Note: Descriptions are shown in the official language in which they were submitted.
~33~3
SALVAGE DRUM
BACKGROUND OF INVENTION
The present application relates to a molded,
one piece polyethylene storage or salvage drum, adapted
to be closed either permanently or temporarily, by means
of suitable covers, for shipping, storing or disposing
of chemicals or toxic and hazardous industrial waste.
Toxic and hazardous industrial waste has
commonly been stored or disposed of by putting the waste
into drums, most commonly standard 55 gallon metal drums,
which are then transported to treatment, storage or
landfill facilities for disposal or burial. Over time,
however, metal drums can corrode, either as a result of
exterior damage or from the corrosive substance within
the drums, and the contents can leak through the ground
and contaminate the groundwater or volatile components
can escape into the atmosphere, causing severe risks to
public health and the environment. The Environmental
Protection Agency (EPA) has estimated that more than 90~
of all hazardous industrial chemical wastes were disposed
of improperly. Recently, more stringent new federal and
state legislation has been enacted in an attempt to
minimize the risks incident to the transportation,
,
:~233~Z3
storage and disposal of toxic or dangerous wastes-in
metal drums
One response by industry to such ].egislation
has been to encapsulate or overpack the standard 55
gallon metal drums when such drums show signs of
corrosion puncture, or other damage The overpack
drums are generally made of steel with specialized
coatings, have a gasket attached to the top and can
be closed by a bolted ring with drop-forged lugs and a
bolt and nut Such overpack drums offer very high
resistance to the further leakage of hazardous waste
from the encapsulated drums They also prolong the
period of safe disposal or storage Although the steel
overpack drums are not specifically intended for reuse,
it has been found that they can be reused from three
to five times in the temporary transportation and storage
of hazardous waste, and then must be discarded However,
in many cases, the overpack steel drums, even if coated
with rust-inhibiting metal primer and enamel, have a
finite life and are also subject to eventual
deterioration and failure, especially if dented or
punctured during handling, or if left in a landfill,
exposed to the elements, or buried
Another response to the problem has been to
permanently encapsulate damaged drums by using
essentially straight-sided, rotationally molded,
cylindrical polyethylene containers adapted to
accommodate 55 gallon drums After placing the damaged
drum into the polyethylene receiver, a cover which is
slightly larger in diameter than the cylindrical
container and which has been cut from extruded flat high
density polyethylene stock, is welded by means of the
application of heat to the top rim, thereby permanently
encapsulating the contents The welding technique is
I,
:~33~3
--3--
similar to the technique employed in polyethylene pipe
welding, and employs a heat source which soiEtens the
mating surfaces. When the polyethylene has softened
sufficiently, the cover is pressed onto the container
and held in place until the joint cools and hardens.
This method, however, has the disadvantage that the
container can only be used for permanently enclosing
the content and lacks the flexibility desired by many
industries, or by waste management facilities for future
treatment of the material and reuse of the container.
In view of the above, it is the principal
object of the present invention to provide an improved
leak resistant salvage drum having a flange at the top,
or open end, which allows optionally either closing the
drum with a standard drum clamp and cover, or with a
polyethylene cover which can be bolted to the flange, or
with a cover which can be spin welded to the flange.
It is a further object of this invention to
provide a salvage drum that will readily receive and
maintain a standard drum in a stable, centralized
position and permit the insertion of absorbent material
in the space around the contained drum.
It is another object of the invention to
provide a drum which can be employed for a variety of
purposes, including (a) the storage of chemical
substances temporarily or essentially permanently;
~b) the transportation of chemical substances safely to
avoid spill episodes; a the storage of damaged metal
drums or other containers, either temporarily or
essentially permanently; or (d) for ultimately disposing
of chemical toxic and hazardous waste safely.
It is also an object of this invention to
provide an overpack or salvage drum which can be safely
reused over and over again.
