GB2186980A - Drip detection - Google Patents

Abstract

To ensure accurate counting of drips which may fall over a relatively wide area concentration means (8) are provided upstream of a detection zone (9) with associated drip detector means (11) (12). The means (8) comprise a funnel with a lower circular edge of smaller diameter than the tube (9) forming the detection zone. Thus drips forming on the edge do not touch the tube (9). The apparatus is used to detect leakage in a central heating system with a header tank (1) and a float valve (5). <IMAGE>

Description

SPECIFICATION Liquid flow detector The present invention relates to a liquid flow detector, and particularly to a liquid flow detector to detect malfunctions in central heating systems.

Central heating systems which utilise a boiler heat exchange liquid are usually provided with a header tank provided with a ball valve to allow replacement of central heating liquid to replace losses by evaporation etc. This header tank is usually positioned in a roof space where it is not generally accessible for regular checking. Accordingly malfunctions in the central heating system often go unnoticed for long periods, occasionally with unfortunate consequences.

Such malfunctions can be, for example, a small leak in the system which provides no visible signs. Such a leak can exist for years without being noticed, and while the system will generallyfunctionsat- isfactorily despite such a leak, the heat exchange liquid is then subject two constant oxidation and scale tends to form in the system. This situation is part icy marly difficult to diagnose because the leaks can be so smallthatno disturbanceofthe headertankis seen to take place from a casual inspection.

Further, with such miniscule leaks, and indeed for other reasons such as evaporation, the heat exchange liquid levels in the headertanktend to drop slowly but progressively over a period of months.

Normallythis drop will be compensated for bythe in-rush of new liquid mediated by the ball valve. Unfortunately the valve members of ball valves tend to jam, mainly because the movement of the ball on the water surface is so slow, and hence the headertank can dry out over a period of months without the problem being realised. The fall in water levels will, in some cases, merely cause portions of the central heating system to fail to heat up. At worst, however, the boiler will start to overheat, and if its automatic cut-out device were to fail the boiler could be seriously damaged. The reduction in heat exchange liquid beyond a desired level will result in vaporised liquid passing up the expansion pipe and 'blowing off' into the headertank.

The present invention seeks to provide a warning of such occurrences on an automatic basis. Accordingly, the present invention provides a liquid flow detector comprising concentration meansto con- centrate a discontinuous flow of liquid into a detection zone, and detector means associated with said zone to detectthe passage of said liquid.

The concentration means may be funnel formed having a frusto conical upper portion and a co-axial spout. The funnel portion may terminate towards its putative apex in a radiallyinwardlydirectedlipdirec- ted towards the apex of the frusto conical portion at its point of junction with the spout. It will be app reciatedthatdripsoriginating in a number of places can thereby be concentrated at the spout. Further, because the lip is positioned between the funnel and the spout small amounts of water which would otherwise flow in a continuous stream down the spoutareformed into drips which are held bysurface tension on the lip until they have reached a certain size.Because drips of only a certain size can fall down the axis of the spout without touching the sides, their presence can be readily detected by a suitable electronic means known per se. Because the drip sizes are known to within fairly precise limits the detector can detect not only the presence of a leak, but also its volume against a time base.

In a preferred form of the invention the frusto conical portion of the funnel at least is formed of a material having a high co-efficientofthermal conductivity. Accordingly, any significant amount of hot vapourwill tend to collect, at least in part, on the inside surface of the frusto conical portion of the concentration means. Thus, the presence of a hot heat exchangeliquidvapourwithinthetankcan bedetected by means of the concentration device.

In a preferred form of the invention the detector device is formed of an infra-red editor and receptor therefor, or an LED and receptive cell. The detector and the emitor are preferably positioned on opposite sides of the spout along a line perpendicularto the axis thereof.

In a preferred form ofthe invention there is provided a gantryforthe support ofthe liquid flow detector relative to the valve. The gantry will support not only the liquid flow detector but also, on a lowerextension thereto, a 'liquid present' sensor. This sensor is inactivated by the presence of water and hence if the liquid level in the header tan k is reduced beyond a certain predetermined level the alarm is activated.

