GB2127177A - Control device for ultra-violet irradiation of liquids - Google Patents

Abstract

A control device to assist in ensuring current operational standards in the use of ultra-violet radiation for the purification of liquids has, within a single module (10), an amplifier (20) for a signal from an external photo-electric sensor (21), a first relay (16) operated by a signal from the amplifier (20), a timer (26) adapted to pass current only when said first relay (16) has been operated, and a second relay (23) adapted to permit liquid to flow through the irradiation system (1, 2) only when said second relay (23) receives current from said timer (26). <IMAGE>

Description

SPECIFICATION Control device for ultra-violet irradiation of liquids The present invention is concerned with the irradiation of liquids with liquid in the ultraviolet band, to achieve biological purification of the liquids.

The purification of water and other clear liquids by exposure to short-wave ultra-violet light is generally recognised to be both effective, subject to adequate radiation intensity and exposure duration, and also economical.

However, many installations for treatment in this way require a very high standard of reliability such that untreated or inadequately treated water cannot pass down stream. For example, if the water is to be used in the production of say soft drinks or beer, it is imperative that no unpurified water should be used. For this reason, various fail-safe devices have been devised to detect the causes and symptoms of inadequate treatment.

It will readily be understood that diminished visual permeability of the liquid will reduce the distance that the ultra-violet light can travel through the liquid. Thus liquid at the limits of the path-length of the light may be inadequately irradiated when the visual clarity of the liquid is impaired. A fail-safe device is therefore available in which a photo-electric sensor (for example a photo-cell), located at the perimeter of the treatment chamber, detects the intensity of the ultra-violet light signal after passage through the liquid and, via an amplifier, operates a visual or audible alarm if the signal drops below the level necessary for adequate treatment of the liquid.

Even when an unsatisfactory treatment condition as above is indicated, liquid may continue to flow until the relevant flow pump or valve is closed and, when the closing entails a manual operation, liquid which has not been effectively treated may pass down-stream into normally uncontaminated areas before the valve can be closed. Thus another commonly offered fail-safe device is a solenoid valve which cuts off the flow of liquid instantly when the sensor signal drops below a pre-set value.

Another optional fail-safe device sometimes offered is a "delay-on-start" timing device which will not permit liquid flow for a pre-set number of seconds after the ultra-violet lamp or lamps have been allowed to reach full power.

In spite of all the above precautions, it remains possible for the plant owner to choose not to include one or more of the above features in his system and it also remains possible for the operator to disconnect or by-pass such devices, or ignore or over-ride alarms and thereby allow inadequately purified liquid to pass down stream.

The main object of the present invention is to provide a control device which reduces or eliminates the possibility of ultra-violet irradiation treatments of the above type being operated in a way which permits inadequate treatment without due management control.

The present invention is a control device for apparatus for the ultra-violet irradiation of a liquid, which device comprises, in a single module, an amplifier for a signal from an external photo-electric sensor, a first relay operated by a signal from the amplifier, a timer adapted to pass current only when said first relay has been operated and a second relay adapted to permit liquid to flow through the irradiation system only when said second relay receives current from said timer.

The incorporation of these components, interconnected in this way, in a single module, ensures that the over-riding control is provided solely by the detecting of an acceptable ultra-violet light intensity level by the photoelectric sensor. Only when that condition is satisfied does the amplifier trigger the first relay and permit passage of current to the timer. After the elapsing of the time interval to which the timer has been set, current is permitted to pass to operate the second relay, which may then in turn cause the flow-control solenoid valve to open and allow liquid to flow through the irradiation system.

By appropriate choice of the individual components, the control device may be constructed as a higly compact module incorporating all of the control features. Thus the amplifier may be an electronic operational amplifier and the timer may be an adjustabledelay electronic timer. The whole module may be sealed to ensure that none of the individual fail-safe features is by-passed or otherwise over-ridden.

The module may be of plug-in design for easy installation or replacement.

Advantageously the first relay, when it is not in a condition in which it is feeding current to the timer, is allowing current to flow to an alarm system, by means of which the operator is warned that normal operation of the irradiation system is not being attained.

The alarm system may comprise an alarm external to the monitor, which alarm may if desired be provided with means for rendering it inoperative. In addition or alternatively, an audible sounder is preferably included in the module, which sounder can only be silenced by restoring normal operation of the irradiation system.

As a further feature of my invention, it may be desired to provide a stand-by module, which may be substituted for the main module in an emergency in which it is judged acceptable that liquid flow should continue even though the liquid is not receiving the level of irradiation treatment which it would normally receive. Such a stand-by module contains the circuitry necessary to energise a flow control solenoid valve directly. Advantageously the main module and the stand-by module are both of the plug-in type and have compatible pin configurations. As a matter of sound management, the stand-by module may be available only to one or more specific senior members of the plant management team, to ensure that emergency operation is permitted only with the full knowledge of the manager responsible.Preferably the stand-by module incorporates a characteristic audible sounder as an indication that emergency operation is in progress.

The invention will now be further described with reference to the accompanying drawings, in which: Figure 1 is a schematic drawing of a preferred form of control device according to the present invention, connected to an irradiation unit; and Figure 2 is a schematic drawing of a preferred form of stand-by unit suitable for use in association with the control device of Fig. 1.

