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Stuffing Box Design
Guidelines for Stuffing Box Dimensions
Rotating
Shifts: Dimension A shown on this drawing
is the total depth of packing including lantern gland.
A standard depth of 7W or 7 times the packing space
has been established when a lantern gland is used.
A depth dimension of 5W is used where lantern gland
is omitted.
| English |
Metric |
| Shaft
Range |
W |
Shaft
Range |
W |
| 5/8"
to and including 1-1/8" shaft |
5/16" |
16mm
to and including 29mm shaft |
8mm |
| 1-1/8"
to and including 1-7/8" shaft |
3/8" |
29mm
to and including 48mm shaft |
10mm |
| 1-7/8"
to and including 3" shaft |
1/2" |
48mm
to and including 75mm shaft |
13mm |
| 3"
to and including 4-3/4" shaft |
5/8" |
75mm
to and including 120mm shaft |
16mm |
| 4-3/4"
to and including 12" shaft |
3/4" |
120mm
to and including 300mm shaft |
19mm |
1.
Lantern Gland Position: It should be
noted that the illustration shows the dimensions of
2W on the pressure side of the lantern ring and 3W on
the gland end of the stuffing box. While this is a common
practice, it should be noted that 3W on the pressure
side and 2W on the gland end of the stuffing box can
also be used. Consult the packing manufacturer of your
choice for the proper set-up to best service your application.
2. Gland Take-up: This gland take-up
is limited to 40% of the packing. The reason for this
limitation is to include those packings which will have
the largest volume loss. Additional gland take-up is
not recommended, in order to prevent galling of the
shafts. This means that complete take-up will take place
before equipment is damaged: therefore, packing replacement
would be indicated. This is based on the theory that
most damage is done during the late running of packing
life.
3.
Lantern Ring: (Also known as Seal
Cage) - The suggested depth or length of lantern ring
is set at 2W.
4.
Chamfer Depth: A minimum of 1/8"
(3mm) is recommended. It is felt that less than 1/8"
(3mm) will not contribute to easy entrance of packing.
5. Chamfer Angle: Wedging or guiding
action is best between 15 and 30 degrees.
6.
Gland Entrance: It is recommended
that a minimum of 1W be maintained to minimize the
probability of gland cocking, and allow for general
variations of soft packings, molded, and other types.
7.
Size Limitation: In designing equipment
with shaft below 5/8" (16mm) diameter, consult
with individual packing manufacturer regarding packing
space required (W).
8.
Clearance: Clearances should be accepted
machining practices, taking into consideration thermal
expansion and contraction of metals.
9.
Finishes: Finishes of rotating elements
in contact with packing should be the best economically
possible, bearing in mid that the finer or smoother
the finish, the longer the packing life expectancy.
10.
Pressures: These standard dimensions
are intended for use up to approximately 1500 psi
(102 bar).
11.
Performance: Performance at various
high speeds is a function of the material used rather
than the stuffing box dimensions, and recommendations
for speed limits are not considered here. Consideration
of high-speed problems should be referred to individual
packing manufacturers.
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