GB2120794A - Pipework testing apparatus - Google Patents

Abstract

Apparatus for automatically testing a pipework system 10a, 10b, for example a gas fuel distribution system in a laboratory, boat or the like, to ensure that there are no open taps or other leaks before it is connected to a main supply (10) has a microprocessor controlled solenoid valve (12) in the supply and a pressure switch (14) downstream thereof, the apparatus operating in a test sequence in which pressured fluid is admitted to the system, the valve is closed for a predetermined proving period, and is only permitted to open if there is no pressure drop within the system in that period. <IMAGE>

Description

SPECIFICATION Pipework testing apparatus The present invention is concerned with testing of pipeworksystems for opentaps or other leakages, for example systems for distributing gases or liquids and particularly inflammable fluids from a main supply to points of use.

The objectofthe invention isto provide apparatus for carrying out an automatictest routine to ensure thatthe system is safe before it can be operatively connected to the mains supply, and to keep the system isolated if leakage is detect until the cause of the leakage has been rectified.

The invention provides apparatus for testing a pipework system for leakage before permitting its operative connection to a supply of pressurised fluid comprising a cut-off valve th rough which said connection is made in use, actuating means selectively operable to open and close the valve, a pressure responsive sensorfor monitoring the pressure level downstream of said valve in use, and automatic control means operating the actuating means in response to input from the sensor in use in a sequence including opening the valve for a predetermined charging period to admit pressured fluid through the system, then closing the valve four a predetermined proving period in which maintenance of pressure within the system is checked by the sensor, and re-opening the valve only if pressure in the system has remained art a predetermined acceptable level in said proving period, said valve otherwise remaining closed to prevent connection to the supply.

Preferablythevalve is a solenoidvalve biased to the closed position and only opened while its actuator is energised, the sensor is a pressure responsive switch, and the control means is a microprocessor programmed to automatically carry out said sequence.

The use of a microprocessor enables operating voltages present at switching components ofthe apparatus, for example a pressure switch serving as the sensor, to be kept to a low level (e.g. volts at less than 1 mA) to eliminate the possibility of arcing. This is particularly important where the apparatus is to be used in connection with an inflammablefluid pipework system.

An embodiment ofthe invention together with certain modifications thereof is now more particularly described with reference to the accompanying drawings, wherein: Figure lisa diagram oftesting apparatus and a pipeworksystem controlled thereby; and Figure 2 is a block diagram illustrating the operation ofthe apparatus of Figure 1; Referring to Figure 1 a pipework system is shown diagrammatically comprising a main supply line 10 leading to, for example, a school laboratory to connect with branch pipes 1 Oa feeding a plurality of user outlets e.g. gas taps 1 Ob on the laboratory benches andlorvarious gas fuelled appliances 1 Oc.Similar distribution systems are used in workshops, kitchens, hospital wards, and other premises for distribution of gases or liquids two points of use, for example liquid fuel, oxygen, or possibly noxious or harmful fluids and undetected leakage, e.g. due to atap being left open, gives rise to substantial risk of hazard, e.g. fire or explosion.

Asolenoid valve 12, such as an oil filled solenoid actuated gas valve, is installed in supply line 10 at a location upstream of any ofthe user outlets 1 Ob, cA pressure responsive switch 14 is also connected into the system, conveniently immediately downstream of valve 12 and both the latter and switch 14 are electrically connected to a control box 16 at a convenient location containing automatic control means comprising a microprocessor programmed to carry out a checksequence described hereafter.

The sequence is initiated by manual operation of key operated master control switch 18 on box 16 which energisesthesolenoid of valve 12to open the latter (the valve is urged to the closed position when the solenoid is u nenerg ised).Th ere is also an emergency stop button 20 connected on the output side of switch 18 whose contacts are normally open but which can be closed at any time, for example in an emergency, so instantly overriding switch 18 and closing the valve to cut-off supply to the pipework system. It is also contemplated that automatic shut-off may be provided by connecting external actuators or sensing devices shown diagrammatically at 21 into said connection, for example automatic fire or smoke detectors, gas orvapour detectors, or a fire alarm circuit.

The microprocessor is programmed to hold valve 12 open for a predetermined charging period, typically from one to eight seconds though longer may be required in some circumstances as determined by experiment during original commissioning ofthe apparatus to suit the particular pipework system. The charging period is selected to permit no more than sufficient pressurised gas to enterthe system to raise the internal pressure to the normal working level.

At the end of the charging period valve 12 is de-energised so that it closes and it remains in this condition for a proving period which is again timed by the microprocessor and has been predetermined during commissioning. Typically the proving period is one, two or three minutes.

When the proving period commences an amber coloured LED 22 on the front of the control box is lit.

During the proving period the contacts ofthe pressure responsive switch 14 are monitored by the microprocessor, an initial check of the contact position being carried outsometwo seconds after the start of the proving period. If the switch 14 does not change over, i.e. the charging pressure within the system is maintained above a predetermined acceptable limit then, atthe end ofthe proving period, valve 12 is actuated to re-open and connect the system to the supply for operation. On the other hand, ifthere is a detectable pressure drop greaterthan the permitted limit during or by the end of the proving period, valve 12 remains closed and cannot be opened by the user until the source of the leakage has been detected and rectified and a further satisfactory automatic checking sequence effected.If the test pressure does so drop th?- somber LED 22 is xtinguished and a red warning tED 23 is 8 lit (possib91i interrnittentlyflashing to call EiCHenUGR} and an audible alarm orotherwarning means can also beenergised.

Typically the pressure responsive switch has a switching diferential of 1 mbar or less and is capable of operating at a selected pressure ranging from 2.5 mbarto 50 unbar. Other forms of pressure responsive sensor or response settings may be used depending on the service pressure of the pipework system, the nature of the gas or other fluid, and other conditions of service.

