MSI LT VALVE TECHNICAL MANUAL
Revision D
April 03, 2014
59
8.0 REPAIR AND INSPECTION
When repairing a MSI plug valve, the following basic guidelines can help
you ensure a good hydrostatic test of the reassembled valve.
Disassemble the valve completely. See section
for detailed instructions on valve disassembly. Remove old grease and debris from
valve pocket with a solvent and inspect for wear or damage such as:
In the adjusting nut seal bore of the pocket: Scratches could be caused by
previous installation of a damaged adjusting nut. Dings can also occur during
assembly. Pitting is usually caused by failure to disassemble and clean valves
after they are in service. Use your fingers to feel for any surface defects
which may either fail to seal against the o-ring or may even damage the o-
ring during assembly.
On the adjusting nut o-ring groove area: Check for scratches, dings, or
pitting. Dings and scratches here are usually caused by careless use of sharp
metal objects when trying to remove old o-rings. Feel for any raised edges
that might scratch the internal seal bore of the valve body and sand or file as
necessary.
On the adjusting nut threads: Check for damaged threads, especially the lead
thread. Use your fingers to check for any raised edges and carefully sand as
needed. Severely damaged threads must be repaired at the factory.
On the pocket walls: Scratches, dings, or pitting, especially in the area
immediately surrounding the valve bore. Use your fingers to feel for any
surface defects which may either fail to seal against the o-ring or may even
damage the o-ring during assembly. Check for any sharp edges around the
valve bore that can cut the insert o-rings. These can be caused by using a
bar when swabbing excess grease or using a bar to carry the valve.
On the internal threads: Check for damaged threads, especially the lead
thread. Use your fingers to check for any raised edges and carefully sand as
needed. Severely damaged threads must be repaired at the factory.
On the plug seal area: Check for scratches, dings, or pitting. Dings and
scratches here are usually caused by careless use of sharp metal objects
when trying to remove old seals.
On the plug outside diameter: Check plug for washout, which will render the
part unusable. Hold part in a well illuminated area and inspect for slight
scratches in plug. If scratches are visible, use a 600 grit sandpaper to
remove them.
On the insert inside diameter: Check segments for washout, which will render the
parts unusable. Hold parts up to a well illuminated area and inspect for slight
scratches in outer and inner diameters of inserts. If scratches are visible, use a 600
grit sandpaper to remove them.
