Fuel filter with air bleed valve

Abstract

A fuel filter 1 comprising: a housing 3 for a filter element 2, a fuel inlet 6 and outlet 7, an air bleed valve 30 for venting air from the housing, and a drain valve 50 for draining water from the ho

Description

The present disclosure relates to a fuel filter having an air bleed valve. Background to the Disclosure A fuel filter may be used to remove contaminants from a flow of fuel. A fuel filter may contain a filter element that carries out the filtering function with the flow of fuel passing from a fuel inlet to a fuel outlet via the filter element. During use water may separate from the fuel. The fuel filter may be provided with a drain valve for draining water from the fuel filter. The drain valve is typically disposed at the bottom of the filter housing and opened via some type of threaded opening with water then draining under the action of gravity. During use the fuel filter is typically a closed system. However, a housing of the fuel filter may need to be opened from time to time to allow replacement of the filter element. Following filter element replacement, air may become trapped within the housing of the fuel filter that may negatively affect filtering performance. The ability to be able to bleed air from the system is therefore desirable. One option is to hand prime the system using a manual hand primer. However, this is time consuming and labour-intensive. For this reason it is known to provide an air bleed valve at the top of the housing to allow air to be bled from the housing interior. Typically, such air bleed valves comprise a threaded hole in an upper part of the housing that receives a hollow banjo bolt and an associated O-ring seal. Unscrewing the banjo bolt provides a vent path for air to bleed out of the housing driven by the pressure of fuel entering the housing via the fuel inlet. However, bleeding the air can lead to emission of fuel out of the top of the fuel filter and fouling of the outer surfaces of the fuel filter by the fuel because a user will only be aware that the air is fully bled from the interior of the housing once fuel has started to be emitted from the air bleed valve. This problem can lead to increased time and effort when performing maintenance on the fuel filter including, for example, replacing the filter element. It may also lead to contamination of the surroundings with fuel. Summary of the Disclosure An embodiment of the present disclosure provides a fuel filter comprising: a housing for containing a filter element; a fuel inlet; a fuel outlet; an air bleed valve for venting air from an interior of the housing; and a drain valve for draining water from the interior of the housing; the fuel filter being configured to define a flow path for fuel that passes from the fuel inlet to the fuel outlet; wherein the drain valve is configured to have: - a closed configuration in which water cannot drain via the drain valve and air cannot vent from the interior of the housing via the air bleed valve; an air bleed configuration in which air can vent from the interior of the housing via the air bleed valve but water cannot drain via the drain valve; and - a water drainage configuration in which water can drain via the drain valve and air can vent from the interior of the housing via the air bleed valve. Another embodiment of the present disclosure provides the combination of a fuel filter of the above embodiment and a filter element received in the housing. Brief Description of the Drawings One or more embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view of a prior art fuel filter containing a filter element; Figure 2 is an enlarged view of a portion of the fuel filter of Figure 1; Figure 3 is an enlarged view of another portion of the fuel filter of Figure 1; Figure 4 is a cross-sectional view of a fuel filter according to the present disclosure, the fuel filter containing a filter element; Figure 5 is an enlarged view of a portion of the fuel filter of Figure 4 showing an air bleed valve of the fuel filter venting air; and Figure 6 is an enlarged view of another portion of the fuel filter of Figure 4 showing the venting of air and the drainage of water from a drain valve. Detailed Description llnless defined otherwise, all technical and scientific terms used in this specification have the same meaning as is commonly understood by the reader skilled in the art to which the claimed subject matter belongs. It is to be understood that the foregoing summary of the disclosure and the following examples are exemplary and explanatory only and are not restrictive of any subject matter claimed. The following description is directed to embodiments of the disclosure. The description of the embodiments is not meant to include all the possible embodiments of the disclosure that are claimed in the appended claims. Many modifications, improvements and equivalents which are not explicitly recited in the following embodiments may fall within the scope of the appended claims. Features described as part of one embodiment may be combined with features of one or more other embodiments unless the context clearly requires