GB2181559A

GB2181559A - Pellet durability tester

Info

Publication number: GB2181559A
Application number: GB08521453A
Authority: GB
Inventors: John David Payne
Original assignee: Holmen Chemicals Ltd
Current assignee: Holmen Chemicals Ltd
Priority date: 1985-08-29
Filing date: 1985-08-29
Publication date: 1987-04-23
Also published as: GB8521453D0; GB2181559B

Abstract

In a pellet durability tester the pellets to be tested enter a test chamber 2 from the pellet production line via a chute 7; a previously vertical sieve disc 6 is then rotated to the horizontal and thereby closes the chamber; after optional partial drying of the pellets, the test chamber 2 and enclosed pellets are weighed by the load cell 8; the pellets are then vigorously agitated e.g. by blower 5 or compressed air and broken pellets, pieces of meal etc., pass through the sieve disc and out of the pellet tester; after agitation the test chamber and pellets are re-weighed and the difference in weight before and after agitation is used to calculate the pellet durability. <IMAGE>

Description

SPECIFICATION Pellet durability tester The present invention relates to a pellet durabilityte- ster, in particularto an automated pellet durability tester four use on a production line in the manufacture of animal feed pellets.

Lignin chemical products are commonly used in the animal feed industry as binders to improve the physical qualities of pelleted feedstuffs and to improve efficiency of manufacture. The production of good physical quality pellets is necessary to reduce wastage, maximisefeed intake and improve efficiency of feed conversion.

Physical quality of pelleted feedstuffs is quantified by measuring "pellet durability" and one generaily accepted method of measuring this is by means of a "tumbling can" which tumbles 500 grammes of pellets for 10 minutes, the weight of whole pellets remaining being expressed as a percentage of the initial weight. This method was devised by Professor Pfost of Kansas State University in the 1960's as a means of measuring the amount of pellet degradation which takes place during mechanical handling in the feed mill. However, it does not take account ofthe degradation which takes place between leaving the mill and being delivered to the customer because in the 1960's the majority of feed was delivered in 25 kilo bags and was therefore not subject to the rigours of bulk handling which today's pellets have to withstand.The adventof bulk transportation now means that the majority of pelleted feedstuffs is delivered by a pressurised bulktankerand blown into the farmer's store which in turn puts greater demands on the feed mill to produce tougher pellets.

In orderto provide the feedmill with information on the sort of condition its pellets would be in on reaching the customer's store,the present inventor developed a tester which would simulate the most rigorous treatment which the pellets would generally undergo, i.e. that of pneumatic handling. This tester circulated a 100 gramme sample of pellets in an airstream for two minutes during which time the pellets negotiated a number of right angle bends and impinged repeatedly upon a hard surface before being deflected into a box at the base of the machine where whole pellets were separated from the broken-off particles of meal.

Pellet-durability testers with a simple operational procedure and the minimum of moving parts are, of course, desirable since they are generally less expensive to produce and more reliable in the continous, sometimes 24 hour a day operation, in which such testers are used.

The present invention relates to pellet testers and proposes a number of features which can be used alone or in combination in a pellet durability tester.

Thus a first aspect of the invention provides a pellet durability tester of a type which determines the durability of pellets by subjecting them to agitation and establishing their durability by sieving the agitated pellets, which tester comprises a chamber in which in use the pellets are agitated, a movable partition which in one position allows whole pellets to enter and leave the chamber and in another position acts as a sieveto allowfines and small piecesofpelletto leavethechamberandweighing meansforestablishing the durability ofthe pellets.

Asecond aspect of the invention provides a pellet durability tester of a type which determines the durability of pellets by subjecting them to agitation and establishing their durability by sieving the agitated pellets, which tester comprises a chamber in which in use the pellets are agitated, and from which fines and small pieces of pellet are removed, and means forweighing the chamber containing the pellets.

As will become apparent from the following description both aspects of the invention may be embodied bya particulartester.

The separating means in the second aspect of the invention may be a moveable partition which in one position allows whole pellets to enterand leave the chamberand in another position only allow pieces of pellet through.

