FIELD OF INVENTION

This invention relates to an air release valve installation for a liquid pipeline.

BACKGROUND TO INVENTION

Air release valves for liquid pipelines such as water supply pipelines, are known. Air release valves are an essential requirement for any liquid pipeline along which a liquid is to be conveyed over relatively large distances and have three basic functions, namely: 1 ) to release large quantities of air during filling of the pipeline, 2) to release any air which collects at high points of the pipeline when the pipeline is under pressure, and 3) to admit large quantities of air during draining or scouring of the pipeline to prevent the pipe from collapsing due to vacuum conditions being established within the pipeline.

In a typical air release valve installation, an isolating valve and an air release valve are mounted on a vertical stand pipe mounted to a T-Section of a water supply pipeline. The isolating valve is mounted to an upper end of the stand pipe and the air release valve is in turn mounted to an upper end of the isolating valve. The sole purpose of the isolating valve is to isolate the air release valve from the pipeline in order to carry out maintenance work on the air release valve. Known air release valves typically have a number of metal components, particularly the valve housing, as these components have to withstand relatively high pressures during operation.

The Applicant has identified a problem with installations of the type described above, in that the air release valves of such installations are increasingly being targeted by thieves for their metal content. In order to remove an air release valve, the isolating valve is closed, thereby isolating the air release valve from the pipeline and permitting removal of the air release valve. Once removed, it will be appreciated that the pipeline system will be at risk of catastrophic damage until the air release valve is replaced.

It is an object of the present invention to ameliorate the abovementioned problems associated with existing air release valve installations.

SUMMARY OF INVENTION

According to the invention that is provided an air release valve installation for a liquid pipeline, the air release valve installation including: an air release valve including: a) an air valve body defining an air valve chamber, the air valve body including an upper air valve end plate defining an air outlet, a lower air valve end plate defining an inlet and a cylindrical side wall extending between the upper and lower air valve end plates; b) a control float movably located within the air valve chamber, the control float being movable in response to changes in liquid level within the air valve chamber; c) at least one valve member movably located within the air valve chamber above the control float, the valve member having an air vent passage extending between upper and lower ends of the valve member which is in register with the air outlet and which is smaller in size than the size of the air outlet so as to restrict the volume of air which can be vented through the air outlet; and an isolating valve which is mounted to the lower end plate of the air valve body, the air release valve installation being characterised in that: the side wall, the upper air valve end plate and the lower air valve end plate of the air release valve are of non-valuable, non-metallic materials; and the isolating valve includes: a) a metal isolating valve body defining an isolating valve chamber, the isolating valve body including an upper isolating valve end plate operatively mounted to the lower air valve end plate of the air valve body in an arrangement wherein the inlet of the lower air valve end plate is in flow communication with the isolating valve chamber; and a lower isolating valve end plate operatively mounted on upper end of a stand pipe of the liquid pipeline; b) a valve member movably mounted within the isolating valve chamber; and c) an actuator for operatively displacing the valve member between open and closed positions; and the air release valve is mounted to the isolating valve by means of a number of metal, tie rods which extend through apertures defined therefor in the lower air valve end plate and which are secured near opposite ends thereof to the upper air valve end plate and the upper isolating valve end plate.

The upper and lower air valve end plates and the side wall of the air release valve may be of a polymeric material, more specifically, of a synthetic polymer such as nylon. The tie-rods may have screw-threaded end regions, permitting the upper air valve end plate and the upper isolating valve end plate, to be secured to one another by means of nuts screwed onto the end regions of the tie rods.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention are described hereinafter by way of a non-limiting example of the invention, with reference to and as illustrated in the accompanying diagrammatic drawings. In the drawings:

Figure 1 shows a side view of a prior art air release valve installation;

Figure 2 shows a side view of an air release valve installation in accordance with the invention;

Figure 3 shows a plan view of the air release valve installation of Figure 2;

Figure 4 shows a sectional side view of the air release valve installation of Figure 2, sectioned along section line IV-IV of Figure 3, illustrating the air release valve installation in a mode of operation wherein the isolating valve is in a closed position; and

