GB2090665A - Detecting leaks in filters - Google Patents

Abstract

In an assembly in which a filter 1 is located in a barrier 2 separating an unfiltered flow 3 along a first duct from a filtered flow along a second duct 4 leakage is most likely to occur at the seating of the filter. To detect a leak tracer material is injected into the duct 3 and sampled at positions S1 S2, and a tubular probe 7 having a plurality of spaced apart apertures therein is arranged within a skirt 10 around the filter adjacent the downstream side of the filter with the apertures facing the filter. <IMAGE>

Description

SPECIFICATION Method and apparatus for detecting leaks in a filter assembly The present invention concerns a method and apparatus for detecting leaks in a filter assembly. In particular the invention concerns a means of testing individual filters in a multi-filter bank.

According to one aspect of the present invention a method of detecting a leak at a filter comprises locating a probe adjacent the downstream side ofthefil- ter, the probe having a configuration to receive flow streaming through leaks at the periphery of the filter and through the body of the filter, and screening the flow passing over the probe by a skirt depending from around the filter.

According to another aspect of the present invention there is provided apparatus for detecting leaks in a filter assembly which comprises a probe associated with each filter of the assembly, each probe being shaped to receive flow streaming through leaks at the filter and a skirt about each probe to channel flow from the associated filter across the probe.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a multi-filter assembly, and Figure 2 is a bottom plan view at the arrow A in Figure 1.

An assembly as shown in Figure 1 comprises four individual filters 1 which are located at openings in a barrier 2 separating the unfiltered flow along duct 3 from the filtered flow along duct 4. The filters 1 are accessible for positioning and changing through removable covers 5 in the wall of the duct 3. This arrangement is conventional and established art.

It is recognised that leakage at a filter is most likely to occur at the rim of the filter due to a faulty seal at the seat in the opening in the barrier 2. When a leak has been identified it is usual to attempt to resit the filter in a leak-tight manner by lifting the filter off its seat and repositioning. This is both time consuming and laborious.

In order to identify a leak a sample of a tracer is injected into the flow along the duct 3 at a position I upstream from the filters 1. Sampling occurs at positions St and S2 at opposite sides of the barrier 2, the samples being compared to indicate the magnitude of the leak. St and S2 are probe detectors capable of detecting the presence of the tracer in the flow and they must be located at positions where the tracer has thoroughly mixed with the fluid flow in the ducts. It is known that streaming occurs in the flow and consequently if St is closely adjacent I and S2 closely adjacent the filters lit is likely that the tracer will stream past the detector probes without being detected.

It is also possible, although less likely, for a leak to develop through the body of a filter away from its seat on the barrier. Again streaming from the leak will take place and thorough mixing with the main flow will only occur at some distance downstream from the filter.

To detect leaks and to overcome the difficulties arising from streaming, the invention employs a tubular sampling head 6 which is located adjacent the downstream side of each filter 1 and which is shaped to straddle the most likely leak stream flow paths. Preferably, each sampling head Swill comprise a peripheral portion having the same configuration as the rim of the filter and intersecting diagonal or cross portions passing beneath the centre of the filter. Both the peripheral portion and the cross portions are formed with spaced apart apertures directed towards the filter whereby to enable flow to enter the sampling head. The head is connected to a detector by means of a conduit passing through the wall of the duct.

In practice, a preferred configuration for the sampling head 6 is an S-shaped tube 7 as shown in Figure 2. The tube is such that its end portions are arranged beneath opposite side edges of the filter, a centre portion extends beneath the centre of the fiiter and the tube portions joining the ends and centre portions extend approximately half-way along the remaining opposite side edges of the filter. End 8 of the tube is closed and the opposite open end of the tube is connected to a conduit which passes through the wall of the duct 4 and leads to a detector. The S-shaped tube is formed with a plurality of spaced apart apertures 9 to receive leakage flow. To prevent distortion of the stream lines and to ensure as far as possible that any leakage flow will contact the tube, the tube is arranged within a skirt 10 which depends from the barrier about the outlet from each filter 1.A skirt 10 is associated with each filter 1 and screens the sampling head within the skirt from the flow passing through the remaining filters into the outlet duct 4.

The illustrated arrangement comprises four filters but it will be realised that the invention can be employed with any number of filters.

1. A method of detecting a leak at a filter comprising locating a probe adjacent the downstream side of the filter, the probe having a configuration to receive flow streaming from leaks at the periphery of the filter and through the body of the filter, and screening the flow passing over the probe by a skirt depending from around the filter.

2. Apparatus for detecting leaks in a filter assem bly comprising a probe associated with each filter of the assembly, each probe being shaped to receive flow streaming through leaks at the filter and a skirt about each probe to channel flow from the associated filter across the probe.

