GB1575618A - Devices for venting gaseous and/or vaporous media - Google Patents

Description

(54) IMPROVEMENTS IN DEVICES FOR VENTING GASEOUS AND/OR VAPOROUS MEDIA (71) I, WILLIAM STEPHEN MARTIN, a British Subject, of Long Barn, Weald, Sevenoaks, Kent, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly des cribed in and by the following statement:: This invention relates to a venting device for venting a gaseous and/or vaporous medium into the atmosphere, the device being of the kind comprising a tubular framework defining a vent for flow therethrough of the medium being vented, and valve means associated with one end of said framework to provide a vent orifice of variable cross-sectional area available for the flow of medium from the vent, said valve means comprising two flaps pivotally mounted on said framework externally of the vent for varying the cross-sectional area of the orifice in response to the volumetric rate of flow for the medium being vented, said cross-sectional area increasing with increasing flow rate of the medium and decreasing with decreasing flow rate of the medium, and biasing means associated with said flaps for urging them into a position in which they close said orifice.

When a venting device of the kind ree ferred to is employed to vent the atmosphere from a tank or other container holding an inflammable substance, for example a tanker containing a petroleum product, care must be taken to ensure that a flame cannot flash back via the venting device and ignite the inflammable substance in the container. In order to prevent such flash back it has been proposed to arrange in association with the venting device a separate flame guard, for example a close mesh wire screen, this flame guard being mounted in a duct through which the medium being vented flows in its passage from the container to the venting device. The employment of a flame guard in this manner is described in my British Patent Specification No. 1,241,170.

When such a separate flame guard is used with a venting device of the kind referred to, it tends to become fouled by the passage therethrough of the medium being vented and it is therefore necessary to remove the flame guard at regular intervals for the purpose of cleaning it. Apart from the nuisance of having to remove the flame guard for this purpose, there is always the danger that someone forgets to replace it, and the container is then unprotected against flash back.

I have now found that it is possible to dispense with a separate flame guard, when employing a venting device of the kind referred to, provided that certain require ments are observed in the design of the venting device.

According to the invention, in a venting device of the kind referred to, one end of said framework has two apertures formed therein which, when the vent orifice is closed, are each closed by a different one of the two flaps, the framework providing an uninterrupted seating around each of said apertures against each of which the associated flap can close, sealing means is associated with each seating/flap combination to prevent leakage of the medium being vented from the venting device when the orifice is closed, and the biasing means associated with each flap is adapted to hold its flap in the orifice closed position until the pressure difference on opposite sides of the flap is at least 0.25 ib. per square inch (p.s.i,), advantageously at least 0.5 p.s.i., and preferably at least 1.0 p.s.i.

Preferably, the sealing means associated with each seating/flap combination is a gasket recessed into a groove in the flap, which gasket bears against the associated seating in the orifice closed position of the flap. It is, however, possible to locate the sealing means, for example a gasket, in a groove in the seating.

In a preferred embodiment of the venting device, each seating/flap combination is designed so that if the associated sealing means is destroyed, for example due to fire, or becomes worn to such an extent that the flap makes direct contact with its seating in the orifice closed position, then in the orifice closed position of the flap the maximum width of the gap between the flap and its seating at any point around the seating is 0.006 inch and the minimum width of the seating confronting the flap is 0.3 inch. In the case of the embodiment in which the sealing means is located in a groove in the seating, this minimum dimension of 0.3 inch for the width of the seating relates to the ungrooved part of the seating, i.e. the minimum width of the seating is 0.3 inch plus the width of the groove which receives the sealing means.

The invention will now be described, by way of example, with reference to the drawing accompanying the Provisional Specification, in which Figure 1 is a sectional end view of a first embodiment of a venting device in accordance with the invention, Figure 2 is a side view of the framework of the venting device of Figure 1, and Figure 3 is a side view of one of the flaps of the venting device of Figure 1, viewed in the direction of the arrow in Figure 1, and with reference to the accompanying drawings, in which Figure 4 is a partly sectioned end view of a second embodiment of a venting device in accordance with the invention, and Figure 5 is a plan of the venting device of Figure 4, partially in section and with parts removed to reveal the underlying structure.

The venting device shown in Figures 1 to 3 is of similar construction to the venting device shown in Figures 7 to 9 of Specifics; tion No. 1,241,170. Like the latter it comprises a framework in the form of a duct 1 of rectangular cross-section, this duct comprising side walls 2, 3 and end walls 4, 5 which, at their upper ends are of triangular configuration. At their upper ends, the two end walls 4, 5 are connected by a crossmember 6 of trapezoidal cross-section.

