GB2056026A

GB2056026A - A Safety Closure Particularly for the Venting Line of a Tank Truck

Info

Publication number: GB2056026A
Application number: GB8011848A
Authority: GB
Original assignee: Linke Hofmann Busch GmbH; Linke Hofmann Busch Waggon Fahrzeug Maschinen GmbH
Current assignee: Alstom Transport Deutschland GmbH
Priority date: 1979-06-08
Filing date: 1980-04-10
Publication date: 1981-03-11
Also published as: FR2458485B1; CH647733A5; DE2923196A1; ATA161480A; GB2056026B; FR2458485A1; AT365135B; DE2923196C2

Abstract

A tubular casing 2 has a pipe connection 1 with a venting valve (not shown) which communicates with the vapour space of a container, for example, a bulk liquid transporter. The casing has two free ends 3, spaced from said pipe connection, each free end having a removable end cap 4, 4. A spring-loaded valve rod 5 extends between said caps, said rod having apertured closures 6 thereon which are capable of coacting with apertures 11 to seal the vapour space from the atmosphere under certain conditions e.g. connection of one end of said casing to the vapour space of another container by a compensation line 12 permits the valve rod 5 to move along the casing to allow closure 6 to seal apertures 11 and thereby to seal the vapour space of the first-mentioned container from the atmosphere. Pumping of liquid from one container to the other causes gases to pass from said other container to said one container instead of passing into and polluting the atmosphere. in a further embodiment, Figs. 3 & 4, (not shown), lift valves coact with seats provided in the casing. <IMAGE>

Description

SPECIFICATION A Safety Closure, Particularly for the Venting Line of a Tank Truck This invention concerns a safety closure, in particular for the venting line of a tank truck.

Such trucks are used for the carriage of inflammable liquids and, in such trucks, it is known practice, prior to discharging, for a domed cover located on the top of the tank to be opened and then for a stationary discharge line to be connected to an outlet pipe at the bottom of the tank. Then a bottom valve located at the junction between the tank and the outlet pipe is opened and the contents can either flow out under the influence of gravity or be sucked out by a pump.

In the process, the inflow of air from the outside through the opened dome cover prevents a vacuum forming and, therefore, any resultant implosion of the tank. However, such a discharge procedure has the disadvantage that somebody has to climb up onto the tank to open and close the top domed cover.

Consequently it has been suggested that the valve disk of the bottom valve be linked by means of rods and cable to a venting valve located on the top of the tank so that said venting valve will be opened automatically when the bottom valve is opened With such a valve system, however, the gases originating from small amounts of residue in the empty tank can escape into the atmosphere when the tank is filled up again later, said gases being forced out by the rising liquid. The escape of the gases into the atmosphere firstly pollutes the environment and secondly there is also the risk of explosion and poisoning.

The principal object of the present invention is to eliminate the disadvantages described above and to provide an arrangement which will automatically ensure pressure equalisation when emptying the tank truck into a stationary tank and with which, during filling, the escaping gas passes from the tank on the truck into the stationary tank.

This is achieved in accordance with the invention in that the attachment of a gas-phase line to the valve breaks the link with the atmosphere and connects the vapour space of the tank truck or container to the vapour space of a stationary tank or another container.

The present invention will now be more particularly described with reference to the accompanying diagrammatic drawing, in which: Figure 1 shows one embodiment of a safety closure in accordance with the invention in longitudinal section; Figure 2 shows the safety closure of Figure 1 with a compensation pipe attached; Figure 3 shows another embodiment of a safety closure in accordance with the invention in longitudinal section; and Figure 4 shows the safety closure of Figure 3 with a compensation pipe attached.

A venting valve for the vapour space of a tank truck, which valve is located on the top of the tank, is connected through a pipe 1 to a tubular casing 2 which advantageously runs horizontally parallel with the tank and is closed off at its two end openings 3 by respective detachable caps 4 and 4a, advantageously a screw-cap, in each case.

