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(11) | EP 0 111 119 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Bulk container closure and system for high purity liquids |
| (57) @ A bung is provided for filling and withdrawal from the bulk container of liquids,
such as high purity chemicals, and still maintain the high purity of the liquid. The
specially designed bung is adapted to fit pails and drums of plastic, plastic lined
steel, stainless steel, or containers of other materials of construction with capacities
from 5 gallons to 55 gallons or more and may be made of a suitable plastic, metal
or other material of construction. The diameter and thread size of an original pail
or drum bung may be duplicated in making the special bung. The special bung has a
threaded opening into which is fitted a dip tube made of the same material as the
bung. The dip tube reaches continguous to the bottom of the container. The special
bung also has an opening into which an inlet air filter can be secured. After installing
an inlet air filter, the contents of the container can be pumped through the dip tube
while maintaining the integrity of the product against contamination. Both openings
in the bung are fitted with plugs to seal the container during the shipment of the
filled containers. Containers fitted with the special bung are designed for repeated
use, i.e., returnable containers. and each container is preferably dedicated to the
packaging of only a single high purity liquid chemical product. |
BACKGROUND OF THE INVENTION
[0001] Various liquids which are shipped in bulk containers are exposed to conditions which adversely affect the level of purity of these liquids. In many situations the maintenance of high purity is necessary for the practical acceptance of the liquid. As an example, in semiconductor applications it is essential that chemicals of high purity be used in various processing steps; otherwise the resulting product is not acceptable. The sources of contamination for these bulk liquids may be introduced at various stages such as when the bulk container is filled or when the liquid in the bulk container is withdrawn and, particularly, when only a part of the liquid is withdrawn and the bulk container is recapped to preserve the balance of the contents for a subsequent use. In such cases the contaminant may be introduced by the bung which is contaminated or even by the air which displaced the amount of liquid withdrawn from the container. In some instances a quantity of liquid already in the bulk container is less than the desired purity due to the original relatively low purity level or because the product has been subsequently exposed to contaminants, and it is important that this purity be upgraded without requiring that the product be returned to the packaging source for reprocessing or otherwise upgrading of the purity.
[0002] It is apparent, accordingly, that a need exists for a bulk packaging arrangement that provides for maintaining a high level of purity of the product in a bulk liquid container and for facilitating the upgrading of the purity of the liquid in the container.
SUMMARY OF THE INVENTION
[0003] The advantageous results of the invention are attained by the provision of a specially designed closure or bung adapted to receive, in combination with one or more openings in the bung, a dip tube which reaches from the bung into the container. The bung arrangement is adapted to be applied to a variety of commercially available commercial shipping containers.
[0004] Bulk containers range in size from five gallon pails through fifty-five gallon and larger drums and/or tanks. These containers may be of standard design and materials of construction available from various vendors or they may be custom designed using special materials of construction.
[0005] The procedure for packaging the high purity liquid products in these bulk containers normally would involve cleaning the bulk containers to be used, both the inside and the outside of the container, preferably with a detergent followed if appropriate by a rinse which may be a fluorocarbon drying solvent, to remove all gross contamination. The traces of drying solvent are expelled by blowing a filtered dry air stream into the container. Other cleaning methods may, of course, be employed.
[0006] The cleaned container would then be fitted with the bung of the invention having outside dimensions adapted to fit the container. The bung may be made of suitable material, e.g., a plastic, such as fluorocarbon resin, polyalkylene resin, nylon, and the like; stainless steel, or other materials of construction compatible with the product to be packaged. The thread type of the bung which secures it to the container conforms to that of the original container. The top of the bung above the threads is preferably formed to be greater in diameter and thickness than the original bung in order to provide two or more wrench flats. The thread type may be national pipe thread (NPT), buttress thread, machine thread, or any other thread type required to match the thread used in the container bung opening.
[0007] The bung has one larger (e.g., 3/4") NPT threaded opening and one relatively smaller (e.g., 1/4") NPT threaded opening. The larger opening is fitted with a dip tube that reaches into the container to a depth contiguous to the bottom. The dip tube preferably is made of the same material of construction as the special bung. Such material of construction may depend on the container contents and on the regulatory requirements and may be either steel, plastic, etc. The filtered product is pumped into and out of the cleaned container through this dip tube.