Two flaps 7, 8 are secured to spindles 9, 10, respectively, these spindles being journalled in lugs 11, 12 secured to the side walls 2, 3, respectively. The spindles 9, 10 are biased by means of counterweights (not shown) arranged in the same way as the counterweights 84, 85 shown in Figures 7 to 9 of Specification No. 1,241,170, so that the flaps are held normally against the framework of the venting device in the positions shown in full lines in Figure 1. When a medium is being vented through the venting device in the direction of the arrow B in Figure 1, the flaps 7, 8 swing in the direction-of the arrows C to provide a vent orifice of variable cross-sectional area between their upper ends, the flaps then occupying positions such as those shown by the chain lines 7a and 8a.The biasing -of the flaps 7 and 8 by the counterweights is such that the flaps remain in the orifice closed position, shown in full lines in Figure 1, until the pressure inside the duct 1 of the medium it is required to vent is at least 0.5 p.s.i., and preferably at least 1.0 p.s.i., higher than the pressure of the atmosphere bearing on the outwardly-facing surfaces of the flaps 7 and 8.

The framework or duct 1 has two apertures 13, 14 formed therein. The aperture 13 is surrounded by an uninterrupted seating formed by the upper edge 15 of the side wall 2, the upper edges 16 and 17 of the end walls 4 and 5, respectively, and the face 18 of the cross-member 6. The aperture 14 is surrounded by an uninterrupted seating formed by the upper edge 19 of the side wall 3, the upper edges 20 and 21 of the end walls 4 and 5, respectively, and the face 22 of the cross-member 6. The minimum width of any of these portions of the two seatings is 0.3 inch.

Referring to Figure 3, each of the flaps 7, 8 is a substantially rectangular plate having a shallow groove 23 formed in its inwardlyfacing surface. This groove is of rectangular outline and receives a sealing gasket 24 which has such a thickness that the inwardly-facing surface thereof stands just proud of the inwardly-facing surface of the flap, for example by about 0.020 inch.

The inwardly-Eacing surface of the flaps 7, 8 and the seatings around the apertures 13, 14 are machined to such an accuracy that if the sealing gaskets are worn to such an extent that a flap comes into physical contact with its seating, or if such physical contact results from destruction of a sealing gasket, for example due to fire, the maximum width of the gap between any part of the seating and the confronting surface of the flap is 0.006 inch.

The venting device shown in Figures 4 and 5 is of similar construction to that of Figures 1 to 3. Like the latter it comprises a framework in the form of a duct la of rectangular cross-section, this duct comprising side walls 2a, 3a and end walls 4a, 5a which, at their upper ends, are of triangular configuration. At their upper ends, the two end walls 4a, 5a are connected by a cross-member 6a of pentagonal crosssection.

Two rectangular flaps 7b, 8b are connected to spindles 9a, 10a, respectively, these spindles being journalled in bearings 30 in lugs lla, 12a forming extensions of the end walls 4a, 5a, respectively. Each of the flaps 7b, 8b is connected to its respective spindle 9a, 10a by an arm 31. Each arm 31 has a boss 32 at one end through which the spindle 9a or 1 0a passes, the boss 32being secured to the spindle by a tapered pin 33.

At its end remote from the boss 32, each of the arms 31 has a further boss 34 provided with a bearing bush 35. The bass 34 of each arm 31 is received between two spaced-apart lugs 36 secured to the flap 7b or 8b associated with the arm. Each of the flaps is pivotally connected to the boss 34 of its associated arm 31 by a bolt 37 passing through the lugs 36 and the bush 35.

The spindles 9a, 10a are biased by means of counterweights 38, 39 respectively, secured to one end of the spindles, so that the flaps are held normally against the framework of the venting device in the positions shown in full line in Figure 4. When a medium is being vented through the venting device in the direction of the arrow B in Figure 4, the flaps 7b, Sb swing in the direction of the arrows C to provide a vent orifice of variable cross-sectional area between their upper ends, the flaps then occupying positions such as that shown for the flap 7b by the chain lines 7c in Figure 4 or that shown for the flap 8b in Figure 5.The biasing of the flaps 7b, 8b by the counterweights 38, 39 is such that the flaps remain in the orifice closed position, shown in full lines in Figure 4, until the pressure inside the duct la of the medium it is required to vent is at least 0.25 p.s.i., and preferably at least 0.5 p.s.i., higher than the pressure of the atmosphere bearing on the outwardly-facing surfaces of the flaps 7b and 8b.

The framework or duct 1 has two rectangular apertures 13a, 14a, formed therein.

The aperture 14a is surrounded by an uninterrupted seating formed by the surface 40a of a frame member 40 welded to the upper edge of the side wall 3a, the surfaces 41a and 42a of frame members 41 and 42 welded to the end walls 4a, 5a respectively, and the surface 6b of the cross-member 6a.

