GB2353593A

GB2353593A - Drain blockage sensor

Info

Publication number: GB2353593A
Application number: GB0021077A
Authority: GB
Inventors: Michael R Barton
Original assignee: FLOW CONTROL SYSTEMS Ltd
Current assignee: FLOW CONTROL SYSTEMS Ltd
Priority date: 1999-08-25
Filing date: 2000-08-25
Publication date: 2001-02-28
Anticipated expiration: 2020-08-25
Also published as: AU6715300A; GB2353593B; GB9920157D0; GB0021077D0; WO2001014653A1

Abstract

A drain blockage sensor comprising a housing 1 divided into two chambers 2 and 3 by a flexible diaphragm 4. Chamber 2 contains a sensing device that responds to the displacement of diaphragm 4 caused by pressure changes in chamber 3. The pressure changes are caused produced by the build up of effluent levels caused by downstream blockages in the drain. The sensing device produces a signal when the pressure difference across the diaphragm exceeds a predetermined value. Diaphragm 4 has a valve therein to compensate for changes in atmospheric pressure and ambient temperature. Alternatively, chamber 2 may include a vent to atmosphere.

Description

2353593 DRAIN BLOCKAGE SENSOR This invention relates to apparatus and

methods for detecting a rise in level of a fluid in a drain, and in particular for detecting a rise in water level caused by a blockage in a 5 waterborne waste drainage system.

In waterbome waste drainage systems, effluent arising from sanitary devices such as toilets, baths, wash hand basins, kitchen sinks and the like is conveyed by a system of waste and soil pipes to a network of underground pipes that eventually connect with a main sewer.

In an installation that has numerous sanitary devices, each outflow is transported via a separate trapped piping arrangement connected to larger bore common pipe work. In most cases this is a single vertical pipe with individual T-connections at various levels.

The bottom end of this pipe eventually connects with the underground system of pipes and the top end is open as a vent to the atmosphere.

From time to time blockages occur causing the pipes upstream of the blockage to fill with effluent. In the case of underground blockages occurring downstream of a manhole space, this space will fill and eventually flood the local area. In the case of blockages occurring before the first manhole space, effluent will fill the down pipe until the level reaches the first T- connection above the blockage. Effluent will then flood the area local to the particular sanitary device.

US 4546346 (Sanity Saver Cap Company) discloses a sewer line backup detection device comprising a housing which can installed in place of the clean-out access cap. in a conventional sewer line. The housing comprises a pneumatic switch activated by a flexible diaphragm which is fitted onto the lower end of the housing which extends into the sewer line. In the event of a blockage of the sewer line, the blocked material exerts pressure directly on the flexible diaphragm which closes the pneumatic switch thereby setting off an alarm.

2 US 5718822 (the Metraflex Company) relates to an apparatus and method for detecting an accumulation of particulates in a fluid stream. A differential pressure switch having an open end covered by a flexible diaphragm is placed in fluid communication with an upstream side of the pipeline. As particulates accumulate in the pipeline (particularly on a screen or filter), the resulting increase in pressure activates the pressure switch and thereby an alarm.

US 4972705 (Phillips Petroleum Company) discloses a method for detecting the presence of a liquid level in a bore hole by using a pressure switch which detects a rise in pressure in a captive air column caused by a rise in liquid level in the bore hole. There is however no indication that the apparatus (which is suitable for bore holes which are several hundred feet long) would be suitable for use in domestic drains.

US 5006833 (CDF, Inc) relates to a pressure sensor in the form of a plug for placing in the access arm of a clean-out location in a sewage system. Changes in pressure in the system urge a diaphragm to close a switch and actuate an alarm. US 5722289 (Tridelta Industries, Inc) discloses a deep fat fryer system including a level 20 sensor which has a pressure sensitive switch for determining the level of cooking fluid in the fiyer. If the oil is below the level of a conduit exit into the vat, then air from a blower can flow freely through the conduit, and the pressure remains low. If however the oil rises above the level of the conduit so that it blocks the end of the conduit, the air produced by the blower cannot pass through the conduit and the pressure rises. This rise in pressure is 25 detected by a pressure sensitive switch.

US 3949610 (ACF Industries, Inc) discloses a pressure indicator for a railway car such as a pressurised hopper car or a pressurised tank car. A change in pressure moves a flexible diaphragm against a movable assembly which indicates the pressure range in the tank.

US 4973950 (Tourtillott) discloses a sewer blockage alarm for a sewer line having a pressure sensor mounted at the top of the clean out branch section of the sewer line. An 3 audible and a visual indicator are activated by slight pressure rises caused by the rise in water level in the sewer.

