U.S. patent application number 09/826356 was filed with the patent office on 2001-12-13 for method of installing a tank liner.
This patent application is currently assigned to Mocoat Services '98 Ltd.. Invention is credited to Heath, Brian.
Application Number | 20010050282 09/826356 |
Document ID | / |
Family ID | 4166459 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010050282 |
Kind Code |
A1 |
Heath, Brian |
December 13, 2001 |
Method of installing a tank liner
Abstract
A method of installing a tank liner in a tank, the method
comprising the steps of: A) adhering a backing sheet to a liquid
permeable sheet with an adhesive to form a first panel outside of
the tank; B) placing the first panel within the tank against a wall
of the tank, with the liquid permeable sheet between the tank wall
and the backing sheet; and C) laying up fiber reinforced plastic
onto the backing sheet inside of the tank to create a tank liner
inside the tank. A tank liner formed of plural panels sealed
together to form an encircling wall and an end wall, each panel
comprising: a liquid permeable sheet; a fabric sheet adhered to the
liquid permeable mesh sheet on one side of the fabric; and fiber
reinforced plastic applied to the other side of the fabric.
Inventors: |
Heath, Brian; (Edmonton,
CA) |
Correspondence
Address: |
THOMPSON LAMBERT
SUITE 703D, CRYSTAL PARK TWO
2121 CRYSTAL DRIVE
ARLINGTON
VA
22202
|
Assignee: |
Mocoat Services '98 Ltd.
Nisku
CA
|
Family ID: |
4166459 |
Appl. No.: |
09/826356 |
Filed: |
April 5, 2001 |
Current U.S.
Class: |
220/62.22 |
Current CPC
Class: |
B65D 90/505 20130101;
B65D 90/045 20130101; B29L 2031/7126 20130101; B29C 63/02
20130101 |
Class at
Publication: |
220/62.22 |
International
Class: |
B65D 001/40; B65D
003/22; B65D 006/14; B65D 008/04; B65D 090/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 9, 2000 |
CA |
2,311,229 |
Claims
I claim:
1. A method of installing a tank liner in a tank, the method
comprising the steps of: A) adhering a backing sheet to a liquid
permeable sheet with an adhesive to form a first panel outside of
the tank; B) placing the first panel within the tank against a wall
of the tank, with the liquid permeable sheet between the tank wall
and the backing sheet; and C) laying up fiber reinforced plastic
onto the backing sheet inside of the tank to create a tank liner
inside the tank.
2. The method of claim 1 in which the backing sheet is initially
semi-permeable and is made impermeable by application of
adhesive.
3. The method of claim 2 in which the backing sheet is a
fabric.
4. The method of claim 1 in which the backing sheet is a
fabric.
5. The method of claim 1 in which the liquid permeable sheet is a
mesh.
6. The method of claim 1 in which the tank comprises an encircling
wall and an end wall and the method further comprising: repeating
steps A and B until at least a lower portion of the encircling wall
and end wall are covered with the multiple panels; sealing the
panels together to form the tank liner; and applying step C to the
multiple panels.
7. The method of claim 1 in which at least one of the edges of the
liquid permeable sheet is exposed when the first panel is placed
against a wall of the tank, and further comprising, before laying
up the fiber reinforced plastic, adhering the first panel to the
wall of the tank by applying adhesive to the exposed edge of the
liquid permeable sheet.
8. A tank liner formed of plural panels sealed together to form an
encircling wall and an end wall, each panel comprising: a liquid
permeable sheet; a fabric sheet adhered to the liquid permeable
mesh sheet on one side of the fabric sheet; and fiber reinforced
plastic applied to the other side of the fabric.
9. The tank liner of claim 6 in which the liquid permeable sheet is
a mesh.
Description
FIELD OF INVENTION
[0001] This invention relates to containment devices, and
particularly a tank liner.
BACKGROUND OF THE INVENTION
[0002] Storage tanks are frequently used to store liquids such as
hydrocarbons, corrosive chemicals, produced water, and other fluids
used in the treatment of water and sewage and other industries.
