WO1990002598A1

WO1990002598A1 - Filter assembly

Info

Publication number: WO1990002598A1
Application number: PCT/GB1989/001044
Authority: WO
Inventors: Susanne Phyllis Hunter
Original assignee: Process Scientific Innovations Limited
Priority date: 1988-09-09
Filing date: 1989-09-06
Publication date: 1990-03-22
Also published as: GB2222535A; GB8821239D0

Abstract

A filter assembly comprises a cartridge (18) containing a filter or a body of adsorbent material and a filter head (17) into which the cartridge (18) is fitted. The cartridge (18) has an inlet port defined by spigot (22) and a body (24) of porous material in the spigot (22) that can trap liquid droplets entrained in a gas stream entering the head (17). The body (24) of porous material is impregnated with a dye responsive to the presence of liquid trapped by the trapping means by changing colour, as is a wick (26) communicating therewith. Colour change at the wick (28) is viewed from outside the filter head (17) through lens (30). By this means the presence of droplet contamination in the gas stream e.g. by reason of an abnormality upstream of the filter head (17) can either be made visible directly from outside the housing or can be detected by remote sensing means. The invention is particularly, but not exclusively, applicable to the detection of oil mist or droplets in an air stream from a compressor.

Description

FILTER ASSEMBLY

This invention relates to a filter assembly.

More particularly the invention relates to a filter assembly . comprising a cartridge containing a filter or a body of adsorbent material and a filter housing into which the cartridge is fitted, said cartridge having an inlet port and liquid droplet trapping means in the inlet port, and said filter housing having means responsive to the the presence of liquid trapped by the trapping means by changing state, and means for providing an indication outside the filter housing whether the state change has occurred .

By this means the presence of droplet contamination in a gas stream entering the filter housing by reason of an abnormality can either be made visible directly from outside the housing or can be detected by remote sensing means. The invention is particularly, but not exclusively, applicable to the detection of oil mist or droplets in an air stream from a compressor.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a diagram showing an airline having a coalescing filter in series with an adsorption element; and

Figure 2 is a section of a filter head showing portions of a cartridge attached thereto.

In Figure 1, an airline for breathing air or for a building air-conditioning system has a compressor 10 whose output is fed by line 11 to a first filter head 12. A pleated or moulded microporous filter cartridge 13 e.g. as described in our patent No's 1603519 and 1557821 is fitted to the head 12 and is contained within bowl 14. Droplets of compressor oil entrained with the air stream are coalesced by the element 13 and drain down the outside thereof to the bottom of the bowl 14, from which coalesced oil is drained through valve 15. The partly purified air stream which contains oil vapour passes via line 16 to a second filter head 17 to which is attached an adsorbent cartridge 18 in bowl 19 and containing activated carbon or other adsorbent material e.g. as described in our patent No. GB-B-2019068 The disclosure of these specifications is incorporated herein by reference. Purified air flows from air-line 20.

A problem associated with the above arrangement is that the bowl 14 is normally of metal or other opaque material and it is impossible to detect by external inspection whether the coalescing cartridge 13 is present. If it is absent or malfunctioning due to O-ring or filter failure, the oil mist may rapidly overwhelm the adsorbent cartridge 18 which will become ineffective, and oil may pass through line 20 and contaminate vulnerable portions of downstream equipment such as valves.

In Figure 2, the filter head 17 has an inlet side including a vertical port 21 in which spigot 22 of the adsorbent cartridge 18 is a push fit. A generally cylindrical body 24 of porous material such as plastics foam fits into spigot 22 and protrudes upwardly into the port 21. It is impregnated with an oil-sensitive dye. The air stream entering the cartridge 18 has to pass through the body 24 which in the event of oil droplet contamination will rapidly become impregnated with oil, activating the dye. A small aperture 26 through the head 17 receives a wick 28 inserted at one end into the body 24 and inserted at its other end in cavity 34 of prismatic end portion 36 of clear lens 30. The wick 28 may also be impregnated with the oil-sensitive dye. The lens 30 is a screw fit into aperture 31 of the head 17 to which it is fluid-tigh ly sealed by means of O-ring seal 32.

The prismatic portion 36 of the lens 30 views the cavity 34 and will normally see the colourless end of the wick 28. But if oil droplets appear at port 21, oil will flow from the body 24 through wick 28 whose far end will change colour. Because of the prismatic shape of lens portion 36, the whole outer face of the lens 30 will change colour, giving a visible warning at the exterior of the filter head 17.

Various modifications may be made to the embodiment described above without departing from the invention. For example, instead, of the lens 30, the wick 26 may be viewed by a remote sensing device. Such a device could include a photodiode to illuminate the wick 26 and a photocell to view the wick 26 in reflection, a change in the state of the photocell indicating a colour change of the wick 26 and hence warning of the presence of oil.

Claims

1. A filter assembly comprising a cartridge containing a filter or an adsorbent material and a filter housing into which the cartridge is fitted, said cartridge having an inlet port and liquid droplet trapping means in the inlet port, and said filter housing having means responsive to the the presence of liquid trapped by the trapping means by changing state, and means for providing an indication outside the filter housing whether the state change has occurred.

2. The assembly of claim 1, wherein the cartridge contains activated carbon adsorbent.

3. The assembly of claim 2, further comprising on the upstream side thereof a coalescing filter for coalescing droplets or mist of the liquid in a gas stream before the gas stream passes to the adsorbent.

4. The assembly according to any preceding claim, wherein the liquid droplet trapping means is a body of porous material in the inlet port.

5. The assembly of claim 4, wherein wick means leads from the body of porous material.

6. The assembly of claim 4 or 5, wherein the body of porous material is impregnated with a liquid-sensitive dye.

7. The assembly of any of claims 4-6, wherein the wick means is impregnated with an oil-sensitive dye.

8. The assembly of any of claims 5-7, wherein a free end of the wick means is visible from outside the filter housing through a lens.

9. The assembly of claim 8, wherein the wick means is received in a cavity of the lens, and a prismatic formation of the lens views the cavity.

10. The assembly of any preceding claim, wherein the filter housing comprises a filter head to which the filter cartridge fits.

11. The assembly of any of claims 1-9, wherein the filter housing comprises a filter head to which the filter cartridge fits and a filter bowl into which the filter cartridge fits and which is a removable fit to the filter head .

12. A filter assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings .

13. A filter or adsorbent assembly for a fluid stream having means for detecting droplets appearing at an inlet side of the assembly and means for indicating when the droplets have been detected.