[0008] The openings in the bung are used in various applications. For example, after a container has been cleaned and fitted with the special bung and dip tube, the container is filled with a micron filtered product. To accomplish this, unfiltered product is pumped from storage tanks or drums through 0.2 micron absolute filters into the clean container passing through the dip tube that is secured in the opening in the bung. As the container fills with product, the air in the container, together with any product fumes, will escape through the smaller opening and filter which is screwed into the opening. The filter is connected to an exhausting system.
[0009] In another application, after a clean container is filled with product, it may be necessary that the liquid contents be recirculated through a filter to remove any particulate contamination which may have been left in the container after cleaning or which may have been introduced in the filling process. In recirculating the product, a pump picks up the material through the dip tube in the bung.opening and pumps the product through the filters and back into the container through a line connected to the smaller opening in the bung.
[0010] Still another application resides in the avoidance of contamination of the pure product during unloading of the product from a bulk container by using a pump. Before the product is pumped out of the container through the dip tube, a filter is attached to the smaller opening. The filter will permit clean air to enter the container as product is removed thus preventing a vacuum build-up in the container.
[0011] A further use relates to unloading the material from the container by using filtered nitrogen or air pressure. The pressuring gas line is connected through a micron filter to the smaller opening. As the gas pressure (of a relatively low order) builds up in the container, the product will flow out of the dip tube which is screwed into the opening in the bung.
[0012] Containers that have been filled, recirculated, and checked for quality are ready for shipment. Any fittings, lines, or filters screwed into the bung are removed.and replaced with plugs. These plugs may be made of the same material of construction as the bung and are provided with a suitable slot in the top to fit a bung wrench or wrench flats projecting above the top.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013]
Fig. 1 is a plan view of the closure or bung element of the invention showing a pair of openings with plugs or closures in the openings.
Fig. 2 is a side elevational view partial in section of the bung of Fig. 1 with plugs displaced from the openings.
Fig. 3 is a side elevational view of a bung with a variant form of thread for securing the bung to the bulk container.
Fig. 3A shows the side elevational view and Fig. 3B the plan view of a variant form of plugs for the. bung openings.
Fig. 4 illustrates by schematic one form of the adaptation of the bung arrangement of the invention in which the contents of a container are recirculated to purify same.
Fig. 5 is a schematic showing another adaptation of the bung arrangement of the invention illustrating the unloading of a container while the replacement air is purified.
Fig. 6 is still another schematic showing a further adaptation of the bung arrangement of the invention in which the container is unloaded by pressure.
Fig. 7 is a schematic to illustrate still a further adaptation of the bung of the invention in which a container known to be clean is filled with purified material.
Fig. 8 illustrates on a larger scale the bung with dip tube secured therein.
Fig. 9 is an illustration similar to Fig. 8 wherein a bung with variant thread design is shown.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] Figs. 1 through 3 illustrate the bung of the present invention which is designed to fit standard metal and plastic commercial bulk containers, for - example, standard 5 gallon or 55 gallon metal, e.g., stainless steel, or plastic containers. The bung is provided in a size and thread design to match that of the bung opening in the container to be serviced.
[0015] The bung 10 comprises a top or closure portion lOa of a relatively larger diameter and a thread portion 10b of relatively reduced diameter. This difference in . diameter affords an ample seat 10c to effect a proper seal of the top of the bung on the container contiguous to the container opening. The seat 10c may optionally accommodate a gasket 10d of suitable composition that is compatible with the container and contents. The bung 10 is provided with a pair of openings, a relatively larger threaded opening 15 which accommodates a dip tube 17 and through which the liquid passes to fill or vacate the container C and a relatively smaller threaded opening 16 through which air or gases or vapors pass. Both openings 15 and 16 extend through the entire plug 10, i.e., through the upper portion 10a and the threaded portion lOb. Threaded plugs 20 and 21 are provided for the openings 15 and 16, respectively. The plugs 15 and 16, optionally, may be tethered, as shown, by a suitable means such as by a link chain 23 to the bung 10. The bung 10 may be made of a suitable plastic, which may be homopolymers or copolymers, ethylene chlorotrifluoroethylene, e.g., polypropylene, polyethylene, co-polymer, polytetrafluoroethylene and other fluoroplastics, nylon and the like or it may be formed of metal, e.g., stainless steel, or of other materials of construction compatible with the chemical composition of the product to be packaged. In fabricating the bung in Figs. 1, 2, and 3, the thread diameter of the bung 10b and the thread type 11 of the original container bung are duplicated. The top of the special bung above the threads is greater in diameter 12 and thickness 13 than the original bung in order to provide for two or more wrench flats 14. The thread type 11 may be national pipe thread, buttress thread, machine thread, or any other thread type required to match the thread used in the container bung opening.