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It is an additional purpose ox this invçntion
to provide a salvage or overpack drum which meets the
V~ So Department of Transportation Specification 173~3
for transporting leaking metal or plastic drums
SUMMARY OF THE INVENTION
The above and other beneficial objectives and
advantages are attained in accordance with the present
invention by providing a polyethylene drum comprising a
rotationally molded one-piece polyethylene body member
with a generally cylindrical wall and a generally flat
bottom The top end of the wall is slightly tapered and
orms a short neck which defines an access opening to
the drum interior The neck terminates in an integral
flange member which allows a choice of closures for the
drum: a standard drum clamp and cover can be attached; a
generally flat polyethylene cover with yasket can be
bolted to the flange; or a polyethylene cover can be
spin welded Jo the flange
The bottom of the polyethylene drum can be
flat, but the preferred embodiment includes a raised
annular section in the interior of the drum, adapted to
provide stability for a metal drum when the polyethylene
drum is used for either temporary or permanent storage
or disposal of a metal drum The raised annular section
in the interior of the polyethylene drum is so contoured
as to engage the bottom rim of a standard metal drum,
thereby enabling the metal drum to remain centered when
transported or stored in a vertical position This
configuration also provides additional strength and
rigidity to the base of the salvage drum
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BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG 1 is an elevational view of an improved
salvage drum in accordance with the present inven~ion~
FIG 2 is a perspective view of the embodiment
of FIG 1, illustrating various closure means
FIG 3 is a bottom view of one preferred
embodiment
FIG 4 is a fragmentary sectional view along
line 4-4 of FIG l
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is illustrated in the
accompanying drawings wherein the same elements bear
identical reference numerals throughout the different
views Accordingly, the present salvage drum 10
comprises a generally cylindrical body member 12 closed
at its bottom end The cylindrical body member is
rotationally molded and is made from either linear low
or high density polyethylene, or high density crosslinked
polyethylene
The wall 14 of the cylindrical body member a
the top is tapered inwardly at about a 45 angle, forming
inclined shoulder 15 and a short neck 16 which terminates
in outwardly extending integral flange 18a The upper
flange surface 20 is smooth and is adapted to receive
one of several different types of covers The underside
21 of the flange 18 is generally flat Flange surfaces
20 and 21 can be contoured and adapted to facilitate the
accomodation of sealing and closure means, as described
below The neck 16 is of sufficient height to accom-
modate the optional closure means, described in detail
below
23
Referring to FIG 3 and FIG 41 it is noted
that the bottom 20 has a raised annular section 22/
which on the inside of the drum lO is adapted to engage
the bottom rim of a standard metal drum when such drum
is being transported, stored or encapsulated A This is an
important feature of the present invention since it
provides for centrally positioning the inserted drum
In addition, the raised annular section 22 provides a
concave region on the outside of the bottom 20 to
facilitate stacking of the drums with mating drum covers
having an appropriate raised contour. As illustrated in
FIG 2A, conventional clamp closure means 31 can be used
to secure a reusable cover 30 to the flange 18~ Cover
30, suitable for sealing off the contents temporarily,
can be made of high density polyethylene, cut from sheet
material, and vacuum formed, or, alternatively the cover
can be molded ln the embodiment of FIG 2A, the
general1y flat cover 30 has a raised segmented annular
section 32 comprising four segments, adapted to engage
the raised section 22 of the bottom ll of another similar
salvage drum, as described above with reference to
FIGS 3 and 4~ The raised segmented annular section 22
o the cover 30 adds rigidity to the cover and, in
addition, permits the drums to be stacked with an added
degree of stability
Alternatively, the drum may be sealed by using
a generally flat cover 36 as is illustrated in FIG 2B,
wherein the flange is provided with about 6 or more
smooth-sided or tapped holes 24~ The cover can be
