AU4379800A - Airlock relief means - Google Patents

Description

Alo

AUSTRALIA

Patents Act 1990 COMPLETE PATENT SPECIFICATION ME1W L

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WOODHOUSE, Brian "Montillo", Adaminaby, NSW, 2630 WOODHOUSE, Brian Paul A Grant and Associates PO Box 60, Fisher, ACT, 2611 INVENTION TITLE: AIRLOCK RELIEF MEANS ASSOCIATED PROVISIONAL APPLICATION: PQ1865 [28/799] The following statement is a full description of this invention, including the best method of performing it known to 2 TITLE: AIRLOCK RELIEF MEANS TECHNICAL FIELD This invention relates to airlock relief means for use with pipelines for conveying liquids over uneven paths, where the term 'air' is used generically to include any gas that may be present in a liquid pipeline.

The invention is particularly, though not exclusively, concerned with airlock relief valves and methods for use in water reticulation systems for farms in which water 1o is fed by gravity through pipes or hoses laid on undulating ground. In many such systems of interest, the outflow from the pipeline is regulated by the use of a ballcock or other device that effects water flow upon demand.

BACKGROUND TO THE INVENTION When water flows under gravity through an irrigation pipe over undulating ground, air tends to accumulate in the pipe at one or more of its intermediate highpoints. If the hydraulic gradient over the whole pipeline is low, such air pockets can stop the flow of water, whether the pipe is acting as a siphon or not. This is particularly so where (as is common) the pipeline is made of black plastic, is laid on the surface of the ground in full sunlight and feeds a ballcock regulator at the sink end. If the ballcock stops or severely restricts flow in the pipeline, the water held in the line will heat up, promoting the generation of pockets of water vapour that rise to the high points. Such airlocks can stop the flow of water through an undulating pipeline even when they occur at high points which are below the dynamic hydraulic gradient.

To re-instigate gravity flow through a non-siphoning undulating pipeline with an airlock at one or more of its high points, it is necessary to manually bleed the air from the pipe at each suspect high point and then reseal the pipe at that point.

This can be quite tricky and laborious. In a siphoning system with an airlock at a high point above the hydraulic gradient, it may be necessary to connect a pump at the supply end in an attempt to temporarily increase the hydraulic gradient and fill the pipeline with water. However, this requires the sink end to be unrestricted while the pump is operating, which requires simultaneous access to both ends of the pipeline. Either remedy is laborious and costly for a farmer, especially where airlocks in a pipeline tend to occur repeatedly because: o there are air-leaks in the portions of the pipeline that can lie above the hydraulic gradient, s 0 it is difficult to prevent some air and dissolved gases being entrained at the source, gas (normally C0 2 is generated by biota drawn into a pipeline in which water is flowing slowly or intermittently, and/or vapour is generated in a pipeline during periods of high solar heating and low water flow.

It is important to note that known so-called anti-siphoning valves are entirely unsuitable in addressing the problems outlined above. Anti-siphoning valves operate automatically to admit air into a pipeline, or otherwise automatically detect and shut off siphoning flow in a pipeline, so that a water tank or dam cannot be inadvertently drained after an irrigation pump has been turned off.

It is also important to note that known automatic air-discharge valves employed with closed liquid vessels such as mains-pressure hot water tanks are unsuited to the purposes of the present invention. These devices typically employ float valves that open air vents while the vessels are filling and close them once the vessels are full of water (or other liquid). Similar known float-operated valves are used to separate gases from liquids in the oil-drilling and exploration industry.

Such valves typically have floats that simply close venting ports once liquid in a pipeline or chamber reaches the level sufficient to raise the float. Like anti-siphon o valves, such gas/liquid separators admit air through the vents when the liquid levels in the chambers or pipelines drop. These known valves are, thus, quite unsuited to the application of the present invention. Examples of such known valves are provided in the following publications: UK patent 1,379,844 to Fujiwara, Soviet patent 966,393 to UKR Hydrotech Recla (Derwent abstract 83-745387/34) and Soviet patent 1550-261 to Zhilkkommuntekhnika (Derwent abstract 318925/42), US patent 4,640,304 to Baird, and various Japanese patents to Kubota Corpn. (viz: 08-338549, 5-10470 and 55-115671).

OBJECTIVE OF THE INVENTION It is an objective of the present invention to provide air-lock relief means suitable for use in liquid pipelines that are laid on undulating land, which depend at least in part upon gravity to effect liquid flow and/or which have restrictable outlets.

