GB2333769A - Quick release vent cap - Google Patents

Abstract

A fuel storage tank (1, fig 1) has a vent stack pipe 10c topped with a vent valve 14, the vent stack pipe having a quick release connection, such as a cam 36 and groove 37 arrangement, located between the storage tank and the vent valve, enabling the vent valve to be removed for inspection, maintenance or replacement without using tools. The quick release connection may include a valve 41 which automatically closes when the connection is released, and may include a pressure relief valve 44. The vent valve may include a pressure relief valve 47 and a vacuum relief valve 48. A vent cap (51, fig 3) is also disclosed for releasable attachment to a vent stack pipe, the cap being released by movement of a sleeve (65, fig 3) which cooperates with a number of balls (67, fig 3).

Description

QUICK RELEASE VENT CAP This invention relates to fuel storage tanks and, in particular, provides an arrangement for quick release of a vent stack cap from a vent stack pipe.

Commonly, in filling stations, the storage tanks, which are generally located underground, are vented through one or more vent pipes. These may often be located close together, adjacent to a building on the filling station site. The vent pipe is normally topped with a vent cap which incorporates a vacuum release valve arranged to release if pressure within the tank should reach a predetermined excess pressure.

The vent cap is generally also provided with a valve which permits air to enter the pipe and thus the tank (a so-called vacuum relief valve), in order to displace liquid when fuel is drawn off through delivery pumps. Further, the vent cap will include a flame arrester to prevent a flash-back of flame down the vent pipe. All these functions of the vent cap require to be checked and maintenance carried out from time to time.

The vent cap normally has a threaded connection with the end of the vent stack pipe and its removal for maintenance purposes necessitates use of a large stiltson or spanner. This is frequently a lengthy and tricky operation, since the threads may be corroded and the cap located at an elevated position. This may constitute a dangerous situation and while the work is being down, the tank may not be used to supply the delivery pumps.

It is towards a solution to the above problem that this invention is directed.

According to one aspect of the present invention there is provided a fuel storage tank which comprises a vent stack topped with a cap housing a vent valve, the vent stack having a quick release connection located between the storage tank and the vent cap, enabling the vent cap to be removed for inspection, maintenance or replacement without using tools By providing a quick release connection, the vent cap can be removed in an instant and replaced as rapidly with a new or refurbished cap or with a temporary cap, while the original cap is inspected and tested. This has the advantage that the 'down time' is minimal and is limited to the short time of the actual change-over.

Preferably, the quick release connection is incorporated in the vent cap since this requires the minimum changes to a conventional vent stack pipe. However, it may be desirable in some cases to provide an automatic closure valve in the vent stack pipe at the point where the quick release connection is made. By arranging the automatic closure valve to close by the action of releasing the quick release connection, the contents of the tank are not exposed to atmosphere. When an automatic closure valve is employed, a pressure relief valve is preferably also associated with the automatic closure valve in order to protect the tank in case excess pressure is developed after the vent cap has been removed.

The quick release connection is preferably situated at the vent cap. As an alternative, it may be located at some point along the length of the pipe. It may be convenient to select a position in the pipe above ground level, at a point which permits disconnection of the cap and a length of attached vent pipe portion, without the use of a ladder or elevated platforms For example, it may be mounted at a height of say 1 to 1.5 metres above ground leveL The quick release connection may comprise a first connector piece which includes a valve which is normally closed and is opened by the action of bringing the two connector parts together. Quick release connections of this kind are used in the fuel distribution industry for connecting a tanker hose to a supply pipe to the fuel storage tank. In such connection devices, the quick release connection is made by a cam lock coupling on one connector part which engages with a groove in the other connector part.

A preferred alternative comprises a locking device which is held in position by a spring, the arrangement being such that by applying a counteracting force to the spring, the locking device is released and the two parts forming the connector can be disassembled. Conveniently, the locking device is a latch, e.g. a pin, segment of a ring or a ball which engages in corresponding grooves or holes in the connector parts.

Several embodiments in accordance with the invention will now be described by way of illustration, with reference to the accompanying drawings, in which: Figure 1 is a general view of a petrol filling station installation, showing a fuel storage tank fitted with vent stack pipes, Figure 2 is a general arrangement drawing showing part of the vent stack pipe, the pipe being fitted with a quick release connector in accordance with one embodiment of the invention, Figure 3 is a part sectional view of a vent cap and stack pipe fitting in accordance with a second embodiment of the invention, and Figures 4 and 5 are part sectional views of a vent cap and stack pipe fitting in accordance with a third embodiment of the invention Referring to the drawings, a fuel storage tank 1 is located underground and is connected via a drop tube 2 and a supply line 5, to a stand pipe 6 having a coupling 7 for coupling to a tanker supply hose. The head space of the tank is vented through a pipe 11 which is connected to a vent stack pipe 10, the latter terminating in a vent cap 14.

