If other types of couplings are used, then follow the maintenance instructions provided by the coupling
manufacturer.
6.4 Shaft-seal maintenance
6.4.1 Packed stuffing box maintenance
Check or instruction
Explanation/comment
When starting a pump with fiber packing for
the first time, make sure that the packing is
slightly loose without causing an air leak. As
the pump runs in, gradually tighten the gland
bolts evenly.
Never draw the gland to the point where the packing is compressed
too tightly and no leakage occurs. This will burn the packing, score
the shaft sleeve, and prevent circulation of the liquid that cools the
packing.
Turn the rotating element by hand.
The stuffing box is improperly packed or adjusted if friction in the box
prevents turning the rotating element by hand. A properly operated
stuffing box runs lukewarm with a slow drip of sealing liquid.
After the pump has been in operation for
some time and the packing is completely run
in, check that the stuffing box leaks at the
rate of 40–60 drops per minute.
This indicates proper packing, shaft sleeve lubrication, and cooling.
NOTICE:
Eccentricity of the shaft or sleeve through the
packing can result in excess leakage. Make sure
that the parts are properly centered.
Check the packing frequently and replace as
service indicates.
Six months is a reasonable expected life, depending on operating
conditions. Use a packing tool in order to remove all old packing from
the stuffing box. Never reuse old packing or add new rings to old
packing. Clean the stuffing box thoroughly before you install new
packing.
Check the condition of the shaft or sleeve for
possible scoring or eccentricity and make re-
placements as necessary.
—
When placing new, non-asbestos packing in-
to the stuffing box, open the molded rings
sideways and push the joints into the stuffing
box first. Then install the rings one at a time,
making sure to seat each ring firmly. Stagger
the joints at a 90° rotation from each preced-
ing joint.
—
If coil packing is used, then cut one ring to
the accurate size with either a butt or mitered
joint. Fit the ring over the shaft to assure the
proper length, and then remove and cut all
the rings to this first sample. When you place
the rings around the shaft, make sure to form
a tight joint. Place the first ring in the bottom
of the stuffing box. Then install each suc-
ceeding ring. Stagger the joints at a 90° rota-
tion.
An accurately cut butt joint is superior to a poorly fitted mitered joint.
Make sure that each ring is firmly seated.
If a seal cage is supplied, check that it is
properly located in the stuffing box under the
sealing water inlet.
The function of the seal cage is to establish a liquid seal around the
shaft, to prevent leakage of air through the stuffing box, and to lubri-
cate the packing. If it is not properly located, then it serves no pur-
pose.
6.4 Shaft-seal maintenance
42
Model 3409 Installation, Operation, and Maintenance Manual
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