These tanks may leak and cause an environmental hazard. It is thus
generally known to be desirable to provide secondary containment
systems where the tank is either provided with a jacket or an inner
liner. In the case of the jacket, the tank remains the primary
containment, while the jacket is the secondary containment. In the
case of the tank liner, the tank becomes the secondary containment
while the tank liner is the primary containment.
[0003] Between the primary containment and the secondary
containment there is typically an interstitial space that requires
monitoring for leaks. Various methods of monitoring an interstitial
space are well known in the art. They include devices as simple as
sight tubes attached to the side of tanks, check valves attached to
the side of tanks, to various electronic devices which can detect
by the presence of chemicals, or odours, or analysis of liquids,
leaks in the primary containment into an interstitial space.
[0004] The tank liner or jacket must have sufficient chemical
resistance and physical strength to contain the liquid or solid to
be held. While several primary and secondary containment devices
exist for installation into existing tanks, such as those described
in U.S. Pat. No. 5,904,265 of Zandbergen et al and U.S. Pat. No.
4,825,687 of Sharp, the inventor considers them difficult to
install. Qualitron of Edmonton, Canada, proposed and installed
systems in 1999 which included a pre-fabricated composite structure
made of an interstitial mesh layer, an elastomeric layer bonded to
the mesh layer, a surface treated polypropylene fabric substrate on
top of the elastomeric layer and a top coat of epoxy. This system
was deficient in failing to provide sufficient strength against
bending stresses when the pre-fabricated strips were installed in
the tank.
[0005] The proposed invention seeks to overcome the problems of the
prior art.
SUMMARY OF THE INVENTION
[0006] Therefore, according to a first aspect of the invention,
there is provided a method of installing a tank liner in a tank,
the method comprising the steps of:
[0007] A) adhering a backing sheet to a liquid permeable sheet with
an adhesive to form a first panel outside of the tank;
[0008] B) placing the first panel within the tank against a wall of
the tank, with the liquid permeable sheet between the tank wall and
the backing sheet; and
[0009] C) laying up fiber reinforced plastic onto the backing sheet
inside of the tank to create a tank liner inside the tank.
[0010] According to a further aspect of the invention, there is
provided a tank liner formed of plural panels sealed together to
form an encircling wall and a bottom wall, each panel
comprising:
[0011] a liquid permeable sheet;
[0012] a fabric sheet adhered to the liquid permeable mesh sheet on
one side of the fabric sheet; and
[0013] fiber reinforced plastic applied to the other side of the
fabric.
[0014] According to an aspect of the invention, the panels are
sealed together to form an encircling wall and an end wall. Putty
may be used to seal the panels together, including along the corner
formed where the encircling wall meets the end wall. The panels may
be adhered to the walls by exposing part of the mesh and applying
putty to the exposed portions.
BRIEF DESCRIPTION OF THE FIGURES
[0015] There will now be described preferred embodiments of the
invention with reference to the figures, by way of example only and
without intending to limit the generality of the invention, in
which like reference characters denote like elements, and in
which:
[0016] FIG. 1 is a cross-section of a fiber reinforced panel formed
according to the invention (not to scale, layer 18 is generally
thicker than layer 12;
[0017] FIG. 2 is a plan view of a grid for use as a permeable layer
according to the invention;
[0018] FIG. 3 is a perspective view of a panel according to the
invention;
[0019] FIG. 4 is a cross-section of a joint between two panels
meeting at a corner of a tank; and
[0020] FIG. 5 is a plan view of two panels with exposed grid to
allow adhering of the panels to the tank wall by applying adhesive
to the exposed grid.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0021] Generally, to make a tank liner, a panel 11 is made by
adhering a backing sheet 12 to a liquid permeable sheet 10 with an
adhesive outside of the tank 24. The panel 11 is then placed within
the tank against a wall 24 of the tank, with the liquid permeable
sheet 10 between the backing sheet 12 and the wall 24. Next, fiber
reinforced plastic 18 is laid up onto the backing sheet 12 inside
of the tank 24 to create a tank liner 20.
