Note: Descriptions are shown in the official language in which they were submitted.
I,
CA 02175333 2003-02-21
SECONDARY CONTAINMENT FLEXIBLE UNDERGROUND PIPING SYSTEM
BACKGROUND OF THE INVENTION
The present invention relates to secondary
containment systems and especially, although not
exclusively to a piping construction and a method for
providing secondary containment systems for hydrocarbon
storage and delivery systems.
A secondary containment system is one which
functions to collect and contain the fluids leaking out
of another and primary containment system. For example,
a primary containment system may store and deliver
gasoline at a filling station. A secondary containment
system would collect and contain the same gasoline if a
primary delivery pipe should rupture or otherwise spill
the gasoline. Secondary containment systems have been
developed to overcome the environmental problems that
have been encountered with respect to leakage of
hazardous fluids from tanks and pipe lines. As
indicated, this has been a particular problem with
respect to underground installations in which undetected
leakage of hazardous fluids into the surrounding terrain
over long periods of time has produced harmful conditions
and extensive pollution which are difficult and expensive
to clean.
Today there is great public concern because
chemicals are penetrating into underground water supplies
contaminating public drinking water and making some of
the food supply unusable, among other things. The entire
environment is being degraded to a serious level which
tends to cast doubt on the future availability of safe
water. Therefore, many government agencies have enacted
and continue to enact laws which require a secondary
containment system designed to capture and contain the
WO 95/I2779 ~~ 3 PCT/US94/12484
r'
'. ;~ t ;
v. ~~ v 2
spilled gasoline or other liquid materials thus
preventing it from leaking into the surrounding earth.
The capture gasoline or other liquid material may then be
pumped out of the secondary container for proper
disposal. This eliminates the possibility of gasoline
spillage to contaminate underground water supply.
Manufacturers of containment systems have
responded by developing and producing a variety of
secondary containment systems for conventional
l0 underground piping which are designed to contain and
prevent any leakage from escaping into the environment.
Many of these systems have proven to be effective
containment systems but have been found to be difficult
and costly to install.
One known approach to secondary containment
systems, and, in particular, the secondary containment of
underground conventional piping has been to line the
piping trench with an impervious flexible membrane liner
or semi-rigid trough. This technique can provide a
measure of secondary containment of leaky product but
such an approach does not allow for effective leaking
detection in that it does not permit the determination of
which pipe is leaking and the location of the leak in the
piping line when the same occurs. It is also difficult
to test such systems using air pressure testing devices.
Additionally, these secondary containment systems do not
provide 360° containment, and therefore can fill with
water and become ineffective.
Another approach toward solving the problem of
underground leakage in such conventional piping systems
has been to install a large semi-conventional piping
system over the conventional underground piping as a
means for providing the secondary containment. With such
an arrangement, the outer secondary containment rigid
pipe is installed simultaneously with the product piping.
The outer secondary containment pipe by necessity has a
larger diameter than the supply pipe to enable secondary
R'O 95/12779
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3
containment pipe to slide over the smaller pipe. The
secondary containment pipe fittings are of a clam shell
design adapted to fit over the supply pipe fitting and
connect to the secondary containment pipe. The clam
shell fitting is sealed to itself and the secondary
container pipe by a variety of sealing techniques.
Depending on the type of secondary containment system
used, these sealing techniques could include metal or
plastic fasteners used with a combination of adhesives,
sealants and the like. Such secondary systems are
generally expensive to install because of the cost of the
components which are used and the time required to
assemble both the product and the secondary containment
piping systems.
Another known approach to solving the
aforementioned problems is to employ a semi-conventional
piping system over the conventional product piping. This
type of containment system differs from the first
described system in that it is not an entirely rigid
straight pipe but rather a combination of rigid straight
pipe with a larger diameter, convoluted plastic pipe over
it which produces a telescoping effect. The convoluted
section of telescopic containment pipe serves as a
fitting of containment of the product, g0 and 45
fittings as well as unions, flexible connectors, swing
joints, should they be so attached. The convoluted pipe
is designed to be flexible and sized to be shifted around
any angles in the production piping system.
Another type of secondary containment piping
system has been developed which utilizes spaced access
chambers interconnected by a secondary containm
t
i
en
p
pe
to provide a sealed housing for a flexible fluid supply
pipe, the ends of which are disposed within the access
chambers and have a connector element at each end forming
a section adapted to be interconnected to other fluid
conduits. The diameter and bending radius of the fluid
supply pipe and the size of the access chamber are such
W 0 95/12779 PCT/IJS94I12484
4
as to permit the fluid pipe, after uncoupling, to readily
be removed from the secondary containment pipe through
one of the access chambers. Should a leak occur in the
piping, the secondary containment system allows the
piping to be removed and replaced.
It is very difficult and expensive to meet all
of the many different environmental and safety standards
at a reasonably acceptable cost, particularly in light of
the many state and local governments writing individual
laws that impose a wide variety of standards which the
manufacturers of such systems must meet.
