GB2243823A

GB2243823A - Effluent sampling apparatus

Info

Publication number: GB2243823A
Application number: GB9010227A
Authority: GB
Inventors: Robert Samuel Murray
Original assignee: SIRCO CONTROLS Ltd
Current assignee: SIRCO CONTROLS Ltd
Priority date: 1990-05-05
Filing date: 1990-05-05
Publication date: 1991-11-13
Anticipated expiration: 2010-05-05
Also published as: GB2243823B; GB9010227D0

Abstract

An effluent sampling apparatus is described for use in cases where the effluent may contain an inflammable or explosive fraction. The apparatus comprises a first unit 30 for connection to a source 32 of effluent and comprising at least one storage container 44 and a remotely controlled valve 36 for controlling the supply of effluent from the source to the storage container 44 and a second unit 10 which comprises an electrical control circuit 14 and which in use is located at a distance from the first unit for remotely controlling the operation of the first unit. The first unit contains no electrically operated components nor electrical sensing elements and is controlled by the first unit without the application of any electrical signal from the first unit to the second unit; eg by pneumatic or hydraulic fluid supplied via outputs 20 and inputs 34. Outlet pipe 42 may be indexed, e.g. via an air motor, to fill containers 44 sequentially. <IMAGE>

Description

EFFLUENT SAMPLING APPARATUS The present invention relates to apparatus for sampling effluent.

Because of the adverse ecological effect of dumping waste materials from factories and processing plants, responsible industries continuously monitor the composition of any effluent discharged. If effluent is being pumped out, for example into a stream, then a small sample may be diverted into a container at regular time intervals and the containers may be stored for later chemical analysis.

Alternatively, the effluent may be drawn by a displacement pump or a vacuum pump from a source which is not under pressure and fed to storage containers. In this way, samples of a predetermined volume are taken at regular time intervals and it is possible to monitor continually the chemical composition of the effluent being discharged.

Such automatic sampling equipment is currently available and utilises electrically controlled solenoid valves for flow control purposes to divert effluent to the storage containers as and when required. However, in certain circumstances such equipment cannot be used safely because of the danger that the effluent may contain a volatile fraction which could possible ignite, or even explode ,if a spark occurs within its vicinity.

The present invention seeks to provide an automatic sampling apparatus which may safely be used for the sampling of effluent which may contain an inflammable or explosive fraction.

According to the present invention, there is provided an effluent sampling apparatus comprising a first unit for connection to a source of effluent and comprising at least one storage container and a remotely controlled valve for controlling the supply of effluent from the source to the storage container and a second unit which comprises an electrical control circuit and which in use is located at a distance from the first unit for remotely controlling the operation of the first unit, wherein the first unit contains no electrically operated components nor electrical sensing elements and is controlled by the first unit without the application of any electrical signal from the first unit to the second unit.

In order to enable the sampling interval and the sampling quantity to be adjusted at will, it is desirable to use an electrical control circuit, preferably incorporating a microprocessor. However, if the electrical output signals of the control circuit are used to operate electric motors or solenoid valves arranged in the vicinity of the effluent then there arises a safety hazard if the effluent contains a volatile inflammable fraction. In the present invention, the electrical control and sampling functions are separated physically from one another, non-electrical components essential for sampling being retained in the vicinity of the effluent and the electrical components required for control being removed to a safe remote location.

Any remotely controlled valves or motors within the first unit cannot be operated electrically but they can be mechanically, hydraulically or pneumatically operated by means of a signal transmitted from the second unit. Most conveniently, the second unit comprises fluid flow regulating valves operated by the electrical output signals of the control circuit and operative to apply pneumatic or hydraulic pressure to fluid control lines extending between the second unit and the first unit.

In a preferred embodiment of the invention, the first unit further comprises metering means to provide control over the quantity of effluent contained in each sample. The metering means may conveniently comprise a cylinder, a first pipe for supplying effluent to fill the cylinder, an overflow pipe for draining from the cylinder any effluent above a predetermined level and an outlet pipe for feeding the quantity of effluent below the overflow pipe to a storage container. Remotely controlled fluid operated valves may be used in each of the pipes to control the operation of the metering means.

If it is required to sense when the effluent reaches a predetermined level within the metering cylinder then it is important not to use electrical sensors. This may be avoided if in accordance with a preferred embodiment of the invention a fibre optic sensor is incorporated. The fibre optic sensor may comprise two fibres leading respectively to an optical transmitter and an optical receiver in the second unit. Until the effluent reaches a certain level there will be no diffusion of light at the end of the optic fibre and therefore no signal will be sensed by the receiver.

It is further preferred that the first unit should comprise a plurality of storage containers so that several samples, taken over a prolonged sampling period, may be retained within the first unit. For this purpose, it is preferred that the metering cylinder be connected to the storage containers by means of a rotatable distribution pipe and that the latter pipe be connected to an indexing mechanism for incrementally moving the end of the distribution pipe from one storage container to the next in the time interval between taking of samples. Once again it is important that the indexing mechanism should not be electrically operated and in the preferred embodiment an indexing wheel is connected to the distribution pipe and is rotated by increments by means of a pawl reciprocated by an air motor driven by a pneumatic signal from the second unit.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of the electrical control unit of a sampling apparatus of the invention, and Figure 2 is a schematic representation of the sampling unit of an apparatus of the invention.

The two units shown in Figure 1 and Figure 2, respectively, are connected to one another by a cord, which is not shown and which contains no wires. The cord consists essentially of conduits for conveying compressed air from the electrical control unit of Figure 1 to the sampling unit of Figure 2.