[0022] The liquid permeable sheet 10 is preferably a mesh sheet 10
made of organic material such as polypropylene. The backing sheet
12 is preferably a fabric made of organic material, preferably
polypropylene. The sheets 10 and 12 are preferably adhered together
with a suitable adhesive resin system.
[0023] A mesh is distinguished from a liquid impermeable sheet by
having sufficient open pores that liquid may pass through the mesh
even after a resin is applied to the mesh to adhere it to an
adjacent sheet. By contrast, a liquid impermeable sheet or coated
fabric sheet as used herein has a sufficient density of fiber that
the liquid impermeable sheet, or the fabric when the fabric is
coated with an adhesive resin system, is essentially impermeable to
liquids such as hydrocarbon liquids and water.
[0024] The mesh sheet 10 may be made of solid organic material such
as polyolefin, polyester, polyamide, aramid, polyvinyl chloride, or
polystyrene material. The preferred material for the mesh 10 is
surface treated extruded polypropylene mesh. A preferred mesh is a
polypropylene bi-planar mesh available from Atlantic Extrusions of
Massachusetts, USA. Polyester sheets may also be used. Polyethylene
sheets are not desirable. The mesh 10 may be made of woven or
non-woven fibres or it may be made by a process well known in the
art to produce a grid, often used in geo-technical applications and
known in the trade as a geo-grid, as for example available from
Tensar Inc. of New Jersey and other manufacturers.
[0025] Fabric sheets may be made of solid strips of polyolefin,
polyester, polyamide, aramid, polyvinyl chloride, or polystyrene
material. The preferred material for the fabric sheets is surface
treated non-woven polypropylene fabric 8400 S2 available from
Albarrie Environmental Services of Barrie, Ontario, Canada. The
strips may be made of woven or nonwoven fibre, whose
cross-sectional dimensions are close to each other, or may be made
from a sheet, in which one cross-sectional dimension is much larger
than the other. If a fiber is used, it should have a length at
least 0.25 cm, and a cross-sectional width in the order of 0.1 cm
or less. A strip may be made of multiple fibers or sheets. Solid
sheets of the same material may also be used. It is preferred that
the fabric sheet be initially semi-permeable, and then become
impermeable after application of the fiber reinforced plastic 18.
The fabric is used to form a platform or substrate for receiving
the fiber reinforced plastic 18.
[0026] The material used for the mesh 10 and also the material used
for the fabric sheet 14 should have a surface energy at least 10
dynes/cm at 20.degree. C. less than the surface tension of the
resin system, and preferably have a surface energy greater than 40
dynes/cm at 20.degree. C. If necessary the material may need to be
surface treated to yield these criteria. Methods of surface
treatment are in themselves well known in the art, and include
exposure to reactive gas atmospheres containing F.sub.2, Cl.sub.2,
SO.sub.3, or O.sub.3; exposure to oxidative liquids such as nitric
acid, sulphuric acid, chromic acid, or H.sub.2O.sub.2; or other
process such as electrostatic discharge, corona discharge, plasma
exposure or flame treatment. Other examples are disclosed in U.S.
Pat. No. 4,880,879.
[0027] The panel 11 is prepared by lying the fabric 12 on a
suitable surface, applying a suitable adhesive resin system to the
fabric 12 and laying the mesh 10 on the fabric 12 or turning the
fabric over and laying it on the mesh 10, depending on which is
more convenient to the manufacturer. The adhesive resin system is
preferably Superior Environmental Technologies, Inc. SP-2000Q.
Pressure is applied to assure a continuous bond between the two
sheets 10, 12 and the resin system is allowed to cure. The adhesive
resin system is preferably a thermosetting resin system having a
sufficiently low surface tension to provide a high level of
bonding. Examples of suitable resins systems include thermosetting
epoxies, polyurethane, unsaturated polyester, unsaturated vinyl
ester, polydicyclopentadiene, acrylic latex, rubber latex,
polysulfide, polyurea, novolacs, and phenolics.