OUTLINE OF THE INVENTION From one aspect, the present invention comprises an air-lock relief valve suitable for connection at an intermediate high point in an undulating liquid pipeline which l0 depends at least in part upon gravity to effect liquid flow therethrough, the air-lock relief valve comprising a chamber having an inlet port, a vent port and floatoperated valve means therein, the valve means being operable to permit gas flow into the chamber via the inlet port and from the chamber via the vent port, (ii) permit liquid flow into the chamber via the inlet port while preventing liquid flow from the vent port and (iii) prevent gas flow from the chamber via the inlet port.

By permitting gas flow through the chamber from inlet to vent, air in the pipeline at the high point that would otherwise form an air lock is vented from the pipeline. By preventing liquid flowing from the vent, liquid is not lost from the pipeline at the highpoint as the line is filled. And, by preventing the re-introduction of air into the line via the inlet port after the line is filled, gravity-driven siphon flow is enabled.

Devices of this type are particularly well suited for use with siphoning pipelines in which the outlets can be restricted by taps, ballcocks or other means since, in such pipelines, a positive hydrostatic pressure will be applied to all siphoning high points above the dynamic hydraulic gradient (but below the level of the source) when the outlets are closed. During this period, therefore, the air pockets can be vented though the valves under virtually no-flow conditions. Where there is a high point above the water level of the source, pump-assisted flushing of airlocks can be effected, using the valve of this invention, without the need for access to the outlet end of the pipeline. Accordingly, from another aspect, this invention comprises either of the methods of removing an airlock from a pipeline just indicated.

From another aspect, the invention comprises an airlock relief valve of the above type in which the vent and inlet ports are opened and/or closed by valve elements operable by the float means.

In one such embodiment, the vent port is formed in the top of the chamber and the inlet port is formed in the bottom of the chamber so that the float means may move up and down therebetween. The float means may itself act to close the vent port when it rises as liquid enters the chamber and to close the inlet port when it falls as liquid flows from the chamber. Conveniently, the float may be a ball that acts as a ball valve for both the inlet and the vent ports. Alternatively, the float means may have a lower valve element adapted to engage with and close the inlet port, in the absence of liquid in the chamber, and an upper valve element adapted to engage with and close the vent port when the chamber is substantially full of liquid.

In an alternative embodiment, valve means may be associated with the vent port to effect its closure and opening, the valve means being operable by the float means to open the vent port when there is insufficient liquid in the chamber to :°:raise the float and to close the vent port when the chamber is substantially full of liquid. In such an arrangement, the inlet port may remain permanently open to the inflow of air and or liquid from the pipeline and it is preferably arranged below the level of the float.

In yet another alternative embodiment, valve means may be associated with the inlet port to effect its closure and opening, the valve means being operable by the float means to open the vent port when there is insufficient liquid in the chamber to raise the float and to close the inlet port when the chamber is substantially full of liquid. In such an arrangement, the vent port may remain permanently open is preferably arranged above the level of the float.

Because there may be a danger of the float means or valve elements being entrained in a rapid flow of air or liquid from the pipeline, fluid flow to or from the chamber can be restricted to ensure that entrainment does not occur. The danger of entrainment suggests that the use of valve means associated with the vent port will be preferable to valve means associated with the inlet port. The danger of entrainment can be further mitigated by ensuring adequate clearance around the float means within the chamber and/or by forming the float means with a fairly high relative density so that it will not be easily entrained in a jet of air.

The float means can be a closed hollow body, it can be a solid formed from a material that is less dense than the liquid in the pipeline, or it can be formed as a bell or inverted cup so that it will trap air as the level of liquid rises in the chamber.

The latter form of float has the advantage that it can be more readily designed to mitigate the danger of entrainment.

DESCRIPTION OF EXAMPLES Having portrayed the nature of the present invention, particular examples will now be described with reference to the accompanying drawings. However, those skilled in the art will appreciate that many variations and modifications can be -e*made to the examples without departing from the scope of the invention as outlined above. In the accompanying drawings: Figure 1 is a schematic drawing of an undulating irrigation pipeline to which 20 air-lock relief valves formed in accordance with this invention are applicable.

Figure 2 is a schematic cross-section of an air-lock relief valve comprising the first example of the invention.

Figure 3 is a schematic cross-section of an air-lock relief valve that forms the second example of the invention.

Figure 4 is a schematic cross-section of an air-lock relief valve that forms the third example of the invention.