3. Apparatus as claimed in claim 2 in which each probe comprises a substantially S-shaped tubular member having spaced apart apertures to receive flow from the associated flilter.

4. A method of detecting a leak at a filter substantially as herein described with reference to the accompanying drawings.

5. Apparatus for detecing leaks in a filter assembly substantially as herein described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Method and apparatus for detecting leaks in a filter assembly The present invention concerns a method and apparatus for detecting leaks in a filter assembly. In particular the invention concerns a means of testing individual filters in a multi-filter bank. According to one aspect of the present invention a method of detecting a leak at a filter comprises locating a probe adjacent the downstream side ofthefil- ter, the probe having a configuration to receive flow streaming through leaks at the periphery of the filter and through the body of the filter, and screening the flow passing over the probe by a skirt depending from around the filter. According to another aspect of the present invention there is provided apparatus for detecting leaks in a filter assembly which comprises a probe associated with each filter of the assembly, each probe being shaped to receive flow streaming through leaks at the filter and a skirt about each probe to channel flow from the associated filter across the probe. The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a multi-filter assembly, and Figure 2 is a bottom plan view at the arrow A in Figure 1. An assembly as shown in Figure 1 comprises four individual filters 1 which are located at openings in a barrier 2 separating the unfiltered flow along duct 3 from the filtered flow along duct 4. The filters 1 are accessible for positioning and changing through removable covers 5 in the wall of the duct 3. This arrangement is conventional and established art. It is recognised that leakage at a filter is most likely to occur at the rim of the filter due to a faulty seal at the seat in the opening in the barrier 2. When a leak has been identified it is usual to attempt to resit the filter in a leak-tight manner by lifting the filter off its seat and repositioning. This is both time consuming and laborious. In order to identify a leak a sample of a tracer is injected into the flow along the duct 3 at a position I upstream from the filters 1. Sampling occurs at positions St and S2 at opposite sides of the barrier 2, the samples being compared to indicate the magnitude of the leak. St and S2 are probe detectors capable of detecting the presence of the tracer in the flow and they must be located at positions where the tracer has thoroughly mixed with the fluid flow in the ducts. It is known that streaming occurs in the flow and consequently if St is closely adjacent I and S2 closely adjacent the filters lit is likely that the tracer will stream past the detector probes without being detected. It is also possible, although less likely, for a leak to develop through the body of a filter away from its seat on the barrier. Again streaming from the leak will take place and thorough mixing with the main flow will only occur at some distance downstream from the filter. To detect leaks and to overcome the difficulties arising from streaming, the invention employs a tubular sampling head 6 which is located adjacent the downstream side of each filter 1 and which is shaped to straddle the most likely leak stream flow paths. Preferably, each sampling head Swill comprise a peripheral portion having the same configuration as the rim of the filter and intersecting diagonal or cross portions passing beneath the centre of the filter. Both the peripheral portion and the cross portions are formed with spaced apart apertures directed towards the filter whereby to enable flow to enter the sampling head. The head is connected to a detector by means of a conduit passing through the wall of the duct. In practice, a preferred configuration for the sampling head 6 is an S-shaped tube 7 as shown in Figure 2. The tube is such that its end portions are arranged beneath opposite side edges of the filter, a centre portion extends beneath the centre of the fiiter and the tube portions joining the ends and centre portions extend approximately half-way along the remaining opposite side edges of the filter. End 8 of the tube is closed and the opposite open end of the tube is connected to a conduit which passes through the wall of the duct 4 and leads to a detector. The S-shaped tube is formed with a plurality of spaced apart apertures 9 to receive leakage flow. To prevent distortion of the stream lines and to ensure as far as possible that any leakage flow will contact the tube, the tube is arranged within a skirt 10 which depends from the barrier about the outlet from each filter 1.A skirt 10 is associated with each filter 1 and screens the sampling head within the skirt from the flow passing through the remaining filters into the outlet duct 4. The illustrated arrangement comprises four filters but it will be realised that the invention can be employed with any number of filters. CLAIMS

1. A method of detecting a leak at a filter comprising locating a probe adjacent the downstream side of the filter, the probe having a configuration to receive flow streaming from leaks at the periphery of the filter and through the body of the filter, and screening the flow passing over the probe by a skirt depending from around the filter.

2. Apparatus for detecting leaks in a filter assem bly comprising a probe associated with each filter of the assembly, each probe being shaped to receive flow streaming through leaks at the filter and a skirt about each probe to channel flow from the associated filter across the probe.

3. Apparatus as claimed in claim 2 in which each probe comprises a substantially S-shaped tubular member having spaced apart apertures to receive flow from the associated flilter.

4. A method of detecting a leak at a filter substantially as herein described with reference to the accompanying drawings.

5. Apparatus for detecing leaks in a filter assembly substantially as herein described with reference to and as illustrated in the accompanying drawings.