otherwise. In this specification, the use of the singular includes the plural unless the context clearly dictates otherwise. In this application, the use of “and / or” means “and” and “or” unless stated otherwise. In this specification, terms denoting relative position or location, for example “top”, “bottom”, “upper” and “lower” are made with reference to the orientation of the fuel filter as shown in the accompanying drawings. However, it will be appreciated that the orientation of the fuel filter in use may not be as shown in the accompanying drawings and such terms are to be interpreted accordingly. Figures 1 to 3 show a prior art fuel filter 1 containing a filter element 2. The fuel filter 1 comprises a housing 3 having a filter body 4 and a filter head 5 that are connected by means of a screw thread connection. An O-ring seal 23 is provided to provide a fluid-tight seal between the filter body 4 and the filter head 5 at this connection. A fuel inlet 6 and a fuel outlet 7 are provided in the filter head 5 allowing connection of suitable conduits for the supply or, and onward flow of fuel. A bottom end of the filter body 4 comprises a water outlet formed by a hollow extension 10 bearing an internal screw thread. A drain valve cap 8 comprising an internal extension 12 bearing a complementary screw thread is received in the hollow extension 10. An O-ring seal 11 is provided for sealing between an end surface of the hollow extension 10 and the drain valve cap 8 when the drain valve cap 8 is fully screwed into the hollow extension 10. The drain valve cap 8 and the water outlet combine to form a drain valve of the fuel filter 1. Drain valve cap 8 comprises a drain outlet 9. An air bleed valve 13 is provided at a top of the fuel filter 1 in the filter head 5. The filter element 2 comprises an annular body of filter media 14 defining an open central passage. The filter element 2 comprises a top end cap 15, a bottom end cap 16 and a perforated central tube 17 defining the open central passage. The top end cap 15 comprises an extension 22 that receives an O-ring seal 21 for sealingly engaging the filter head 5. In use, fuel enters the fuel filter 1 through the fuel inlet 6 and passes down around an exterior of the filter element 2 and then passes through the filter media 14 of the filter element 2 in a radially-inward direction towards the open central passage during which it is filtered. The incoming flow of unfiltered fuel is shown schematically in Figure 1 by arrows 25. The filtered fuel emerges into the open central passage and is diverted upwards towards and out of the fuel outlet 7. The outgoing flow of filtered fuel is shown schematically in Figure 1 by arrows 26. O-ring seal 21 functions to prevent by-pass of unfiltered fuel to the fuel outlet 7. During use water may separate from the fuel and sediment towards a sedimentation zone 18 located at the bottom of the filter body 4 below the filter element 2. The sedimenting flow of water is shown schematically in Figure 1 by arrows 28. Water may be periodically drained from the fuel filter 1 by unscrewing the drain valve cap 8, thereby unsealing the drain valve. Water then can flow out of the drain outlet 9 of the drain valve cap 8 under gravity as shown schematically by arrow 29 in Figure 3. In addition, air may become trapped within the interior of the housing 3 within a headspace chamber 19 located at a top of the housing 3. Air may be periodically vented from the fuel filter 1 by opening the air bleed valve 13. Figures 4 to 6 show a fuel filter 1 according to the present disclosure that differs from the prior art fuel filter of Figures 1 to 3 in a number of respects. The same or like reference numerals have been used for the same or like components. As shown in Figure 4, the fuel filter 1 of the present disclosure comprises a housing 3 for containing a filter element 2, a fuel inlet 6, a fuel outlet 7, an air bleed valve 30 for venting air from an interior of the housing 3, and a drain valve 50 for draining water from the interior of the housing 3. The fuel filter 1 is configured to define a flow path for fuel that passes from the fuel inlet 6 to the fuel outlet 7. The drain valve 50 is configured to have a closed configuration in which water cannot drain via the drain valve 50 and air cannot vent from the interior of the housing 3 via the air bleed valve 30, an air bleed configuration in which air can vent from the interior of the housing 3 via the air bleed valve 30 but water cannot drain via the drain valve 50, and a water drainage configuration in which water can drain via the drain valve 50 and air can vent from the interior of the housing 3 via the air bleed valve 30. The housing 3 may have a filter body 4 and a filter head 5 that may be connected by means of a screw thread connection. A seal 23, for example an O-ring seal, may be provided to provide a fluid-tight seal between the filter body 4 and the filter head 5 at this connection. The fuel inlet 6 and the fuel outlet 7 may be provided in the filter head 5 allowing connection of suitable conduits for the supply or, and onward flow of fuel. The filter head 5 may define a