The chosen examples or air-lock relief valves are applicable to irrigation systems of the general type represented in Figurel, in which water from a source such as a tank or dam 10 is fed under gravity to a lower use point- such as a stock water-trough 12 via a pipeline 14 laid over undulating ground. The flow of water into trough 12 is controlled by a ballcock valve 15 at the level indicated at 16, it being assumed that the outlet 18 of pipeline 14 is below the normal level 16 of the water in trough 12 and that the level 22 of the water in source tank 10 is constant.

Thus, the static head of water (ie, the pressure at outlet 18 when ballcock 15 is closed) is indicated at Hs while the dynamic hydraulic gradient when the ballcock is fully open, is indicated by the sloping line Hd running from the water surface 22 of tank 10 to the water surface 16 of trough 12. For simplicity, the pipeline system of Figure 1 is shown with only two high points, 24 and 26; point 24 being upstream 1o of point 26 but below gradient Hd, and point 26 being downstream of point 24 but above gradient Hd. Airlock relief valves 30a and 30b are connected to pipeline 14 by T-joints 31 located in the pipeline at points 24 and 26 (respectively) so that the valves stand upright therefrom.

It will be seen from Figure 1 that only high point 26 will act as a siphon because, when ballcock 15 is open and water flows in pipeline 14, the pressure in the line at this point will be below atmospheric. [Note that all points in the pipeline above the I dynamic gradient Hd will be at negative pressure while all points in the pipeline below gradient Hd will be at positive pressure (relative to atmosphere), provided ballcock 15 is open and water flows in an unrestricted manner in pipeline 14.].

When ballcock 15 is closed any air or vapour in pipeline 14 will rise and collect at the high points to form air pockets. Unless these pockets are very small, they will be sufficient to form airlocks that will stop the siphoning flow of water in the pipeline 14 when ballcock 15 is reopened. It might be noted that, during normal siphoning flow in pipeline 14, air will be sucked into any hole or leak in any part of the pipeline above Hd and that 'inhaled' air will rise and accumulate at high point 26 to eventually cause or contribute to an airlock.

Referring to Figure 2 which illustrates relief valve 30 in detail, it will be seen that the valve is hollow and generally cylindrical, being formed by screwing or gluing an upper inverted cup-like portion 32 at joint 33 to a lower cup-like portion 34 to form an enclosed chamber 35. Upper portion 32 has a central vent port 36 that leads to restricted vent passages 37 in an integral dome shaped cap 38, while lower portion 34 has a central inlet port 40 that opens into a threaded socket 42.

8 By the use of socket 42, valve 30 can screwed onto a threaded spigot on T-piece 31 in an airtight manner. In this example, the float means comprises a ball 44 enclosed in chamber 35. Ball 44 is preferably formed from a plastic material that is less dense than water and is resilient so that it will form an hermetic seal against s either vent port 36 or inlet port 40. If desired, ball 44 can be formed hollow and from hard material and O-ring seals (not shown) may be let into suitable grooves (not shown) formed around the inside openings of ports 36 and 40 to form seats for ball 44.

The valves 30a and 30b operate with the system of Figure 1 in the following manner. When the pipeline is first connected to tank 10 and trough 12, it can be assumed that the trough is empty and ballcock 15 is open. Water will commence to flow through the first pipeline section 14a under gravity to highpoint 24, possibly expelling some air from valve 30a by lifting ball 44 off inlet port 40, before flowing into the downward-sloping pipeline section 14b to fill it and the next rising section 14c until the level reaches valve 30b, again possibly expelling air from valve Sby raising its ball 44 off inlet port 40. At this point any air trapped at high point 24 will have been expelled and chamber 35 of valve 30a will be filled with water, causing ball to float and seal vent port 36. As the filling water flows into the final pipeline section 14d, it will commence to siphon and finally discharge into trough 12, which will commence to fill. At this point, the hydraulic gradient will be approximately as shown at Hd. Thus, there will be a positive pressure at valve so its chamber 35 will be full of water and ball 44 will float to close off vent 36 preventing the loss of water from valve 30a, and there will be a negative pressure at valve 30b so that its chamber will be empty and its ball 44 will be drawn onto inlet port 40 to prevent the inflow of air into pipeline 14 from valve When ballcock 15 closes, the entire pipeline will be subject to a positive static hydraulic head. This will not affect valve 30a, but it will cause water to flow into chamber 35 of valve 30b, raising its float 44 and, in the process, discharging any air that might have accumulated at high point 26. If the pipeline now sits for some time in the sun without flow, gas will accumulate in both highpoints 24 and 26.