[0028] Panels 11 of the flexible mesh-fabric composite are then cut
to the appropriate size for the application and may be rolled up to
a size allowing them to be inserted into the man-way hatch of a
tank. Prior to installation provisions are made to clean the tank
wall surface and to provide an interstitial space monitoring
device, various of which are known in the art.
[0029] Fabric at edges 22 of the panels 11 is stripped away to
expose the mesh 10 along the edges of the panels 11. The panels 11
are applied to the inside of the tank by suspending them vertically
from the top of the tank, or by stacking them circumferentially
within the tank. Double sided tape may be used to suspend the
panels 11 in the tank long enough (about 24 hours) for the
installation of the panels 11 to be completed. The panels 11 are
glued into place with the mesh 10 against the wall 24 of the tank
by applying putty to the exposed mesh 10 at the edges of the panels
11, including along the top of the topmost panels. The system is
structurally supported by the direct adhesion of the panels to the
tank wall along the joints between the panels, as well along the
upper edges of the topmost panels. Putty is a mastic material made
up of adhesive resin and filler. Filler may be short fibers of
polyethylene that have been treated to have a surface energy
greater than 70 dynes/cm at 20.degree. C. or other suitable filler.
The filler is mixed with a suitable resin such as the resin system
used to provide the chemically resistant coating to the fabric 12.
Other glue like materials could be used as appropriate to
requirements. The putty is allowed to cure and then the fiber
reinforced plastic 18 is laid up onto the panels 11 in conventional
fashion to form a continuous inner tank liner that provides the
primary containment of the liquid being stored. The original tank
of vessel then becomes the secondary containment structure.
[0030] As shown in FIG. 4, a vertical tank will typically have an
encircling wall 24 and an end or bottom wall 26. In a horizontal
tank, the relative positions of the encircling wall and the end
wall are interchanged as shown in the figure. The encircling wall
24 meets the bottom wall 26 at a corner. One panel 11 is placed
against the encircling wall 24, and another panel 11 is placed
against the bottom wall 26, with the two panels 11 forming a joint
at the corner. As many panels 11 are used as are required to cover
the bottom wall 26 and encircling wall 24 up to the required
height. A bead of putty 28 is then laid along the joint at the
corner and along all other joints between adjacent panels,
preferably thicker at corners between panels. The fiber reinforced
plastic 18 is then laid up over all of the panels 11 including over
the beads of putty at the joints where two panels join, including
where the encircling wall 24 meets the bottom wall 26.
[0031] The bonded fabric and mesh sheets create a tank liner, with
the mesh 10 creating a stand-off space between the fabric and tank
wall 24. This stand-off is such that an interstitial space 34 is
created between the fabric sheet 12 and the wall 24 which is
adjacent to the mesh 10. The interstitial space 34 provided by the
panel 11 may be monitored by a conventional monitor to assure no
leakage in the primary storage device and assure the integrity of
the primary containment structure.
[0032] Various fiber reinforced plastics (FRP) are well known in
the art. Various fabrics (including woven fibre, unidirectional
fiber, and roving fiber) such as fiberglass, carbon fiber, basalt
fiber, ceramic fiber, metal filament, aramid fiber, and others may
be combined by techniques well known in the art with various resin
systems to create composites of varying strength, flexibility and
durability. Preferably, glass fiber mats are used, which are laid
up in two layers. Preferred resins are unsaturated polyester,
unsaturated vinyl ester and thermosetting epoxy.
[0033] In some applications, it may be important to make the mesh
10 more thermally stable, as for example in heated tanks. For that
purpose, filler such as talc may be added to the polypropylene
forming the mesh to reduce thermal expansion. At higher operational
temperatures, epoxies may be more suitable as the resin, such as
ICI coatings, or Dupont fluoropolymers may be more suitable as the
resin.
[0034] Immaterial modifications may be made to the invention
described here without departing from the essence of the
invention.
* * * * *