the boiler water sample contains sediment. In this case,
deterioration of the piping. As long as only one boiler is
the time between blowdowns should not exceed 24
steaming, the effects of chemical carryover on the boiler
hours. You will not have to secure a waste heat boiler
water chemistry will be minimal. This is because most
before you perform a bottom blowdown.
of chemicals leaving the boiler will be washed to the
feedwater tank and then returned to the boiler. In this
If you follow the procedures for separator or surface
case, it will be easy for you to recognize excessive
blowdowns, you can reduce the alkalinity, phosphate,
carryover by the entries in the boiler water logs. When
conductivity, and chloride of a steaming boiler by about
two boilers are steaming, however, an increase in the
10 percent. If you need more than a 10 percent reduction,
chemical levels can occur in one boiler while a loss of
repeat the blowdown cycles as necessary. Wait 1 minute
chemicals can occur in the other. This is an indication of
between blowdown cycles to allow the water to
carryover. The problem is complicated by the fact that
circulate.
each of the boilers may carry over at different rates.
When a different set of boilers is steaming, the boiler
that was losing chemicals may start gaining them.
CAUTION
Excessive carryover will cause the salinity/conductivity
indicators to read higher than normal for the chemical
chloride test. Another sign of carryover is any detection
Do not blow down a steaming boiler more
of alkalinity in the condensate or feedwater (feedwater
than 50 percent at one time. This time period
sample pink to phenolphthalein).
equates to five 3-inch blowdowns on the
You will need to use specific treatment procedures
CONSECO or 5 minutes on the CE. If you
designed to compensate for chemical carryover. The
overlook these precautions, an excessive
batch dosage will not increase the alkalinity or the
chemical loss occurs. Sample and test as
phosphate to the upper limits to allow for some increase
needed, and base further actions on the test
in the chemicals. The low treatment levels reduce the
results.
amount of chemicals that leave a boiler having excessive
carryover. When you discover that one boiler carries
You are required to record the percentage of
over more than another, secure the continuous treatment
blowdown on a steaming boiler in the boiler water
system to the boiler that is collecting the chemicals.
treatment log. To determine the percentage of
Adjust the continuous treatment to the boiler that is
blowdown, use the following formula:
carrying over to maintain the chemical levels as low as
possible. Excessive carryover may cause the indicator
alarms to activate. If this happens, just bypass the alarm.
When contamination occurs, the boiler water chloride
will carry over and cause high chloride test results in the
feedwater. To reduce the contamination, it is more
effective to blow down the boiler than to dump the
feedwater. If the carryover is so severe that it is
Remember, the conductivity is proportional to the
impossible to maintain the water chemistry, a problem
concentration of all of the dissolved solids present in the
with the steam separator may be indicated.
b o i l e r water from treatment chemicals and
Slowdowns.--
Once you have identified
contaminants. The conductivity will remain within
contaminants and additional chemicals in boiler water,
limits as long as the other test results are within the
how do you remove them? To remove the contaminates
proper ranges.
and excess chemicals, you must blow down the boiler.
The chloride level will provide you with an
You must use either a separator blowdown for
overview of the level of contamination entering the
CONSECO boilers or a surface blowdown for
boiler. You can maintain an acceptable chloride level of
combustion engineering (CE) boilers. You must use
less than 1.0 epm by maintaining good distillate quality
either a separator or surface blowdown any time your
and correcting any in-leakage of seawater or potable
test results indicate the need. You must also perform
water.
periodic bottom blowdowns to control sludge buildup.
You do these weekly, or as needed, to make sure the time
Now that we have discussed the testing and
between blowdowns does not exceed 168 steaming
treatment of boiler water, let's talk about where the
hours. You must perform a bottom blowdown daily if
boiler water comes fromthe feedwater.
