Metal Seated Trunnion Ball Valve
Metal Ball valves will undergo a metal finishing process to further insulate the base metal from its environment and prevent corrosion and wear.
Key Specifications / Features
Advantages of trunnion ball design is the lower operating torque, ease of operation, minimized seat wear
(Stem/ball isolation prevents side loading and wear of downstream seats improving performance and service
life), superior sealing performance at both high and low pressure (a separate spring mechanism and upstream
line pressure is used as the sealing against the stationary ball for low pressure and high pressure applications).
For a meatal seated trunnion ball valve, the seat is coated and lapped to match ball, creating a positive seal.
Coating of Metal Seats
Often to prolong their life and especially in connection with severe service applications, Metal Ball valves will undergo a metal finishing process to further insulate the base metal from its environment and prevent corrosion and wear.
Electroless Nickel Plating – ENP provides a high level of corrosion protection and has an advantage in being an autocatalytic process meaning the Nickel itself will act as a catalyst for the plating mechanism. It will deposit evenly on uneven services making it ideal for Ball Valves.
Chrome Plating – Hard Chrome Plating has often been utilised in the design of Ball Valve Seats but may be coming under threat from increased environmental concerns over the process. Hard Chrome provides a high level of hardness and wear resistance.
Tungsten Carbide – For more severe environments where severe flashing or hydraulic shock is expected, a harder coating will be required. If temperatures are below 150 Degrees Celsius then most often HVOF applied Tungsten Carbide coating will add a high level of corrosion and wear resistance whilst also offering low porosity.
The leakage rate for metal seated ball valves within API STD 598 is similar to ANSI/FCI 70-2. API 598 requires zero bubbles per minute seat leakage for resilient seated isolation valves. Bi-directional sealing to Class V (Class VI available).