As in the second aspect of the invention the means for weighing the pellets in the first aspect ofthe invention may be arranged to do this by weighing the chamber.

In use of the first aspect of the invention, the movable partition is first in a position such that the pellets may pass through. The chamber is filled with there- quired quantity of pellets to be tested and the chamber containing the pellets is weighed. The movable partition is then moved to a position in which only fines and small particles may pass through and the pellets inside the chamber are vigorously agita ted for the required length oftime, e.g. one halfto two minutes. The debris, i.e. broken pellets, meal, etc., pass through the partition leaving the whole pellets inside the chamber. After the agitation is completed, the chamber is re-weighed and the difference in weight before and after agitation is used to calculate the "pellet durability"; the weighing and calculation may be done electronically.

When a pellet tester is used on-line, it may be inconvenientto have to dry the pellets after pressing and priorto testing in the tester. Accordingly, a further aspect ofthis invention provides an on-line pellettesterwhich is provided with means for at least partially drying pellets straight from the pellet press priorto testing them in the pellettester.Thusina third aspect the invention provides an automated pellet durability tester which incorporates means for at least partly drying pellets prior to testing.

Provided the conditions underwhich each batch of pellets is dried are consistent from sampleto sample, for a given plant it should be possible to determine experimentally a one-to-one relationship between the numerical results obtained with such partially dried and tested pellets and sample batches of pellets which have been fully dried and cooled.

The pellet-durability tester may be controlled by a computer used for controlling the operation of the pellet production line. The computer may control ac tuators within the tester for operating the movable partition and the agitating means and also receive signals from the load cell indicating the weight ofthe sample. Alternatively, the tester may be an "intelligent" tester i.e. it may be provided with its own in ternal control circuitry which co-ordinates the operation ofthe actuators, handles analogue to digital conversion of the pellet weights and communicates with the production line computer via a data link.

The invention will be further described byway of example with referencetothe accompanying fig- ures: Figure 7 shows a side elevation of one embodimentofthe present invention.

Figure2showsthe end elevation viewed from Aof the embodiment of Figure 1.

The pellet-durability tester, generally designated 1 is positioned on a production line such that sample batches offeed pellets are taken offthe production line (not shown) and enterthe testervia a chute 7 and aftertesting the pellets, pieces of pellets and fines are removedfromthe bottom ofthetesterand returned to the production line.

The pellet-durability tester 1 comprises an outer housing 11 within which is a funnel shaped test chamber 2 with an imperforate side-wall. Aslide 3 is slideable to fully or partly open a gap 4 between the chamber bottom and an airsource 5, in this case a blower unit which may have a variable speed. When the gap 4 is open the contents ofthetest chambercan be agitated by means ofthe blowerunit.The moveable partition 6, in this case a sieve disc, is supported above the chamber in a manner such as to be rotatable about a diameter between a vertical position in which it permits whole pellets to enterthe chamberfrom a chute 7 and a horizontal position in which it prevents their leaving intact.The sieve disc 6 is pivoted from its starting, vertical position to the horizontal position by means of a pneumatic actuator 12. The test chamber 2 and slide 3 are supported by a load cell 8 on support brackets 1 4which weighs the chamber and its contents.

Once a sample batch of pellets has been loaded into the test chamber via the chute 7, they may be dried or partially dried before testing if desired by starting the blower unit 5 and positioning slide 3 in its slid fully open position; the pellets gently "boil" in the warm airstream,which cures them and removes "fines" which are blown through the sieve disband out ofthetester e.g. via the gap 9 backto the feed mill's production process. After, say, about one minute (which time may be programmable to be an exact period of e.g. 30 seconds to 3 minutes) the slide 3 is closed and the blower5 switched off. The load cell 8 then weighs the test chamber, slide and dried or partially dried pellets.

