Ball valve technology
Figure 3
What sets the KT valve apart?
To appreciate the KT Valve’ s innovation, consider how traditional trunnion-mounted ball valves operate. These rely on floating seats with coil springs providing pre-tension. System pressure pushes the seats against the ball to create a seal. However, if friction between the seat and its pocket exceeds the spring force, the seat may stick, preventing contact with the ball— resulting in leakage.( figures 2 and 3) Media deposits( e. g., asphalt, chemicals, hardened hydrocarbons, scale) can obstruct seat-ball contact, around the 3 and 9 o’ clock positions,( figure 4) causing further leakage. One of the key drawbacks of standard trunnion ball valves— whether SR, DIB1, or
Figure 4
DIB2— is their behaviour during opening under differential pressure( DP) or closing while media is flowing. At the initial and final stages of valve operation, the small opening creates high velocity flow, which can lead to cavitation and erosion. So, what sets the KT valve apart? KT valves feature a wedging ball design, which is fundamentally different from standard trunnion ball valves. The most significant distinction lies in the seat configuration:
• Fixed Seats: Unlike floating seats that rely on movement to achieve sealing, KT valves have fixed seats that do not shift.
• Angled Seats: These are designed to wedge the ball into the seats, enhancing sealing performance.
• Self-Cleaning Action: Any deposits on the ball or seats are scraped off during the last closure, maintaining valve integrity.
Additionally, KT valves are non-contact and DIB valves. Meaning: During opening, the flow area is distributed evenly around the seat circumference, rather than being concentrated in a small elliptical opening on one side of the ball. There is no contact between the ball and seats during normal operation— contact only occurs during the first and last 2 % of the ball’ s rotation to / from closed position. Finally, the KT valve is a Double isolation and bleed valve( DIB).
About the author Norwegian consultant and valve instructor Mr. Ingolf Fra Holmslet writes a series of articles for Valve World. Klyde Consultants AS www. valve. no ingolf @ valve. no