headspace chamber 19 in which is located the air bleed valve 30. The filter head 5 in the region of the headspace chamber 19 may comprise a raised, for example dome-shaped, portion such that an upper extent of the headspace chamber 19 lies above the level of the fuel outlet 7. The filter element 2 may comprise an annular body of filter media 14 defining an open central passage. The filter element 2 may comprise a top end cap 15, a bottom end cap 16 and a perforated central tube 17 defining the open central passage. The top end cap 15 may comprise an extension 22 that may receive a seal 21, for example an O-ring seal, for sealingly engaging the filter head 5. The air bleed valve 30 and the drain valve 50 may be located at opposite ends of the fuel filter 1. For example, the air bleed valve 30 may be located at or towards a top of the fuel filter 1 and the drain valve 50 may be located at or towards a bottom of the fuel filter 1, for example at a bottom of the filter body 4. An air bleed conduit 32 may be provided for passage of air from the air bleed valve 30 to an air vent outlet 35 through which air may be ventable to an exterior of the fuel filter 1. The air vent outlet 35 may be positioned at an opposite end of the fuel filter 1 from the air bleed valve 30, for example at or towards a bottom of the fuel filter 1. The air vent outlet 35 may be proximate the drain valve 50. The air bleed conduit 32 may extend through the interior of the housing 3. For example, the air bleed conduit 32 may extend from the headspace chamber 19 located within the filter head 5 to the air vent outlet 35 located at a lower end 34 of the air bleed conduit 32 at the bottom of the filter body 4 of the housing 3. The air bleed conduit 32 may comprise a tube. The air bleed conduit 32 may be fixedly connected to or integrally formed with a drain valve cap 8 of the drain valve 50 so as to be rotatable in unison. The air bleed valve 30 may comprise a first sealing element 31 that is configured to provide a fluid-tight seal at an upper end 33 of the air bleed conduit 32 when the drain valve 30 is in its closed position. The upper end 33 may reside towards in an upper portion of the headspace chamber 19. In particular, the upper end 33 may be located at a level above the level of the fuel outlet 7. The first sealing element 31 may be a plug or bung seal configured to sealingly engage an open end of the air bleed conduit 32. The air bleed valve 30 may be configured to open when the drain valve 50 is in its air bleed position by longitudinal movement of an open end of the air bleed conduit 32 out of engagement with the first sealing element 31 driven by operation of the drain valve 50. A bottom end of the filter body 4 may comprise a water outlet formed by a hollow extension 10 bearing an internal screw thread. The hollow extension may comprise an inwardly-directed shoulder on an inner face. The drain valve cap 8 may comprise an internal extension 12 bearing a complementary screw thread that may be received in the hollow extension 10. The internal extension 12 may be provided with one or more axial grooves passing through the screw thread of the internal extension 12. A second sealing element 11, for example an O-ring seal, may be provided for sealing between a surface, for example an end surface or a surface of the inwardly-directed shoulder or another surface, of the hollow extension 10 and the drain valve cap 8 when the drain valve cap 8 is fully screwed into the hollow extension 10. The drain valve cap 8 and the water outlet may combine to form the drain valve 50 of the fuel filter 1. Drain valve cap 8 may further comprise a drain outlet 9. The second sealing element 11 may in particular be configured to provide a liquid-tight seal between the drain valve cap 8 and the housing 3 when the drain valve 50 is in its closed and air bleed configurations. The second sealing element 11 may be configured to unseal the liquid-tight seal when the drain valve 50 is in its water drainage configuration. The drain valve 50 may comprise a valve seat 40 comprised on the housing 3 and / or the drain valve cap 8, wherein the valve seat 40 has a longitudinal length along which the second sealing element 11 is moved during movement of the drain valve 50 from its closed configuration to its air bleed configuration, during said movement the second sealing element 11 retains a sealing engagement with the valve seat 40. For example, as shown in Figure 6, the valve seat 40 may comprise an axial portion of the hollow extension 10, for example a portion of the hollow extension 10 distal the inwardly-directed shoulder. The second sealing element 11 may be retained on an enlarged portion 41 of the internal extension 12 so as to move axial along the valve seat 40 as the drain valve cap 8 is screwed and unscrewed into and from the housing 3. The bottom end cap 16 of the filter element 2 may be provided with a hollow extension 37 through which the air bleed conduit 32, e.g. the tube of the air bleed conduit 32, passes. The hollow extension 37 may define a valve seat for a third sealing element 36 that may be provided to seal between the air bleed