The key operated master control switch 18 ensures thatthe checking and connection sequence can only be initiated b;dan authorised user(e.g.the person in charge of a laboratory orworkshop) and the routine would be carried out underthat person's supervision, for example &commat;P atthe beginning of each working day orof a session or lesson. If there is loss of pressure during the proving period the apparatus may be arranged so that a repeat test can only be carried out after first switchingoffandthen re-initiatingthe routine using the key operated switch.

If the pressure test is satisfactory and the supply is connected a green LED 24 remains illuminated but the supply can be turned off at anytime by the use of the key operand switch or, in emergency, by stop button 20 or in response to any external sensor 21. The supply will also lea turned off automatically bythe operation of a mastertimer, if one is fitted, as referred to below at the end of a preset period.

As a further safety provision, if there is an electrical powerfailure Ath the apparatus in operation, solenod valve 12will close autsmaticallyto shutoffthe supply. When the power is restored, even if the key operated switch 18 has been left switched on, the apparatus will not carry out the pressure test routine permitting re-connection of the supply until the switch 18 has been manually re-set.

Set to the most sensitive response level the apparatus will prevent connection to the supply even if there is a very small leakage e.g. less than the consumption of a "pilot light" of an appliance butthe acceptable leakage level can be predetermined and it may be satisfactoryforthis to be higher e.g. where the pipework system is old and minor leakage does not cause any hazard.

The apparatus may include a programmable electro/mechanical clock or other mastertimer 30 within the control box, the latter being preferably locked to prevent unauthorised access. Timer 30 operates to automatically turn off the solenoid valve at the end of a school dayorotherworking period and to keep the system disabled e.g. throughout the night or at weekends. It may be arranged to override even the master switch 18 making it impossible to turn the system on during preset periods. This is a further safeguard against accidental omission to turn the system off, failure orto checkthatall taps etc are closed e.g. at the end of the day, and against unauthorisedtampering or vandalism e.g. by intruderstwhile a building is unoccupied.

The apparatus meets the requirements of safety regulations such as the Health and Safety at Work Act which calls four regular pressure drop tests of gas supply systems and readily accessible localised master on/off controls.

Preferably the pressure responsive sfEtch 1 4 has contacts which are held closed onlywhilethe pressure is at or above the presentthreshold,thus providing "fail safe" operation in that the system will not respond if there is afaultsuch as leakage in a diaphragm of the switch itself. The low operating current is a furthersafetyfeature, and as explained above the solenoid valve is also "fail safe".

While the apparatus above described is powered from a main electric supply a reserve battery may be included to keep the master timer 30 in operation, and forsome applicationsthe entire apparatus may be battery powered e.g. from a 12 or 24 volt supply enabling its use in caravans, boats or portable buildings.

In some applications the apparatus may include a pump for raising the pressure in the pipework system above the normal working level during the proving period, the excess pressure being relieved following the test.

Apparatus according to the invention may be adapted fortesting a number of pipework systems from a central location, each system having its own solenoid or other cut-off valve and pressure responsive switch or sensor which are selectively connected in turn e.g. by means of a rotary switch to a single automatic control means to apply the pressure test to each pipeworksystem. One application of such an arrangementwould beforagroupofbungalowsor housesforold peopleordisabled persons,thecontrol box being underthe supervision of a warden who could thus ensure that all gas isturned off at night and thatthe supplies to the individual bungalows or houses are not reconnected until leakage checks have been made in each case. Each house, mom or other location would be provided with an individual emergency stop button connected through the central control unitto its respective solenoid valve enabling emergency cut off of that particular supplywithout affecting the others.

Claims (13)

1. Apparatus for testing a pipework system for leakage before permitting its operative connection to a supply of pressured fluid comprising a cut-offvalve through which said connection is made in use, actuating means selectively operable to open and close the valve, a pressure responsive sensorfor monitoring the pressure level downstream of said valve in use, and automatic control means operating the actuating means in response to input from the sensor in use in a sequence including opening the valve for a predetermined charging period to admit pressurised fluid, to the system then closing the valve for a predetermined proving period, then re-opening the valve only if pressure in the system has remained at a predetermined acceptable level throughout said proving period, said valve otherwise remaining closed to prevent connection to the supply.

2. Apparatus as in claim 1 wherein the valve is a solenoid valve.

3. Apparatus as in claim 1 or2whereinthesensor is a pressure responsive switch.

4. Apparatusasinclaim 1,20r3whereinthe control means is a microprocessor programmed to automatically carry out said sequence.

5. Apparatus as in any preceding claim including a pump selectively operable to charge the system at a pressure above its normal working pressure priorto said proving period.

6. Apparatus as in any preceding claim including an emergency switch operabletocausethecut-off valve to close.

7. Apparatus as in any preceding claim including a key operated master switch arranged so that it must be operated to initiate each said sequence.

8. Apparatus as in any preceding claim including signal means for indicating when the sequence is being carried out and whether or not pressure remains at said level.

9. Apparatus as in any preceding claim including a mastertimerwhich can be preset to prevent operation and connection to the supply during predetermined periods.

10. Apparatusasin any preceding claimfortesting a plurality of pipework systems, including a cut-off valve, actuating means, and sensor respective to each said system, central automatic control means common to all the systems, and switching means for selectively connecting each actuating means and sensorto the control means to carry out said sequence on each system in turn.

11. Apparatus as in claim 10 including an emergency switch associated with each system operable to cause the cut-offvalve of that system to close.

12. A pipework system or systems including apparatus according to any one of the preceding claims.

13. Apparatusfortestinga pipeworksystem substantially as hereinbefore described with reference to and as shown in the accompanying drawings.