Bulk container system for high purity liquids

A system is provided for filling, for purifying liquids in a shipping container and for maintaining the high purity during withdrawal from the bulk shipping container of liquids, such as high purity liquids. In the system a specially designed bung adapted to fit shipping containers, such as pails and drums which may be made of a suitable plastic, metal, e.g. stainless steel, or other material of construction. The special bung has at least two openings, including an opening into which is fitted a dip tube that reaches contiguous to the bottom of the container. The special bung also has an opening into which a gas filter can be secured. In the system, the contents of the container can be pumped through the dip tube while maintaining the integrity of the product against contamination. The purity of the liquid can be upgraded by pumping, i.e., recirculating the liquid through a filtration media and returned to the container. A gas filter to purify air or vapor passing into or out of the container avoid pressure or vacuum buildup. 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.

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when the liquid in the bulk container is withdrawn and, particularly, when 
only a part of the liquid is withdrawn and the bulk container is recapped 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or even by the air which displaced the amount of liquid withdrawn from the 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. 
It is apparent, accordingly, that a need exists for a bulk packaging 
purification and delivery system 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 
The advantageous results of the invention are attained by the provision of 
a circulating system for the chemical which uses a specially designed 
closure or bung adapted to receive, in combination with one or more 
openings in the bung and 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 shipping containers. 
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. 
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. 
The cleaned container would then be fitted with the bung described in 
therein 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 bung may comprise any appropriate 
configuration which is suitable to match the container opening. 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. 
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 out of the cleaned container through this dip tube. 
The openings and the dip tube secured in one of 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 liquid product of suitable purity. To accomplish this, 
unfiltered product is pumped from storage tanks or drums through an 
appropriate filtration system, such as a 0.2 micron absolute filter, into 
the clean container. As the container fills with product, the air in the 
container, together with any product fumes, will escape through the 
smaller opening and vent (gas) filter which is screwed into the opening. 
The filter may be connected to an exhaust system. 
In another application, after a clean container is filled with product, it 
may be necessary that the liquid contents be recirculated through a liquid 
filter to remove any particulate contamination which may have been in the 
container or which may have been introduced into the liquid product or the 
container 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 filter(s) and back into the container. 
Advantageously the system provides the capability of readily upgrading 
and/or maintaining the high purity of a chemical in a shipping container 
or drum by utilizing the bung with a plurality of holes, i.e., at least 
one hole in which is secured a dip tube and at least one other hole in 
which a gas filter element may be connected. The arrangement of shipping 
container and bung with dip tube, and a gas or vent filter, as above 
described, in combination with a liquid pump, a liquid product filter and 
interconnecting liquid conduits, i.e., plumbing, provides a system which 
markedly facilitates the maintenance and immediate availability for use in 
a high purity state of the liquid product. While the invention is 
primarily aimed at liquid chemicals employed in processing electronic, 
e.g., semiconductor components in which high purity of chemicals to avoid 
contamination is essential, it will be apparent that the system may be 
applied also to other liquid products, e.g., deionized water, where a high 
state of purity in the liquid is important. 
In general in a preferred embodiment the purification system of the 
invention involves recirculating of the liquid in the container to reduce 
impurities that may be present therein. In so doing the liquid product is 
withdrawn through the dip tube by a pump and fed through a product filter 
and then returned to the container through a second bung (opening) in the 
container. A gas filter positioned in the second opening in the bung, 
contiguous to the dip tube, avoids build-up of pressure or vacuum in the 
system. 
The system also advantageously avoids the contamination of the pure product 
during unloading of the product from the bulk container. When the product 
is pumped out of the container through the dip tube, the vent filter 
attached to the smaller opening permits only clean air or other inert gas 
to enter the container as product is removed; this also prevents vacuum 
build-up in the container. 
An additional use of the invention 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. 
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 or span wrench or wrench flats projecting above 
the top.