conduit 32 and the bottom end cap 16. The third sealing element 36 may act to provide a seal in use between the filtered and unfiltered flows of fuel. The lower end 34 of the air bleed conduit 32 may extend through the drain valve cap 8. For example, the lower end 34 of the air bleed conduit 32 may pass through a centre of the drain valve cap 8 and emerge and / or project from a bottom of the drain valve cap 8 as shown in Figure 6. The drain valve cap 8 may define the drain outlet 9 for discharging water to an exterior of the fuel filter 1. The drain valve cap 8 may comprise both the air vent outlet 35 and the drain outlet 9. The air vent outlet 35 may be located at a centre of the drain valve cap 8 and the drain outlet 9 may be located towards a periphery of the drain valve cap 8. In use, as shown in Figure 4, the drain valve 50 and the air bleed valve 30 may both be put in a closed configuration or state by fully screwing the drain valve cap 8 into the hollow extension 10. This sealingly engages the upper end 33 of the air bleed tube 32 against the first sealing element 31 and at the same time sealingly engages the second sealing element 11 between the drain valve cap 8 and the housing 3, e.g. the valve seat 40 of the hollow extension 10. Fuel may be passed from the fuel inlet 6 to the fuel outlet 7 via the filter element 2. In particular, fuel may enter the fuel filter 1 through the fuel inlet 6 and pass down around an exterior of the filter element 2 and then pass through the filter media 14 of the filter element 2 in a radially-inward direction towards the open central passage during which it is filtered. The filtered fuel emerging into the open central passage is diverted upwards towards and out of the fuel outlet 7. Seal 21 may function to prevent by-pass of unfiltered fuel to the fuel outlet 7 and provide separation between the filtered and unfiltered flows of fuel. During use water may separate from the fuel and sediment towards the sedimentation zone 18 located at the bottom of the filter body 5 below the filter element 2. In addition, air may become trapped within the interior of the housing 3 within the headspace chamber 19 located at a top of the housing 3. In particular, air may be trapped within the upper portion of the headspace chamber 19 such that the upper end 33 of the air bleed tube 32 is within an air pocket. The drain valve 50 may be used to both vent air from the headspace chamber 19 and to drain water from the sedimentation zone 18. In particular, the air bleed valve 30 may be configured to be moved between its closed state and its open venting state by operation of the drain valve 50. The drain valve 50 and the air bleed valve 30 may be integrated such that the drain valve 50 adopting its air bleed configuration necessarily causes the air bleed valve 30 to adopt its open, venting configuration. The drain valve cap 8 may be configured to be rotated in a first sense to move the drain valve 50 from its closed configuration to its air bleed configuration and then further rotated in the first sense to move the drain valve 50 from its air bleed configuration to its water drainage configuration. For example, partial unscrewing of the drain valve cap 8 may be operable to move the drain valve 50 from its closed configuration to its air bleed configuration and then further unscrewing of the drain valve cap 8 may be operable to move the drain valve 50 from its air bleed configuration to its water drainage configuration. In some examples the drain valve cap 8 may be configured to be rotated by between 90 and 180 degrees to move the drain valve 50 from its closed configuration to its air bleed configuration and by a further 90 degrees or more to move the drain valve 50 from its air bleed configuration to its water drainage configuration. In the air bleed configuration the first sealing element 31 is unsealed from the upper end 33 of the air bleed conduit 32 but the second sealing element 11 is still held in sealing engagement with the valve seat 40, e.g. the second sealing element 11 may have been moved axially down the valve seat 40 but is still within the limits of the valve seat 40 so as to provide a liquid-tight seal. Figures 5 and 6 show the fuel filter 1 in the water drainage configuration wherein the second sealing element 11 has been unsealed from the valve seat 40 to provide a passage for flow of water from the sedimentation zone 18 to the drain outlet 9 - shown schematically in Figure 6 by arrow 29. In particular, water may, for example, then pass along the axial grooves passing through the screw thread of the internal extension 12 and then through a gap between the now separated valve seat 40 and the second sealing element 11. During unscrewing of the drain valve cap 8, the seal 36 may be moved axially along its valve seat on hollow extension 37. This seal may be retained during both the air bleed configuration and the water drainage configuration so as to prevent water entering the open central passage 17. Industrial Applicability The present disclosure provides a fuel filter comprising: a housing for containing a filter element; a fuel inlet; a fuel outlet; an