US 3803917 (Western Liquid Level, Inc) discloses a differential pressure sensor which utilises two diaphragms to provide an accurate reading of the liquid level in a closed tank or container.

The problems with existing apparatus are that it is not suitable for detecting the relatively small pressure changes caused by blockage in a drain system; there is a risk that fluid and possibly effluent might come into contact with sensitive parts of the apparatus; or that there is a risk that changes in atmospheric pressure or in ambient temperature might cause the apparatus to activate or to be desensitised.

According to a first aspect of the present invention, there is provided apparatus for detecting an increase in fluid pressure in a drain, comprising a housing divided into a first chamber and a second chamber by a flexible partition, the first chamber having means for fluid communication with the drain, and the apparatus having means for sensing deflection of the partition into the second chamber, whereby in use an increase in fluid pressure within the drain causes a rise in air pressure in the first chamber, thereby deflecting the partition into the second chamber and activating said means for sensing, the partitionbeing spaced apart from said means for fluid communication with the drain such that said means for sensing activates before a rising level of fluid in the drain meets the partition, and wherein the partition includes a valve for allowing air to pass from the second chamber to the first chamber but not from the first chamber to the second chamber.

In many situations, such as those in which the unit is fitted outside of a manhole or vessel, the outside air pressure can vary considerably. If the pressure inside the second chamber is higher than atmospheric pressure, then this will exert a pressure on the partition towards the first chamber of the chamber, i.e. towards the drain. This will desensitise the apparatus, because effectively the partition will have to push harder against the increased air pressure in the second chamber in order to activate the means for sensing.

4 The provision of a valve in the partition addresses this problem. Specifically, the valve allows air to pass from the second chamber into the first chamber in order to relieve a build-up in pressure within the second chamber.

In a preferred embodiment, the valve comprises a hole in the partition, and a flap or partial diaphragm adjacent the partition on the same side of the partition as the first chamber and in alignment with the partition so as to at least partially cover the hole. Thus, in use, pressure build-up in the first chamber caused by a rise in fluid level in the drain will urge the flap against the partition so as to seal the hole, such that a further increase in pressure causes the partition to deflect into the second chamber and activate said means for sensing.

If, however, there is a pressure build-up in the second chamber, this causes the flap to move away from the hole into the first chamber, thereby allowing air to be expelled through the hole to equalise pressure in the first and second chambers.

The apparatus may also have a vent from outside the apparatus into the second chamber for stabilising the apparatus to changes in ambient temperature and atmospheric pressure. The vent may for example be a pipe or tube which leads from the apparatus to the outside of a manhole. The provision of a vent keeps the second chamber at atmospheric pressure, which means that it is not desensitised by a drop in atmospheric pressure, nor is it sensitised by an increase in atmospheric pressure.

The disadvantage of providing a vent into the second chamber is that fluid or damp may enter the second chamber through the vent and harm the apparatus, for instance by harming electronic equipment housed within the second chamber. Accordingly, in a preferred embodiment, the vent includes means for allowing the air to pass into and out of the second chamber, but for preventing the passage of liquid.

Since the provision of a vent alone (that is, without there being a valve in the partition) addresses at least partly the problem of changes in atmospheric pressure and temperature, there is provided in a second aspect of the invention apparatus for detecting an increase in fluid pressure in a drain, comprising a housing divided into two parts by a flexible partition, the first chamber having means for fluid communication with the drain, and the apparatus having means for sensing deflection of the partition into the second chamber, whereby in use an increase in fluid pressure within the drain causes a rise in air pressure in the first chamber, thereby deflecting the partition into the second chamber and activating said means for sensing, the partition being spaced apart from said means for fluid communication with the drain such that said means for sensing activates before a rising level of fluid in the drain meets the partition, and the apparatus having a vent from outside the apparatus into the second chamber for stabilising the apparatus to changes in ambient temperature and atmospheric pressure, wherein the vent includes means for allowing air to pass into and out of the second chamber, but for preventing the passage of liquid.

In a particular preferred embodiment, the means for allowing air to pass into and out of the second chamber is adapted to allow an air flow of approximately 150Cin 3 of air per minute in either direction.

In situations of high humidity, a vent tube may be fitted to the apparatus which is long enough so that the distal end of the tube can reach a place of lower humidity. The distal end of the tube can be fitted with said means for allowing air to pass into and out of the second chamber, but for preventing the passage of liquid.

Additional protection of the electronic equipment within the unit may be provided by encapsulation of the equipment using low viscosity silicone rubber.

