Unique Design Features

A. COMPLETELY TOP LOADED
Allows complete disassembly without removing valve from line.
Threaded bonnet gland facilitates maintenance and reduces number of pressure boundary parts.

B. LEAKPROOF VALVE STEM
Teflon foot seal keeps static seal o-ring from contacting stem -- eliminating wear.

C. SEPARATE BALL and STEM
Ball and seat self align. Separate stem eliminates shaft seal leakage and stem galling normally caused by ball shifting when subjected to pressure surges or pressure reversals. Separate stem reduces vertical load on stem.

D. HYDROYNAMICALLY ENERGIZED SEAL
Single seat provides bi-directional sealing with minimum seat loading in direct proportion to line pressure.

E. BELLVILLE SPRING
Provides constant seat loading for low pressure sealing. Valves remain bubble tight at zero and even negative (vacuum) pressures.

F. BEARING SUPPORTED BALL
Bearings "FIX" ball relative to body, reducing operating torque and enhancing smoothness of rotation. Heavy loads on ball are carried by integral trunnions supported in low friction sleeve bearings.

G. LOW OPERATING TORQUE
Use of trunnion bearings reduces ball friction and consequently lowers breakout and running torque. For example, the 0.5 inch bore valve at 5ksi pressure, requires only 85 INCH-pounds of breakout torque. Running torque is about 30% less. When actuators are required, they will be smaller, lighter and require less energy to operate.

INTERNAL BLEED CIRCUIT
Water hammer is a concern whenever valves are opened and flow initiated. The single seat design allows a BLEED hole to be positioned near the seat seal diameter. By rotating the ball a few degrees this small bleed port initiates downstream flow. Thus, water hammer can be reduced to near zero before fully opening the valve. This is an INTERNAL circuit unique to the single seat valve design and requires no external plumbing or valving. The BLEED option is called by the digit "4" in the part number code: VT3642.

Sealing Characteristics of Dynaflow Valves

The Dynaflow seal is pressure energized which results in bubble tight sealing under all pressure conditions-even vacuum. The single seal operates effectively against pressure differentials in either direction. The sealing force is determined by line pressure - the higher the pressure, the greater the sealing force.	Initial sealing force results from compressing a belleville spring. Seal areas are carefully controlled to prevent excessive loading of the seat. Seat wear is compensated for by relaxation of the Belleville spring.
Unbalanced sealing areas create a resultant force of seat against ball, increasing seat force against the ball. The effective sealing diameter of the static seal is at its outside diameter and the dynamic seal diameter creates a controlled force against the ball.	Unbalanced sealing areas create a resultant force of seat against ball, increasing seat force against the ball. The effective sealing diameter of the static seal is at its inside diameter, and thus there is an annular area subjected to the higher pressure.