Referring to the drawings, a bank of ultraviolet lamps, shown diagrammatically as a single lamp 1 in an irradiation chamber 2, receives its power from a 240-volt AC source via a switch 3 ("the lamp switch"). From the switch 3, power is also supplied to contact 7 of a contactor 5. Contact 7 is normally open but, in the event of lamp failure, a coil 4 of the contactor 5 is energised and closes the contact 7, thereby energising a red "lampfail" warning light 8. Except when coil 4 is energised, a second contact, 6, of contactor 5 is closed; energising of coil 4 also opens contact 6 and shuts off power to the control unit.

Except when contact 6 is open, operation of a switch 9 ("the monitor switch") delivers the 240-volt supply to the control device 10 ("the monitor") at 11 and, via a transformer 12 and a rectifier 18, delivers a 1 2-volt regulated DC supply to the monitor 10 at 13. The 12volt supply is fed to the two switches 14 and 15 of a first relay 16. Both switches are shown full-line in the "at rest" or start-up position.

The switch 14, in the start-up position, supplies current to an external alarm 17, which may afford both visual and audible warning of the fact that liquid flow has not yet been established (or has been interrupted).

The switch 15, in the start-up position, energises an alarm 19, internal to the monitor 10 and therefore not able to be switched off by hand or by-passed. The DC output of the rectifier 18 also powers an amplifier 20.

A photocell 21 (incorporating a pre-filter, not shown), disposed at the furthermost part of the light path from the ultra-violet lamps 1, is sensitive only to short-wave ultra-violet light of about 254 nano-metres wave-length and detects the intensity of that light after passing through the liquid in the irradiation chamber 2. The outputifrom the cell 21 is amplified via the amplifier 20 within the monitor 10 and fed to a coil 22 of the relay 16. Provided that the signal from the amplifier 20 indicates an acceptable intensity level of light arriving at the cell 21, the relay 16 is activated and the switches 14 and 15 are switched to the positions shown dotted in the drawings. Activation of the alarms 17 and 19 thereby ceases.

The 240-volt supply to the monitor 10 is fed to a second relay 23 which includes a switch 24 which is in the position shown in full line when "at rest". In this position, a red light 25 is illuminated to show that power is on to the monitor but that liquid is not flowing.

The switching of switch 15 initiates electronically the internal timer 26, which does not pass current until the lapsing of a predetermined time interval of a few seconds.

When that time has passed, a coil 27 in the relay 23 is energised and the switch 24 thereupon moves to the dotted position. The 240-volt supply is thereby diverted to a line 28, which feeds a solenoid in the flow control valve (not shown) and opens the valve, to initiate liquid flow to the irradiation chamber 2. At the same time, the red warning light 25 is extinguished and a green "flow-on" light 29 is illuminated.

Flow of liquid through the chamber 2 continues until an emergency, for example clouding of the liquid, causes the relay 16 to be deenergised. When this occurs, the alarms 17 and 19 are again activated and the power to the relay 23 is interrupted, thereby closing the liquid flow valve automatically and instantly. Thus the triggering of the alarms is not a warning that the liquid has become cloudy but rather an indication that liquid flow has been stopped. The system has truly "failed safe".

When such an emergency arises, it is open to the plant management to decide that liquid should nonetheless be allowed to continue to flow. For example, a marginally lower irradiation level may be judged to be acceptable. In that situation, the whole of the monitor 10 may be unplugged and a stand-by unit 30, shown in Fig. 2, may be substituted. The pin configuration of the stand-by unit 30 is compatible with that of the monitor 10.

In the stand-by unit 30, components corresponding to those of monitor 10 are given corresponding numbers. As is shown, the relays 1 6 and 23 are dispensed with and the 240-volt input at 11 is fed direct to the line 28 feeding the solenoid of the liquid flow control valve, and to the light 29. The DC output of the rectifier 18 is fed to a pulsing unit 31, which delivers a pulsed signal to the audible sounder 19 and to a red light emitting diode display 32, thus giving a clear warning that the stand-by unit and not the normal monitor is being used. Simultaneously a signal at 33 illuminates a separate 3-digit light emitting diode display (which normally gives a numerical indication of the ultra-violet light intensity at the photo-cell 21) with a simple signal such as "E E E", indicating emergency operation.

It should also be pointed out that the circuit illustrated is such that, whether the monitor 10 or the stand-by unit 30 (or neither) is in use, it is possible to keep power on to the ultraviolet lamps even when a no-flow condition prevails. Thus the liquid within the chamber may continue to receive bactericidal protection indefinitely.

Claims (9)

1. A control device for apparatus for the ultra-violet irradiation of a liquid, comprising, in a single module, an amplifier for a signal from an external photo-electric sensor, a first relay operated by a signal from the amplifier, a timer adapted to pass current only when said first relay has been operated, and a second relay adapted to permit liquid to flow through the irradiation system only when said second relay receives current from said timer.

2. A control device as claimed in claim 1, in which the amplifier is an electronic operational amplifier.

3. A control device as claimed in claim 1 or claim 2, in which the timer is an adjustable-delay electronic timer.

4. A control device as claimed in any of claims 1 to 3, in which the module is sealed to control access thereto.

5. A control device as claimed in any of claims 1 to 4, provided with pins to enable it to be plug-in connected.

6. A control device as claimed in any of claims 1 to 5, having also, in the module, an audible alarm adapted to indicate that the first relay is not in the operated condition.

7. A control device for apparatus for the ultra-violet irradiation of a liquid, which control device is substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

8. A control device as claimed in any of claim 1 to 7, having also a separate stand-by unit to receive and deliver the same power supplies as said control device but without any provision for interruption or control thereof.

9. A control device as claimed in claim 8, in which the stand-by unit is substantially as hereinbefore described with reference to Fig.

2 of the accompanying drawings.