Temperature Responsive Pressure Relief Filter Vent Device for Storage Drums

A temperature responsive pressure relief filter vent device for a storage drum having an annular sleeve member composed of a fusible material, such as a polymer or low melt temperature metal. The mating portion of the device is externally threaded and the fusible sleeve member is internally and externally threaded. With this structure, the fusible sleeve is mated with the eternally threaded mating portion and this assembly is then mounted into the threaded opening of a drum, thereby securing the pressure relief device onto the drum. Under elevated temperature conditions, as the temperature of the fusible sleeve approaches or reaches the melting point of the fusible material, the sleeve will soften or melt sufficiently such that pressure buildup within the drum causes the pressure relief device to be expelled from the drum.

BACKGROUND OF THE INVENTION

This application relates generally to the field of plugs, valves, vents and/or filters, such as used with storage drums or containers (hereinafter referred to collectively as “drums”), and more particularly relates to such devices that are temperature responsive devices designed to release pressure in emergency situations to avoid catastrophic failure of the drum, i.e., ejection of the drum lid or rupture of the drum wall, and which comprise a venting and filtering mechanism such that internally created gases are gradually released to reduce pressure.

Ejection of the drum lid is designated as a catastrophic failure since in many circumstances the extreme pressure required to eject the drum lid combined, with the sudden release of extreme internal pressure results in the ejection of the drum contents into the ambient as well. This is especially dangerous when the drum contents are hazardous or radioactive materials.

Plugs, valves, vents, filters and similar closure components are well known for use in conjunction with storage drums, such as for example 30- or 55-gallon drums made of metal or polymer. Many of these devices are pressure release or relief devices, such that when a threshold pressure is exceeded inside the drum, the devices provide a means for release of gases from the interior of the drum. Increased pressure may result from internal factors, e.g., the chemical reaction of various materials contained in the drum or radioactive decay, or from external factors, e.g., a fire in the storage area containing the drums. In some circumstances, the dram lid is mounted onto the drum body such that the entire lid will release if internal pressure exceeds a maximum amount.

Some pressure relief devices operate passively, such as filter vents that allow gradual passage of non-hazardous gases such as hydrogen from a drum by diffusion through filter media that precludes passage of hazardous gases. Others operate mechanically in response to a rise in internal pressure, such as a valve maintained in the closed position by a spring until the biasing strength of the spring is exceeded. Others utilize fusible material, i.e., material that melts or softens under elevated temperatures, such as a polymer or low melt temperature metal, and are temperature responsive, such that internal pressure is released when the fusible material blocking a bore or passageway softens or melts to the point that the internal pressure is sufficient to move or flush the fusible material, thereby opening the bore or passageway and allowing gas to escape from the drum prior to catastrophic failure of the drum. The fusible material pressure release means are effective since they address internal chemical reactions or radioactive decay and external fires or excessive ambient temperatures which result in temperature elevation within the drum.

These pressure relief devices, whether activated mechanically or with a fusible material, suffer from a problem in that the diameter of the bore or passageway within the pressure relief device, while sufficiently sized to meet the need for release of small quantities of gases occurring from long-term chemical reactions or decay, is typically too small to allow for rapid release of the large quantity of gases that develop under extreme circumstances, which may occur as a result of internal combustion within the drum or from external fires. In these cases, the pressure build-up within the drum will exceed the relief ability of the pressure relief devices and catastrophic failure of the drum will occur.

To address this, it is known to provide pressure relief devices, which may or may not include a slow pressure buildup release means providing for the escape of gases through bores or passageways in the device, which also include pressure release means responsive to rapid, high temperature elevation within the drum. For example, U.S. Pat. No. 4,325,398 to Green, U.S. Pat. No. 5,240,027 to Vertanen, and U.S. Pat. No. 5,551,470 to Duvall show pressure relief devices that utilize a fusible material which allows a major portion of or the entire pressure relief device to be expelled or blown off from the drum, thereby presenting a large opening for the immediate release of the internal gases. A drawback to each of these known devices is that they possess complex designs to accommodate the fusible material. Since the storage of hazardous or radioactive materials is highly regulated, the complex designs may not meet the acceptable standards as currently written, or may require extensive testing to prove that the complex designs are suitable. The complex designs also result in increased manufacturing and material costs.

It is an object of this invention to provide a temperature responsive pressure relief filter vent device Which incorporates a fusible material such that the pressure relief device is expelled from the drum in response to a rapid elevation in temperature within the drum, thereby creating a relatively large opening such that a sufficiently large quantity of gases may be rapidly released, thereby preventing catastrophic failure of the drum. It is a further object to provide such a device wherein the fusible material is structured to be externally mountable to the operational portion of the filter vent component such that redesign of the internal structure of the filter vent component is not required, the fusible material being a sleeve or collar having external mechanical mating structure to mate with the standard mating structure found in drum lids.

