TESTING PERMEABILITY

Abstract: The permeability of a block of material is tested by compressing the material in a container (11) by means of a plunger (31) and applying fluid under pressure to the compressed material, measuring the flow or drop in pressure of the fluid so applied, the fluid being applied while the plunger (31) is still in position compressing the material. It is not necessary to remove the plunger (31) from the container (11) after the compression step and before the testing step and the fluid is preferably applied to the material through the plunger (31) through a conduit (35) whose downstream end is remote from the face of the plunger (31) contacting the material to be compressed. Material to be tested can be weighed in a weighing hopper (22) and transfer of the material into and out of the hopper (22) can be achieved by gravity, using bases of the weighing hopper (22) and of the container (11) which open when required.

Description: TESTING PERMEABILITY In testing the permeability of a block of material, it has been proposed to compress the material within a chamber by means of a plunger, withdraw the plunger completely from the container, insert a bung above the compressed material within the container, and test the permeability of the compressed material with the bung in position in the container. Permeability is tested by applying a fluid under pressure to the compressed material and testing the flow or the drop in pressure of the fluid so applied. According to the σresent invention, the material is compressed in a container by means of a plunger, and this plunger is retained in this position during the test permeability. It is not necessary to withdraw the plunger completely from the container, nor is it necessary to apply a separate bung to the container. This speeds up the procedure, and avoids disturbance of the compressed material. An example of the invention will now be described with reference to the accompanying drawings in which: Fig. 1 is a central section through a testing container, Fig. 2 shows the container of Fig. 1 at a loading station, Fig. 3 shows the container of Fig. 1 at a testing station. The container 11 shown in Fig. 1 has a main cylindrical portion 12 with an inwardly tapering mouth 13 at the top and a hinged bottom plate 14 provided with a central apertured portion 15 over which filter paper 16 can be laid for use during the test. The plate 14 is secured to the main portion 12 by magnetic means and the plate 14 can be opened by forcing it away from the main portion 12 until the magnetic attraction is in- sufficient to support the weight of the hinged plate and any contents within the main portion 12. Material to be tested is placed in a main hopper (not shown) and fed by a vibratory feed 21 to a weighing hopper 22 as shown in Fig. 2. The weighing hopper 22 is supported on a load cell 23 which controls operation of the vibratory feed 21 so as to weigh a measured amount of the sample material into the hopper 22, The empty cylinder 11 is placed beneath the hopper 22 and when the correct amount of material is present in the hopper 22, its bottom plate is open to allow the material to fall into the container 11, being guided by the tapered mouth 13 into the main cylindrical portion 12. The bottom plate 14 is held closed at this stage of the cycle. The material in the main cylindrical portion 12 is tamped according to a British Standard by tapping it with a solenoid armature (not shown). The container 11 is moved to the testing station as shown in Fig. 3 where a plunger 31 is lowered into the main cylindrical portion 12 to compress the material in the bottom of the portion 12. The plunger 31 has a main portion 32 which fits closely within the cylindrical portion 12 of the container 11 and is provided with a pair of O-rings 33 around an upper narrower section 34• A central air conduit 35 passes axially through the O-rings 33 and connects with six radial air passages 36 spaced around the junction between the two portions 3 arid 34 of the plunger. During the testing step, the plunger 31 is lowered into the container 11 to compress the material. With the plunger 31 its lowest position, air is supplied to the conduit 35 an passes through the compressed material and the filter paper 16 through the bottom of the container 11. The permeability of the compressed material is measured from the flow rate or pressure drop of the air supply. After the test, the container is moved to an unloading position at which the hinged bottom plate 14 is opened and a further tamping solenoid is provided to cause the material to fall out of the open bottom end of the container 11 to waste. If the permeability test is conclusive, the material remaining in the main hopper is also emptied to waste. If the test has to be repeated, then further material from the .main hopper is fed into the weighing hopper 22, a new filter paper 16 is placed in the cylinder 11 and the bottom plate 14 closed again, and the test is repeated. The construction of the plunger 31 with the outlets of the air supply 35 not in direct contact with the compressed material has the advantage that there is less chance of the material blocking the air outlets than if the air outlet were at the bottom of the plunger 31- The test can then be carried out with the plunger at its lowest position, whereas previous testing 9 - 4 - procedures involved a raising of the plunger a little above the compressed material in order to blow out an material blocking the air supply outlet and leading to less accurate results. The apparatus described above can be modified in many ways. For example, it is not necessary to have a pair of O-rings 33 > any number can be used. It is not necessary to weigh the material in a separate weighing hopper 22 - the container 11 could be placed on a weighing pan and material fed directly into it until the desired weight increase is recorded. The air supplied to the inlet 33 of the plunger is preferably dry, oil-free, compressed air at room temperature regulated to a pressure not exceeding 12 inches water gauge. A temperature sensing probe may be mounted in the hopper feeder responsive to the temperature of the material to be tested above a given threshold, and to prevent testing taking place if the material is above the threshold temperature. This will avoid damage occurring in the testing apparatus due to over-hot materials. The hopper feed may contain a mesh for regulating the maximum size of particles to be tested.

Claims: C L A I M S : 1. A method of testing the permeability of a block of material comprising compressing the material in a container by means of a plunger and, while the plunger is still in position compressing the material, applying a fluid under pressure to the compressed material and measuring the flow or drop in pressure of the fluid so applied. 2. A method as claimed in Claim 1 comprising applying fluid under pressure to the compressed material through a conduit in the plunger whose downstream end is at a face of the plunger not in contact with the material. 3- A method as claimed in Claim 1 or Claim 2 comprising feeding material into a weighing hopper until a desired weight is reached and then transferring the material from the hopper to the container before the plunger is placed in position. 4. A method as claimed in Claim 3 comprising placing the weighing hopper over the container, said transferring step comprising allowing the material to fall from the base of the hopper to the container. 5- A method as claimed in any one of the preceding claims comprising emptying the container after the measuring step by allowing the container contents to fall from its base. 6. Apparatus for performing the method of Claim 1 comprising a container having an open mouth, a plunger shaped to fit the internal bore of the container and movable from a retracted position to a position compressing the contents of the container, said plunger being provided with a fluid conduit whose downstream end is remote from the face of the plunger adapted to contact the contents of the container. 7- Apparatus as claimed in Claim 6 wherein said plunger has a first portion adapted to contact the contents of the container and a second portion remote from said contents and of a smaller cross-section than the first portion, the downstream end of said conduit being located at the junction between the first and second portions. 8. Apparatus as claimed in Claim 6 or Claim 7, wherein said container has a lower end which is releasable to allow the contents of the container to fall therefrom. 9. Apparatus as claimed in Claim 8, wherein said lower end is releasably held in position by magnetic means. 10. Apparatus as claimed in any one of Claims 6 to 9 comprising a weighing hopper for receiving material to be tested and means to transfer the contents of the weighing hopper to the container. 11. Apparatus as claimed in Claim 10 wherein said weighing hopper and said container are movable relative to one another to place the weighing hopper above the container, the transfer means being arranged to open the bottom of the weighing " hopper to release its contents into the container.

Inventors: KAY JOSEPH BRIAN, KAY, JOSEPH, BRIAN
Applicants: MICROSPAN PROCESS CONTROLS
Application year: 1986
Main classification: G01N15
IPC codes: G01N15