A soft-seated ball valve can leak through its seat for
the following reasons:
The valve is not being closed fully.
Make sure to close the valve fully, but do not use cheaters.
Valve has a motor actuator with a position limitor set
incorrectly. Actuator motor stops when valve reaches a position limit
but valve is still partially open.
Consult actuator manufacturer's manual for limit switch
adjustment procedure. Position seating of a ball valve is a difficult
operation and cannot be done by eyeballing. If you require assistance
verifying actuator position limit switches, please contact Velan Field
Engineering Services.
Circumferential contact between the seat and ball is
not 100%. Minor imperfections on the either the seat or ball create
paths for fluid to escape.
Circumferential contact between the seat and ball is
not 100%. Minor imperfections on the either the seat or ball create
paths for fluid to escape.
Misalignment in the piping was overcome during installation
by using valve flange or lugs to force alignment. This can lead to
distortion or body flexing, especially in smaller valves. A full seal
is no longer present between the seat and the ball.
Contact Velan Field Engineering Services as a certified
Velan service technician will probably be required to repair the valve.
Valve is not closing properly due to damage from welding
procedure.
Valve should be welded onto the line in the closed position
in order to prevent spatter from contacting the ball. The ball can
be inspected for damage. Small weld spatter can be polished off. If
damage is substantial, ball should be replaced.
Soft seats melted during the welding procedure. Contact Velan Field
Engineering Services to either replace seats or the entire valve.
Corrosion of seat opened a leak path.
The application may not be suitable for a soft-seated
valve. Soft-seated valves should not be used in temperatures over
XYZ or with the following working fluids:
If the valve is not suited for the application, consider switching
to a metal seated valve.