Accordingly, an object of the invention is to
provide a new and improved secondary containment system
which will draw all spilled fluids that may leak from a
primary supply pipe to a preselected collecting point
which may be monitored.
Another object of the present invention is to
provide a practical secondary containment system which
may be manufactured in a factory, shipped and installed
at a reasonably low cost in a fully usable manner and yet
one which meets all requirements of the environment
within which they must be used.
It is a further object of the present invention
to provide an economical, easily installed, highly
durable and environmentally secure flexible piping
system. It is a further object of the present invention
to provide such a flexible piping system which may
optionally eliminate coextrusion.
$UM~LA~ty OF THE INVENTION . .
The present invention addresses and solves the
problems enumerated above. The present invention
comprises a secondary containment piping system,
comprising an inner supply pipe. The piping system
further comprises a flexible, fuel impervious outer
secondary containment pipe, within which the inner supply
pipe is carried. One of an outer surface of the inner
supply pipe and an inner surface of the outer pipe has a
CA 02175333 2003-02-21
plurality of radially outwardly projecting flanges
adapted to engage the other of the outer surface of the
inner supply pipe and the inner surface of the outer pipe
when the pipes are buried. This provides a locking
5 engagement of the pipes with respect to each other, and
provides for a flow passage between the pipes. The inner
pipe is comprised of a first, inner layer being
fabricated from nylon; a second layer comprising a wrap
having two opposed longitudinal edges in overlying
relationship, the wrap being fabricated from a polyester
film; a third layer comprising a nylon reinforced braid;
and a fourth, outer layer comprising a polyethylene
material. The outer pipe is comprised of a first, inner
layer comprised of one of a polyethylene or an ethylene
vinyl acetate material, the first layer having a
plurality of radially inwardly projecting flanges; a
second layer comprising a wrap having two opposed
longitudinal edges, the wrap being fabricated from a
metallized polyester film; and a third, outer layer
comprising a polyethylene material.
According to one aspect of the invention, there
is provided a secondary containment piping system,
comprising an inner supply pipe, and a flexible,
hazardous fluid-impervious outer secondary containment
ripe, within which the inner supply pipe is carried, one
of an outer surface of the inner supply pipe and an inner
surface of the outer pipe having a plurality of radially
projecting flanges adapted to engage the other of the
outer surface of the inner supply pipe and the inner
surface of the outer pipe when the pipes are buried to
provide a locking engagement of the pipes with respect to
each other, and to provide for a flow passage between the
pipes, the improvement comprising:
~i
CA 02175333 2003-02-21
5a
a first, inner layer of the inner pipe being
fabricated from nylon;
a second layer comprising a wrap having two
opposed longitudinal edges in overlying relationship, the
wrap being fabricated from a polyester film;
a third layer comprising a nylon reinforced
braid; and
a fourth, outer layer comprising a polyethylene
material;
wherein the outer secondary containment pipe
comprises:
a first, inner layer comprised of one of a
polyethylene and an ethylene vinyl acetate material, the
first layer having a plurality of radially inwardly
projecting flanges;
a second layer comprising a wrap having two
opposed longitudinal edges, the wrap being fabricated
from a metallized polyester film; and
a third, outer layer comprising a polyethylene
material.
According to another aspect of the invention,
there is provided a secondary containment piping system,
comprising an inner supply pipe, and a flexible,
hazardous fluid-impervious outer secondary containment
pipe, within which the inner supply pipe is carried, one
of an outer surface of the inner supply pipe and an inner
surface of the outer pipe having a plurality of radially
projecting flanges adapted to engage the other of the
outer surface of the inner supply pipe and the inner
surface of the outer pipe when the pipes are buried to
provide a locking engagement of the pipes with respect to
each other, and to provide for a flow passage between the
pipes, the improvement comprising:
CA 02175333 2003-02-21
5b
a first, inner layer of the inner pipe being
fabricated from nylon;
a second layer comprising a wrap having two
opposed longitudinal edges in overlying relationship, the
wrap being fabricated from a polyester film;
a third layer comprising a nylon reinforced
braid; and
a fourth, outer layer comprising a polyethylene
material;
wherein the outer secondary containment pipe
comprises:
a first, inner layer comprising a wrap having
two opposed longitudinal edges in overlying relationship,
the wrap being fabricated from a polyester film;
a second layer comprised of one of a
polyethylene and an ethylene vinyl acetate material, the
second layer having a plurality of radially inwardly
projecting flanges;
a third layer comprising a wrap having two
opposed longitudinal edges in overlying relationship, the
wrap being fabricated from a metallized polyester film;
and
a fourth, outer layer comprising a polyethylene
material.