Alternatively, a group of vent pipes 10a can be linked to a single vent stack 16, topped with a single vent cap 14. Fuel is drawn from the tank 1 through a delivery line 17 to a fuel delivery pump 12. Suction through the pipe 17 causes a reduction in pressure in the head space 20 and this is relieved by a vacuum relief valve in the vent cap 14.

Similarly, should an excess pressure be developed in the head space 20, e.g. by a sudden rise in temperature or during the supply of fuel from a tanker to the tank, such excess pressure can be vented through a pressure relief vent valve located in the cap 14.

In accordance with one embodiment of the invention, it is proposed to provide a quick release connection in the vent stack pipe 10 or vent stack pipe 16, at a convenient height above the ground level 21 so that the vent cap can be serviced without requiring access via a ladder or other similar means. The general arrangement is shown in Figure 2, in which the vent cap 14 is connected to the upper portion lOb of the vent stack pipe 10. The lower part 1 Oc ofthe vent stack pipe 10 is connected to a first part 30 of a quick release coupling, while the upper part lOb of the vent stack pipe is connected to a second part 31 of the quick release coupling. Lower part 1 Oc is connected to the vent pipe 11 leading from the head space 20.

The design of the coupling is similar to that used for coupling tanker supply hoses to a supply pipe such as pipes 5 and 6 shown in Figure 1. Essentially, the coupling comprises a male part 32 dimensioned to enter a female part 33 and to seat against a petrol-resistant, flexible sealing ring 34 (e.g. Viton). When the part 32 is in place in the recess 33, arms 35 can be pivoted into a vertical position when the cam surfaces 36 engage in the annular depression 37. The arms 35 can be locked in their vertical position by security padlocks extending through holes 38 in the ends of the arms and through corresponding holes 39 in a lock yoke fitted to a collar 40.

In the open position of the arms 35, vent stack pipe lOb, coupling part 31 and vent cap 14 can be removed in one piece and taken to an on-site workshop for testing and inspection of the vent cap.

In order to prevent undesired escape of vapour from the vent pipe 1 Oc, after removal of the vent cap, the coupling part 30 includes a valve 41 which automatically closes when the coupling part 31 is uncoupled and removed. Valve 41 is spring biased into the closed position as shown in Figure 2, but is opened by downward pressure on a central post 42 so as to take up the position shown in dotted lines in the Figure. Downward pressure is exerted on post 42 by spigot 43 on the other coupling part 31 when the two parts of the coupling are brought together. However, it will be appreciated that in the condition in which part 31 is uncoupled from part 30, that the valve 41 is automatically closed and seals the storage tank from atmosphere. The length of spigot 43 is selected so that valve 41 closes just before the two coupling parts separate.

In order to guard against an undue pressure being developed in the storage tank 1, the coupling part 30 includes a pressure relief valve 44 which opens when pressure above a predetermined level is developed in the tank. Also, in order to permit fuel to be drawn from the storage tank 1 while the vent cap is removed for maintenance, the valve 41 can be arranged to open in response to a reduction in pressure in the storage tank.

As shown in Figure 2, the coupling part 30 may include a manometer 45 for testing for any leaks within the connection between coupling part 30 and the tank 1.

Such manometer or other test gauge may be connected to the coupling part 30 by means of a quick release connector 46.

The vent cap 14 shown in Figure 2 is generally of conventional construction, and includes a pressure relief valve 47 and a vacuum relief valve 48. Both of these valves can conveniently be checked for their proper fimctioning during the maintenance of the equipment. To facilitate handling of the upper part of the vent stack pipe and associated components, the vent cap, vent stack pipe portion lOb and the coupling part 31 are preferably manufactured from a light-weight metal, e.g. aluminium or an aluminium alloy.

Figures 3, 4 and 5 show two embodiments in accordance with the invention which are somewhat similar to each other but significantly different from the embodiment shown in Figure 2.

Referring to Figure 3, this is a partially sectioned view of a vent cap 51 fitted with a quick release connection incorporated within the cap. The cap comprises a top portion 52 which is connected by a quick release connection to a fitting 53 having an internally threaded lower part 54 for attaching the fitting 53 to the upper end of the vent pipe, indicated in dotted lines within the part 54.

