U.S. patent number 3,654,009 [Application Number 04/798,447] was granted by the patent office on 1972-04-04 for pressure vessels.
This patent grant is currently assigned to The Secretary of State for Defence in Her Britannic Majesty's Government. Invention is credited to Nigel Cecil William Judd, Thomas Lloyd, Charles Trevor Mann.
United States Patent |
3,654,009 |
Judd , et al. |
April 4, 1972 |
PRESSURE VESSELS
Abstract
Pressure vessels are formed on a hollow aluminum mandrel having
an external surface of a configuration corresponding to the desired
internal shape of the vessels. An impervious vessel inner liner is
formed on the mandrel as by electro-deposition, and the vessel wall
is then formed by winding filamentary reinforcing material on the
inner lining, impregnating such material with a resinous material,
curing the resinous material, and then removing the hollow aluminum
mandrel chemically by use of an aqueous solution of caustic
soda.
Inventors: |
Judd; Nigel Cecil William
(Sandhurst, Camberley, EN), Lloyd; Thomas (Crondall,
Farnham, EN), Mann; Charles Trevor (Frimley,
Camberley, EN) |
Assignee: |
The Secretary of State for Defence
in Her Britannic Majesty's Government (London,
EN)
|
Family
ID: |
25173425 |
Appl.
No.: |
04/798,447 |
Filed: |
February 11, 1969 |
Current U.S.
Class: |
156/155; 156/150;
156/173; 264/317; 264/221 |
Current CPC
Class: |
B29C
33/52 (20130101); F16J 12/00 (20130101); B29C
63/24 (20130101) |
Current International
Class: |
B29C
33/52 (20060101); F16J 12/00 (20060101); B65h
054/64 () |
Field of
Search: |
;156/150,151,155,173
;117/217,71 ;72/54 ;18/DIG.12,47R ;264/221,DIG.44 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Quarforth; Carl D.
Assistant Examiner: Lehmann; E. E.
Claims
We claim:
1. A method of making a fluid-tight pressure vessel comprising
copper plating a hollow aluminum mandrel which presents an external
surface which corresponds in external configuration and dimensions
with the required internal configuration and dimensions of a
pressure vessel to be made, depositing an impervious nickel liner
on to said copper plating in a nickel sulphamate bath as
follows:
winding filamentary or fibrous reinforcing material on to said
nickel liner and mandrel, impregnating said reinforcing material
with resinous material during said winding thereof, curing the
resinous material on said inner liner to form the vessel wall, and
thereafter removing the hollow aluminum mandrel chemically by use
of an aqueous solution of caustic soda.
2. A method of making a fluid-tight pressure vessel as claimed in
claim 1 in which the aluminum mandrel is removed by pumping hot
aqueous caustic soda solution, of about 10 percent weight in volume
concentration through it at a temperature of not more than
80.degree. C., and the copper plating is then removed by means of a
solution of nitric acid of at least 50 percent weight in volume
concentration strength.
3. A method of making a vessel of hollow cylindrical form with
externally convex ends of which one is closed and the other is
formed with an integral open neck extending radially from it
comprising the following steps:
copper plating a hollow aluminum mandrel which presents an external
surface which corresponds in external configuration and dimension
with the required internal configuration and dimensions of the
vessel to be made,
depositing an impervious nickel liner on said copper plating in a
nickel sulphamate bath as follows:
winding on to the nickel plated mandrel at least two layers of
glass fibre rovings at a helix angle of about 27.degree. to the
axis of the vessel to cover the circular cylindrical centre section
and the two end sections with the exception of the end
connection,
impregnating these glass fibre rovings during winding with a
polyester resin mix having a methyl ethyl ketone peroxide catalyst,
60 percent by weight solution in dimethyl phthalate, and a cobalt
napthenate accelerator, a solution in styrene containing the
equivalent of 1 percent cobalt, and cured at room temperature, hoop
winding on two and a half layers of glass fibre rovings over the
first fibre layers on the cylindrical portions of the vessel and
impregnating them with the same resin mix as in the step above
which is cured by subjecting it to a temperature of approximately
100.degree. C., for a period of substantially 16 hours, removing
the aluminum mandrel by pumping hot aqueous caustic soda solution,
of about 10 percent weight in volume concentration into it at a
temperature of not more than 80.degree. C., and,
removing the copper plating by means of a solution of nitric acid
of at least 50 percent weight in volume concentration strength.
Description
This invention relates to improved filament wound pressure vessels
incorporating very thin impervious metal linings.
