AU726581B2 - Vent assembly - Google Patents

Description

S F Ref: 402950

AUSTRALIA

PATENTS ACT 1990 COMPLETE

SPECIFICATION

FOR A STANDARD

PATENT

ORIGINAL

9 6, 399 9* 9. 9.

3* Name and Address of Applicant: Actual Inventor(s): Address for Service: ~9-The--E~pi~e Cave: Boach Ne South Wale: 228

A

Jolke EC.JtOIk~-t- 6,rc 4 rc-e lo eckij -c~leL13 John Warland ADDRESS FOR SERVICE

ALTERED

S44~ Level 33 St r,30Mre6Sre Fuelling Nozzle and Vent Assembly Invention Title: ASSOCIATED PROVISIONAL APPLICATION

DETAILS

[31] Application No(s) [33) Country P04185

AU

[32] Application Date 12 December 1996 The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5815 VENT ASSEMBLY Technical Field The present invention relates to tank refuelling systems and in particular to an improved vent assembly.

Background of the Invention Australian Patent No 586028 discloses a fuel tank vent adapted to be installed in the wall of a fuel tank for venting during tank refuelling operations. The known vent comprises a main body which defines a communicating path between the interior of the tank and the external atmosphere via a breather port in a dome cap secured to an upper surface of the body. An elongated tube is disposed centrally in the body, with a helical spring disposed inside the dome cap acting on an upper surface of the elongated tube to maintain a seal between a flange surface of the tube and a mating surface within the body. A float valve cage is secured to the lower end of the tube in which is disposed a heavy ball and three light float balls in such a way that the heavy ball sealingly engages the lower end of the tube when the fuel level rises to a predetermined level and when the tank is inverted. After closure of the lower end of the tube, when pressure within the tank reaches a predetermined level, fluid pressure overcomes the spring action and 9 9the tube is forced toward the domed cap, thereby displacing the tube flange surface from the body mating surface and providing an annular gap between the tube and body 20 for passage of fluids out of the pressurised tank. This provides protection from So pressure build up during expansion of the tank contents and overfilling due to faulty fuelling nozzles or operator procedure. A longitudinally extending shroud is provided to cover the float valve cage assembly to prevent fuel surges and splashes caused by movement of fuel within the tank from deforming the assembly so as to displace the 9 25 ball elements and allow the fuel surges and splashes to enter the tube.

The known vent, however suffers from the disadvantage that the raised domed cap protrudes well above the surface of the tank to which it is installed; thereby limiting its application to fuel tanks about which large clearances are available. The known vent is also only able to discharge of the order of 450 L/min of fuel, and does not open until 30 a pressure of approximately 100 kPa. Modern fuelling operations are, however, often carried out at rates up to and above 1000 1/min, and fuel tanks are relatively light weight and are prone to rupture at such pressures, rendering the vents to be of limited effectiveness. Typical known vents are also manufactured at least partially from aluminium and are hence unsuitable for underground coal mine refuelling operations in which flammable methane gases may be present. In the known vent the breather port is also directly open to the external atmosphere, and hence any airborne contaminants can Sreadily contaminate the fuel tank.

[I:\DayLib\LIBLL]O1 194.DOC:KEH:TCW Object of the Invention It is the object of the present invention to overcome or substantially ameliorate at least one the above disadvantages and/or more generally, to provide an improved vent assembly.

Summary of the Invention There is disclosed herein a vent assembly comprising: a main body adapted to be installed in an upper wall of a fuel tank or a vent box communicating with said fuel tank, said main body including a passageway therethrough adapted to communicate with an interior of said fuel tank, an elongated tube located through said passageway so as to form an annular portion of said passageway about said elongated tube, said elongated tube being provided with a flange at an upper end thereof adapted to substantially seal said annular passageway portion, a cap secured to, or integral with, said main body, including a cavity in which said flange is slideably received such that said cavity communicates with said elongated tube, means for urging said flange into a substantially sealing relationship with said annular passageway portion and a breather port communicating the external atmosphere with said cap cavity, and means for sealing a lower end of said elongated tube through hole when fuel 20 within said fuel tank reaches a predetermined level, thereby substantially sealing said tank from said external atmosphere, wherein if pressure builds up in said fuel tank beyond a predetermined 40:1, pressure said built up pressure acts against said means for urging said flange to lift said flange element out of said sealing relationship with said annular passageway portion S 25 allowing venting of fuel through said annular passageway portion to said external :i atmosphere, and wherein said cap is adapted to protrude beyond said fuel tank wall or 0 said vent box by less than 50 mm.

Typically said main body, said elongated tube and said cap are all manufactured from steel.

Typically said means for sealing said lower end of said elongated tube through hole comprises a float ball cage in which is disposed a relatively heavy ball and at least one float ball adapted to lift said heavy ball into a sealing relationship with said elongated tube through hole when said fuel reaches said predetermined level.