A valve rod 5 extends axially and centrally of the casing 2 and is displaceable axially of said casing. In the embodiment of Figure 1 and 2, this rod has two slide valves 6 spaced axially from one another at one end thereof and one slide valve 7 at the other end thereof, these slide valves 6 and 7 having apertures 8. By means of thrust buttons 9 and compression springs 10 and 1 0a, the caps 4 and 4a respectively exert pressures in opposite directions on the valve rod 5 so that, as shown in Figure 1, the two valves 6 are positioned one at each side of diametrically opposed openings 11 in the casing 2.As soon as a bottom valve located at the junction between the tank and the outlet pipe is opened together with the venting valve in order to empty the tank, air can flow from the outside through the openings 11 and the apertures 8, along the tubular casing 2, along the pipe 1 and through the venting valve into the tank.

In order to attach a compensation line 12, one cap, for example the cap 4a as shown in Figure 2, is removed and the compensation line 1 2 is fitted in its place. When the cap 4a is removed, the valve rod 5 together with the slide valves 6 and 7 fixed on it are moved by the force exerted by the compressing spring 10 and the openings 11 are closed by the axially outer of the slide valves 6.

The stroke of the released compressing spring 1 Oa is limited by a restrictor (not illustrated) so that the compression spring 1 Oa only extends into the compensation line 12 to a limited extent.

Now, when emptying the tank on the truck, after opening the bottom and venting valves, gas (instead of air from outside) flows out of the stationary tank through the slide valve 7 and into the tank on the truck and, when filling the tank on the truck, the gas flows out of this into the stationary tank. On the other hand, if the compensation line 12 is fitted in place of the cap 4, the valve rod 5 is moved in the other direction by the force exerted by the compression spring 1 Oa so that now the axially inner of the valves 6 closes the openings 11. But then the venting of the tank or the gas exchange between tank and stationary tank takes place through the slide valve 6 (as already described).

Referring now to Figure 3, openings 1 3 for the entry of air from the outside are disposed in the caps 4 and 4a and are directed axially of the casing 2, so that now, to achieve the same operation as that described above, the valve rod 5 has valve disks 14 and 1 4a at its respective ends.

These disks are held equidistant from respective annular valve seats 1 5 and 1 5a, which are fixed in the casing 2, by the respective compressing springs 10 and 1 0a on both sides.

When the venting valve is opened, the air from outside flows in from both sides through the openings 13 and the central openings 1 6 in the valve seats 1 5 and 15a into the pipe 1 and thence into the vapour space in the tank.

When a compensation line 1 2 is attached in place of the cap, for example in place of the cap 4, the valve disk 14a is forced against the valve seat 1 5a by the force of the spring 1 Oa, as shown in Figure 4, and thus seals this side of the casing 2 to prevent air from the outside entering, so that now there is only a connection between the vapour space of the tank on the truck and that of the stationary tank. Here again, the stroke of the compression spring 10 or 1 Oa is restricted when the cap 4 or 4a, respectively, is removed.

Claims

1. A safety closure for the venting line of a container for a liquid which vapourises, said closure consisting of a spring-loaded valve which is so mounted as to be displaceable longitudinally of and within a tubular casing which is connected to a venting valve on the top of said container, a compensation line attachable to one end of said casing, whereby the attachment of said line breaks the link with the atmosphere and connects the vapour space of the container to the vapour space of another container for said liquid.

2. A safety closure as claimed in Claim 1, wherein said valve consists of an axially displaceable valve rod which carries two fixed axially spaced slide valves at one end thereof which are slidable within said casing to open and close openings disposed radially in the casing and which carries one fixed slide valve at the other end thereof, the slide valves having apertures therein.

3. A safety closure as claimed in Claim 1, wherein said valve consists of an axially displaceable valve rod which carries valve disks to open and close axially directed openings in annular valve seats which are fixed in the casing and through which said valve rod extends.

4. A safety closure as claimed in any one of the preceding Claims, wherein the casing has open ends which are closed by readily removable caps.

5. A safety closure as claimed in Claim 4, wherein the valve rod is provided at each of its ends with a compression spring and a thrust button, of which the button bears against the respective cap, the stroke or extent of elongation of the compression spring when released by removal of the cap being limited by a restrictor.

6. A safety closure for the venting line of a container for a liquid which vapourises, constructed, arranged and operable substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 or Figures 3 and 4 of the accompanying diagrammatic drawing.

7. Any features of novelty, taken singly or in combination, of the embodiments of the invention hereinbefore described with reference to the accompanying drawing.