Generally, boiler feedwater will contain oxygen and
dissolved minerals. Inside the boiler, the heat will cause
the oxygen to separate from the water.
F. Foaming, Bouncing, & Carryover
1.
Causes of Foaming
It is normal for the water line of Lattner boilers to
fluctuate about one inch. However, excessive foaming
and bouncing (an unstable water line) can be caused by
several different conditions. The presence of oil or
grease in the boiler water will cause serious foaming.
Foaming can also be caused by excessive
concentrations of boiler water solids. A third cause is
excessive alkalinity (high pH level). Water that's too soft
will also cause the water level to bounce.
2. New Boiler Foaming
In a new boiler, foaming has two primary causes. Oil
from the steam piping and the boiler metal has
accumulated at the water line. Secondly, Lattner clean
out compound contains trisodium phosphate. This must
be thoroughly flushed out of the boiler. Trisodium
phosphate, if left in the boiler, will raise the alkalinity,
causing foaming.
3. Carryover
Carryover ( often called priming) is small droplets of water
leaving the boiler with steam. Foaming, as described
before, is a key cause of carryover. If the foaming
problem is eliminated, the carryover should stop as well.
If the system uses steam faster than the boiler can make
steam, water carryover may occur as well. Be certain that
all steam traps function properly, all piping is insulated,
there are no leaks in the steam piping, and the burner
combustion is set properly.
G. Water Treatment Summary
These are general guidelines for water treatment. Lattner
is not a water treatment company and cannot make
specific recommendations for each boiler installation. To
ensure proper operation and extend the life of the boiler,
a complete water treatment program must be used.
Contact a qualified company with experience in this field
to provide a treatment program for your installation.
Insufficient or too much chemical treatment can damage
your boiler. The following are guidelines for boiler water
quality:
H
Total Dissolved Solids
Chloride
Sodium Phos hate
H. Slowdown
1.
Purpose of Slowdown
8.5 to 10
2,000 ppm or 116.8
rains maximum.
16
treatment. Whenever a softener is used, chemical treatment
is still necessary for oxygen scavenging and controlling pH.
The water treatment chemicals keep these substances
suspended in the water. Eventually, the concentration of
these substances increases and must be removed. This
is done by blowdown. Slowdown removes a portion of
the water in the boiler in order to reduce the amount of
dissolved solids. Slowdown will also remove some of
the loose deposits that may be in the boiler.
2. Slowdown Instructions
The boiler may be blown down at any pressure,
provided the blowdown piping is piped to a safe location
(see Installation Instructions). To blowdown, open the
boiler bottom blowdown valve (see assembly print) to
the fully open position. Watch the sight glass. When the
boiler water level drops about one inch, close the
blowdown valve. Lattner recommends 30 psi.
NEVER
blowdown a hot boiler to a level where no water
is visible in the sight glass.
3. Control Slowdown
Scale can also deposit in the water level controls and
piping, just as it can deposit in the boiler. The
McDonnell Miller level control and auxiliary low water
cut-off water column
MUST
also be blown down daily. If
scale blocks these controls or the piping connected to
them, the boiler may dry fire. Dry-firing the boiler will
permanently damage the boiler shell.
I. Feedwater System
1.
General
A boiler cannot operate without water. For proper
operation, the boiler must have a reliable water supply.
2. Pump Cavitation
Always use spring-loaded check valves in the feedwater
piping. Swing check valves (even when new) are not
suitable for boiler feed applications.
A bad check valve will allow hot water from the boiler to
back-feed to the pump. When the pump starts, this
water flashes to steam. This condition, known as
cavitation, causes the pump to sound like there are ball
bearings in the water and prevents the pump from
working properly, especially when the boiler pressure
rises.
Bad steam traps may also cause the pump to cavitate.
Bad traps allow steam to return to the condensate tank
and heat the water in the tank. As the water
temperature gets above 180
°
F, cavitation becomes
more likely and prevents the pump from working
properly.
3. Check Valves
&
Steam Traps
To check for bad steam traps or check valves, look at
