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 ( b ) Q u a r t e r l y . T e s t setting point using a calibrated test gauge.
R e a d j u s t setting if necessary by changing the spring compression.
D i s m a n t l e the valve and look for the following:
(c) Yearly.
q Damaged seats
q Lodging
of
foreign
matter
between
seat
and
feather
q Corrosion, erosion, worn out or defective parts
q Distortion caused by uneven tightening of bolts
q Deposits of foreign matter
q Defective installation of exhaust piping
q Damaged gaskets
w e a r , wire-drawing, and grooving
q Damaged seats and feathers:
Perform the following maintenance procedure.
6 MAINTENANCE OF VALVES.
( a ) Repair leaks by tightening loose connections and packing glands.
R e p a c k glands and repair or replace defective parts. Never reuse old packing,
even if it looks satisfactory.
(b) Repair damaged insulation. B e sure to use insulating material of
t h e proper t y p e required for the service.
( c ) P a i n t exposed valves for protection against external corrosion. Do
n o t paint the stem. Exposed stem threads of gate valves of the rising stem
t y p e should be protected by a piece of thick rubber hose placed over the stem.
(d) Repair valve seats and disks by lapping with a grinding compound to
a smooth, e v e n finish, removing as little metal as possible. The disk seating
surfaces may be coated with Prussian blue and lowered against the seat to
c h e c k t h e f i t . T h e valve is tight when a good, continuous contact is
To remove cuts and scratches, it may be necessary to use a valve
obtained.
r e s e a t i n g machine or lathe. Avoid removing too much metal.
( e ) Replace worn out, corroded, or damaged stems, disks, and seats.
( f ) Remove and discard old packings. Clean the stuffing box. Clean
i n s i d e of valve bonnet and other parts, removing all dirt and scale.
Replace gasket of proper size and
(9) Remove and discard old gaskets.
q u a l i t y for the service intended.
( h ) Estimate the cost of extensive valve repairs. Installing a new
v a l v e is often less expensive than repairing an old one.
7 MAINTENANCE OF PRESSURE RELIEF VALVES. Make necessary repairs or
r e p l a c e m e n t s after the yearly inspection of paragraph 5(c). Check the setting
7-17
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