The aperture 13 is surrounded by an uninterrupted seating formed by the surface 6c of the cross-member 6a and surfaces of frame members equivalent to the frame members 40v2.

Each of the seating just described has a continuous shallow groove 43 formed therm in. Each of these grooves is of rectangular outline and receives a sealing gasket 44 which has such a thickness that the outwardly-facing surface thereof stands just proud of the surface of its associated seating, for example by about 0.020 inch. In the embodiment illustrated in Figures 4 and 5 the aforementioned seating have a minimum width of 0.5 inmh and the associated gaskets 44 have a maximum width of 0.2 inch.

The inwardly-facing surfaces of the flaps 7b, 8b and the seatings around the apertures 13a, 14a are machined to such an accuracy that if the sealing gaskets 44 are worn to such an extent that a flap comes into physical contact with its seating, or if such physical contact results from destruction of a sealing gasket, for example due to fire, the maximum width of the gap between any part of the seating and the confronting surface of the flap is 0.006 inch.

The venting devices of Figures used in the same way as the venting device described with reference to Figures 7 to 9 of Specification No. 1,241,170 and they may be made of the same materials as - set out in said specification. It will be observed, however, that the flaps 7, 8 and 7b, 8b of the abovedescribed venting devices are different from the flaps 68a and 68b of the venting device described with reference to Figures 7 to 9 of Specification No. 1,241,170 in that they do not comprise the hinged members 72a and 72b. In the earlier venting device these hinged members were provided to accommodate over-pressures and under-pressures occurring when the venting device was in its orifice closed position.If desired, such hinged members could be provided on the flaps 7, 8 and 7b, 8b of the venting devices described above with reference to the drawings. Alternatively, separate provision may be made for accommodating over- and under-pressures, for example separate bypass valves may be connected in parallel with the duct 1 or la.

In modified embodiments of the venting devices described above with reference to the drawings, the flaps 7, 8 and 7b, 8b are biased into their closed positions by means of weights secured to the inwardly-facing surface of the flaps and located within the duct 1 or la. These weights would replace the counterweights referred to above.

WHAT I CLAIM IS:- 1. A venting device for venting a gaseous and/or vaporous medium into the atmosphere, the device comprising a tubular framework defining a vent for flow therethrough of the medium being vented, and valve means associated with one end of said framework to provide a vent orifice of variable cross-sectional area available for the flow of medium from the vent, said valve means comprising two flaps pivotally mounted on said framework externally of the vent for varying the cross-sectional area of the orifice in response to the volumetric rate of flow for the medium being vented, said cross-sectional area increasing with increasing flow rate of the medium and decreasing with decreasing flow rate of the medium, and biasing means associated with said flaps for urging them into a position in which they close said orifice, characterised in that one end of said framework has two apertures formed therein which, when the vent orifice is closed, are each closed by a different one of the two flaps, the framework providing an uninterrupted seating around each of said apertures against each of which the asociated flap can close, in that sealing means is associated with each seating/flap combination to prevent leakage of the medium being vented from the