According to a further aspect of the invention,
there is provided a secondary containment piping system,
comprising an inner supply pipe, and a flexible,
hazardous fluid-impervious outer secondary containment
pipe, within which the inner supply pipe is carried, one
of an outer surface of the inner supply pipe and an inner
surface of the outer pipe having a plurality of radially
projecting flanges adapted to engage the other of the
outer surface of the inner supply pipe and the inner
CA 02175333 2003-02-21
5c
surface of the outer pipe when the pipes are buried to
provide a locking engagement of the pipes with respect to
each other, and to provide for a flow passage between the
pipes, the improvement comprising:
a first, inner layer of the inner pipe being
fabricated from nylon;
a second layer comprising a wrap having two
opposed longitudinal edges in overlying relationship, the
wrap being fabricated from a polyester film;
a third layer comprising a nylon reinforced
braid; and
a fourth, outer layer comprising a polyethylene
material;
wherein the inner pipe outer surface has a
plurality of radially outwardly projecting flanges, and
wherein the outer pipe is comprised of:
a first layer comprised of one of a
polyethylene and an ethylene vinyl acetate material;
a second layer comprising a wrap having two
opposed longitudinal edges in overlying relationship, the
wrap being fabricated from a polyester film;
a polyethylene based heat seal adhesive
extending between the overlying wrap edges and forming a
seamless wrap; and
a third, outer layer comprising a polyethylene
material.
According to another aspect of the invention,
there is provided a secondary containment piping system,
comprising an inner supply pipe, and a flexible,
hazardous fluid-impervious outer secondary containment
pipe, within which the inner supply pipe is carried, one
of an outer surface of the inner supply pipe and an inner
surface of the outer pipe having a plurality of radially
CA 02175333 2003-02-21
5d
projecting flanges adapted to engage the other of the
outer surface of the inner supply pipe and the inner
surface of the outer pipe when the pipes are buried to
provide a locking engagement of the pipes with respect to
each other, and to provide for a flow passage between the
pipes, the improvement comprising:
a first, inner layer of the inner pipe being
fabricated from nylon;
a second layer comprising a wrap having two
opposed longitudinal edges in overlying relationship. the
wrap being fabricated from a polyester film;
a third layer comprising a nylon reinforced
braid; and
a fourth, outer layer comprising a polyethylene
material;
wherein the second layer overlying edges form a
first seam, and wherein the inner pipe further comprises:
a first intermediate layer, disposed between
the second layer and a second
intermediate layer, comprising a wrap having
two opposed longitudinal edges in overlying relationship,
the overlying edges forming a second seam, the second
seam being rotated 180° from the first seam, the wrap
being fabricated from a copper foil; and the second
intermediate layer, disposed between the first
intermediate layer and the third layer, comprising a wrap
having two opposed longitudinal edges in overlying
relationship, the overlying edges forming a third seam,
the third seam being rotated 180° from the second seam,
the wrap being fabricated from a polyester film.
According to a further aspect of the invention,
there is provided a secondary containment piping system,
comprising an inner supply pipe, and a flexible,
CA 02175333 2003-02-21
5e
hazardous fluid-impervious outer secondary containment
pipe, within which the inner supply pipe is carried, one
of an outer surface of the inner supply pipe and an inner
surface of the outer pipe having a plurality of radially
projecting flanges adapted to engage the other of the
outer surface of the inner supply pipe and the inner
surface of the outer pipe when the pipes are buried to
provide a locking engagement of the pipes with respect to
each other, and to provide for a flow passage between the
pipes, the improvement comprising:
a first, inner layer of the inner pipe being
fabricated from nylon;
a second layer comprising a wrap having two
opposed longitudinal edges in overlying relationship, the
wrap being fabricated from a metallized polyester film;
a third layer comprising a nylon reinforced
braid;
a fourth, outer layer comprising a polyethylene
material; and
a polyethylene based heat seal adhesive
extending between the overlying wrap edges and forming a
seamless wrap.
According to another aspect of the invention,
there is provided a secondary containment piping system,
comprising an inner supply pipe, and a flexible,
hazardous fluid-impervious outer secondary containment
pipe, within which the inner supply pipe is carried, one
of an outer surface of the inner supply pipe and an inner
surface of the outer pipe having a plurality of radially
projecting flanges adapted to engage the other of the
outer surface of the inner supply pipe and the inner
surface of the outer pipe when the pipes are buried to
provide a locking engagement of the pipes with respect to
I'
CA 02175333 2003-02-21
5f
each other, and to provide for a flow passage between the
pipes. the improvement comprising:
a first, inner layer of the inner pipe being
fabricated from nylon;
a second layer comprising a wrap having two
opposed longitudinal edges in overlying relationship, the
wrap being fabricated from a polyester film;
a third layer comprising a nylon reinforced
braid; and
a fourth, outer layer comprising a polyethylene
material;
wherein the second layer overlying edges form a
first seam, the second layer wrap being fabricated from a
metallized polyester film, and wherein the inner pipe
further comprises:
a polyethylene based heat seal adhesive
extending between the second layer overlying wrap edges
and forming a seamless wrap; and
an intermediate layer, disposed between the
second layer and the third layer, comprising a wrap
having two opposed longitudinal edges in overlying
relationship, the overlying edges forming a second seam,
the second seam being rotated 180° from the first seam,
the wrap being fabricated from a polyvinyl fluoride
coated polyester film.
