News

Bomb-Proof Ball Valve
Article reprint from Design News, June 23, 1997

MARC Analysis FEA model shows exaggerated, bulged sides of ball-valve housing used in Navy submarine in response to a simulated underwater explosion.	Simulated underwater explosion causes rapid stress rise in valve body used for ballast systems of Navy submarines.

The ocean presents a uniquely hostile environment for engineered equipment. And the boats that ply beneath her waves, the submarines, are some of the most robustly built and secret of all military vessels.

Fitted to each sub are numerous ball valves used to regulate such critical systems as ballast and trim. Specialty & Ball Valve Engineering (SBVE), Tustin, CA, has supplied such valves to the Navy for more than 25 years, and under several different corporate identities.

Recently, the company applied extensive finite element analysis to design special versions of its Dynaflow valves for a classified, manned underwater vehicle. The customer asked that the valves not only be as light as possible, but also able to withstand sudden, high-energy pressure spikes without failing.

The source of these spikes? "Submarines can get shot at," says Harry Buehrle, the company's marketing director, "and our valve would see the pulse from the resulting explosion." The ballast tanks are tied directly to the subs' external environment, and any pressure surges would pass like shock waves through the ball valves.

By using FEA, engineers eliminated the need to physically test for the dynamic shock criteria, saving substantial time and money. Computer modeling also helped them trim 4-8 lbs. each on the more than 400 valves fitted to the boat.

Dynaflow ball valves meet the Navy's most stringent criteria. Level 1/Subsafe. Standard models come in five sizes weighing from 12 to 250 lbs, and with orifices from 0.5 to 2.5 inches. Materials include stainless steel, Monel, titanium, and Inconel.

While designed primarily to handle gases, the valves can regulate fluids as well. All offer zero leakage at up to 6,000 psi and top loading of the internal components for easy maintenance.Consulting engineer Zach Pursell of Mechanical Analysis & Design Consultants (MADC), Oceanside, CA performed the finite element modeling of the custom "lightweight" valve using MARC Analysis' (Palo Alto, CA) FEA code. "The biggest questions we had to answer were, would the valve body survive the shock impulse?" he says, "And, if so, what about the seals and internal components?"While weight was also a design driver, the dynamic impulse condition proved to be about five times more important in determining the valve's final configuration.

Pursell modeled each valve part separately and used MARC's adept handling of nonlinearities and contact to analyze interaction between components. "There really is no other code on the market that will model contacting bodies like MARC will" he says.

MARC analysis FEA model shows exaggerated, bulged sides of ball valve housing used in Navy submarine in response to a simulated underwater explosion.