Accumulators are pressure vessels that store hydraulic energy and deliver that energy back to the system on demand. This is analogous to the way a car battery stores energy. In hydro-pneumatic accumulators, compressible gas (nitrogen) is used to keep stored fluid pressurized. Hydro-pneumatic accumulators are used extensively in the global fluid power industry. In process plant operations, accumulators have multiple uses: pulsation dampeners, emergency power source, thermal expansion, transfer barrier for fluid separation, as prefill for large volume press applications, noise attenuation, leakage compensators, dispensers for pressurized lubricants, auxiliary power, and others. There are different designs to separate gas from fluid. Bladder accumulators use a flexible closed bladder. Diaphragm accumulators use a flexible open diaphragm (membrane). Piston accumulators use a moveable piston with a system of seals. Float accumulators allow a buoyant valve to open and close the accumulator when necessary. For seamless high pressure bladder accumulators, chrome-moly steel has been used extensively for more than 40 years. This material has a high tensile strength, equivalent to AISI 4130. This material lends itself well to forming and machining and has a burst pressure more than 350% of design, that being 3.5:1 safety factor conforming to the ASME Code, Section VIII, Div. I. for unfired pressure vessels. Various applied coatings can enhance resistance to rust, corrosion, and …