When ballcock opens again, the water in pipeline section 14d will flow out causing a low pressure at point 26 thus releasing ball 44 from vent 36 and again closing 9 off inlet port 40. If there is an air pocket at high point 24, it will have risen to fill chamber 35 of valve 30a and, together with the reduction in pressure caused by downstream water flow, will cause ball 44 to drop from vent 36 allowing the accumulated air to be discharged until the chamber again fills with water and ball 44 floats to close off vent 36 again. In this way, air pockets accumulating at high points 24 and 26 are periodically and automatically vented by valves 30a and without affecting the flow of water through siphoning pipeline 14.

The second example of an airlock relief valve is valve 100 illustrated in Figure 3 0io and is of essentially the same design as that of Figure 2. It is formed from a tubular barrel 102 that is externally screw-threaded at each end to take correspondingly threaded top and bottom caps 104 and 106 that can be substantially identical, each cap having a central bore that forms a seat 108 and 110 respectively for the ball float 112. End caps 104 and 106 each has an internally threaded spigot or boss 114 and 116 adapted for connection to T-piece 31 (Figure Since valve 100 is entirely symmetrical, it can be mounted either way up. Assuming valve 100 is mounted so that end cap 104 is at the top, its seat 108 and spigot 114 will form the vent while seat 110 and spigot 116 of cap 106 will form the inlet. As depicted in Figure 2, valve barrel 102 can be assumed to be full of water so that ball 112 has floated upwards to engage seat 108 and close the outlet formed by the bore of spigot 114.

It is preferable according to this example to screw a plug 116 into spigot 108 (which serves as the vent) so as to both restrict the flow of air from the port and protect the port from the ingress of dirt. Plug 116 has a hollow cylindrical body 118 that is externally threaded to fit spigot 108, body 118 having axial vent-slots 120 formed therein and having a disc-like cap portion 122 that has a downwardly extending skirt 124. Skirt 124 is provided with inwardly extending flaps or ribs 126 that frictionally engage the exterior of spigot 108. Thus, by screwing plug 116 into spigot 108 by a greater or lesser amount, more or less of vent-slots 120 will be exposed so that the flow of air from valve 100 will be less or more restricted, respectively. Skirt 124 and flaps 126 serve to inhibit movement of plug 116 once the desired setting has been achieved.

The third and final example of an airlock relieve valve is shown in Figure 4. In this example, valve 200 has an open-topped cup-like body 202 with a tubular and internally threaded socket 204 in its base 206 to take the spigot of a T-piece 31 (Figure Body 202 is externally threaded at its top to take an internally threaded cap 208 that has a central bore 210 which forms the vent, the inlet in this case being formed by tubular socket 204. A float 212 in the form of a bell or inverted cup is located within the chamber 214 formed by body 202, float 212 being provided with a plurality of radially extending fins 216 to centre it in chamber 214 and guide it for vertical movement therein.

A central spindle 220 extends upwardly from the centre of float 212 and passes through vent 210, the top of float 212 being flat and being fitted with an 0-ring 224 that encircles spindle 220 and vent 210. A disc 226 is attached to the top of spindle 220 above cap 208 and the upper face of cap 208 is fitted with an O-ring 228 that also encircles spindle 220 and vent 210. Disc 226 is fixed to spindle 220 so that skirt 218 of float 212 is supported off base 206; that is, the weight of float 212 is normally supported by disc 226 resting on O-ring 228.

In operation, air entering chamber 214 under pressure through inlet 204 passes through vent 210 and lifts disc 226 to escape. The flow of air does not tend to entrain float 212 and drive its 0-ring 224 against the underside of cap 208 (thereby closing vent 210) because there is a low resistance path around float 212 between fins 216 and (ii) the flow out of vent 210 is restricted by disc 226 and the weight of the float. When water flows into chamber 214 via inlet 204, however, air is trapped in the bell like float 212 and causes it to rise, closing off vent 210 by bringing O-ring 224 into contact with the underside of cap 208. When water then flows out of the chamber 214 via inlet 204, the float will drop again bringing disc 226 onto 0-ring 228 and thereby preventing the in-flow of air into chamber 214 and the pipeline 14.

A feature of valve 200 is that disc 226 can be depressed manually to vent air and/or water from the chamber of the valve if desired to check on the condition at a high point in a line.

11 While three examples have been described, it will b appreciated that many variations to these examples can be made without departing from the scope of the present invention as outlined above. It will be appreciated, for example, that the valve of the third example (Figure 4) can be operated in similar manner when inverted, provided a closed hollow float is used or the bell-like float is also inverted within the chamber.

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