SUMMARY OF THE INVENTION

The invention comprises in general a filter vent drum closure device comprising an annular collar or sleeve member composed of a fusible material, such as a polymer or low melt temperature metal, the sleeve member adapted to mate with a standard lid opening or bung hole of a drum lid. In a preferred embodiment, the main body of the drum closure device is externally threaded and the fusible collar member is internally and externally threaded. With this structure, the fusible collar is threadingly mated onto the external threading of the main body of the drum closure device and the drum closure device is then mounted into the threaded opening of a drum lid, thereby securing the device onto the drum. Under elevated temperature conditions, as the temperature of the fusible collar approaches or reaches the melting point of the fusible material, the collar will soften or melt sufficiently such that the pressure buildup within the drum will cause the drum closure device to be expelled from the drum, completely unblocking the lid opening to provide for a controlled pressure release. The material of composition and structural configuration of the annular sleeve is chosen such that the drum closure device will be expelled at an internal drum pressure much below the pressure which would result in catastrophic failure of the drum, either through ejection of the drum lid or rupture.

Alternatively expressed, the invention is a temperature responsive pressure relief filter vent device adapted to seal an internally threaded storage drum lid opening, said device structured to filter and gradually release gases from inside the storage drum, said device comprising a mating portion comprising external threading and a fusible sleeve member, said fusible sleeve member comprising internal threading and external threading, said fusible sleeve sized to receive said mating portion and to mount into the internally threaded drum lid opening, in further embodiments, the device wherein the storage drum has an internal drum pressure X at which catastrophic failure occurs, and wherein the material of composition of said fusible sleeve member is chosen such that in ambient temperature said device is retained within said drum lid opening at internal pressures up to internal drum pressure X, whereas in an elevated temperature said fusible sleeve member softens or melts such that said device is ejected from said drum lid opening at an internal drum pressure less than X; wherein said device is ejected from said drum lid opening prior to the internal drum pressure reaching two-thirds of the internal drum pressure X; wherein said fusible sleeve member is composed of a polymer; wherein said external threads of said mating portion and said external threads of said fusible sleeve member are both righthanded or both lefthanded; and/or wherein the pitch of said external threads of said mating portion and said internal threads of said fusible sleeve member are different from the pitch of said external threads of said fusible sleeve member.

Alternatively, the invention is a method of preventing catastrophic failure in a storage drum, said drum having a threaded lid opening, comprising the steps of: providing a temperature responsive pressure relief filter vent device adapted to seal an internally threaded storage drum lid opening, said device structured to filter and gradually release gases from inside the storage drum, said device comprising a mating portion comprising external threading and a fusible sleeve member, said fusible sleeve member comprising internal threading and external threading, said fusible sleeve sized to receive said mating portion and to mount into the internally threaded drum lid opening; mounting said fusible sleeve member onto said mating portion; and screwing said fusible sleeve member into the threaded lid opening of the drum. Furthermore, this method further comprising the step of: determining the internal drum pressure X at which catastrophic failure of the drum occurs; and choosing the material of composition of said fusible sleeve member such that in ambient temperature said device is retained within the drum lid opening at internal pressures up to internal drum pressure X, whereas in an elevated temperature said fusible sleeve member softens or melts such that said device is ejected from said drum lid opening at an internal drum pressure less than X; and/or wherein said step of choosing the material of composition of said fusible sleeve member such that in ambient temperature said device is retained within the drum lid opening at internal pressures up to internal drum pressure X, whereas in an elevated temperature said fusible sleeve member softens or melts such that said device is ejected from said drum lid opening at an internal drum pressure less than X, comprises choosing the material composition such that said device is ejected at an internal pressure less than two-thirds of the internal pressure X.

DETAILED DESCRIPTION OF THE INVENTION

In general, the invention is a temperature responsive pressure relief filter vent device10adapted to seal a drum30, the device10having an annular collar or sleeve member20composed of a fusible material, such as a polymer, e.g., a polyethylene, or a low melt temperature metal, as well as its method of use. The pressure relief device10is structured such that gas is gradually filtered and vented from the drum30over time in small amounts to maintain an acceptable and safe internal drum pressure. The term “fusible” as used herein shall mean a material that softens or melts at a temperature elevated above ambient. The term “drum” as used herein shall mean a storage container having a wall or walls31, a lid32and a circular, internally threaded lid opening33, the lid32being mounted to the wall or walls31of the drum30by mechanical interconnection, e.g., threading, clamping, bonding, crimping or any other suitable mechanism. Examples of such drums30are 30- and 55-gallon drums made of metal or rigid polymer. As illustrated representationally inFIG. 1, the drum30is shown as having a wall31, a lid32and a lid opening33having internal threading34, the lid32being secured to the drum wall31by mating external threading35on the lid32with internal threading36on the drum wall31. The term “catastrophic failure” as used herein shall mean the sudden rupture of the drum wall31or the ejection of the drum lid32when the internal drum pressure increases to pressure X such that the strength of the material composing the wall31or the strength of the connection between the lid32and the wall31is insufficient to withstand the increased pressure. While the pressure relief device10is capable of releasing small amounts of gas to reduce the internal pressure of the drum30, the venting capacity is too small to respond to emergency situations, such as when the drum31is exposed to fire and the temperature within the drum30rises rapidly, which in turn rapidly increase the internal pressure.