air bleed valve for venting air from an interior of the housing; and a drain valve for draining water from the interior of the housing; the fuel filter being configured to define a flow path for fuel that passes from the fuel inlet to the fuel outlet; wherein the drain valve is configured to have: - a closed configuration in which water cannot drain via the drain valve and air cannot vent from the interior of the housing via the air bleed valve; an air bleed configuration in which air can vent from the interior of the housing via the air bleed valve but water cannot drain via the drain valve; and - a water drainage configuration in which water can drain via the drain valve and air can vent from the interior of the housing via the air bleed valve. Advantageously, drainage of water from the housing and bleeding of air from the housing may be carried out in a controlled manner. Bleeding of the air may allow air to be bled from a closed system incorporating the fuel filter in a manner that is convenient, simple and fast. Use of the fuel filter may be applied, for example, in the case of mechanical engines that are not equipped with an electric feed pump. The ability to bleed air from the fuel filter may reduce the amount of hand priming required for such systems or reduce or eliminate the need to perform excessive cranking of an engine of such systems. The drain valve may be configured such that the water drainage configuration of the drain valve is reached only after passing through the air bleed configuration of the drain valve. This may ensure that air can be bled from the interior of the housing without necessarily requiring the water to be drained. The air bleed valve may be configured to be moved between a closed state and an open venting state by operation of the drain valve. Advantageously, operation of both the air bleed valve and the drain valve may be carried out using one control - the drain valve. This may reduce the complexity of operation of the fuel filter. The drain valve and the air bleed valve may be integrated such that the drain valve adopting its air bleed configuration necessarily causes the air bleed valve to adopt an open, venting configuration. This may allow precise synchronisation of when the air bleed valve and the drain valve are opened relative to each other. The air bleed valve and the drain valve may be located at opposite ends of the fuel filter. The air bleed valve may be located at or towards a top of the fuel filter and the drain valve may be located at or towards a bottom of the fuel filter. It is advantageous to locate the air bleed valve at or towards a top of the fuel filter to maximise the volume of air that can be bled from the interior. Similarly, it is advantageous to locate the drain valve at or towards the bottom of the fuel filter to reduce ullage and maximise the volume of the water that can be freely drained from the interior under gravity. The housing may comprise a filter body and a filter head that is mountable to the filter body. The filter head may comprise the fuel inlet and the fuel outlet and define a headspace chamber in which is located the air bleed valve. The drain valve may be positioned at a bottom of the filter body. Providing a headspace chamber in the filter head may allow air in the interior of the fuel filter to propagate upwards due to its reduced density compared to the fuel allowing the air to be collected in a position in fluid communication with the air bleed valve. The fuel filter may further comprise an air bleed conduit for passage of air from the air bleed valve to an air vent outlet through which air is ventable to an exterior of the fuel filter. Advantageously, provision of the air bleed conduit may allow the air bleed valve to be located at or towards the top of the fuel filter while permitting the air vent outlet to be located elsewhere on the fuel filter. The air vent outlet may be positioned at an opposite end of the fuel filter from the air bleed valve, optionally at or towards a bottom of the fuel filter. Advantageously, positioning the air vent outlet at the opposite end, for example at or towards the bottom of the fuel filter may prevent any fuel that may be emitted from the air bleed valve from fouling the outer surfaces of the fuel filter since the fuel may be emitted immediately away from the housing of the fuel filter, e.g. in a downward direction, rather than overflowing in an uncontrolled manner down the outer surface of the fuel filter. In some examples the air vent outlet may be proximate the drain valve. The air bleed conduit may extend through the interior of the housing. For example, the air bleed conduit may extend from a headspace chamber located within a filter head of the housing to the air vent outlet located at a bottom of a filter body of the housing. Advantageously, extending the air bleed conduit through the interior of the housing may allow the air bleed valve to be located at or towards the top of the fuel filter and at the same time allow the air vent outlet to be located at or towards a bottom of the fuel filter with the consequential benefit of a cleaner and more controlled