim, wherein the gas analysis probe adaptor engages with the elongate body by frictional engagement.
I I. A valve as claimed in any preceding claim, further comprising a dust cap for sealable engagement with the second end.
12. A gas flue safety valve testing system comprising a safety valve as chimed in any one of claims 1 to 8 and a gas analysis probe adaptor, the gas analysis probe adaptor having a first end adapted for engagement with the second end of the elongate body and a second end adapted for engagement with gas analysis apparatus.

13 A method of testing gas emissions at a gas flue test point inlet, the method comprising the steps of: a. Providing a safety valve as claimed in any one of claims 1 to I I; b. Engaging the first end of the safety valve with the gas flue test point inlet; c. Engaging a gas analysis probe adaptor with the second end of the safety valve so as to move the spool from the first closed configuration to a second open configuration so as to bring the gas analysis probe adaptor into fluid communication with the gas flue test point inlet.