According to a further aspect of the invention,
there is provided a secondary containment piping system,
comprising an inner supply pipe, and a flexible, fuel
impervious outer secondary containment pipe, within which
the inner supply pipe is carried, one of an outer surface
of the inner supply pipe and an inner surface of the
outer pipe having a plurality of radially projecting
flanges adapted to engage the other of the outer surface
i
CA 02175333 2003-02-21
5g
of the inner supply pipe and the inner surface of the
outer pipe when the pipes are buried to provide a locking
engagement of the pipes with respect to each other, and
to provide for a flow passage between the pipes, the
improvement comprising:
the inner supply pipe, comprising;
a first, inner layer fabricated from nylon;
a second layer comprising a wrap having two
opposed longitudinal edges in overlying relationship, the
overlying edges forming a first seam, the wrap being
fabricated from a metallized polyester film;
a polyethylene based heat seal adhesive
extending between the overlying wrap edges and forming a
seamless wrap;
a third layer comprising a wrap having two
opposed longitudinal edges in overlying relationship, the
overlying edges forming a second seam, the second seam
being rotated 180° from the first seam, the wrap being
fabricated from a polyvinyl fluoride coated polyester
film;
a fourth layer comprising a nylon reinforced
braid; and
a fifth, outer layer comprising a polyethylene
material; and
the outer secondary containment pipe,
comprising:
a first, inner layer comprising a wrap having
two opposed longitudinal edges in overlying relationship,
the wrap being fabricated from a polyester film;
a second layer comprised of one of a
polyethylene and an ethylene vinyl acetate material, the
second layer having a plurality of radially inwardly
projecting flanges;
CA 02175333 2003-02-21
5h
a third layer comprising a wrap having two
opposed longitudinal edges, the wrap being fabricated
from a metallized polyester film; and
a fourth, outer layer comprising a polyethylene
material.
According to another aspect of the invention,
there is provided a secondary containment piping system,
comprising an inner supply pipe, and a flexible, fuel
impervious outer secondary containment pipe, within which
the inner supply pipe is carried, one of an outer surface
of the inner supply pipe and an inner surface of the
outer pipe having a plurality of radially projecting
flanges adapted to engage the other of the outer surface
of the inner supply pipe and the inner surface of the
outer pipe when the pipes are buried to provide a locking
engagement of the pipes with respect to each other, and
to provide for a flow passage between the pipes, the
secondary containment piping system further comprising
spaced, underground chambers which are interconnected in
a fluid tight manner through walls thereof by the
secondary containment pipe which passes therethrough, the
inner supply pipe having end couplings attached to the
ends thereof the end couplings being disposed within the
chambers at a point beyond the termination of the outer
secondary containment pipe, the inner and outer pipes
being impervious to the fluids to be transmitted
therethrough, the improvement comprising:
the inner supply pipe, comprising:
a first, inner layer fabricated from nylon;
a second layer comprising a wrap having two
opposed longitudinal edges in overlying relationship, the
wrap being fabricated from a polyester film;
a third layer comprising a nylon reinforced
CA 02175333 2003-02-21
5i
braid; and
a fourth, outer layer comprising a polyethylene
material; and
the outer secondary containment pipe,
comprising:
a first layer comprised of one of a
polyethylene and an ethylene vinyl acetate material, the
first layer having a plurality of radially inwardly
projecting flanges;
a second layer comprising a wrap having two
opposed longitudinal edges, the wrap being fabricated
from a metallized polyester film; and
a third, outer layer comprising a polyethylene
material.
According to a further aspect of the invention,
there is provided a secondary containment piping system,
comprising an inner supply pipe, and a hazardous fluid-
impervious outer secondary containment pipe, within which
the inner supply pipe is carried, one of an outer surface
of the inner supply pipe and an inner surface of the
outer pipe having a plurality of radially projecting
flanges adapted to engage the other of the outer surface
of the inner supply pipe and the inner surface of the
outer pipe when the pipes are buried to provide a locking
engagement of the pipes with respect to each other, and
to provide for a flow passage between the pipes, the
improvement comprising:
a first, inner layer of the inner pipe being
fabricated from nylon;
a second layer comprising a wrap having two
opposed longitudinal edges in overlying relationship, the
wrap being fabricated from a polyester film;
a third layer comprising a nylon reinforced
CA 02175333 2003-02-21
5j
braid; and
a fourth, outer layer comprising a polyethylene
material;
wherein the second layer overlying edges form a
first seam, the second layer wrap being fabricated from a
metallized polyester film, and wherein the inner pipe
further comprises:
a polyethylene based heat seal adhesive
extending between the second layer overlying wrap edges
and forming a seamless wrap; and
an intermediate layer, disposed between the
second layer and the third layer, comprising a wrap
having two opposed longitudinal edges in overlying
relationship, the overlying edges forming a second seam,
the second seam being rotated 180° from the first seam,
the wrap being fabricated from a polyvinyl fluoride
coated polyester film.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, advantages and applications of
the present invention will become apparent to those
skilled in the art of underground piping systems when one
example of the best mode of the present invention is read
in conjunction with the accompanying drawings, in which:
Fig. 1 is a schematic layout of an exemplary
gasoline storage and delivery system;
Fig. 2 is an enlarged side view of a portion of
the fuel dispensing system of Fig. 1 as seen generally
along line 2-2 thereof;
Fig. 3 is an enlarged view of a portion of the
system illustrated in Fig. 2;
Fig. 4 is an enlarged perspective view of the
inner and outer pipes utilized in the secondary
containment piping system of the present invention with
W095112779 . PCT/US94112484
;;y;..