The blower unit5 is then restarted and the slide 3 is partially opened such thatthe airflow produced in the test chamber bythe blower unit is greatly increased from that used to dry the pellets. The pellets circulate rigorously inside the test chamber for, say, 30 seconds to 2 minutes (the exact period of this agitation may be programmable). The pieces of broken pellets, meal and fines etc., are blown through the sieve disc 6 and fall out of the tester via the gap 9 back to the feed mill's prodcuction process.Whenthere- quired amount of agitation hastaken place, the slide 3 is closed and the blower unit 5 is switched off. The load cell 8 is then used to re-weigh the chamber, slide and pellets remaining inside the chamber.The difference in weight of the pellets in percent is taken to calculate the durability of them.

Once the second weighing is complete, the sieve disc 6 may be rotated to be in a vertical position again, the blower 5 may be started up again and when the slide 3 is fully opened the remaining pellets in the test chamber are blown out of the chamber and out of the pellet tester leaving the tester ready to ac ceptthe next sample of pellets.

Preferably both the actuator 12 for the sieve disc6 and the actuatorforthe slide 3 are driven by a small geared motor 13 as shown in Figure 2. The sieve disc, its support mounting and actuator as shown are completely independent ofthe test chamber so that they are not weighed bythe load cell. However, the slide 3 as shown is carried by the test chamber and therefore is included in the load cell's measurement.

Preferablythe slide is driven electricallysothatthere is no bias as there would be from an air pipe had it been driven pneumatically. Optionally the nozzle opening of the blower unit 5 may also be controlled by a slide which may work in unison with the slide 3.

As shown in Figure 2the load cell 8 has a housing 15 around itto preventthe build up of dust in the load cell.

Other methods of agitating the pellets inthetest chamber may also be used e.g. a source of compressed air in place ofthe blower unit 5 or means four agitating the chamber itself. As shown in Figure 2 the blower unit 5 is supported underneath the test chamber by a duct 16 with louvres 17 on the side of the duct which forms part of the outer housing.

The movable partition 6 may be rotatable as shown in the figure or e.g. slideable or pivotable.

Preferably, as shown in the figure, air is blown into the test chamber 2 via a nozzle 10. As the air leaves the nozzle 10 it expands rapidly thus creating a negative pressure upstream from the nozzle head causing air and pellets to be drawn into this region. The pressure head below the nozzle 10 is converted into a velocity head above it and this venturi action makes it possible to maintain a constant re-circulation of pellets in the airstream. Preferably the blower is arranged so that its windings, which get hot during operation, are outside and so do not heat the air being discharged into the test chamber. For this purpose the blower may be of the axial flowtype.

Claims

1. A pellet durability tester of a type which determines the durability of pellets by subjecting them to agitation and establishing their durability by sieving the agitated pellets, which tester comprises a chamber in which in use the pellets are agitated, a movable partition which in one position allows whole pellets to enter and leave the chamber and in another position acts as a sieve to allowfines and small pieces of pellet to leave the chamber and weighing means for establishing the durability ofthe pellets.

2. Atester as claimed in claim 1 in which the movable partition is a pivotable, rotatable orslideable sieve.

3. Atester as claimed in claim 1 or 2 in which the weighing meansweighsthechambercontainingthe pellets.

4. A pellet durability tester of a type which deter mines the durability of pellets by subjecting them to agitation and establishing theirdurability bysieving the agitated pellets, which tester comprises a chamber in which in use the pellets are agitated, and from which fines and small pieces of pellet are removed, and means forweighing the chamber containing the pellets.

5. Atesteras claimed in any one of claims 1 to 4in which the pellets are agitated by an airflow.

6. Atester as claimed in claim 5 which comprises a sliding member between the chamber and a source which produces the airflow, the position of the sliding member controlling the flow ofairto the chamber.

7. Atester as claimed in claim 6 in which the sliding member has three positions: where the test chamber is open, approximately half open or closed to the airflow.

8. Atesteras claimed in anyone of claims Sto 7 in which the airflow enters the test chambervia a nozzle inside the test chamber.

9. Atester as claimed in any one of claims 1 to 8 in which the chamber is supported by a load means which is capable of weighing the chamber, its contents and, if present, the sliding member.

10. A pellet durability tester constructed and arranged to operate substantially as described herein with reference to and as iilustrated in the accompanying drawings.