emission of any fuel emitted from the air vent outlet. In some examples the air bleed conduit extends through a length of the housing from top to bottom of the housing. This may allow the volume of ventable air to be maximised and the ullage of sedimented water to be minimised. The air bleed conduit may comprise a tube. The air bleed conduit may be fixedly connected to or integrally formed with a drain valve cap of the drain valve so as to be rotatable in unison. Beneficially, the drain valve and the air bleed valve may be operated with a single control. The air bleed valve may comprise a first sealing element that is configured to provide a fluid-tight seal at an upper end of the air bleed conduit when the drain valve is in its closed position. The air bleed valve may be configured to open when the drain valve is in its air bleed position by longitudinal movement of an open end of the air bleed conduit out of engagement with the first sealing element driven by operation of the drain valve. The first sealing element may be a plug or bung seal configured to sealingly engage an open end of the air bleed conduit. The drain valve may comprise a water outlet and a drain valve cap received in the water outlet. The drain valve cap may be configured to be rotated in a first sense to move the drain valve from its closed configuration to its air bleed configuration and then further rotated in the first sense to move the drain valve from its air bleed configuration to its water drainage configuration. Beneficially, the requirement for further rotation may be utilised to allow the drain valve to be operated to allow air to be bled from the interior without requiring water to be drained. Thus, the simplicity of a single control for operation of both the air bleed valve and the drain valve may be obtained while retaining the flexibility of enabling bleeding of air only or the bleeding of air and the drainage of water. The water outlet may comprise a first screw thread and the drain valve cap may comprise a complementary second screw thread for screw-fitting the drain valve cap in the water outlet. Partial unscrewing of the drain valve cap may be operable to move the drain valve from its closed configuration to its air bleed configuration and then further unscrewing of the drain valve cap may be operable to move the drain valve from its air bleed configuration to its water drainage configuration. In some examples the drain valve cap may be configured to be rotated by between 90 and 180 degrees to move the drain valve from its closed configuration to its air bleed configuration and by a further 90 degrees or more to move the drain valve from its air bleed configuration to its water drainage configuration. The drain valve may further comprise a second sealing element that is configured to provide a liquid-tight seal between the drain valve cap and the housing when the drain valve is in its closed and air bleed configurations. The second sealing element may be configured to unseal the liquid-tight seal when the drain valve is in its water drainage configuration. The drain valve may comprise a valve seat comprised on the housing and / or the drain valve cap, wherein the valve seat has a longitudinal length along which the second sealing element is moved during movement of the drain valve from its closed configuration to its air bleed configuration, during said movement the second sealing element retains a sealing engagement with the valve seat. In some examples, the second sealing element is an O-ring seal. The drain valve cap may define a drain outlet for discharging water to an exterior of the fuel filter. The drain valve cap may comprise both the air vent outlet and the drain outlet. The air vent outlet may be located at a centre of the drain valve cap and the drain outlet may be located towards a periphery of the drain valve cap. Beneficially the controlled collection or disposable of the drained water may be enabled. Providing a separate outlet for the bled air may enable a controlled collection of any emitted fuel while ensuring that it may be kept separate from the drained water. Thus, the different liquids, water and fuel, may be recycled, or disposed of more appropriately. The present disclosure provides the combination of a fuel filter as discussed above claimed and a filter element received in the housing. The filter element may comprise an annular body of filter media defining an open central 5 passage, wherein the flow path for fuel passes from an outside of the filter element radially inwards through the filter media and into the open central passage. It is to be understood that at least some of the figures and descriptions of the disclosure have been simplified to focus on elements that are relevant for a clear understanding of the 10 disclosure, while eliminating, for purposes of clarity, other elements that the reader skilled in the art will appreciate may also be required. Because such elements are well known to the reader skilled in the art, and because they do not necessarily facilitate a better understanding of the disclosure, a description of such elements is not provided herein. 15