Pressure relief venting valves and pressure relief filtering and venting valves are known in the art, and the invention as described herein may incorporate various venting and/or filtering mechanisms or techniques that allow for the gradual release of small amounts of gases from the interior of the storage drum30. The invention in effect provides a structure that transforms any of these pressure relief valves into a temperature responsive pressure relief valve that prevents catastrophic failure during rapid temperature/pressure elevation. Examples of pressure relief, filter vent valves are shown in U.S. Pat. Nos. 6,550,492, 5,353,949, 2,271,786, the disclosures of which are incorporated herein by reference.

As shown, a representative embodiment of the pressure relief device10comprises an exterior flange11, typically polygonal in configuration to allow for easy rotation by hand or tool in order to mount or remove the device10form a drum30. Extending beneath the flange11is a cylindrical body portion12of lesser width or diameter than the flange11. An O-ring or similar gasket member40is mounted onto the body portion12and will be compressed against the drum lid32by the flange11when the device10is tightened onto the drum lid32. The device10further comprises a tubular or cylindrical insertion or mating portion13having external threading14. Internal passageways, bores or conduits, filter media, check valves and the like (not shown) facilitate and control the slow passage of gases through the device10for pressure relief under normal (i.e., ambient or near ambient) conditions.

The fusible collar or sleeve member20is a tubular member having external threading21and internal threading22. The internal diameter of the sleeve member20and the pitch, size and other dimensional characteristics of the internal threading22is chosen such that the sleeve member20is tightly received onto and connects with the externally threaded mating portion13such that the two members13/20are joined in a manner that precludes passage of gases between the two members13/20.

The external threading of the mating portion13and the internal threading22of the sleeve member20may be the same as or different than the external threading21of the sleeve member20with regard to number of threads, thickness of threads, pitch, etc. Most preferably, the direction of all threading should be the same, i.e., the threading should all be righthanded or all be lefthanded, such that tightening the mating portion13into sleeve member20also tightens the sleeve member20within the lid opening33.

The external diameter of the collar member20and the pitch, size and other dimensional characteristics of the external threading21is chosen such that the sleeve member is tightly received within and connects with the internal threading34of the lid opening33in a manner that precludes passage of gases between the sleeve member20and the drum lid opening. With this structure, the drum lid opening33is completely sealed when the pressure relief device10with fusible sleeve member20is screwed into and mated to the drum30.

The material of composition of the fusible sleeve member20may be a polymer (e.g., polyethylene) or metal which is sufficiently rigid under ambient or near ambient temperature to maintain the connection and seal with the drum30, but which softens or melts at an elevated temperature, such as at a temperature of 800-1000 degrees C. as might be encountered in a fire. The thickness, length, number of threads, thickness of threads, pitch, etc., will also determine at what point the pressure relief device10is expelled from the drum lid32.

Under rapidly elevating temperature conditions as might be encountered in a warehouse fire, the internal temperature of a drum10will rise, which in turn elevates the internal pressure within the drum10. The rapid increase in internal pressure cannot be accounted for by the standard pressure relief mechanisms within the device10, the size of the conduits and the filter media acting to limit the amount of gas than can be released. As the temperature of the fusible sleeve member20approaches or reaches the melting point of the fusible material, the sleeve member20softens or melts sufficiently such that the pressure buildup within the drum30will cause the device10to be expelled from the drum lid opening33, thereby clearing the entire drum lid opening33for rapid relief of the internal pressure prior to catastrophic failure of the drum30.

A drum30will have catastrophic failure when the pressure inside the drum30reaches a pressure X due to rapid external temperature increase, at which point the wall31will rupture or the lid32will be ejected from the drum30. Upon determining the pressure X for a drum, the material of composition and/or structure of the fusible sleeve member30is chosen such that it softens or melts at the elevated temperature such that an internal drum pressure less than X will forcibly eject the device10from the drum lid opening33, thereby allowing sufficient gas to escape the drum30to preclude catastrophic failure. Most preferably, the device10will be ejected at an internal drum pressure less than two-thirds of X. Thus, if catastrophic failure occurs at 15 psi, then the device10is ejected at 10 psi or less in elevated temperatures.

With this structure, the internal structure or mechanisms of a standard pressure relief filter vent device do not need to be altered to provide the safety pressure relief in emergency situations, as the internal structures and mechanisms are independent of the drum closure retention member, i.e., the fusible collar member20. Utilization of the temperature responsive pressure relief assembly merely requires proper sizing of the drum closure insertion portion13, the fusible collar member20and the drum opening33, along with proper matching of the mating threads.

It is understood that equivalents and substitutions for certain elements set forth above may be obvious to those of skill in the art, and therefore the true scope and definition of the invention is to be as set forth in the following claims.