DESCRIPTION 
FIGS. 1 through 3 illustrate one form of a bung suitable for use with the 
invention designed to fit standard metal or 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. 
The bung illustrated comprises a top or closure portion 10a 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 secured to the opening 15 and 
extending downward in the container to a point continuous to the bottom of 
the container and through which the liquid passes to 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 10b. Threaded 
plugs 20 and 21 are provided for the openings 15 and 16, respectively. The 
dip tube 17 is shipped with the container C and is secured to the bottom 
opening 15 in the bung. 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. 
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. 1), 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. These plugs are secured in the openings 
15 and 16 when the container is shipped. In use, the smaller opening in 
the bung, e.g. plug 21 is removed from the opening 16 and replaced with a 
gas filter. In the case of the larger opening, which has the dip tube 
already in place secured at the bottom of opening 15, the plug 20 is 
replaced with a suitable fitting at the end of the liquid withdrawal line 
that is connected to the container bung opening 15 
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 and is secured to the bung in any suitable air tight 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 0.2 micron, liquid 
filter. 
The system illustrated in FIG. 4 provides the capability of readily 
upgrading and/or maintaining the high purity of a chemical in a shipping 
container or drum by utilizing a bung 10 with a plurality of holes, i.e., 
at least one hole 15 in which is secured a dip tube 17 and at least one 
other hole 16 in which a vent or gas filter element 18 may be connected at 
the time of use. The arrangement of shipping container C and bung 10 with 
dip tube 17 and a vent or gas filter 18, as above described, in 
combination with a liquid pressurizing means, e.g., pump P4, a liquid 
product filter 19 and interconnecting liquid conduits, i.e. plumbing lines 
L2, L3, L4, L5 and L6, provides a system which markedly facilitates the 
maintenance and immediate availability for use in a high purity state of 
the liquid product. The system may incorporate one or more sampling parts 
as shown at S.sub.1 accompanied by suitable shut off valves V.sub.1 and 
V.sub.1, the latter normally open is shut and the former (normally shut) 
is opened when a sample is to be drawn. Additionally a second sampling or 
withdrawal port S.sub.2 may be incorporated with accompanying valves 
V.sub.2 and V.sub.2, which function similarly to the valves v, and 
v.sub.1, respectively. The invention has primary utility in processing 
liquid chemicals employed in processing electronic, e.g. semiconductor 
components in which high purity of chemicals to avoid contamination is 
essential. It will be apparent, however, that the system may be applied 
also to other liquid products, e.g., hydraulic fluids, where a high state 
of purity in the liquid is important. 
The purification system of the invention in a most productive application 
involves the recirculation of the liquid in the container C to reduce 
impurities that may be present therein. In so doing the liquid product is 
withdrawn through the dip tube 17 by the pump P4 and fed through the 
product filter 19 and then returned to the container C through the second 
opening in the container C shown capped by a second bung 25. A vent filter 
18 positioned in the second opening in the bung 10, contiguous to the dip 
tube 17 avoids build-up of pressure or vacuum in the system. 
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. 
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. 
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 
P7, line L13, filter 18 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. Alternatively, the product may be introduced through line L14' (shown 
in broken line) in the bung 25 in which case the opening 15 would be 
sealed. 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. Of course, when liquid 
is being withdrawn from the container C, the vent filter 18 functions to 
purify air entering the container. 
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 may 
be 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 out of the cleansed 
container through dip tube 17. 
The 1/4" NPT or smaller 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. 
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 is filled with 
a product of suitable purity. To enhance the purity of the product, for 
example, unfiltered product is pumped from storage tanks or drums through 
a filter (or filters) 19 into the clean container. 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 filter 18 which is 
screwed into the opening 16. The filter 18 may be connected to an 
exhausting system. 
II. In a more typical application, a clean container is filled with 
product, the material is recirculated through one or more 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, a 
pump draws up the material through the dip tube 17 which is secured in the 
bottom of 3/4" NPT opening 15 in the special bung 10 and pumps the product 
through filter 19 and back into the container C through suitable plumbing, 
lines L5 and L6 through a 3/4 inch opening in bung 25. A gas filter 18 is 
connected to the 1/4" NPT opening 16 in the special bung 10. The liquid 
filter element 19 has been shown as a single unit; it will be understood, 
however, that multiple units may also be used depending at the flow rate 
desired. 
The sampling ports S.sub.1 and S.sub.2 may be using for monitoring the 
purity of the product or optionally these ports may be used to withdraw 
the liquid product. 
III. A further 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 filter 18 is 
attached to the 1/4" opening 16 as shown 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. 
IV. In still another 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 
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 suitably attached to the 3/4" opening 15 in the special 
bung. 
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. 
Although the invention has been described and illustrated in connection 
with preferred embodiments, it will be understood that modifications and 
variations may be made without departing from the essence and scope of the 
invention as defined in the appended claims.