A waterproof test switch may be mounted on top of the unit to enable engineers to test the electronic circuits.

The body of the apparatus which forms the chamber is preferably moulded from UPVC as a one-piece unit. This allows the housing to expand as a single unit, which reduces the likelihood that the apparatus will crack at high temperatures. In order to cope with extreme conditions found in the confines of certain drainage systems and in particular fire 6 hazardous areas, the shell of the unit may be constructed out of 4mm copper. The venting of this unit is by additional pipe work. In addition, a fire retardant coating may be applied to the inner surfaces of the unit.

The spacing of the partition from the means for fluid communication with the drain ensures that the fluid or effluent in the drain does not foul the apparatus. The partition is preferably extremely flexible and offers very little resistance to a change in pressure in the first chamber of the chamber. This means that the limiting factor in 10 triggering the apparatus is the triggering of the means for sensing, rather than the deflection of the partition. Preferably, the partition is constructed from a very thin material in order that it is sufficiently flexible. A particularly suitable material is nitrile rubber coated nylon having a thickness of about 0.25mm. Its temperature range is from -30'C to 100'C, and its burst strength Mullens is in the region of 300 psi. 15 The problem with making the partition this flexible is that it is liable to rupture on repeated deflection and relaxation. Accordingly, in a preferred embodiment, there is provided a guard for limiting the deflection of the partition in order to prevent the partition from being damaged. The guard is preferably about 4mm from the partition when the partition is in its 20 relaxed state. Preferably, the distance moved by the partition f7om its relaxed state to its fully deflected state is from I mm to 3mm, and preferably about 2mm. Accordingly, in normal circumstances the partition does not impact on the guard. The guard acts to limit 25 deflection of more than 4mm, however, and thereby to reduce rupturing of the partition.

In a preferred embodiment, the partition and the means for sensing deflection of the partition are sufficiently sensitive to detect a change in pressure of about 0.07 psi. The means for sensing deflection of the partition is preferably an electrical contact switch which is arranged to be contacted by the partition when the partition moves a predetermined distance into the second chamber. However, in alternative embodiments, the means for sensing may be electromagnetic, electropneumatic, clectro-optical or fibre- 7 optical in nature.

In a preferred embodiment, the first chamber of the chamber is an elongate member, wherein said member tapers away from the partition to a section of minimum cross section.

The means for fluid communication with the drain is preferably at the end of the first chamber distal to the second chamber. Said means is preferably adapted to be connected to a network of pipes. The connection may be of any known type, for example a bayonet fitting or a male or female screw thread.

In a preferred embodiment, the means for sensing deflection of the partition is connected to an alarm for indicating when the fluid level in the drain has risen a predetermined amount.

The connection between said means and said alarm may be of any suitable type, for example it may be a hard wired electrical connection or the connection may be by means of optical fibres, pneumatic pipes, or by means of an electromagnetic link such as an RF (radio ftequency) link.

In an alternative embodiment, a cellular phone network may be used to convey information about the status of the apparatus. Some form of paging system may be devised so that contact closure is uniquely annunciated by telephone. Such a system would be endowed with the national and global coverage of the cellular network allowing executive monitoring over great distances.

Wireless single event telemetry systems can be envisaged whereby a battery operated RF transmitter is incorporated in each unit. Closure of the contact switch causes an RF signal to be transmitted that is picked up by a suitable remote RF receiver, whereby annunciator circuits at the receiver output are activated. When a number of units are involved, discrimination is brought about by each unit having an arrangement so that the transmitter carrier wave is modulated in a unique way corresponding to the unit location.

The apparatus may include a "connection lost" feature. In this embodiment, the transmitter 8 within the unit automatically transmits a signal to a remote control panel, for example once every 24 hours. If the receiver within the control panel does not receive the signal then an LED on the transmitter will illuminate to indicate a lost connection and a pre-recorded lost connection telephone message will be sent by means of an auto-dialler in the control panel. 5 A low battery status transmission feature may also be present.

In a further aspect of the invention, there is provided a method for detecting a rise in level of fluid in a drain, comprising putting the apparatus described above into fluid communication with the drain, and monitoring the status of the means for sensing deflection of the partition.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 shows the general arrangement of the parts of the invention incorporating by way of an example a cylindrical chamber and an electrical sensor (a microswitch).

Figure 2 illustrates two alternative ways in which the sensor can be used.

Figure 3 depicts an alternative arrangement in accordance with the invention.

