Does anyone know how to calculate the mass of compressed hydrogen tank at certain pressure. The tank is cylindrical with hemispherical ends. I have pressure,radius,wall thickness and length,internal volume and density of the material. The tank is a Type IV tank.(Composite tank with polymer liner.)Is it reasonable to assume that the polymer liner weight is neglible since it is a non-load bearing structure and just there to prevent hydrogen permeation. Are there any formulas that calculate the weight of the tank valves and regulators and pumps as a factor of the tank weight. Thanks for your help.