A metal-seated top-entry ball valve may leak through
the body/bonnet connection for the following reasons:
The body/bonnet bolts have inadequate torque.
Body studs and nut bearing surfaces must
be properly lubricated with a HD grease. As much as 50% of the applied
nut torque can be wasted in the case of improper lubrication.
Remove one nut at a time and lubricate the stud threads and the nut
side facing the body end. Torque each bolt to the required level.
Torque values for side-entry ball valves are found in the appropriate
manuals which can be requested from the Velan website.
The gasket is damaged.
Remove the gasket and replace with a new gasket. Velan
does not recommend ever reusing a gasket. Each time a valve is disassembled,
a new gasket is required upon reassembly.
There is a casting leak in the valve body around the
gasket area. Leakage might appear to be coming through the gasket
area but is really coming through a crack.
Inspect the leak and determine exactly where it is coming
from. A dye penetrant test is sometimes required to reveal a casting
crack. Most casting cracks can either be repaired in the field or
at a Velan authorized service shop. Velan recommends that it be consulted
prior to the repair of any casting crack on a valve body.
