GB2100345A

GB2100345A - Pressure relieving devices

Info

Publication number: GB2100345A
Application number: GB8117640A
Authority: GB
Original assignee: Hitachi Zosen Corp
Current assignee: Hitachi Zosen Corp
Priority date: 1981-06-09
Filing date: 1981-06-09
Publication date: 1982-12-22
Also published as: GB2100345B

Abstract

A pressure relieving device comprising a round flexible plate 4 bent downward and having its periphery welded to the inner surface of a cylindrical hatch coaming 3 at appropriate intervals, a sealant 11 for sealing the gap between the remaining part of the plate periphery and the coaming inner surface, a reinforcing rigid plate 5 provided on the flexible plate 4, a beam 7 extending across the coaming 3 under the flexible plate 4, and a rupture bar 6 connecting the flexible plate 4 through the reinforcing plate 5 to the beam 7. If an abnormally high pressure acts on the flexible plate 4, the rupture bar 6 breaks and the flexible plate bends upward. With the upward bending of the plate 4, the welds 10 between the plate 4 and the coaming 3 are deformed and broken, allowing the plate 4 to be blown off from the coaming. Thus the device, if installed on a fuel tank, serves to relieve the pressure in the tank for the maintenance of safety. <IMAGE>

Description

SPECIFICATION Device for emergently relieving pressure The present invention relates to a device for emergently relieving pressure in a fuel tank for safety purpose when the pressure in the tank grows abnormally high.

It is a usual practice to provide a fuel tank, with a device for automatically releasing the internal gas from the tank to prevent the tank from breaking when the internal pressure becomes abnormally high. However since fuel tanks are becoming larger and larger in recent years, pressure relief devices therefor must correspondingly be larger or otherwise a number of small such devices must be provided. To make the matter more difficult there has been a growing demand to relieve pressure at a much lower level.

Thus the present requirements for pressure relief devices are diverse, and conventional devices, if modified to meet these requirements, become complicated mechanically, hence undesirable from the view point of cost and maintenance.

Japanese Utility Model Application No.

53-147271 discloses a simple device which comprises a thin round plate curved downward and having its entire periphery welded to the inner surface of a cylindrical coaming. With this construction, the plate which has been initially bent downward bends upward when subjected to an abnormally higher pressure, so that the weld between the plate and the coaming is deformed and finally broken. As a result, the plate is blown off from the coaming to release the pressure.

However, since the bending stress is evenly distributed over the entire length of the weld, there is a possibility that even if the plate is subjected to a high pressure, the weld and the peripheral portion of the plate remains as initially mounted while only the centrai portion of the thin plate projects upward. Thus the intended pressure relief cannot be dependably achieved with this device.

An object of the present invention, in view of the above problem, is to provide a simple device for a fuel tank which can reliably relieve the pressure in the tank when the internal pressure reaches a specified value, 0.4 kg/cm2, for example.

In order to fulfil this object, the present invention provides a device for emergently relieving pressure comprising a flexible plate bent downward and having its periphery welded to the inner surface of a hatch coaming at appropriate intervals, the gap between the remaining part of the plate periphery and the coaming inner surface being sealed with a sealant.

With this arrangement, since a large bending load produced when the plate is subjected to a high pressure tending to bend it upwards acts concentratively on a reduced total length of the welds, the welds are easily broken and the plate is sure to be blown off from the coaming to relieve the pressure.

According to a preferred embodiment of the present invention, the device further comprises a beam extending across the coaming under the plate, and a rupture bar designed to break under a specified load and connecting the beam and the plate.

This arrangement prevents the plate from prematurely and locally deforming at a pressure below a specified value. This prevention effect can be further enhanced by providing a reinforcing rigid plate on the central portion of the flexible plate.

Various features and effects of the invention will become apparent from the description of an embodiment given with reference to the accompanying drawings, in which: Fig. 1 is a view in section taken along the line A-A in Fig. 3 and showing a device according to the invention, Fig. 2 is a view in section taken on the line B-B in Fig. 3 and showing the same, Fig. 3 is a top view of the same, and Fig. 4 is a view in section of the same taken along the line X-X in Fig. 1.