Claims

1. A fuel filter comprising:a housing for containing a filter element;a fuel inlet;a fuel outlet;an air bleed valve for venting air from an interior of the housing; and a drain valve for draining water from the interior of the housing;the fuel filter being configured to define a flow path for fuel that passes from the fuel inlet to the fuel outlet;wherein the drain valve is configured to have:- a closed configuration in which water cannot drain via the drain valve and air cannot vent from the interior of the housing via the air bleed valve;an air bleed configuration in which air can vent from the interior of the housing via the air bleed valve but water cannot drain via the drain valve; and- a water drainage configuration in which water can drain via the drain valve and air can vent from the interior of the housing via the air bleed valve.

2. The fuel filter of claim 1, wherein the drain valve is configured such that the water drainage configuration of the drain valve is reached only after passing through the air bleed configuration of the drain valve.

3. The fuel filter of any preceding claim, wherein the air bleed valve is configured to be moved between a closed state and an open venting state by operation of the drain valve.

4. The fuel filter of any preceding claim, wherein the air bleed valve and the drain valve are located at opposite ends of the fuel filter.

5. The fuel filter of any preceding claim, wherein the housing comprises a filter body and a filter head that is mountable to the filter body; the filter head comprising the fuel inlet and the fuel outlet and defining a headspace chamber in which is located the air bleed valve, and the drain valve is positioned at a bottom of the filter body.

6. The fuel filter of any preceding claim, further comprising an air bleed conduit for passage of air from the air bleed valve to an air vent outlet through which air is ventable to an exterior of the fuel filter.

7. The fuel filter of claim 6, wherein the air vent outlet is positioned at an opposite end of the fuel filter from the air bleed valve, optionally at or towards a bottom of the fuel filter.

8. The fuel filter of claim 6 or claim 7, wherein the air bleed conduit extends through the interior of the housing.

9. The fuel filter of any one of claims 6 to 8, wherein the air bleed conduit extends from a headspace chamber located within a filter head of the housing to the air vent outlet located at a bottom of a filter body of the housing.

10. The fuel filter of any one of claims 6 to 9, wherein the air bleed conduit is fixedly connected to or integrally formed with a drain valve cap of the drain valve so as to be rotatable in unison.

11. The fuel filter of any one of claims 6 to 10, wherein the air bleed valve comprises a first sealing element that is configured to provide a fluid-tight seal at an upper end of the air bleed conduit when the drain valve is in its closed position.

12. The fuel filter of claim 11, wherein the air bleed valve is configured to open when the drain valve is in its air bleed position by longitudinal movement of an open end of the air bleed conduit out of engagement with the first sealing element driven by operation of the drain valve.

13. The fuel filter of claim 12, wherein the first sealing element is a plug or bung seal configured to sealingly engage the open end of the air bleed conduit.

14. The fuel filter of any preceding claim, wherein the drain valve comprises a water outlet and a drain valve cap received in the water outlet.

15. The fuel filter of claim 14, wherein the drain valve cap is configured to be rotated in a first sense to move the drain valve from its closed configuration to its air bleedconfiguration and then further rotated in the first sense to move the drain valve from its air bleed configuration to its water drainage configuration.

16. The fuel filter of claim 14 or claim 15, wherein the water outlet comprises a first screw thread and the drain valve cap comprises a complementary second screw thread for screw-fitting the drain valve cap in the water outlet, wherein partial unscrewing of the drain valve cap is operable to move the drain valve from its closed configuration to its air bleed configuration and then further unscrewing of the drain valve cap is operable to move the drain valve from its air bleed configuration to its water drainage configuration.

17. The fuel filter of any one of claims 14 to 16, wherein the drain valve cap is configured to be rotated by between 90 and 180 degrees to move the drain valve from its closed configuration to its air bleed configuration and by a further 90 degrees or more to move the drain valve from its air bleed configuration to its water drainage configuration.

18. The fuel filter of any one of claims 14 to 17, wherein the drain valve further comprises a second sealing element that is configured to provide a liquid-tight seal between the drain valve cap and the housing when the drain valve is in its closed and air bleed configurations.

19. The fuel filter of claim 18, wherein the second sealing element is configured to unseal the liquid-tight seal when the drain valve is in its water drainage configuration.

20. The fuel filter of claim 18 or claim 19, wherein the drain valve comprises a valve seat comprised on the housing and / or the drain valve cap, wherein the valve seat has a longitudinal length along which the second sealing element is moved during movement of the drain valve from its closed configuration to its air bleed configuration, during said movement the second sealing element retains a sealing engagement with the valve seat.

21. The fuel filter of any one of claims 18 to 20, wherein the second sealing element is an O-ring seal.

22. The fuel filter of any one of claims 14 to 21, wherein the drain valve cap defines a drain outlet for discharging water to an exterior of the fuel filter.

23. The combination of a fuel filter as claimed in any preceding claim and a filter element received in the housing.5 24. The combination of claim 23, wherein the filter element comprises an annular bodyof filter media defining an open central passage, wherein the flow path for fuel passes from an outside of the filter element radially inwards through the filter media and into the open central passage.10

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