Figure 5 shows a sectional plan view of the air release valve installation of Figure 2, sectioned along section line V-V of Figure 4. DETAILED DESCRIPTION OF THE INVENTION

With reference to Figure 1 of the drawings, a typical prior art air release valve installation for a water supply pipeline, is shown wherein a prior art air release valve 1 and an isolating valve 2 are mounted to a T-Section 3 of a water supply pipeline 4. The air release valve and the isolating valve are mounted within a chamber 5 having a manhole opening 6 which is closable by means of a manhole cover 7. The isolating valve is mounted to an upper end of a vertical stand pipe 8 which is mounted to the T- section 3 of the pipeline. The air release valve 1 is in turn mounted to an upper end of the isolating valve.

The sole purpose of the isolating valve is to isolate the air release valve 1 from the pipeline 4 in order to carry out maintenance work on the air release valve. Thus, during normal operation of the pipeline, the isolating valve remains in an open condition to allow the air release valve to fulfil its essential functions of admitting and/or releasing quantities of air into and from the pipeline. When it is required to perform repair work on the air release valve, the isolating valve 2 is closed thereby isolating the air release valve from the pipeline and permitting the removal of the air release valve for maintenance work to be carried out on the air release valve, which typically includes replacement or repair of seals. It will be appreciated that it is important that the isolating valve 2 remains closed only for so long as is required for the maintenance work to be carried out on the air release valve so as to minimize the risk of damage to the pipeline.

With reference to Figures 2 to 4 of the drawings, an air release valve installation in accordance with the invention, is designated generally by the reference numeral 10. The air release valve installation 10 is adapted for use with a water supply pipeline 4. A typical installation of the air release valve installation 10 is shown in Figure 2, wherein the air release valve installation 10 is mounted to a vertical stand pipe 8 which is mounted to a T-Section 3 of the pipeline 4. The air release valve installation is located within a chamber 5 having a manhole opening 6 closable by means of a manhole cover 7. The air release valve installation 10 comprises an air release valve 12 and an isolating valve 14. The isolating valve 14 is mounted to an upper end of the stand pipe 8 and the air release valve 12 is in turn mounted to an upper end of the isolating valve.

The operation of the air release valve 12 insofar as it is not pertinent to the novel and inventive concepts of the present invention, is not described in detail in this specification. The general operation of air release valve of this type is described in the Applicant’s South African Patent 2018/01741 .

The air release valve 12 comprises, broadly, an air valve body 13 which defines an air valve chamber 16, a control float 18 which is movably located in the air valve chamber, a lower valve member 20 and an upper valve member 22 which are movably located within the air valve chamber above the control float.

The air valve body 13 has an operative upper end and an operative lower end. More specifically, the air valve body includes an upper air valve end plate 24 which defines the upper end of the air valve chamber and a lower air valve end plate 26 which defines the lower end of the air valve chamber. The air valve body further includes a cylindrical wall 28 which extends between the upper and lower end plates. The upper air valve end plate 24 defines a central outlet opening 30 which is in communication with the atmosphere and through which air is admitted into the valve chamber or purged therefrom during particular modes of operation of the air relief valve. The lower air valve end plate 26 defines a central inlet opening 32 which is in flow communication with water flowing in the pipeline 4.

The control float 18 and the valve members 20, 22 are axially displaceable within the valve chamber 16. The valve members 20 and 22 define air vent passages 34 and 36, respectively, which are in register with the outlet 30 but which are smaller in size than the outlet thereby restricting the effective size of the outlet. The air vent passages extend between upper and lower ends of the valve members. The upper air valve end plate 24, the side wall 28 and the lower air valve end plate 26 are of a non-valuable, non-metallic material. More specifically, the end plate 24, the side wall 28 and the end plate 26 are of a nylon material.

