Why might you choose a metal seated ball valve over a soft seated one? This all depends on your process and applications. Generally, metal seats are better for severe service applications. While metal seated valves often come at a higher cost, they offer a longer-lasting option to reduce the need for frequent replacement of soft seat options, as well as non-productive time for seat leakage in harsh conditions.
The Difference Between Metal Seated Ball Valve and Soft Seated
Both soft and metal seated ball valves work in a similar way. The valve creates a seal when the ball comes into contact with the seat. Soft seated options use thermoplastics like polytetrafluoroethylene (PTFE) and nitrile butadiene rubber (NBR). By contrast, metal seated options use materials like stainless steel, nickel alloys, and other metals.
In general, soft seated valves may be in a higher leakage class, sometimes providing a bubble tight shut off. However, metal seated products still provide a high performance seal, generally achieving ANSI class IV or V. With class IV, that means that less than 0.01% of the total valve capacity in its full open position leaks during the pressure test.
When to Choose Metal Seated Options
How do you choose between the two types of ball valve seats? Start by knowing your process and conditions thoroughly. For example, fluid temperatures, whether the fluid is abrasive or corrosive, and how high the pressure is. In many heavy duty, industrial applications, a metal seated ball valve is the right choice. This is because these valves can withstand more harsh conditions.
Metal seated isolation valves can withstand a wide range of severe service applications, including:
- High temperatures
- Cryogenic temperatures
- Abrasives
- Dirty fluids
- Corrosives
- High pressures
The type of metal seated ball valve you choose also depends on the type of fluid you’re isolating. Often, this affects the type of seat metal, type of ball mount, and also the hard coating used. For example, trunnion mounted balls are better for high pressure applications, while floating ball mounted valves do well for low to medium pressure processes. Hard coatings of tungsten carbide on seats are rated for temperatures lower than 302° F. For higher temperatures, you might opt for chrome carbide or other hard coatings on the metal seated ball valve.
Also, you will need to decide between a cast and forged ball valve. Forged options are generally more resistant to high pressures and temperatures. However, cast options usually offer faster turnaround and lower pricing.
When you need severe service valves, contact our team at Copeland Valve & Coating Technologies. We’ve been proudly manufacturing ball valves since 1940 and offer solutions for all your custom and standard valve needs. We manufacture everything right here in the U.S.A. for exceptional quality control and fast delivery. Call us today at (713) 926-7481 to request a quote for our high performance valves.