[0016] As shown in Fig. 3, the bung 10 may be provided with a different thread type 11B and is made to accommodate plugs as shown in Figs. 3A and 3B which may be of different configuration. The plugs 20 and 21 of Figs. 1 and 2 and plugs 20a and 21a of Fig. 3A and Fig. 3B may be made of the same material of construction as the bung. Plug styles may vary in that plastic plugs may have a slot 22 in the top to fit a bung wrench (Fig. l), while stainless steel plugs may have wrench flats 24 projecting above the top .(Fig. 3A). As noted above, these plugs may be secured to the bung by a tether (shown as 23 in Figs. 1 and 2) which tether may be made of wire, chain, plastic, or other material.
[0017] Illustrated in Figs. 8 and 9 with dip tubes 17a and 17b attached are the bungs of Fig. 2 and Fig. 3, respectively. The dip tube 17 is sized to extend close to, but preferably not engage, the bottom of the bulk container. Shown in Fig. 4 through Fig. 7 are several systems in accordance with the invention adaptable with the bung hereinabove described. In general, the invention, in conjunction with the bung described in the present application, permits a variety of means for facilitating the packaging, shipment and use of high purity liquids so as to effectively minimize contamination and meet the high standards required in such fields as semiconductor manufacturing and in the pharmaceutical industries, for example. The system, in addition to the special bung and standard bulk container, utilizes one or more of several additional components, i.e., an air filter, a pump, and a highly effective, such as a 0.2 micron, liquid filter.
[0018] The system illustrated in Fig. 4 comprises a container C fitted with a bung 10 of the kind described in Figs. 2 and 3. A dip tube 17 is fitted in the larger opening 15 in the bung 10 and is connected to a suitable pump P4 which draws the contents from the container C through line .L2 and circulates it through line L3 through a fine pore filter 19 and returns it to the container C through a line L4 passing through the opening 16 in the bung. The system, as described further hereinafter, may be used to upgrade the purity of the liquid in the container, for example, prior to shipment by the packer or by the user prior to the use of the product.
[0019] In Fig. 5 an arrangement that maintains the purity of the product in the container C is illustrated. As described in further detail hereafter, the product withdraws through line L5 by the action of pump P5 through the dip tube 17 positioned in the larger 15 of the two holes in the bung 10 and is transported for use through line L6. If desired, an additional filtration may be performed by passing the liquid through a suitable filter such as a 0.2 micron filter 19 and then to the discharge line L7. To preclude entry of contaminated air into the container C as the product is withdrawn, an air filter 18 is positioned in the smaller 16 of the two openings in the bung 10.
[0020] Fig. 6 illustrates a system similar to that of Fig. 5, except that instead of withdrawing the product from the container C by pump, a pressure system is used. As shown, pressurized air through line L8 is passed through filter 18 into the container C through the smaller 16 of the holes in the bung 10 to displace the liquid in the container and force it up through dip tube 17, positioned in the bung opening 15, line L8, the filter 19, and finally exit line L10.
[0021] Shown in Fig. 7 is an arrangement for filling a clean container C containing a filtered product with an unfiltered or relatively impure product. Product drawn from a source through line L12 passes through pump P9, filter 19 and line L14 and is introduced into the container C through the dip tube 17 positioned in the larger opening 15 of the bung 10. Air displaced from the container C as the container fills is suitably cleansed or purged by passing through a suitable filter 18 of vapors which would otherwise contaminate the atmosphere or create a hazard before the extract is discharged through line L15.