Referring to the drawings, a fuel tank 1, such as an oil reserve tank, having a hatch opening 2 is provided with a cylindrical hatch coaming 3. A round flexible plate 4 is fitted in the upper portion of the coaming 3 as curved spherically downward.

A reinforcing plate 5 of rigid material is removably mounted on the flexible plate 4 coaxially therewith as shown in Fig. 3. A rupture bar 6 having a thin intermediate portion extends through the reinforcing plate 5 and the flexible plate 4, and is connected to an I-beam 7 extending across the coaming 3 under the plate 4. A collar plates 8 and 9 hermetically attached to the rupture bar 6 are welded to the flexible plate 4 and the reinforcing plate 5 respectively. The rigidity of the reinforcing plate 5 may be enhanced by stiffeners 12 indicated in phantom lines in Figs. 1 and 3.

As best illustrated in Fig. 3 the flexible plate 4 is welded at 10 to the inner surface of the coaming 3 at appropriate intervals. Between the welds 10 are provided sealants 11 to seal the gap between the remaining portion of the periphery of the plate 4 and the coaming inner surface.

The total length of the welds 10 is suitably 10 to 25% of the circumference of the flexible plate 4, and the strength of the welds 10, i.e., the strength of the connection between the flexible plate 4 and the coaming 3, should be such as to barely endure normal pressures (0.14-0.07 kg/cm2) in the tank 1. The sealant 11 may be made of any material, such as silicone rubber, which is resistant against water, weather, ozone, and heat. The flexible plate 4 is made of a thin steel plate, preferably a thin stainless steel plate.

With the construction described above, the device operates in the following manner. At normal pressures the rupture bar 6 and the welds 10 would not break, and the flexible plate virtually remains as initially mounted. In this state the reinforcing plate 5 serves to prevent local deformation of the flexible plate 14, so that slight variations in pressure due to temperature variations will not cause a significant stress in any of the welds 1 0.

If for some reason the internal pressure in the tank 1 develops to a specified level, 0.4 kg/cm2, for example, the rupture bar 6 breaks at its thin intermediate part, whereupon the pressure causes the flexible plate 4 to bend upward. Since the sealants 11 pose substantially no resistance to the upward bending of the plate 4, a large stress is concentratively produced in the welds 10. As a result, the welds 10 immediately break and the flexible plate 4 is blown off from the coaming 3 to release the pressure. Thus the device can reliably fulfil the intended safety function when the internal pressure rises to a specified level.

The present invention is not limited to the illustrated embodiment but can be modified in various ways. For example, the reinforcing plate 5 and/or rupture bar 6 can be dispensed with. Thus the scope of the present invention should be understood from the appended claims.

Claims

1. A device for emergently relieving pressure comprising a flexible plate bent downward and having its periphery attached to the inner surface of a hatch coaming, wherein the periphery of the plate is welded to the inner surface of the coaming at appropriate intervals, and the gap between the remaining part of the periphery of the plate and the coaming inner surface is sealed by a sealant.

2. A device as defined in claim 1 wherein the total length of the welded portion of the plate periphery is 10 to 25% of the circumference of the plate.

3. A device as defined in claim 1 or 2 wherein the sealant is synthetic resin.

4. A device as defined in claims 1 to 3 further comprising a beam extending across the coaming under the plate, and a rupture bar designed to break under a specified load and connecting the beam and the plate.

5. A device as defined in claim 4 wherein the rupture bar has a thin intermediate portion.

6. A device as defined in claim 4 or 5 wherein a reinforcing rigid plate is provided on the flexible plate, and the flexible plate is connected through the rigid plate to the bar.

7. A pressure relief device for a container substantially as described herein with reference to and as illustrated in Figures 1 to 4 of the accompanying drawings.