6
layers of the inner pipe removed for illustrative
purposes; ,
Fig. 4A is a fragmentary perspective view of
the outer secondary containment pipe illustrated in Fig.
4;
Fig. 5 is a cross sectional view taken
generally along line 5-5 prior to the backfilling of the
trench within which the pipes are located;
Fig. 6 is a view similar to Fig. 5
illustrating, in a slightly exaggerated manner, the
secondary containment piping system after backfilling;
Fig. 7 is an enlarged perspective view of the
inner and outer pipes utilized in the secondary
containment piping system of the present invention with
layers of the inner and outer pipes removed for
illustrative purposes;
Fig. 8 is a cross sectional view of the first
layer of the inner supply pipe showing, in an exaggerated
manner, a single polyester film wrap thereover;
Fig. 9 is a cross sectional view of the first
layer of the inner supply pipe showing, in an exaggerated
manner, a double polyester film wrap thereover, with the
wrap seams rotated 180° from each other;
Fig. 10 is a cross sectional view of the first
layer of the inner supply pipe having a single polyester
film wrap thereover and showing, in an exaggerated
manner, the wrap edges overlapping with a heat seal-
adhesive therebetween;
Fig. 11 is a view similar to Fig. 10, with an
additional polyester film wrap over the first wrap;.
Fig. 12 is the outer pipe showing, in an
exaggerated manner, a single polyester film wrap
thereover and a polyethylene covering layer; and
Fig. 13 shows the outer surface of the inner
supply pipe having outward projections, the outer pipe
having a smooth inner surface, and showing, in an
exaggerated manner, a single polyester film wrap
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7
thereover with a heat seal adhesive between the
overlapping wrap edges and a polyethylene covering layer.
I)EECRTPTTON OF THE PREFFRRFT1 FMR(1TITMFrTme
Referring now to the drawings, and, in
particular, to Figs. 1 and 2, wherein there is
illustrated an underground fuel storage and dispensing
system generally indicated at 10 comprising fuel tanks 12
from which a plurality of underground fuel supply pipes
14 extend for distribution of fuel to dispersion areas 16
in a conventional manner. The system includes one or
more access chambers 20 which are also disposed below the
surface dispensing station 16. The access chambers 20
and the fuel tanks 12 are interconnected by containment
pipe segments 22 while the access chambers are connected
via pipe segments 24 to a conventional drip pan 26
beneath the dispenser 16 and is connected thereto through
suitable elbow connectors 28. The access chamber 20 and
the pan 26 are interconnected in a fluid sealing manner
through their side walls just above the bases thereof by
means of the secondary containment pipe 24.
As can best be seen in Fig. 3, the side wall 30
of the access chamber 20 has an opening 32 through which
the end of the pipe 24 extends. A conventional seal 34
surrounds the outer surface of the containment pipe 24
and provides a fluid tight seal for the interior of the
access chamber 20.
As will be described in greater detail
hereinafter, the secondary containment piping system
comprises a flexible inner supply pipe 40 which is
completely encased within a flexible outer containment
- pipe 42: It should be noted by reference to Fig. 3, that
the outercontainment pipe 42 extends into the access
chamber 20 a sufficient distance so that it clears the
interior of the wall 30 of the access chamber 20. During
fabrication this will permit the insertion on the
terminated end 39 of pipe 42 of a suitable air pressure
device to permit testing as will be explained
i
CA 02175333 2003-02-21
hereinafter. The inner pipe 40 extends past the
terminated end 39 of the outer pipe 42 a sufficient
distance to permit it to be coupled by suitable
conventional couplings 44 to another inner pipe 40 which,
in turn extends outwardly from the access chamber 20
through an outer containment pipe 42. At the drip pan
26, the pipe 40 exits therethrough and continues through
a containment pipe 42 on to the next island.
The access chamber 20 leas a removable cover 70
to permit easy access thereto for removal of~any fuel
that might be captured by the containment pipe 40. A
fluid sensor 72 is disposed in the bottom of the access
chamber ~2 and is electrically connected to an
appropriate i-ndicator or alarm 74. When there is an
accumulation of fluid, such as due to leakage from the
primary pipe 40, the fluid will actuate the alarm.
As can best be seen in Figs. 4 and 5, the inner
pipe 40 is made from a fuel impervious material and is
comprised of three layers of material which are extruded
together and comprise an interior layer 50, which is
fabricated from a nylon 12 material; an intermediate
layer 52 consisting of a nylon 6 yarn reinforcement wrap;
and an exterior outer material 54 which is preferably
fabricated from a polyethylene material. The inner layer
50 is .080" thick and the outer layer is preferably .060"
thick. In the preferred embodiment, the pipe 40 has an
inside diameter of 1.68" and an outside diameter of
1.960", a maximum operating pressure of 150 psi and a
minimum burst pressure of 750 psi. The material is
flexible and has a bend radius of 12" to 24".