Referring to the drawings, Figure 1 shows the sensor comprising a chamber 1 divided into two parts 2 and 3 by an impermeable diaphragm 4 that is backed by an over pressure support plate 5. Part 2 has venting aperture 24. Venting aperture 24 includes a damp seal known as a "breather" (not shown) for allowing the passage of air but not water into part 2. Attached to the partition is a reinforcing pad 6 that protrudes through the over pressure plate 5 and is in close proximity or touching the actuating plunger of a switch 7.

The switch 7 is mounted relative to diaphragm 4 so that a predetermined displacement of the Partition towards the switch will cause the contacts 8 to change state. An external electrical connection to these contacts is by wires 10 through the side of part 2 via feedthrough device 9. In one example switch 7 may be of a type known as a microswitch 9 where the contact set chosen is normally open and is closed when displaced by the partition. This normally open condition is preferred because for signalling purposes it corresponds to a zero power consumption in the quiescent or non-displaced condition of the partition.

The purpose of the over pressure plate 5 is to provide support to prevent diaphragm 4 rupturing in the event of a gross over-pressure situation.

Part 3 is in the form of an open-ended cylinder which converges such that the diameter at the open end is smaller than that adjacent to the partition. Alternatively the cylinder may be the same diameter over the whole length.

The operation of the sensor is dependent on the pressure volume product of the trapped volume of part 3 being constant. Whereby the reduction in the trapped volume by the rising level of effluent is accompanied by a pressure increase in the trapped air causing diaphragm 4 to be displaced.

By way of example the deliberations that follow demonstrate the order of sensitivity to effluent level change that the special combination of well known principles and components of the invention can achieve and is necessary to implement a viable early warning sensor.

If the force required to displace diaphragm 4 against the spring pressure of the switch 7 so that the contacts 8 close is Fs and the effective area of the partition is A the required increase in pressure of the air trapped in part 3 will be Fs/A. Typical values for Fs and A used in working models of the invention are 1 Newton and 0. 0044 square meter (partition diameter of 75mm) giving a required pressure of 227 Pascal.

Atmospheric pressure at sea level is of the order 0. 1 Nwa so required pressure increase is of the order 0.00227 of an atmosphere. In units of water gauge atmospheric pressure can be expressed as of the order 3 90 inches and pressure increase require as 0. 88 inches water gauge. This corresponds to the dimension defining the distance between level 17 and 18 or 33 and 34 show on drawing Fig 2.

In this particular example the percentage reduction in the trapped volume to produce the required increase in pressure can be expressed as 227/100, 000 x 100% = 0.227 %. This will be manifest as the change in volume produced by the effluent level 18 or 3 being above the effective trapping level of part 3.

When part 3 is the same diameter over the whole length the volume percentage change is the same as the distance of level 16 or 34 above the trapping level expressed as a percentage of the total length and for a divergent case is somewhat greater.

The possibility of using a divergent volume adjacent to diaphragm 4 allows higher sensitivities (due to greater diameter and area) to be set up than otherwise are possible with the smaller diameter of the open end of part 3.

Fig.2 illustrates two ways in which the sensor can be used. It shows a representation of a typical form of a drainage system comprising a vertical down pipe 11 that terminates in an underground trap 12 that is connected to a system of pipes 13 having manhole spaces 14 at various locations. The outflow from various sanitary devices such as baths and kitchen sinks etc. are typically connected to down pipe 11 at appropriate levels by trapped pipe work 15.

When the sensor is used to detect blockages such as that shown at 16 it is installed in a manhole space 14. When used in this way part 3 can be of a standard length or extended by a piece of straight pipe. The sensor is mounted with the axis vertical and can be supported from a wall of the manhole space such that the open end of part 3 is just clear of any flowing effluent. A blockage at 16 will cause the level of effluent in the manhole space to rise. When the surface of the effluent reaches the lower end of the sensor, air in part 3 will be trapped and sealed. As the level rises, the trapped air will be compressed and the diaphragm 4 will be displaced. At a pre-determined displacement corresponding to effluent level 17 in the manhole space and level 18 in the sensor space the switch will operate signalling that a blockage has occurred.

11 The sensor can be used to give early warning of blockages in the vertical down pipe as indicated at 19. In this case the open end of the sensor is connected via an elbow connector 20 to a Tjunction 21. A blockage at 19 will cause effluent to backfill the down pipe and the level will rise to the Tjunction 21 and beyond so that the air in the lower part of the sensor is trapped, sealed and compressed, causing the partition to be displaced. At a predetermined displacement corresponding to effluent level 33 in the vertical pipe 11 and level 34 in the sensor space the switch will operate signalling that a blockage has occurred.