The control unit 10 comprises a casing 12 within which is a control panel 14. The control panel 14 has an LCD display and various control buttons and is connected to an electronic circuit which can allow the user to program the unit, for example to select the sampling interval. Such a control panel need not be different from those currently used in sampling apparatus and for this reason it is not believed necessary to describe the electrical control circuitry in the present context.

Conventionally, the electrical output signals of the control circuit would be used in the same housing to control flow control valves to effect sampling of the effluent. As earlier mentioned, this may prove dangerous in certain applications and in the illustrated embodiment of the present invention the electrical output signals are used within the control unit 10 to operate solenoid valves 18 which control the supply of a compressed air to output lines 20 connected by the cord to the sampling unit.

A pump, not shown, acts to supply the compressed air to the input of the regulating valve 16. The pressure of the compressed air supplied to selected ones of the solenoids valves 18 is regulated within the control unit by a regulating valve 16 so that the control pressures supplied to selected elements of the sampling unit 30 of Figure 2 are maintained constant. It should be mentioned that instead of compressed air another gas or hydraulic fluid may be used, it being only important to avoid electricity and any risk of a spark.

The sampling unit 30 has an input connection 32 for effluent, under pressure. The effluent is normally pumped from a factory along a discharge pipe and the connection 32 enables the sampling unit to be connected to such a discharge pipe. The sampling unit 30 also comprises a metering cylinder 40, to be described in greater detail below, a magazine 48 which may be withdrawn from the sampling unit by means of handles 50 and holding several sample containers 44 and a distribution pipe 42, increment ally advanced by an indexing mechanism 46 for supplying effluent samples from the metering cylinder 40 to the storage containers. The storage containers in this case are bottles of sector shaped cross section arranged in a circle about the centre of the magazine 48.

The sampling cylinder 40 has three pipes 52, 54, 56 leading into it from above and is connected at its lower end to the distribution pipe 42 for supplying its contents to one of the storage containers 44 in the magazine 48.

When a sample is to be taken, an isolation valve 36, having the form of a ball valve driven by an air motor, is opened for a period of time to allow effluent to flow through the pipe 52 to fill the cylinder up to a level higher that the lower end of the pipe 56 in the cylinder 40. Next the cylinder is pressurised by compressed air supplied from the control unit via one of the connectors 34 to the pipe 54 to eject surplus effluent through the pipe 56 leaving the quantity required in the metering cylinder. Lastly, a further air motor operated valve is opened to allow the effluent to be discharged through the distribution pipe 42 into one of the storage containers 44 in the magazine 48. The level to which the pipe 56 enters the cylinder 40 may be adjusted to set the volume of each sample transferred to one of the storage containers 44.

The indexing mechanism 46 is a pawl and ratchet. The pawl is driven by an air motor supplied with compressed air from the control unit over the line 58 and pulls the ratchet by an amount equal to the angular separation between the storage containers 44. The pawl slips over the ratchet on its return movement.

In some cases, the supply of effluent may not be under pressure and it may be desired to use a vacuum to suck effluent into the metering cylinder 40. In this case, it is necessary to monitor the level of effluent in the cylinder 40 to stop from being drawn into the vacuum pump.

In this case, it is not possible to use an electrical sensor to monitor when the level of affluent reaches the vacuum pipe but a fibre optic sensor may be used with safety. Light is introduced through the fibre and reflections caused by diffusion of the light in the effluent are detected to sense when the level of the effluent reaches the optic fibre. Alternatively, the effluent may obstruct the light path between two optic fibres. Once the effluent level reaches the optic fibre, the vacuum may be disconnected from the control unit.

Claims

CLAINS

1. An effluent sampling apparatus comprising a first unit for connection to a source of effluent and comprising at least one storage container and a remotely controlled valve for controlling the supply of effluent from the source to the storage container and a second unit which comprises an electrical control circuit and which in use is located at a distance from the first unit for remotely controlling the operation of the first unit, wherein the first unit contains no electrically operated components nor electrical sensing elements and is controlled by the first unit without the application of any electrical signal from the first unit to the second unit.

2. An apparatus as claimed in claim 1, wherein the second unit comprises an electrical control circuit incorporating a microprocessor.

3. An apparatus as claimed in claim 2, wherein electrically operated valves are provided in the second unit which are operated by the electrical output signals of the control circuit and serve to control the supply of a pressurised fluid along pipes contained in a cord leading to the first unit.

4. An apparatus as claimed in any preceding claim, wherein the first unit comprises metering means for controlling the quantity of effluent contained in each sample.

5. An apparatus as claimed in claim 4, wherein the metering means comprises a cylinder, a first pipe for supplying effluent to the cylinder, an overflow pipe for draining from the cylinder any effluent above a predetermined level and an outlet pipe for feeding the quantity of effluent below the overflow pipe to a storage container.

6. An apparatus as claimed in claim 5, wherein fluid operated valves remotely controlled from the second unit are provided in the respective pipes to control the operation of the metering means.

7. An apparatus as claimed in any of claims 4 to 6, further comprising a fibre optic sensor for sensing the level of the effluent in the metering cylinder.

8. An apparatus as claimed in any preceding claim, wherein the first unit comprises a plurality of storage containers so that several samples, taken over a prolonged sampling period, may be retained within the first unit.

9. An apparatus as claimed in claim 8, wherein a remotely controlled fluid operated indexing mechanism is provided to supply samples sequentially to the storage containers by way of a movable distribution pipe.

10. A sampling apparatus constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.