The inner pipe 40 is completely encased in the
outer containment pipe 42 which, as can best be seen in
Figs. 4, 4A and 5, comprises an integrally extruded
member having a wall 60, the interior of which is
provided with a plurality of angularly spaced, radially
inwardly extending ribs or projecaions 64 that define
thereinbetween U-shaped cross sections 66. Outer pipe 42
CA 02175333 2003-02-21
9
may be extruded separately from inner pipe 40, or may be
coextruded therewith. The projections extend along the
full length of the interior of the wall 60 (Fig. 4A).
The outer pipe 42 is sized to permit the inner pipe 40 to
be inserted therein with little or no resistance and is,
preferably, assembled in the combined arrangement at the
factory, ready for positioning in the pipe trenches when
delivered onsite. The outer pipe 42 is very flexible and
can bend as needed to accommodate the bending of the
primary inner pipe 40. The outer pipe 42 is made from a
fuel impervious material such as a nylon or polyethylene,
clear acrylonitrile or clear polyurethane material.
In another preferred embodiment, in order to
achieve greater permeation resistance, outer pipe 42 may
optionally be formed from a plasticized nylon li, or a
polyester elastomer used as a thermoplastic rubber. One
such polyester elastomer is commercially available from
E.I. du Pont de Nemours Co. under the tradename HYTREL.
Outer pipe 42 may further be optionally formed from a
coextrusion of low density polyethylene or SURLYN ionomer
as an inner layer, and nylon li as an outer layer.
In practice, trenches are laid out and the
various lengths of piping ar~,laid ~.n the trenches and
connected to the various underground access chambers 20
and drip pans 26 via the sealing members 34.; Once
connected, a portion of the outer pipe 42 is cut and
removed so that a Buff icient amount of the inner pipe 40
extends past the termination end 39 of the outer pipe 42
to permit the inner pipe 40 to be attached to a suitable
coupling 44.
Before a coupling 44 is attached to the inner
pipe 40, an appropriate seal may be placed over the
outside of the inner pipe 40 to sealingly engage the
outer pipe 42 whereby pressurized air may be communicated
to the annular space (Fig. 5) formed between the inner
and outer pipes 40 and 42 to test the same to be sure
that there are no leakage points in the containment
I,
CA 02175333 2003-02-21
1
system. Obviously, the opposite ends of the pipe 42 of
each of the access chambers 2~2 and drip pans 26 must be
sealed in order to effectively perform such a test.
Likewise, the inner pipes 40 can be subjected to air
pressure to test their integrity. Once the installer is
satisfied that the containment piping system is able to
perform its function without concern for leakage, the
trenches within which the containment pipes 14 have been
laid are backfilled.
The weight of the earth on the flexible outer
pipe 42 deforms the pipe 42 in the manner similar to that
illustrated in Fig. 6 of the drawings, until the outer
ends of the projections 64 abut the outer wall of the
inner pipe 40. The abutment of the projections 64 with
the wall 40 provides a two-fold purpose. First, it
snugly and lockingly engages the pipe 40 and prevents
relative movement between the inner and outer pipes
providing for a more secure system. Secondly, the space
between U-shaped cross sectional areas and the space
between the inner and outer walls always insures a flow
path for any fuel that may leak into the annular space
between the inner and outer pipes. The view illustrated
in Fig. 6 is illustrative of~the condition that may exist.
However, it should be noted that the outer tube 42 may be
deformed in a variety of different shapes. Suffice it to
say that a continuous flow path will exist in the event
there is a leakage from the primary inner pipe 40. While
it is preferred that the primary pipe 40 and secondary
containment pipe 42 be assembled at a factory location,
there may be situations in which the pipes are assembled
on site before burial. The pipe 40 may be removed and
either pipe may be replaced if a leak is found during
testing. Once buried, the weight of the fill collapses
appropriate portions of the outer containment pipe 42
around the primary pipe 40 and the primary pipe 4o may no
longer be removed after burial.
CA 02175333 2003-02-21
11
An alternate preferred embodiment comprises the
use of one or multiple wrapped barrier films included in
the structure of inner supply pipe 40 and/or outer
secondary containment pipe 42. The addition of such
barrier films allows for a greater degree of alcohol or
hydrocarbon permeation resistance, thereby further
enhancing the protection of the environment within which
the secondary containment piping system is placed.
Referring now to Figure 8, there is shown a
preferred embodiment of use of a barrier film. The
first, inner layer 50 of inner pipe 40 is fabricated from
any suitable material, however, in the preferred
embodiment, this is a plasticized nylon l2 material. It
may be of any suitable diameter and the cross-sectioned
wall may be of any suitable width. In the preferred
embodiment, the width of first, inner layer is
approximately .080 inches. A second layer 110 comprises
a wrap having .two opposed longitudinal edges 112, 114 in
overlying relationship. The second layer 110, as with
2o all the barrier films described Herein, may be made from
any suitable material having barrier properties.
