Pressure vessels

Claim 1

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* 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.

Claim 2

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: 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* C. Current Density 30 amps per sq. ft. winding on to the nickel plated mandrel at least two layers of glass fibre rovings at a helix angle of about 27* 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* 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* C., and, removing the copper plating by means of a solution of nitric acid of at least 50 percent weight in volume concentration strength.