The detector means is preferably connected by means of wiresfollowing the course ofthe expansion pipe to a position adjacentthe boiler. A trigger circuit is then provided to lock on as soon as a drip is detected, or to lock on as soon as a number of drips have been detected within a certain time period. Having locked on, an alarm (audial orvisual) can be activated. The alarm can only be switched off by means of a reset button.

The invention will now be described, byway of il- lustration only, with reference to the accompanying drawings wherein Figure 1 shows a device in accordance with the present invention applied to a header tank in a central heating system in partial crosssection, Figure2 shows an enlargement of a portion of Figure 1, and Figure3shows a diagrammatic representation of the mode of operation of the detector means.

With reference to Figure 1 a headertankshown generally at (1) is provided with a heat exchange liquid (2).The heat exchange liquid is mainlywater with minor amounts of additives therein. The header tank (1 ) is provided in accordance with standard practice with an over-flow (3) and a liquid inlet (6).

The liquid inlet (6) is operatively connected with a ball valve body (5) which is provided with a ball and arm arrangement (4)which controls the liquid supply to the tank in standard fashion. With refer ence particularly to Figure 2 the present invention consists, in this particular embodiment, of a gantry (13) which is formed of a flat plate of plastics material pierced towards its uppermost end in Figure 2 by an aperture of a size sufficient to accommodate the screw threaded stem of a ball valve body (5). This is effected byway of an elongate slot so that the gantry (13) can be affixed in a correct vertically spaced arrangement below the outlet of the valve body(5).

The gantry (13) is provided with a funnel support bracket (10) disposed in angled relation to the plane ofthe gantry (13). The angle selected is such that the bracket is downwardly directed relative to the horizontal so that any liquid forming thereon will tend to drip intothe liquid (2).Thefunnelsupportbracket (10) supports the funnel (7) formed of two distinct parts:-the upperfrusto conical portion (8) and, coaxially therewith and adjoined thereto, a spout (9). At the point atwhich the frusto conical portion (8) and the spout (9) are conjoined informed a lip (8a).Lip (8a) is of a generally annular configuration which on its uppersurface is contiguous with the surface of the frusto conical portion (8).The lower portion of the lip (8a) is provided, in section, with a re-entrant portion so asto provide a clear rim upon which drips may form.The annular aperture defined by the lip (8a)issubstantiallysmallerthantheannular aperture defined by the spout (9). Accordingly, drips forming on the lip (8a) will not come into contactwith the spout (9). The lip (8a) is machined such that drips of a predetermined size will form thereupon.Accord- tingly, liquid from a numberof positions adjacent the aperture of the ball valve body (9) can form together atthelip(8a) intoa pluralityofdripsofheatex- change liquid of a predetermined size. As these fall down the spout (9) when theirweight has exceeded the surface tension applied by the rim, they are counted buy a combination of an infra-red source (11) and a pulse detector (12).

In its simplestform the invention provides an infrared source (11) and a pulse detector (12) adapted to send a pulse of a predetermined value to a sensing means remote therefrom. The sensing means is part of a trigger circuit which triggers a relay to actuate an alarm system. In a preferred form ofthe invention the trigger circu it is also provided with a counting meansandaread-out. Sincethevolumeofeachdrip is constant, afactor can be supplied to the read-out device to convert the numberof pulses into a Figure indicative of the central heating liquid lost. The system is provided with a reset button to manually resetthe device when the leak has been cured.

The gantry (13) is also provided at a position below the intended upper level ofthe heat exchangefluid (2), with a 'liquid present'sensor(15).

In use gantry (13) is assembled with the header tank (1 ) when the valve body (5) is attached thereto.

Theflat plate gantry (13) lies along the innersurface of the header tank such that 'liquid present' sensor (15) is belowthe intended water line and the upper mouth ofthe funnel (7) is positioned below the outlet ofthe valve body (5). Because the gantry (13) is provided with an elongate slot the gantry may be positioned vertically atwill relative to the valve body (5).

The fixing nuts of the valve body (5) are then tight enedtosecurethevalve body (5) and the gantry(13) to the headertank. Thetank maythen befilledwith the heat exchange liquid in the ordinary way. Of course initially liquid will flowthe funnel (7) activating the alarm, but this can be disenabled forthis purpose. Further, greater volumes of liquid then can be readily accommodated via the lip (8a) will enterthe system. This can be conveniently dealt with by providing on the upper edge ofthe frusto cone (8) remote from the gantry(13) adepressionorslotsuchthat excess liquid flows into the headertank (1 ) via this alternative route.