However, in the preferred embodiment, this second layer
is fabricated from a polyester film having a very. high
tensile strength. One such polyester film is
commercially available from E.I. du Pont de ~lemours
Company under the trade name MYLAR.
It is to be understood that the embodiment
shown in Figure 8, as well as each of the embodiments
shown in Figures 7-13, may be used interchangeably with.
each other, and-with the embodiments described more fully
above. For example, the embodiment shown in Figure 8 may
further comprise a third layer-comprising a nylon
reinforced braid 52, such as a nylon 6 yarn. It may
further comprise a fourth, outer layer 54 comprising a
polyethylene material, such as a low density
polyethylene. Examples of suitable widths of the layers
just mentioned may be .0015 inches for the polyester film
R'O 95112779 PCTIUS94112484
r '.
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12
layer 110, .015 inches for the nylon reinforced braid
layer, and .060 inches for the polyethylene layer. The
nominal inner diameter for inner pipe 40 in the
embodiment just described may be about 1.680 inches, with
a nominal outer diameter of approximately 1.990 inches. '
Referring now to Figure 12, there is shown a
preferred embodiment of the outer secondary containment
pipe 42. This pipe 42 has an outer layer 116 having two
opposed longitudinal edges 118, 120 in overlying
relationship, the wrap being fabricated from a polyester
film as described above. More specifically, outer pipe
42 comprises a first, inner layer 122 comprised of one of
a polyethylene or an ethylene vinyl acetate material. It
is to be further understood that this layer 122 may be
made of any suitable material including, but not limited
to any of the exemplary outer pipe 42 materials listed
more fully above. First layer 122 has a plurality of
radially inwardly projecting flanges 64.
Wrap layer 116 preferably may comprise a
metallized film, and a third, outer layer 124 comprises
any suitable polyethylene material.
As stated above, in a similar fashion, the
diameters and cross-sectional widths of outer pipe 42 may
be determined as desired. In a preferred embodiment, the
wrap layer 116 is approximately .002 inches, and the
outer pipe 42 nominal inner diameter may be 2.050 inches,
and the nominal outer diameter may be 2.38 inches.
In addition to opposed edges 118, 120 being in
overlying relationship as shown in Figure 12, these edges
may also be butt sealed. Further, overlying edges 118,
120 may have a polyethylene based heat seal adhesive I26,
as shown with the embodiments in Figures 10, 11 and 13.
It is to be understood that these figures are slightly
exaggerated for illustrative purposes, in that the edges
in overlying relationship would be nearly undetectable,
and, when the heat seal adhesive 126 is used, due to its
WO 95/12779 PCT/US94112484
13
polyethylene base, this will form a substantially
undetectable seamless wrap.
Another alternate embodiment of the outer pipe
42 is shown in Figure 7. In this embodiment, the outer
secondary containment pipe 42 comprises a wrap layer 128
having two opposed longitudinal edges in overlying
relationship, the wrap being fabricated from a polyester
film. This layer 128 may be used as a separating layer
between outer pipe 42 and inner supply pipe 40. A second
layer 122 is comprised of one of a polyethylene and an
ethylene vinyl acetate material, the second layer 122
having a plurality of radially inwardly projecting
flanges 64. A third layer 116 comprises a wrap having
two opposed longitudinal edges, the wrap being fabricated
from a metallized polyester film. A fourth layer 124
comprises a polyethylene material.
Referr-ing now to Figure 13, there is shown an
alternate embodiment of the outer layer 54 of inner pipe
40. Outer layer 54 of inner pipe 40 has a plurality of
radially outwardly projecting flanges 130 extending from
the outer surface 132 of outer layer 54. Modified first
layer 122' has a smooth inner surface and is comprised of
one of a polyethylene and an ethylene vinyl acetate
material. A second layer comprises a wrap 116 having two
opposed longitudinal edges 118, I20 in overlying
relationship, the wrap 116 being fabricated from a
polyester film. A polyethylene based heat seal adhesive
126 extends between the overlying wrap edges 118, 120 and
forms a seamless wrap. A third, outer layer 124
3o comprises a polyethylene material.
- For any of the embodiments shown and those not -
specifically shown, any of the wrap layers may be
"cigarette" wrapped or spiral wrapped, or wrapped by any
other suitable method. Further, although one wrap,
either simply in overlying relationship, butt sealed or
adhesively sealed is sufficient to provide desirable
barrier properties, two or more wraps may be successively
WO 95!12779
217 5 3 3 3 PcT~s94/12484
4.,~Y.~4, ':~,
14
applied to the inner pipe 40 and/or outer pipe 42. When
this is done, it is preferable to rotate the successive
seams 180° from the seam of the immediately preceding
wrap.
Further, each wrap does not have to be formed
from exactly the same polyester film. For example, a
first wrap layer may be a formed from a polyester film; a
second wrap layer may be formed from a copper foil, with
the foil seam rotated I80° from the first polyester film
seam; and a third wrap layer may comprise a polyester
film, with the polyester film seam rotated 180° from the
copper foil seam.
