GB2232098A

GB2232098A - Magnetic removal of debris

Info

Publication number: GB2232098A
Application number: GB9005679A
Authority: GB
Inventors: David Brian Jones
Original assignee: Swansea University
Current assignee: Swansea University
Priority date: 1989-05-04
Filing date: 1990-03-13
Publication date: 1990-12-05
Anticipated expiration: 2010-03-13
Also published as: GB2232098B; GB9005679D0

Abstract

A method and apparatus are provided for the removal and analysis of a sample of ferrous debris from lubricated machinery. The apparatus comprises a plug 11 having a magnetic tip 12, provided with a close fitting removable sleeve 1 locatable thereon. The sleeve may be of Al, Cu, plastics or rubber and may be transparent. The sleeved tip is removed from the machinery and placed (Figure 3) in a sleeve extractor housing 19 having a magnet 16 and a receptacle 18 which may contain adhesive. The sleeve 1 is retained by the housing 19 when the tip is removed. The housing 19 may also be removed (Figure 5) to allow examination of the ferrous debris 15. <IMAGE>

Description

Removal of debris The present invention is concerned with means for removal of debris from magnetic plugs.

Removable magnetic plugs are frequently used in lubricated machinery and other systems employing moving fluids so as to provide a means for collection of (magnetic) debris; such plugs are periodically removed so that the debris can be removed from the plug and either viewed under a microscope or quantitatively measured (or both).

The conventional way of removing the debris from the plug is by means of a pressure-sensitive adhesive, which may be provided on tape, card, disc or the like; in use, the plug is grasped manually and rolled and pressed into the adhesive surface in order to transfer the debris from the plug to the adhesive. As can be readily envisaged, this is a quite messy and difficult operation, because the plug will inevitably be contaminated with oil.

We have now devised improvements in means for removing debris from such magnetic plugs used in lubricated machinery.

According to a first aspect of the invention, there is provided a method of removing debris from a plug provided with a ferro-magnetic tip which has been used in operation of lubricated machinery with a sleeve fitted snugly over said tip, with said sleeve exposed to lubricant present in said machinery, which method comprises removing at least said tip, together with said sleeve, from said machinery; placing said tip and fitted sleeve into a receptacle; removing said tip from said sleeve and depositing debris which has accumulated on said sleeve into said receptacle.

The deposition of debris into the receptacle may be before, during (which is preferred), or after removal of the tip from the receptacle.

At least part of the sleeve in the region of the magnetic tip is preferably not permanently ferro-magnetic (that is it may be non-ferromagnetic, or magnetically induceable so as to be temporarily ferromagnetic). It is particularly preferred that the abovementioned part of the sleeve is of non-ferromagnetic material (that is, material in which ferro-magnetism is not induceable).

In some embodiments, a magnet may be disposed in such a location that, when the plug tip and fitted sleeve are placed in the receptacle, a wall of the receptacle is located between the magnet and the fitted sleeve, so as to remove ferrous debris from the sleeve by magnetic forces and deposit the same in the receptacle. When the plug tip is removed from the sleeve following deposition of the accumulated debris in the receptacle, the tip may be removed from the sleeve either within or outside the receptacle.

The machinery from which the debris is removed in the method according to the invention may be, for example, a turbine, a diesel engine, a gearbox, aviation engine or the like.

The debris may be analysed whilst still in the above-mentioned receptacle; this is particularly preferred where the receptacle is provided with a substantially transparent portion.

The present invention further comprises apparatus for the removal of a sample of debris (typically ferrous debris) from lubricated machinery, which apparatus comprises: a) a plug for a wall of said machinery, at least part of said plug, or a member attached thereto, being removable from said machinery and being of a ferro-magnetic material; b) a sleeye, removably locatable on either said part or said member -such that said sleeve is close fitting thereon, said sleeve being arranged in use to be exposed to lubricant used in said machinery, at least a portion of said sleeve being preferably of a material which is not permanently ferromagnetic.

It is preferred that the plug is provided with a magnetic tip, in which case that portion of the sleeve which is preferably not permanently ferromagnetic is preferably arranged to be adjacent the tip when the sleeve is located on the plug.

