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 or replace defective parts as required. The following items are the main
p o i n t s to consider during inspection and m a i n t e n a n c e of slip joints.
Check alignment at least once a year.
(a) Alignment.
( b ) P a c k i n g . A d j u s t or replace packing, as required, to prevent leaks
a n d assure a free working joint. I n the gun-packed type of joint, the
a d d i t i o n of a few plugs of plastic packing (depending on the size of the
j o i n t ) i s a l l t h a t i s r e q u i r e d . T h i s can be done while in operation. The
f r e q u e n c y depends on the operating conditions and type of joint used. In
c o n v e n t i o n a l gland-packed joints, the gland nuts must be evenly tightened
u n t i l signs of leakage disappear, e s p e c i a l l y during the first few days after
t h e packing is put into service. A f t e r the initial adjustment, the packing
r e q u i r e s only periodic inspection. I t is very important to immediately stop
any leaks through the packing glands; otherwise, leaks may cut channels in
b o t h the packing and the slip. The frequency of packing replacements depends
o n the operating conditions. W h e n replacing old packing, the joint must be
t a k e n out of service.
( c ) T r a v e l . C h e c k the flange-to-flange distance of the joint once a
y e a r , first when cold and then when hot, and compare with the travel limits
shown in the manufacturer's data. I f slip travel has changed, it may indicate
a shift in the anchorage and/or pipe guide. The source of the problem should
be located and corrected.
( d ) L u b r i c a t i o n . L u b r i c a t e slip joints every 6 months, using the
c o r r e c t quantity, type, and method of lubrication recommended by the
m a n u f a c t u r e r for the service conditions.
5 . 2 Inspection and Maintenance of Bellows Type Joints.
Inspect joint
a n n u a l l y for alignment, fatigue, corrosion, and erosion. Check travel between
c o l d and hot conditions and compare with manufacturer's instructions. In case
o f failure, the bellows section must be replaced.
5 . 3 Inspection and Maintenance of Flexible Ball Joints. Usually no
lubrication is required with this type of joint as there is little frictional
wear. E x t e r n a l takeup is provided for adjustment if necessary. Replace
g a s k e t s as required. The frequency of gasket replacement depends on the
o p e r a t i n g conditions.
7-1o
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