The addition of successive wraps is a safeguard
in the event that the alcohol, hydrocarbon, or other
environmentally unsafe fluid escapes through the seam of
the first wrap. If this did occur, such fluid would have
to travel a full 180° in order to escape from the seam of
a second wrap; if such occurred, the fluid would have to
turn around and travel a full 180° to escape from a third
wrap, and so on. It can be seen that, since there is
little likelihood that such fluid would escape from the
first seam, the chance of the fluid traveling in such a
manner through a second, third, fourth, etc. wrap to
eventually escape is substantially non-existent. As
such, a point of diminishing returns may be reached, and
the manufacturer and/or user, may see no necessity in
providing more than perhaps one or two barrier film
wraps.
Two such wraps are shown in Figure 9, and are
designated as 110, 134. wrap 110 has opposed overlying
edges 112, 114; and wrap 134 has opposed overlying edges
136, 138. As can be seen in Figure 9, the seam formed by
edges 136, 138 is rotated 180° from the seam formed by
edges I12, 114.
With any of the single or multiple wrap layers
shown, the polyester film may be a metallized polyester
film, as stated above. Further, this metallized
WO 95/I2779 PCT/U594I12484
zl~$~33 - ,. , . . .~
polyester film more specifically may be aluminized.
Further, the wrap layer may be comprised of a polyvinyl
fluoride coated polyester film, or a
polytetrafluoroethylene plastic-impregnated polyester _
5 film. One such polytetrafluoroethylene plastic material
is commercially available from E.I. du Pont de Nemours
Company under the trade name TEFLON.
Further, the polyethylene based heat seal
adhesive 126 may be used in any of the embodiments shown
10 or described. The heat seal adhesive is shown used in
Figure 10 with a single wrap over inner layer 50. The
embodiment shown in Figure 10 may preferably be suitable
for suction piping and/or vent piping. Further, as in
Figure 11, the heat seal adhesive 126 may be used in
15 conjunction with a second wrap non-adhesively sealed.
The second wrap is designated as 110'
with opposed
,
longitudinal edges 112'
114'. The embodiment shown in
,
Figure 11 may preferably be suitable for pressure piping.
It is to be understood that the adhesive may be coated in
any suitable quantity on the inner or outer surface of
wrap layers. Further, in the embodiment shown in Figure
12, the wrap layer 116 is adhesively coated along its
entire outer surface to outer layer 124 by adhesive 140.
Some of the many advantages of using a wrapped
barrier film layer are as follows. The addition of extra
extruders and the time, expense and general problems
involved in coextruding is substantially eliminated.
Further, since the wrap is applied at a simple and
conventional wrapping machine, it allows a manufacturer
to use materials like the polyvinyl fluoride coated
MYLAR, which material would be very difficult to set up
in a coextrusion process.
In an alternate embodiment not shown, the
secondary containment system may comprise an inner supply
pipe comprising a first layer of crosslinked
polyethylene; a second layer comZ~rised of a wire helix
material; a third layer comprised of a polyester fiber _
WO 95112779 PCTIUS94/12484
21?5333 $.~ :~.
16
reinforcing material; and a fourth layer comprised of an
oil and gasoline resistant nitrile cover. The outer pipe
42 may be as generally described hereinabove.
It is to be further understood that the barrier
films of the alternate preferred embodiment may be used '
in secondary containment systems having
removable/replaceable inner supply pipes, such as any of
those systems mentioned hereinabove having rigid outer
secondary containment pipes or a combination of rigid
straight pipe with the larger diameter, convoluted
plastic pipe. Any of the embodiments of inner supply
pipe 40 having one or more barrier film wraps described
above, including those embodiments shown in Figs. 7-13,
may be used in conjunction with such a removable or
replaceable secondary containment system.
Still further, it is to be understood that the
barrier films of the alternate preferred embodiment may
be used in primary piping systems. Primary piping
systems contemplated include, but are not limited to
automotive fuel lines, chemical plant hose, and tank
truck hose for unloading, for example, gasoline.
Depending upon the application, these primary piping
systems may be buried in, the ground, run through
buildings, motor vehicles, etc. The barrier films
mentioned above may prove particularly useful when such
primary piping systems are transporting hazardous fluids.
Any of the embodiments of inner supply pipe 40 having one
or more barrier film wraps described above, including
those embodiments shown in Figs. 7-13, may be adapted for
use in conjunction with such primary piping systems.
Further, it is contemplated that the outer secondary
containment pipe 42 as described above, including any
' embodiments shown in Figs. 7-13, may also prove useful in
some circumstances in the chemical, automotive, etc.
applications listed above.
While preferred embodiments of the invention
have been described in detail, it will be apparent to
WO 95/12779 PC1YUS94/12484
z1 ~'~'~33
those skilled in the art that the disclosed embodiments
may be modified. Therefore, the foregoing description is
to be considered exemplary rather than limiting, and the
true scope of the invention is that defined in the
following claims.