fabricated from polyethylene of the types described
above, or from other suitably resistant material A
chemical resistant gasket 37 is inserted between the
flange and the cover and serves as a sealing means
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The gasket can be formed from expanded, closed cell
polyethylene foam, or such other suitable materials which
are chemically resistant The cover 36 is provided with
holes 34 corresponding to those in the flange 18, whlch
holes are adapted to accept bolts 33 for bolting the
cover 36 to the flange 18 by either threading them into
the tapped holes 24 in the flange or by insertion through
smooth-sided holes and securing them with nuts 35~ To
provide additional stability upon stacking, and to
improve the rigidity of the cover itself, the reusable
cover is provided with a segmented raised annular section
as described above with reference-to FIG 2A~
A third type of cover 38 is illustrated in
FIG 2C and comprises a generally flat, linear low density
polyethylene cover of a diameter slightly larger than the
flange This cover is fabricated by rotational molding
and can be friction welded, or spin welded, to the flange
to provide a permanent, air-tight bond between the salvage
drum and the cover To accomplish this method of sealing
the salvage drum, the cover, while spinning, is forced
onto the flange under sufficient pressure to create
substantial frictional heat which melts the interface and
fuses the cover to the flangeO When the spinning is
stopped, the interface cools off and the cover is welded
to the flange Equipment for spinning the covers to
obtain the welded joint has been developed under the
auspices of the U.S. Environmental Protection Agency
This friction or spin welding closure method offers the
maximum leak resistance and is advantageous for permanent
storage and disposal When spin welded closures are to
be employed, it is preferred to use drums made of linear
high or low density polyethylene For other closures,
the drum can either be made of linear high or low density,
or cros~linked polyethylene
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The capacity of the polyethylene drum can range
from about one-half pint ~OA5 liter up to about 110-120
gallons (416-45q livers), (All metric conversions are
approxima~e~) r~ypical dimensions for a preferred
embodiment suitable for containing a standard 55 gallon
drum result in a salvage drum having a volume of about
85 gallon ~322 liters This drum has an outer flange
and outer wall diameter of about 27 ~69 cm3; the inside
diameter of the flan9e 18 and neck lÇ are about 24 1/2~
(62~2 am which is wide enough to accept a standard 55
gallon ~208 liters) drum; the neck height is about 3
1~2~ t8~9 cm), which includes the area where the wall
tapers off at a 45 angle to form the shoulder l and
neck 16. The total height of the drum is about 38~
l 96~ 6 cm) The annular section at the bottom of the
pslyethylene drum has an outside diameter of about 22~
(55~9 am the inside diameter of 12 1/2~ (3108 cm), and
the height of this raised section is 3/4" ~1~9 am
. salvage drum of these approximate dimensions with a wall
thickness of one-quarter inch weighs about 43 pounds
(18~2 kg); a wall thickness of three-ei~hts inches
results in a weight of about 60 pounds After a ~$andard
55 gallon (208 liters) drum is inserted, there is still
sufficient space in the interior of the salvage drum to
add filler or absorbent material to minimize movement of
the drum during tranSportatioQ~ and to absorb any liquid
waste which may leak from a damaged drum duriny
transportation and storage The larger drum is
particularly useful to accommodate dented or deformed
drums that are not perfectly cylindricala
A salvage drum having a capacity of 85 gallons
and containing a 55 gallon steel drum filled with. water
was sealed usiny a vacuum formed cover, polyethylene
foam gasket and conventional drum closuxe clumping means
. .
~33~'~3
as described a3bove~ A completely water-tight sea1 was
maintained when the salvage drum was drop-tested from
four feet After a fifteen foot drop-test the salvage
drum and cover were unaffected; the steel drum, however,
had ruptured and the conventional clamp had partially
failed resulting in some leakage When the cover is
secured with nuts and bolts, the salvage drums survives
the fifteen foot drop test without leakage or failure of
any type This test far exceeds the performance of any
known salvage drums, and of any current governmental
requirements for such drums