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

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. or 8b associated with the arm. Each of the flaps is pivotally connected to the boss 34 of its associated arm 31 by a bolt 37 passing through the lugs 36 and the bush 35. The spindles 9a, 10a are biased by means of counterweights 38, 39 respectively, secured to one end of the spindles, so that the flaps are held normally against the framework of the venting device in the positions shown in full line in Figure 4. When a medium is being vented through the venting device in the direction of the arrow B in Figure 4, the flaps 7b, Sb swing in the direction of the arrows C to provide a vent orifice of variable cross-sectional area between their upper ends, the flaps then occupying positions such as that shown for the flap 7b by the chain lines 7c in Figure 4 or that shown for the flap 8b in Figure 5.The biasing of the flaps 7b, 8b by the counterweights 38, 39 is such that the flaps remain in the orifice closed position, shown in full lines in Figure 4, until the pressure inside the duct la of the medium it is required to vent is at least 0.25 p.s.i., and preferably at least 0.5 p.s.i., higher than the pressure of the atmosphere bearing on the outwardly-facing surfaces of the flaps 7b and 8b. The framework or duct 1 has two rectangular apertures 13a, 14a, formed therein. The aperture 14a is surrounded by an uninterrupted seating formed by the surface 40a of a frame member 40 welded to the upper edge of the side wall 3a, the surfaces 41a and 42a of frame members 41 and 42 welded to the end walls 4a, 5a respectively, and the surface 6b of the cross-member 6a. The aperture 13 is surrounded by an uninterrupted seating formed by the surface 6c of the cross-member 6a and surfaces of frame members equivalent to the frame members 40v2. Each of the seating just described has a continuous shallow groove 43 formed therm in. Each of these grooves is of rectangular outline and receives a sealing gasket 44 which has such a thickness that the outwardly-facing surface thereof stands just proud of the surface of its associated seating, for example by about 0.020 inch. In the embodiment illustrated in Figures 4 and 5 the aforementioned seating have a minimum width of 0.5 inmh and the associated gaskets 44 have a maximum width of 0.2 inch. The inwardly-facing surfaces of the flaps 7b, 8b and the seatings around the apertures 13a, 14a are machined to such an accuracy that if the sealing gaskets 44 are worn to such an extent that a flap comes into physical contact with its seating, or if such physical contact results from destruction of a sealing gasket, for example due to fire, the maximum width of the gap between any part of the seating and the confronting surface of the flap is 0.006 inch. The venting devices of Figures used in the same way as the venting device described with reference to Figures 7 to 9 of Specification No. 1,241,170 and they may be made of the same materials as - set out in said specification. It will be observed, however, that the flaps 7, 8 and 7b, 8b of the abovedescribed venting devices are different from the flaps 68a and 68b of the venting device described with reference to Figures 7 to 9 of Specification No. 1,241,170 in that they do not comprise the hinged members 72a and 72b. In the earlier venting device these hinged members were provided to accommodate over-pressures and under-pressures occurring when the venting device was in its orifice closed position.If desired, such hinged members could be provided on the flaps 7, 8 and 7b, 8b of the venting devices described above with reference to the drawings. Alternatively, separate provision may be made for accommodating over- and under-pressures, for example separate bypass valves may be connected in parallel with the duct 1 or la. In modified embodiments of the venting devices described above with reference to the drawings, the flaps 7, 8 and 7b, 8b are biased into their closed positions by means of weights secured to the inwardly-facing surface of the flaps and located within the duct 1 or la. These weights would replace the counterweights referred to above. WHAT I CLAIM IS:-

1. A venting device for venting a gaseous and/or vaporous medium into the atmosphere, the device comprising a tubular framework defining a vent for flow therethrough of the medium being vented, and valve means associated with one end of said framework to provide a vent orifice of variable cross-sectional area available for the flow of medium from the vent, said valve means comprising two flaps pivotally mounted on said framework externally of the vent for varying the cross-sectional area of the orifice in response to the volumetric rate of flow for the medium being vented, said cross-sectional area increasing with increasing flow rate of the medium and decreasing with decreasing flow rate of the medium, and biasing means associated with said flaps for urging them into a position in which they close said orifice, characterised in that one end of said framework has two apertures formed therein which, when the vent orifice is closed, are each closed by a different one of the two flaps, the framework providing an uninterrupted seating around each of said apertures against each of which the asociated flap can close, in that sealing means is associated with each seating/flap combination to prevent leakage of the medium being vented from the

venting device when the orifice is closed, and in that the biasing means associated with each flap is adapted to hold its flap in the orifice closed position until the pressure difference on opposite sides of the flap is at least 0.25 p.s.i.

2. A venting device according to claim 1, in which the biasing means associated with each flap is adapted to hold its flap in the orifice closed position until the pressure difference on opposite sides of the flap is at least 0.5 p.s.i.

3. A venting device according to claim 2, in which the biasing means associated with each flap is adapted to hold its flap in the orifice closed position until the pressure difference on opposite sides of the flap is at least 1.0 p.s.i.

4. A venting device according to any of the preceding claims, in which the sealing means associated with each seating/flap combination is a gasket recessed into a groove in the flap, which gasket bears against the associated seating in the orifice closed position of the flap.

5. A venting device according to any of claims 1 to 3, in which the sealing means associated with each seating/flap combination is a gasket recessed into a groove in the seating, which gasket bears against the assoc ciated flap in the orifice closed position of the flap.

6. A venting device according to any one of the preceding claims, in which each seating/flap combination is designed so that if the associated sealing means is destroyed or becomes worn to such an extent that the flap makes direct contact with its seating in the orifice closed position, then in the orifice closed position of the flap the maximum width of the gap between the flap and its seating at any point around the seating is 0.006 inch and the minimum width of the seating confronting the flap is 0.3 inch.

7. A venting device according to any of the preceding claims, in which each flap is pivotally mounted at one end of a respective arm which at its other end is pivotally mounted with respect to said framework.

8. A venting device for venting a gaseous and/or vaporous medium into the atmosphere constructed and arranged substantially as herein described with reference to, and as illustrated in, Figures 1 to 3 of the drawings accompanying the Provisional specification.

9. A venting device for venting a gaseous and/or vaporous medium into the atmosphere constructed and arranged substantially as herein described with reference to, and as illustrated in, Figures 4 and 5 of the accompanying drawings.