Seen from another aspect, the present invention further comprises a sleeve, which is shaped and dimensioned to fit snugly over a magnetic tip of a plug to be fitted in lubricated machinery with the sleeve exposed to lubricant present in said machinery, at least part of the sleeve being not permanently ferromagnetic.

Apparatus according to the invention may further comprise a receptacle arranged to receive a sleeve as described above, in which case it is preferred that the sleeve and receptacle are provided with respective complementary shaped formations engageable with one another so as to retain the sleeve in place in the receptacle. It is preferred that engagement of the respective formations provided on the sleeve and receptacle substantially seals a zone between the sleeve and receptacle.

It is particularly preferred that the wall of the receptacle is of a substantially transparent material, in order to facilitate microscopic examination of the debris.

Seen from a further aspect, the present invention therefore comprises a hollow receptacle and a sleeve as described above received therein, the receptacle and the sleeve being provided with complementary shaped formations such that engagement of the formations substantially closes an open portion of the receptacle.

Reference will now be made to the accompanying drawings, in which: Figure 1 is a schematic sectional view of an exemplary sleeve for a magnetic plug for use according to the invention; Figure 2 is a schematic sectional view showing the sleeve fitted in place over a magnetic plug; Figure 3 is a schematic view of an assembly for separation of the sleeve from the plug; Figure 4 shows the removal of the plug from the sleeve; Figure 5 shows the receptacle for debris after the sleeve has been removed therefrom; Figure 6 shows an exemplary sleeve in place over a magnetic tip; and Figure 7 shows a sleeve as illustrated in Figure 6, when removed from a magnetic tip and inserted in a receptacle.

Referring to Figure 1, the sleeve, generally designated 1, comprises a tubular body member 2 with a smooth-surfaced cylindrical internal face 3, a stepped external face 4, a peripheral flange 5 around the open end 6 thereof, and a membrane 7 which forms the closed end of the sleeve.

The membrane 7 is relatively thin (typically about 0.025mm thick), compared with the wall thickness of the tubular body member (typically about 0.375mm), and may be of any suitable non-ferromagnetic material, such as aluminium, copper foil, plastics film, rubber or the like. The membrane 7 (and/or some other portion of the sleeve 1) can be transparent or translucent, if wished. It is preferred that the sleeve should be a unitary integral moulding, in order to avoid possible leakage around seams (and therefore contamination of the plug).

Referring to Figure 2, there is shown a magnetic plug housing 10 having passing therethrough a plug 11 with a protruding magnetic tip 12 which protrudes, typically into the sump of an engine, and is shrouded by a close-fitting sleeve 1 such as that illustrated in Figure 1. The fluid containing debris comes into contact with the sleeve 1 through port openings 13 in the housing 10.

When it is required to check on the debris 15 which has collected, the plug 11, complete with sleeve 1, is removed from the housing 10. For extracting the debris from the sleeve, the assembly shown in Figure 3 is used.

In this assembly, a magnet 16 is fitted into a support ring 17. A debris receiver 18 (shown as a pot in Figures 3,4 and 5) located in the support ring rests on the surface of the magnet 16. The plug 11, complete with sleeve 1, is carefully lowered into the sleeve extractor housing 19 (see Figure 3). The grub screw 20, fitted in the wall of the sleeve extractor housing, is adjusted to gently tighten against the sleeve 1. The plug 11 is then removed leaving the sleeve in position in the sleeve extractor housing 19 (see Figure 4).

The receiver 18 can typically be a pot (as shown in Figure 5), a slide coated with an adhesive, or an adhesive tape. The nature of the debris distribution on the receiver depends on the configuration of the magnet assembly 16; for example, a larger spread of the particles would be obtained by increasing the diameter of the magnet.

The sleeve extractor housing 19 can then be removed leaving the debris receiver, containing the debris, resting on the support ring 17 (see Figure 5). The receiver can then be removed from the support ring 17 and the debris examined and/or quantified as desired.

