Catalina Cylinder Corporation manufactured high-pressure aluminum cylinders until December of 1991. In the crown forming operation of the manufacturing process, flame heat was used to heat the end of the product prior to forming the crown of the cylinder. After the product was heated, the product was forced from the base end into a die to form the crown end. Sometimes the flame heat was insufficient to properly allow the product to flow and form the crown end of the cylinder without causing uniform distortion of the lower sidewall of the cylinder. This distortion would appear as a uniform bulging of the cylinder’s lower sidewall starting about two inches up from the base of the cylinder. The distortion would not be localized but would be uniform around the cylinder. In addition, the distortion would only be located in the lower sidewall of the cylinder and nowhere else.
If you have a Catalina Cylinder Corporation cylinder manufactured in the late 1980’s that has a uniform bulge all the way around the lower sidewall of the cylinder just above the base of the cylinder, the manufacturing process most likely caused it. Hydrostatically test the cylinder and if the cylinder passes hydrostatic test, then the cylinder is acceptable for further service.
If you have a cylinder that has a localized bulge (not bow) in the sidewall of the cylinder, then the cylinder should be condemned and taken out of service.