Quantcast Development of Internal Corrosion

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4.2.1 Maintenance.  W h i l e a steam distribution line is shutdown, maintenance
o f the piping and fittings should be performed. Although not all inclusive,
t h e following is a listing of suggested action areas.
( a ) Repair or replace traps known to be malfunctioning.
( b ) Bench test traps which are in need of inspection.
( c ) Insert traps at points known to require a trap but do not have one.
( d ) Where appropriate, change type of trap to one more effective.
( e ) Remove scale, dirt, flaking, and other residue from strainers.
( f ) Replace damaged or worn strainer screens.
( g ) Lubricate valve stems and replace dried packing.
( h ) Inspect and repair entrainment separators.
( i ) Inspect and repair pipe joints, expansion joints, and elbows.
( j ) I n s p e c t , r e p a i r , a n d calibrate any in place metering devices.
(k) Inspect and repair or replace sump pumps in pits and manholes.
4 . 2 . 2 Development of Internal Corrosion.  The development of corrosion during
a shutdown period is a possibility, but only if the lines and fittings are not
p r o p e r l y and continually maintained.  There are two basic types of chemicals
u s e d for preventing condensate corrosion, n e u t r a l i z i n g i n h i b i t o r s a n d f i l m i n g
i n h i b i t o r s .  A d d i n g the selected amines to the boiler water counteracts
c o r r o s i o n .  A d d i n g filming amines prevents corrosion in piping that is in good
condition, but the Navy does not sanction the use of filming amines and
s p e c i f i c a l l y p r o h i b i t s t h e i r u s e f o r c o l d - i r o n s u p p o r t .  I f scaling and
f l a k i n g are prevalent, a neutralizing inhibitor is required. The most comonly
u s e d neutralizing inhibitors are amines such as morpholine, cyclohexylamine,
and  diethylaminoethanol  (DEAE).  Channeling  in  drain  lines,  caused  by  the
presence of oxygen, can be reduced by the addition of cyclohexylamine as a
boiler-water additive.  Because of their differing vapor-to-liquid ratios, two
or more of the neutralizing amines may be used together to provide highly
e f f e c t i v e neutralization programs for complex systems.  The choice of
a d d i t i v e s is a matter of judgment.
4.2.3 Safe Usage of Amines.  Special caution must be observed when using live
s t e a m in humidification systems.  Problems have been experienced with
additives such as morpholine and DEAE.  Special care should be observed where
steam may be in direct contact with food.  Under the Code of Federal
R e g u l a t i o n s (Title 21, Section 173.310), boiler-water additives may be safely
u s e d in the preparation of steam that will contact food under the following
conditions.
( a ) The amount of additive does not exceed that required for its
functional purpose, and the amount of steam in contact with food does not
e x e e d that required to produce the intended effect in or on the food.
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