GB2034667A

GB2034667A - Sampling Granular Material

Info

Publication number: GB2034667A
Application number: GB7937774A
Authority: GB
Original assignee: Rowell A S
Current assignee: Rowell A S
Priority date: 1978-11-06
Filing date: 1979-10-31
Publication date: 1980-06-11
Also published as: GB2034667B

Abstract

An apparatus for extracting a sample of flowable material as it falls under gravity in a stream includes a sample collector (8) which is moved through the stream rapidly and symmetrically in an arc about an axis located centrally in the stream. The sample collector is discharged by opening a door (16) when it has passed through the stream. <IMAGE>

Description

SPECIFICATION Sampling Method and Apparatus My invention relates to a method of and apparatus for taking a sample of flowable material from a falling stream. The invention is particularly applicable to the sampling of particulate material such as minerals.

In the supply of coal for example to generating stations it is required to take occasional samples in order to check the ash and moisture content upon which the value of the coal to some extent depends. It is convenient to extract a sample of the coal as it falls in a stream from, say, an upper to a lower conveyor, but as there is a tendency for the coal to vary in some regard, such as composition or particle size, transversely to the stream, it is desirable, in order to minimize bias, to take as the sample a complete length portion of the stream.

In an attempt to meet the above requirement, a sampling apparatus has been used which comprises a sample bucket which is passed rapidly through a stream of coal by means of a horizontal conveyor, inverted to deposit the collected sample at a receiving station spaced from the stream and is returned, inverted, through the stream to its stationary point by a return reach of the conveyor. This equipment is, however, expensive to manufacture and occupies a considerable space and it is an object of the present invention to provide a method and apparatus which to some extent avoid these disadvantages, whilst other advantages of the invention will appear as the description proceeds.

According to one aspect of the invention there is provided a method of taking a sample of flowable material falling in a stream comprising passing a collector through the stream in an arcuate path about an axis in or vertically above the stream. The axis is preferably in or vertically above the centre of the stream and is particularly advantageously arranged in rather than above the stream. The collector may be passed forwardly and backwardly in the path to collect a double sample. The method preferably also comprises the step of discharging the collected sample at a receiving station spaced from the stream.

The flowable material may comprise mineral solids such as coal.

According to a further aspect of the invention there is provided apparatus for taking a sample of flowable material falling in a stream comprising a collector and means for moving the collector about an axis arranged or for arranging in or vertically above the stream whereby the collector passes through and collects a portion of the stream. The axis may be above or, preferably, in the centre of the stream.

The apparatus may further comprise means for discharging collected material from the collector at a receiving station spaced from the stream. The discharging means preferably comprises a door in the collector and means for opening the door above the receiving station, and the arrangement is preferably such that the collector is passed through the stream from the side adjacent the receiving station and returns through the stream before the door is opened whereby a double sample is collected and subsequently discharged.

Barrier means may be provided to prevent inadvertant displacement of stream material to the receiving station. The means may comprise a barrier plate movable about the same axis as the collector between a first position blocking the passage of stream material to the receiving station and a second position allowing movement of the collector to a position above the receiving station.

The apparatus may further comprise funnel means for reducing in use the cross-sectional area of the stream.

Embodiments of my invention will now be described by way of example and with reference to the accompanying drawings of which: Fig. 1 shows the apparatus in side elevation; and Fig. 2 is a section on line Il-Il of Fig. 1.

The apparatus comprises a housing 1 provided with a ractangular inlet opening 2 at the top, an outlet 3 at the bottom and having to one side of the discharge opening a screw conveyor 4 for the lateral discharge of collected samples.

The apparatus is for location below the discharge end of a conveyor belt on which mineral solids such as coal are continuously being conveyed and particularly so that the solids falling from the conveyor pass in a stream into the inlet opening 2. Immediately below the inlet opening is an inner funnel comprising a pair of opposed plates 5 which converge to somewhat less than half the width of the opening 2 As shown in Fig. 2 the side plates 6 of the funnel are vertical and parallel to the walls of the housing 1. Between these walls and the adjacent side plates 6 of the funnel are mounted a pair of stub shafts upon which a sample collecting bucket 8 and a barrier door 9 are pivotally mounted respectively on arms 10 and 11.

Under the action of an electro-hydraulic ram 12 the bucket 8 is swung in a clockwise direction from the position shown in Fig. 1 so that it passes through the stream of mineral solids leaving the funnel and reaching a position shown in phantom lines in Fig. 1 with the supporting arms approximately horizontal. As the bucket passes through the stream, its top being open, the solids enter the bucket so that in effect a length portion of the stream is diverted to a position above the discharge conveyor 4. The stub shafts 7 are arranged centrally of the funnel so that the open mouth of the bucket passes through the stream symmetrically. The object of this arrangement is to minimize bias in sampling material from a stream which is not homogeneous across its width. With the same object in mind the swing of the bucket across the stream is effected in a short time.