Top portion 52 comprises a housing 55 having a valve body 56 contained therein. Valve body 56 has an annular seat 57 which seals against a sealing ring 58.

Valve 56 is a 'dead weight' valve and is normally closed. In the event of excessive pressure in the tank, pressure exerted on the face 59 lifts the body off its seat and allows vapour to vent through apertures 60,61.

Valve body 56 also has an internal bore 62 into which is received a poppet valve 63. The latter valve is normally closed by a spring 64 onto a valve seat 65.

When a reduced pressure occurs within the vent stack pipe, e.g. fuel is drawn off via a petrol delivery pump, valve 63 opens to admit air to displace the fuel which is delivered. Surrounding the housing 55 is a tubular sleeve 65. This is urged downwardly into the position shown in figure 3 by a spring 66 which acts between a land at the upper end of the housing and an internal face of the sleeve. In the position shown, the sleeve traps a number of balls 67 in corresponding holes in the housing and also within a groove or indentation 68 in the fitting 53. It will be appreciated that by moving the sleeve 65 upwardly against the pressure of the spring 66, the balls will be disengaged from the groove 68 and the housing and sleeve pulled off the fitting 53. A fresh vent cap can be immediately snapped over the fitting 53 and the original one inspected.

The vent cap shown in Figures 4 and 5 is similar to that shown in Figure 3 and the same reference numerals have been used to indicate corresponding parts.

The main difference is that the sleeve 65 is in two parts, 65a and 65, the lower part 65b encloses a number of vertically arranged coil springs 66a which act between a lower face of the upper sleeve part and an internal face of the lower sleeve part.

Upward movement of the lower sleeve part against the force exerted by springs 66a releases balls 67 from their corresponding groove and enables the housing to be lifted offthe fitting 53.

The vent cap shown in Figure 4 has a number of advantageous features. For example, valve body 56 seats on a plastic (Delrin) sealing ring 70, which reduces corrosion problems. Another important feature is that the valve body 56 is formed with longitudinal ribs, e.g. by forming it from polygonal stock such as hexagonal bar.

This reduces fiction when the valve body slides up and down in the housing. Further reductions in fiction are achieved by coating the internal surface of the housing with a low friction material such as Teflon (p.t.f.e.).

Finally, the vent ports 61 and the upper sleeve part are shaped so that there is no recess for rain water to accumulate and large drain holes 71 are provided to drain water away from the interior of the upper sleeve part. Accumulation of water within conventional vent caps not only causes corrosion but, in freezing conditions, can prevent the valves within the vent cap from operating.

An advantage which the enbodiments of Figures 3 and 4 share is that it is not obvious from casual inspection how the vent cap is removed and this reduces the risk of unauthorised interference in the cap.

In all the embodiments a flame arrester mesh 72 is fitted over the outlets from the pipe.

Claims (8)

CLAIMS:-

1. A fuel storage tank which comprises a vent stack pipe topped with a vent valve, the vent stack having a quick release connection located between the storage tank and the vent valve, enabling the vent valve to be removed for inspection, maintenance or replacement without using tools.

2. A tank as claimed in claim 1 wherein said quick release connection comprises a first connector part which is attached to a portion of the vent pipe leading to the tank and a second connector part which is attached to the portion of the vent pipe on which the vent valve is mounted, said first connector part including an automatic closure valve which automatically closes the vent stack pipe on releasing said quick release connection.

3. A tank as claimed in claim 2 in which the first connector part includes a valve which is normally closed and is opened when the two connector parts are connected together.

4. A tank as claimed in claim 2 or 3 wherein said first connector part includes a pressure relief valve which opens in response to a predetermined excess pressure in the tank.

5. A tank as claimed in any one of the preceding claims in which the quick release connection is mounted at a point above ground level which permits disconnection of the vent valve and attached vent pipe portion without use of a ladder or elevated platform.

6. A tank as claimed in claim 1 wherein the quick release connection is located at the top of the vent stack pipe as part of a vent cap containing said vent valve.

7. A tank as claimed in claim 6 wherein the vent cap is retained on the top of the vent stack pipe by a locking device which is released by relative movement of parts of said cap to disengage the locking device.

8. A vent cap for releasable attachment to a vent stack pipe, said cap including a housing having one or more openings permitting escape of vapour to atmosphere, a valve member which is slidable within the housing and normally rests in a closed position on a valve seat, and a locking device for releasably holding the cap on a valve stack pipe, said cap being released by movement of a sleeve member relative to said housing.