Page 243 - Root Cause Failure Analysis

Seals and Packing 231

secured. Deviation indicates pipe strain. If severe strain exists, corrective measures
should be taken or damage to the pump and unsatisfactory seal service can result.

Seal Checkpoints

The following are important seal checkpoints:

Ensure that all parts are kept clean, especially the running faces of the seal
ring and insert.
Check the seal rotary unit and make sure the drive pins and spring pins are
free in the pin holes or slots.
Check the set screws in the rotary unit collar to see that they are free in the
threads. Set screws should be replaced after each use.
Check the thickness of all gaskets against the dimensions shown on the
assembly drawing. Improper gasket thickness will affect the seal setting and
the spring load imposed on the seal.
Check the fit of the gland ring to the equipment. Make sure there are no
obstructions or binding with the studs or bolts. Be sure the gland-ring pilot, if
any, enters the bore with a reasonable guiding fit for proper seal alignment.
Make sure all rotary-unit parts of the seal fit over the shaft freely.
Check both running faces of the seal (seal ring and insert) and be sure there
are no nicks or scratches. Imperfections of any kind on either of these faces
will cause leaks.

Installation of the Seal
The following steps should be taken when installing a seal:

Instruction booklets and a copy of the assembly drawing are generally
shipped with each seal. Read the instructions and study the drawing before
starting installation.
Remove all burrs and sharp edges from the shaft or shaft sleeve, including
sharp edges of keyways and threads. Worn shafts or sleeves should be
replaced.
Check the stuffing-box bore and face to ensure they are clean and free of
burrs.
Lightly oil the shaft or sleeve before assembling the seal to allow the parts
to move freely over it. This is especially desirable when assembling the seal
collar because its bore usually has only a few thousandths of an inch clear-
ance. Take care to avoid cocking the collar.
Install the rotary-unit parts on the shaft or sleeve in the proper order.
Be careful when passing the insert and gland ring over the shaft. Do not
bring the insert against the shaft because it might chip away small pieces
from the edge of the running face.
Wipe the seal faces clean and apply a clean oil film before completing the
equipment assembly. A clean finger, which does not leave lint, is best for the
final wipe of the seal face.