Original and retrospective installations are possible. The manhole use is similar in both cases whereas the original connected use is made via an installed T-piece and the retrospective use by an in situ. modification.

Turning to Figure 3, diaphragm 4 has a small hole 30 therein (shown enlarged for effect in the figure) and flap 40 overlaying diaphragm 4 and hole 30 to create a valve. In the embodiment shown, flap 40 has an area which is approximately 75% of that of diaphragm 4, which is the preferred ratio. However, a flap of any size will work to some extent, as long it covers or at least partially hole 30.

The apparatus shown in Figure 3 has vents 24 with a damp seal "breather" as in Figure 1. However, in an alternative embodiment, the vent may be dispensed with entirely, provided that there is a valve in diaphragm 4.

In operation, a build-up of pressure in upper chamber 2, due for example to an increase in temperature can be compensated for by the expulsion of air through either vent 24 or hole 30 or both in extreme cases. If however there is a rise in pressure in lower chamber 3 due to a rise in fluid level in the drain, then flap 40 will seal hole 30 and diaphragm 4 will be deflected by the increase in pressure into upper chamber 2, activating the switch and circuitry as above.

12

Claims

1 Apparatus for detecting an increase in fluid pressure in a drain, comprising a housing divided into a first chamber and a second chamber by a flexible partition, the first chamber having means for fluid communication with the drain, and the apparatus having means for sensing deflection of the partition into the second chamber, whereby in use an increase in fluid pressure within the drain causes a rise in air pressure in the first chamber, thereby deflecting the partition into the second chamber and activating said means for sensing, the partition being spaced apart from said means for fluid communication with the drain such that said means for sensing activates before a rising level of fluid in the drain meets the partition, and wherein the partition includes a valve for allowing air to pass from the second chamber to the first chamber but not from the first chamber to the second chamber.

2. Apparatus as claimed in claim 1, wherein the valve comprises a hole in the partition and a flap on the same side of the partition as the first chamber, the flap being adjacent the partition and covering the hole.

3. Apparatus as claimed in claim 1 or 2, wherein the apparatus comprises a vent from outside the apparatus into the second chamber for stabilising the apparatus to changes in ambient temperature and atmospheric pressure.

4. Apparatus as claimed in claim 3, wherein the vent includes means for allowing the air to pass into and out of the second chamber, but for preventing the passage of liquid.

5. Apparatus for detecting an increase in fluid pressure in a drain, comprising a housing divided into a first chamber and a second chamber by a flexible partition, the first chamber having means for fluid communication with the drain, and the apparatus having means for sensing deflection of the partition into the second chamber, 13 whereby in use an increase in fluid pressure within the drain causes a rise in air pressure in the first chamber, thereby deflecting the partition into the second chamber and activating said means for sensing, the partition being spaced apart from said means for fluid communication with the drain such that said means for sensing activates before a rising level of fluid in the drain meets the partition, and the apparatus having a vent from outside the apparatus into the second chamber for stabilising the apparatus to changes in ambient temperature and atmospheric pressure, wherein the vent includes means for allowing air to pass into and out of the second chamber, but for preventing the passage of liquid.

6. Apparatus as claimed in any preceding claim, wherein the second chamber includes a guard for limiting the deflection of the partition in order to prevent the partition from being damaged.

7. Apparatus as claimed in any preceding claim, wherein the partition and the means for sensing deflection of the partition are sufficiently sensitive to detect a change in pressure of about 0.07 psi.

8. Apparatus as claimed in any preceding claim, wherein the first chamber is an elongate member and wherein said member tapers away from the partition to a section of minimum cross section.

9. Apparatus as claimed in any preceding claim, wherein the means for sensing deflection of the partition is an electrical contact switch which is arranged to be contacted by the partition when the partition moves a predetermined distance into the second chamber.

10. Apparatus as claimed in any preceding claim, wherein the means for sensing deflection of the partition communicates with an alarm for indicating when the fluid level in the drain has risen a predetermined amount.

14 11. Apparatus as claimed in claim 10, wherein the means for sensing deflection of the partition communicates with the alarm by means of a hard wired electrical connection, optical fibres, pneumatic pipes, an electromagnetic link or via a cellular telephone 5 network.

12. A method for detecting a rise in level of fluid in a drain, comprising providing apparatus as claimed in any preceding claim, putting the apparatus in fluid communication with the drain, and monitoring the status of the means for sensing 10 deflection of the partition.

13. An effluent drainage system comprising apparatus as claimed in any of claims 1 to 11.

14. App aratus for detecting a rise in level of fluid in a drain substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.