With the central heating system completelyfilled and broughtto a state of equilibrium the infra-red source (11 is switched on. The system may then be left on stand-by. If a malfunction occurs, such as a leak in a portion of the central heating system,the level ofthe liquid (2) in the headertank (1) will fall allowing small amounts of heat exchange liquid to enterthe headertank (1 ) via the inlet (6) and thevalve (5). Even if the rate of liquid replacement is fairly low drips of liquid will form on the outlet ofthe valve (5).

These may form at any point aboutthe outlet (5) which is generally of about halfto one centimetre.

These then fall into the frusto conical portion (8) and run down the same until they reach the lip (8a). If the amounts of liquid are sufficiently small they will there form the beginnings of a drip held to the lip by means ofsurface tension. Shortly afterwards more liquid will ru n run the inner surface of the frusto conical portion (8) and so form a drip, the weight of which exceedsthe surface tension in the lip (8a), and hence falls pasttheinfra-red source (11) and the det- ector (12). A pulse is generated which causesthe triggercircuitto lock on sounding an alarm oractuat ingavisualwarning until reset.

The funnel (7), and particularly the frusto conical portion (8), may be formed with an inner surface at least which has a high co-efficientthermal conductivity. A non-corrodable metal, such as stainless steel, may be used for this or a suitable plastics material may be chosen. In these circumstances if a vapour issues from the expansion pipe into the hea dertank a portion thereof wili condense on the inner surface ofthefrusto conical portion (8) and form a drip. This will then actuate the warning system.

Thus, malfunctions such as insufficient heat exchange liquid in the system and 'pump over' can be detected by the device.

An additional 'liquid present' sensor of known type (15) is present. This is disenabled by the presence of liquid. If the level ofthe liquid (2) falls below the level of the sensor (15) again the trigger circuit will beac- tuated.

If the device is installed when the central heating system itself is installed it will be appreciated that the lead wires (14a, b, and c) can be readily taken down the same route as the expansion pipe to the boiler.

Accordingly, the alarm can be readily situated nextto the boiler. It will further be appreciated that the current required to actuate the infra-red source (11 ),the detector (15) will be so low that it is entirely safe.

The present invention has been described with re ferenceto a central heating system. Obviouslythe leale detector ofthe present invention can be readily adapted to other systems in which it is desired to detect a leak. Accordingly, the present invention relates to a leak detector, a Ieakdetectorwhen used in a central heating system, and a central heating system comprising a leak detector.

Claims (11)

1. A liquid flowdetectorcomprising concentra- tion means to concentrate a discontinuous flow of liquid into a detection zone, and detector means associated with said zone to detect the passage of said liquid.

2. AdetectoraccordingtoClaim 1 whereinthe concentration means is a funnel having a frusto conical upper portion and a co-axial spout.

3. A detector according to Claim 2 wherein the frusto conical upper portion terminates towards its putative apex in a radially inwardly directed lip directed toward said apex of said frusto cone at its point of junction with the spout.

4. A detector according to any one of Claims 1 to 3 wherein the concentration means is formed of a material having a co-efficient of thermal conductivity.

5. A detector according to any preceding Claim wherein the detector means comprises an infra red or LED emitter and receptor therefor adapted to generate an electrical signal on actuation.

6. A detector according to any preceding Claim mounted upon a gantry which also supports a "liquid present" sensor.

7. A detector substantially as hereinbefore set forth with reference to and/or as illustrated in, the accompanying drawings.

8. A method forthe detection of a leakwhich comprises concentrating a discontinuous liquid flow into a plurality of drips of known size, counting and timing said drips as they pass a detection station, and outputting a signal indicative thereof.

9. A method according to Claim 8wherein the concentration step is effected in part by causing condensation ofavapourised liquid to form said drips.

10. A method according to either of Claims8 or9 wherein the concentration step includes configuring a lip ofa material of high thermal conductivityand high surface tension so that vapourised liquid will flow to the lip and form drips of a comparatively large size.

11. A method substantially as hereinbefore set forth with reference to, and as illustrated in,the accompanying drawings.