[0022] As noted above, the bung 10 is provided with at least a pair of openings 15 and 16 with closure plugs 20 and 21 for use in stopping the product. In a preferred embodiment, the, bung 10 has one 3/4" NPT threaded opening 15 and one 1/4" NPT threaded opening 16 drilled and tapped from both sides of the bung. The 3/4" NPT opening 15 is fitted with a 3/4" dip tube 17 (Figs. 8 and 9, and which is shown diagrammatically in Figs. 4-7) which reaches into the container to within about 1/4" of the bottom. The dip tube 17 is made of the same material of construction as the special bung which, depending on the contents and regulatory requirements, may be either steel, plastic, etc. The filtered product is pumped into and out of the cleaned container through this dip tube 17.
[0023] The 1/4" NPT opening 16 in the special bung is used in various different applications, of which the following four, made by reference to Figs. 4-7, are typical.
[0024] I. After a container has been cleaned and fitted with a special bung (Figs. 1, 2, and 3) and dip tube 17 (Figs. 8 and 9), the container must be filled with 0.2 micron filtered product as shown in Fig. 7. To accomplish this, unfiltered product is pumped from storage tanks or drums through 0.2 micron absolute filters 19 into the clean container passing through the dip tube 17 which is screwed into opening 15 in the special bung. As the container fills with product, the air in the container, together with any product fumes, will escape through the 1/4" NPT opening 16 and a 0.2 micron filter 18 which is screwed into the opening 16. The filter 18 is connected to an exhausting system.
[0025] II. After a clean container is filled with product, the material is recirculated through 0.2 micron absolute filters 19 as in Fig. 4. This step is important to remove any particulate contamination which may have been left in the container after cleaning or which may have been introduced in the filling process. In recirculating the product, the pump picks up the material through the dip tube 17 which is screwed into the 3/4" NPT opening 15 in the special bung and pumps the product through the 0.2 micron absolute filters 19 and back into the container through a line connected to the 1/4" NPT opening 16 in the special bung.
[0026] III. A third application for the 1/4" NPT opening 16 resides in the avoidance of contamination of the pure product during unloading of the product from a bulk container by using a pump. Before the product is pumped out of the container through the dip tube 17, a 0.2 micron filter 18 is attached to the 1/4" opening 16 as in Fig. 5. Filter 18 will permit clean air to enter the container as product is removed thus preventing a vacuum build-up in the container.
[0027] IV. In a fourth use for the 1/4" opening 16 also relating to unloading, the material is withdrawn from the container by using filtered nitrogen or air pressure. The pressuring gas line is connected through a 0.2 micron filter 18 to the 1/4" NPT opening 16 as in Fig. 6. As the gas pressure (7 psig max.) builds up in the container, the product will flow out of the dip tube 17 which is screwed into the 3/4" opening 15 in the special bung.
[0028] After a cleaned container has been filled, recirculated, and checked for quality, it must be made ready for shipment. To accomplish this, any fittings, lines, or filters screwed into the top side of the 3/4" NPT opening 15 or the 1/4" NPT opening 16 in the special bung must be removed and replaced with 3/4" NPT plug 20 and 1/4" NPT plug 21 as shown in Fig. 1 and 2.
1. A bung for containers adapted to facilitate the purification of the contents of
said container comprising an external screw threaded body having at least two flow
openings therethrough, at least one for mounting therein a dip tube and through which
liquid passes and a second flow opening which accommodates the passage of liquid when
the contents of the container is being recirculated and accommodates the passage of
air or vapor when said container is being filled or vacated.
2. The bung of claim 1 wherein a first flow opening comprises a threaded opening of
larger diameter and a second opening having a threaded opening of smaller diameter
each of said openings being provided with a threaded closure plug which mates with
said first and second openings.
3. The bung of claim 2 wherein the closure plugs are tethered with a flexible tie
to retain the plugs and prevent misplacement when the plugs are removed from the bung
flow openings.
4. The bung of claim 1 in combination with an air or vapor filter and a pressure pump.
5. The bung of claim 1 in combination with a filter and a vacuum pump.