Typically said means for urging said flange comprises a vent spring.

Typically said predetermined pressure is between 20 and 50 kPa.

Preferably said cap includes two said breather ports.

Typically one of said breather ports enables a fuel flow rate in excess of 250 ~1/min to pass therethrough.

[I:\DayLib\LBLL] 194.DOC:KEH:TCW Typically said breather ports in combination enable a fuel flow rate in excess of 600 1/min to pass therethrough.

Brief Description of the Drawings Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawing wherein: Figure 1 is a front elevation partially sectioned view of a vent assembly.

Detailed Description of the Preferred Embodiments The vent valve assembly 10, depicted in Figure 1 is provided with a main body 11 having an external screw thread 12 enabling the main body 11 to be fastened to a corresponding through fitting in an upper wall of a fuel tank or vent box by a spanner or similar engaged with a nut-like peripheral surface 13 provided on the main body 11.

The main body 11 is provided with a passageway 14 therethrough which, in use, communicates with the interior of the tank.

An elongated tube 15 is provided at its upper end 15a with a flange 16. The elongated tube is located through the main body 11 passageway 14 so as to form an annular portion 14a of the passageway about the elongated tube 15. The flange 16 is adapted to sealingly mate with a seal member 17 provided on an internal shoulder 18 of the main body 11 to thereby substantially seal the annular passageway annular portion 14a. The seal member is preferably an elastomeric ring. A restrictive bleed passage 19 is provided through the flange 16 so as to communicate opposing ends of 9 the main body 11 passageway 14 when the flange 16 is sealingly engaged with the seal member 17, allowing pressure equalisation over a period of time.

A cap 20 is secured to, or integral with, the main body 11. In the current embodiment the cap 20 is provided with an internal cavity 21 adapted to slidingly 25 receive the elongated tube flange 16. The cap 20 is fitted to the main body 11 such that ""the tube 15 flange 16 is received within the cavity 21 and an outer peripheral surface 22 of the cap 20 abuts an internal surface 23 of the main body 11 adjacent to the nut-like •999* peripheral surface 13. A further sealing member 24, such as a further ring seals any gap between the cap outer peripheral surface 22 and the main body internal surface 30 23, thereby preventing leakage of fluids therethrough.

The cap 20 may be secured to the main body 11 by any suitable means. In the current embodiment set screws 25 passing through the nut-like peripheral surface 13 of the main body engage a slot 26 provided around the periphery of the outer peripheral surface 22 of the cap 20, thereby enabling the cap 20 to be rotated freely with respect to the main body 11. Means are provided far urging the flange 16 to seal against the seal member 17, here in the form of a vent spring 27 provided in the cap cavity 21.

Opposing ends of the vent spring 27 act against the end wall 28 of the cavity 21 and the [I:\DayLib\LBLL 1I1 94.DOC:KEI:TCW tube first end 15a, respectively, such that the action of the spring tends to sealingly seat the tube flange 16 to against the seal member 17. A force applied to the tube 15 toward the cap 20 tends to act against the vent spring 27 allowing the flange 16 to unseat and slide within the cavity 21 toward the cap cavity end wall 28.

At least one breather port 29 is provided through the side wall of the cap cavity 21, communicating the cavity 21 with the external atmosphere. In the preferred embodiment two diametrically opposing breather ports are provided to increase the flow rate of fuel and air able to be passed through the vent assembly 10. The breather ports 29 may be adapted to engagingly receive hose fittings 30 which may be used to direct overflowing fuel as required away from operators or equipment.

The simplified arrangement of the cap 20 and main body 11 allows the same to have a particularly low profile when installed in a fuel tank upper wall. The cap 20 of the preferred embodiment has a diameter of 81 mm and protrudes only 22.5 mmn beyond the main body 11. Consequently, when the external screw thread 12 of the main body 11 is threaded into a through fitting provided in the fuel tank upper wall, the cap 20 of the current embodiment protrudes from the tank wall by less than 40 mm, enabling installation in areas of low clearance above the fuel tank wall.

To seal the elongated tube lower end 15b, a float ball valve cage 32 is secured thereto. A heavy ball 33 and three low density float balls 31 are provided in the float 20 ball valve cage 32, with the heavy ball 33 located closest to the tube lower end S.The heavy ball 33 is sized such that, when urged against the tube lower end 15b it ,°sealingly mates with a sealing surface 34 provided inside the tube lower end 1 Sb.

*Here the sealing surface 34 comprises a further ring seal.