A method of making a fluid-tight pressure vessel according to the
invention consists essentially in preparing a hollow aluminum
mandrel which presents an external surface which corresponds in
external configuration and dimensions with the required internal
configuration and dimensions of a pressure vessel to be made,
building up by electro-deposition of nickel on to said external
surface of the mandrel an impervious nickel inner liner of the
vessel, forming the vessel wall by winding filamentary or fibrous
reinforcing material on to said inner liner and mandrel and
impregnating said reinforcing material with resinous material,
during said winding thereof and curing the resinous material, and
the reafter removing the hollow aluminum mandrel chemically by use
of an aqueous solution of caustic soda. In place of impregnating
the reinforcing material during the winding operation, it may be
done before winding or after winding, but the impregnation is
believed to be more effective if carried out during the winding
operation.
In general, the purpose of the inner layer of a vessel according to
the invention is mainly, if not entirely, to provide reliability of
impermeability over a wide range of temperatures even as low as
those of liquified gases and its thickness may be small, e.g. in
the range of some two to five thousandths of an inch, except where
it may be of locally changing or quite substantial thickness, e.g.
one-tenth of an inch, for example where the main body is shaped
progressively into a neck-like formation at an outlet or inlet
opening thereof.
It has been found very satisfactory to use a copper coated mandrel
of pure aluminum and to nickel plate this in a nickel sulphamate
bath as follows:
Nickel Sulphamate 300 gm./liter. Boric Acid 35 gm./liter. pH
(adjusted with Sulphuric acid) 4.0 Sodium Lauryl Sulphate --
Sufficient to reduce surface tension to 28 dynes/cm. Temperature
50.degree. C. Current Density 30 amps per sq. ft.
After plating as above and applying the composite reinforcement and
resinous material to the nickel inner liner while still on the
mandrel, the whole of the material of the mandrel may conveniently
be removed from the interior of the vessel by simply pumping hot
aqueous caustic soda solution, 10 percent w./v. through it at a
temperature of not more than about 80.degree. Centigrade. The
copper coating may then be removed by means of a 50 percent w./v.
or stronger solution of nitric acid. The expression w./v. is used
herein to represent "weight in volume concentration".
One example of the manufacture of a pressure vessel in accordance
with the invention is described below.
The vessel is of hollow cylindrical form with externally convex
ends of which one is closed and the other is formed with an
integral open neck extending co-axially from it.
The method included the following steps:
1. A hollow aluminum former was copper plated externally to a depth
of about 0.003 inches by a standard plating process.
2. The copper plated mandrel was nickel plated to the required
thickness in a nickel sulphamate bath as indicated above to form a
vessel of the configuration indicated above.
3. Two layers of glass fibre rovings were wound onto the surface of
the nickel liner at a helical angle of about 27.degree. to the axis
of the vessel to cover the circular cylindrical centre section and
the two end sections with the exception of the end connection.
4. During winding these layers were impregnated with a polyester
resin mix having a methyl ethyl ketone peroxide catalyst (60
percent by weight solution in dimethyl phthalate) and a cobalt
naphthenate accelerator (a solution in styrene containing the
equivalent of 1 percent cobalt) and cured at room temperature.
5. Two and a half layers of glass fibre rovings were hoop wound
over the first fibre layers on the cylindrical portion of the
vessel and impregnated with the same resin mix as used on the first
layer, and cured at 100.degree. C. for 16 hours.
6. The aluminum former was dissolved away by pumping a hot 10
percent w./v. caustic soda solution at up to 80.degree. C. through
the hollow former until all the aluminum was removed.
7. The copper coating and any residual matter was removed in a
nitric acid solution of at least 50 percent w./v.
At and near the junction of the main body with the neck the
thickness of the nickel inner layer is of progressively increasing
thickness to a constant greatly increased thickness to provide
ample strength at the neck for the fixture of a charging and
closure valve assembly.
With this process a pressure vessel with impermeable walls is
formed, having a high strength/weight ratio and good insulating and
corrosion resistant properties.
In one example a pressure vessel manufactured in accordance with
the invention was pressure tested to 1,500 lb. per sq. inch with
liquid nitrogen, the pressure being raised and lowered repeatedly.
Subsequent inspection of the vessel showed that the nickel liner
remained unwrinkled and gas tight.
In a further example according to the invention a vessel
constructed in the manner described was filled with liquid hydrogen
pressurised to 200 p.s.i. and held at this pressure for 10 minutes
and this cycle of operations was repeated many times with no
deleterious effects to the vessel.
While particularly useful for the production of pressure vessels,
the invention is also applicable for the production of tanks and
pipes for handling gases, corrosive and cryogenic fluids and in
fact to any reinforced plastic structure which is required to be
impervious to liquids or gases at low and high temperatures.
* * * * *