The sleeve locked in extractor housing 19 can then beremoved by loosening off the grub screw 20; the sleeve can bereused if'desired.

Alternatively, a sleeve such as that shown in Figures 6 and 7 may be used. (In these Figures, like parts to those of Figures 1 to 5 are denoted by like reference numerals).

Referring to Figure 6, the sleeve 1, which fits snugly over the magnetic tip 12, is provided with a peripheral rib 21 just below the flange 5. Referring to Figure 6, the sleeve 1 may be removed from the tip 12 and fitted into a generally cylindrical receptacle 18a having a peripheral groove 22 which is shaped, positioned and dimensioned to receive peripheral rib 21, typically as a snap-fit. When the sleeve is received in the receptacle as shown in Figure 7, a space 23 is left for receiving the debris 15.

The assembly of the sleeve and the receptacle can be transported to a suitable location for analysis, with the debris kept secure until analysis can take place.

It can be seen that the whole sequence of operations can be carried out cleanly, without the need to handle the oil-contaminated tip of the plug.

There is, furthermore, no need to wash the debris prior to removal of the plug (unlike in the conventional system when using adhesives). Finally, quantitative analysis can be more sensitive and more consistently accurate because the debris can be less widely spread out than it would be in the conventional system and more consistent in its distribution.

Claims

1. A method of removing debris from a plug provided with a ferro-magnetic tip which has been used in operation of lubricated machinery with a sleeve fitted snugly over said tip, with said sleeve exposed to lubricant present in said machinery, which method comprises removing at least said tip, together with said sleeve, from said machinery; placing said tip and fitted sleeve into a receptacle; removing said tip from said sleeve and depositing debris which has accumulated on said sleeve into said receptacle.

2. A method according to claim 1, wherein at least part of said sleeve in the region of the magpetic tip is not permanently ferromagnetic.

3. A method according to claim 2, wherein said part is non-ferromagnetic.

4. A method according to any preceding claim, wherein said debris is deposited in said receptacle during removal of said tip from said sleeve.

5. A method according to any preceding claim, wherein said debris is analysed while present in said receptacle.

6. A method according to any preceding claim, wherein said receptacle has a wall of substantially transparent material.

7. Apparatus for the removal of a sample of debris from lubricated machinery, which apparatus comprises: a) a plug for a wall of said machinery, at least part of said plug, or a member attached thereto, being removable from said machinery and being of a ferro-magnetic material; b) a sleeve, removably locatable on either said part or said member such that said sleeve is close fitting thereon, said sleeve being arranged in use to be exposed to lubricant used in said machinery.

8. Apparatus according to claim 7, wherein at least a portion of said sleeve is of a material which is not permanently ferromagnetic.

9. Apparatus according to claim 7 or 8, wherein said sleeve is provided with shaped formations which are arranged to engage with complementary shaped formations provided internally of a receptacle for receiving said sleeve.

10. A sleeve for a removable magnetic plug for lubricated machinery, which sleeve is shaped and dimensioned to fit snugly over a magnetic tip of a plug to be fitted in lubricated apparatus with said sleeve exposed to oil present in said apparatus, at least part of said sleeve being of a material which is not permanently magnetic.

11. A sleeve according to claim 10, which is provided with shaped formations arranged to engage with complementary shaped formations provided internally of a receptacle for receiving said sleeve.

12. A hollow receptacle having received therein a sleeve according to claim 11, said sleeve and said receptacle being provided with complementary shaped formations such that engagement of the formations substantially closes an open portion of said receptacle.

13. A hollow receptacle according to claim 12, wherein said sleeve has a wall of a substantially optically transparent material.

14. A method of removing debris from a plug, substantially as described herein with reference to the accompanying drawings.

15. Apparatus for the removal of a sample of debris from lubricated machinery, substantially as described herein with reference to the accompanying drawings.

16. A sleeve for a removable magnetic plug for lubricated machinery, substantially as described herein with reference to the accompanying drawings.

17. A hollow receptacle having received therein a sleeve according to claim 12, substantially as described herein with reference to the accompanying drawings.