In use, during early stages of a refuelling operation, the tube flange 16 is seated against the main body seal member 17, thereby preventing venting of gases S° within the fuel tank through the passageway annular portion 14a. The heavy ball 33, however sits in the valve cage 32 away from the tube 15 and hence gases can freely vent through the elongated tube 15, main body 10 passageway 14 and breather ports 29 to atmosphere as the fuel level rises within the tank. As the fuel level rises to the level of the valve cage 32, the fuel lifts the float balls 31, thereby forcing the heavy ball 33 S.Z against the sealing surface 34 of the tube lower end This action seals the tank from the external atmosphere (except for the restricted bleed passage 19 which only allows small flow rates to pass therethrough).

Pressure consequently rises within the tank as the fuel level rises. Under normal circumstances this pressure rise should shut off the fuel supply and complete the fuelling operation. The restricted bleed passage 19 then allows the pressure within the tank to equalise to atmospheric pressure over time.

If there is a failure in the fuel supply shut off system, or there is significant R41 A Q thermal expansion in a near full tank, the pressure rise builds to a stage where the tube [I:\DayLib\LIBLL]O1 1 9 4.DOC:KEH:TCW is lifted from its sealing engagement with seal member 17, allowing an overflow of fuel through the main body passageway annular portion 14a and out to the atmosphere through the breather ports 29, thereby preventing damage to the fuel tank or forced overflow of fuel from the fuel tank into the engine which would flood the same.

The length of the elongated tube 15 may be varied to cause the fuel supply to shut off at a desired level. Increasing the length of the tube 15 results in the float balls 31 lifting the heavy ball 33 at a lower fuel level, with a resultant shut off of the fuel supply at a corresponding lower level.

The arrangement of the current valve assembly 10, and in particular the provision of a softer spring enables the valve assembly 10 to open at pressures of the order of 35 kPa, as opposed to the typical 100 kPa opening pressure of the valve of the Fig.R1. The lower opening pressure is required to prevent damage to the lighter fuel tanks now commonly in use. Different opening pressures may be readily achieved by replacement of the spring with a softer or stiffer spring as required to achieve the desired opening pressure. The provision of two breather ports 29 also enable a high flow rates of up to 600 1/min to be discharged through the valve assembly ;If the tank becomes inverted, the heavy ball 33 will fall under gravity and become sealingly engaged with the sealing surface 34 of the tube 15, thereby preventing escape of fuel from the tank.

To enable safe use of the vent assembly 10 in underground coal mining operations where flammable gases such as methane may be present, the valve assembly should be primarily manufactured from passivated steel.

•o o •.go •o 0 0 o 0 °0 [1\DayLib\LBLLJO1 194.DOC:KEH:TCW

Claims (6)

1. A vent assembly comprising: a main body adapted to be installed in an upper wall of a fuel tank or a vent box communicating with said fuel tank, said main body including a passageway therethrough adapted to communicate with an interior of said fuel tank, an elongated tube located through said passageway so as to form an annular portion of said passageway about said elongated tube, said elongated tube being provided with a flange at an upper end thereof adapted to substantially seal said annular passageway portion, a cap secured to, or integral with, said main body, including a cavity in which said flange is slideably received such that said cavity communicates with said elongated tube, means for urging said flange into a substantially sealing relationship with said annular passageway portion and a breather port communicating the external atmosphere with said cap cavity, and means for sealing a lower end of said elongated tube through hole when fuel within said fuel tank reaches a predetermined level, thereby substantially sealing said tank from said external atmosphere, wherein if pressure builds up in said fuel tank beyond a predetermined pressure said built up pressure acts against said means for urging said flange to lift said flange element out of said sealing relationship with said annular passageway portion Callowing venting of fuel through said annular passageway portion to said external atmosphere, and wherein said cap is adapted to protrude beyond said fuel tank wall or Csaid vent box by less than 50 mm. o The vent assembly of claim 1, wherein said main body, said elongated tube and said cap are all manufactured from steel. c

3. The vent assembly of claim 1 or claim 2, wherein said means for sealing said lower end of said elongated tube through hole comprises a float ball cage in -which is disposed a relatively heavy ball and at least one float ball adapted to lift said heavy ball into a sealing relationship with said elongated tube through hole when said fuel reaches said predetermined level.

4. The vent assembly of any one of the preceding claims, wherein said means for urging said flange comprises a vent spring. The vent assembly of any one of the preceding claims, wherein said predetermined pressure is between 20 and 50 kPa.

6. The vent assembly of any one of the preceding claims, wherein said cap includes two said breather ports.

7. The vent assembly of any one of the preceding claims, wherein one of said breather ports enables a fuel flow rate in excess of 250 L/min to pass therethrough. A 4 [I:\DayLib\LIBLL]O1

194.DOC:KEH:TCW 8. The vent assembly of any one of the preceding claims, wherein said breather ports in combination enable a fuel flow rate in excess of 600 1/min to pass therethrough. 9. A vent assembly, substantially as hereinbefore described with reference to the accompanying drawing. Dated 5 October, 1999 Patria Virola Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON .9 *9 9 9* [1:\DayLib\LBLLJo1 194.DOC:KEH:TCW