The leading wall 13 of the bucket is inclined backwardly from the bucket mouth with respect to the clockwise movement described above so that as the bucket moves through the stream of mineral particles, as few particles as possible will be deflected above the top of wall 14 separating the discharge opening 3 from the sample conveyor 4.

Further to ensure that material other than that collected in the bucket is not diverted from the stream over the wall 14, the barrier door 9 rests under the influence of gravity with its lower edge in contact with the top of the wall 14 so as effectively to increase the height of the enclosure in which the sample conveyor operates.

As the bucket swings beyond the stream to the position shown in phantom lines in Fig. 1, a projection on arm 10 of the bucket engages with a corresponding projection on arm 11 of barrier 9, so that the barrier door is carried ahead of the bucket allowing the bucket to pass over the top of wall 14.

The trailing wall 1 6 of the bucket is pivoted at the mouth of the bucket to form a door which is kept closed by spring 1 5 as the bucket moves through the stream. However, when the bucket reaches a position above the sample conveyor 4, the door is opened against the action of the spring 1 5 and material contained in the bucket is released, the door 16 acting as a guide to ensure that none of the material passes to the opening 3.

In an alternative embodiment the door 1 6 of the bucket is pivoted by torsion bushes and the spring 1 5 is dispensed with. When, under the action of the reverse movement of the ram 12 the bucket is returned in an anti-clockwise direction to the position shown in Fig. 1, the barrier 9 which is freely pivoted on the stub shafts 7 returns under gravity to engage against the top of wall 14.

In the preferred method of operating with the apparatus described the sampling cycle begins with the bucket in a rest position above the sample conveyor 4 having its door 16 open and holding barrier 9 in elevated position. At predetermined intervals dictated by the sampling requirements the ram 12 is caused to swing the bucket anti-clockwise through the stream to the position shown in Fig. 1, the door 1 6 closing as the bucket swings and the barrier 9 being allowed to fall against the top of wall 14. The capacity of the bucket is arranged to be such that it is less than half filled by a single pass through the stream.The bucket is then swung back to its original position, collecting a further sample of mineral as it passes through the stream, and the double sample is discharged on the opening of door 16 whereupon conveyor 4 removes it for sampling as required. In another embodiment of the invention the screw conveyor is replaced by a conveyor belt. Stream material which is not collected by the bucket passes through the apparatus and is discharged through the opening 3. The width of the bucket mouth corresponds to the width of the discharge opening of the funnel, both being, if so required by sampling requirements not less than 2 times the maximum particle size in the stream of material. It is possible to design a sampler on this principle to cope with larger particle sizes than can be handled with existing sampling machines.

By sampling on both clockwise and anticlockwise swings any bias caused by direction is cancelled out. Compared with existing machinery the unit, which is essentially self-contained is more robust, has fewer moving parts and is thus more easily maintained.

Claims

1. A method of taking a sample of flowable material falling in a stream comprising passing a collector through the stream in an arcuate path about an axis in or vertically above the stream.

2. A method according to Claim 1 in which the axis lies in or vertically above the stream. The axis is preferably in or vertically above the centre of the stream.

3. A method according to Claim 2 in which the axis lies in the stream.

4. A method according to any one of Claims 1-3 wherein the collector is passed forwardly and backwardly in the path to collect a double sample.

5. A method according to any one of the preceding claims and further comprising the step of discharging the collected sample at a receiving station spaced from the stream.

6. Apparatus for taking a sample of flowable material falling in a stream comprising a collector and means for moving the collector about an axis arranged or for arranging in or vertically above the stream whereby the collector passes through and collects a portion of the stream.

7. Apparatus according to Claim 6 in which the axis lies or is arranged for lying in or vertically above the stream. The axis is preferably in or vertically above the centre of the stream.

8. Apparatus according to Claim 7 in which the axis lies or is arranged for lying in the stream.

9. Apparatus according to any one of Claims 6-8 and further comprising means for discharging collected material from the collector at a receiving station spaced from the stream.

10. Apparatus according to Claim 9 wherein the discharging means comprises a door in the collector and means for opening the door above the receiving station.

1 Apparatus according to Claim 10 arranged so that the collector is passed through the stream from the side adjacent the receiving station and returns through the stream before the door is opened whereby a double sample is collected and subsequently discharged.

12. Apparatus according to any one of Claims 6-11 1 wherein barrier means are provided to prevent inadvertant displacement of stream material to the receiving station.

13. Apparatus according to Claim 12 wherein the barrier means comprise a barrier plate movable about the same axis as the collector between a first position blocking the passage of stream material to the receiving station and a second position allowing movement of the collector to a position above the receiving station.

14. Apparatus according to any one of Claims 6-1 3 and further comprising funnel means for reducing in use the cross-sectional area of the stream.

15. A method of taking a sample of flowable material falling in a stream substantially as described with reference to the drawings.

1 6. Apparatus for taking a sample of flowable material falling in a stream substantially as described with reference to the drawings.