The isolating valve 14 is in the form of a resilient seated gate valve comprising a metal isolating valve body 48 defining an isolating valve chamber 50, a bonnet 52 bolted onto the valve body, a yoke 54 integrally formed with bonnet, a valve stem 56, a rubber gate 58 connected to an end of the stem and a handwheel 60 for turning the stem relative to the yoke for displacing the gate between extended closed positions and retracted open positions, preventing and allowing the passage of water therethrough, respectively.

The isolating valve body 48 includes an upper isolating valve flanged end plate 62 and a lower isolating valve flanged end plate 64. The end plate 64 defines an inlet opening 66 which is in register with an opening at the upper end of the stand pipe, allowing for air/water flow into the isolating valve from the stand pipe.

The air release valve installation 10 includes four circumferentially-spaced stainless steel tie-rods 70 which extend through apertures defined therefor in the upper and lower air valve end plates and the upper isolating valve flanged end plate 62 and nuts 72 which are screwed onto screw-threaded end regions of the tie-rods 70. A single nut 72 is screwed onto a threaded upper end of each tie-rod at an upper side of the upper air valve end plate 24, while two nuts 72 are screwed onto each tie-rod at an inner side of the lower air valve end plate 26 and a lower side of the upper isolating valve end plate 62, respectively. The tie-rods secure the upper air valve end plate 24 and the upper isolating valve 62 to one another thereby securely mounting the air release valve 12 to the isolating valve 14. Forces acting on components of the air release valve 12 during operation thereof, are transferred to the metal isolation valve body 48 via the end plate 62. As the structural rigidity and strength provided by the metal isolating valve body is sufficient to accommodate forces acting on the air relief valve under operational conditions, the end plates 24 and 26 and the side wall 28 of the air release valve can be of a non-metallic material such as nylon which would otherwise not have adequate rigidity and strength to withstand forces acting on the air release valve under normal working conditions.

The side wall 28 of the air release valve is clamped between the upper and lower air valve end plates 24 and 26. O-ring seals 42 are located between the side wall and inner sides of the end plates providing fluid-tight seals between the side wall and the end plates. An O-ring seal 44 is seated around an unthreaded part of the upper end region of each tie rod 70 and a flat annular metal disc 46 is provided for compressing the O- ring seal 44 for forming a fluid-tight seal around the tie rods 70 when the nuts 72 are tightened. The metal disc 46 also spreads the force applied by the nuts upon tightening so as to prevent the upper air valve end plate 24 from deforming. An O-ring seal 44 is also seated around a threaded lower end of each tie rod 70 and a flat annular metal disc 46 is provided for compressing the O-ring seal 44 for forming a fluid-tight seal around the tie rods 70 when the nuts 72 are tightened. More specifically, as the tie-rods are threaded at lower end regions thereof and specifically, in the region of the O-ring seals 44, a sealing compound such as Loctite™ is applied between the metal discs 46 and the threaded tie-rods for forming a fluid-tight seal between the metal discs and the tierods. The O-ring seals 44 form fluid-tight seals between the lower air valve end plate 26 and the metal discs 46.

During operation of the air release valve 12, the gate 58 of the isolating valve 14 is in the open position allowing flow of air / water into the air relief valve, thereby permitting venting of air through the outlet 30 as may be required. Should it be necessary to perform maintenance on the air release valve, for example, to replace seals, the handwheel 60 is turned so as to displace the gate 58 into its closed position thereby isolating the air relief valve from water flowing in the water supply pipeline 4. The nuts 72 on the tie-rods 70 are then loosened and the upper air valve end plate 24 removed, providing access to the interior of the air valve body 13. As the upper and lower air valve end plates 24, 26 and the side wall 28 of the air release valve are of non-valuable nylon, there is no incentive for potential thieves to disassemble the air release valve installation in order to steal the end plates 24, 26 or the side wall 28 of the air release valve. The aforementioned components of the air release valve 12 are made of non- corrosive materials, which renders the components suitable for use in corrosive environments such as in de-salination systems for conveying water having a high saline content. For use in corrosive environments, the isolating valve body 48 may be of a stainless steel.