Columbia L-24, Руководство пользователя, Страница: 26 / 60

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• Another test which is sometimes used as a gauge of solids is to measure the chloride present in the
boiler water. The ratio of chlorides in the boiler water to that of the feed water can be used as a means
to determine the amount of blow down required. The chloride test is unsuitable for feed water with low
incoming concentrations and the concentrations in the feed water must be averaged over time for
accuracy.
• High boiler solids will lead to foaming, priming, surging, and carry over. These items may only be over
come by proper blow down of the boiler.
Alkalinity
•
The alkalinity of boiler water should be sufficiently high enough to protect shell and plates against
acidic corrosion, but not that high to produce carryover. A minimum value for alkalinity for adequate
protection is 200 p.p.m.
• High boiler alkalinity in excess of 700 p.p.m. should be avoided. Values higher than 700 can lead to
embritlement of the steel.
Phosphates
•
Phosphates are used to react with calcium hardness in the boiler water. In order for this reaction to take
place it is important to maintain a Ph at a minimum value of 9.50. It is desirable to keep the concentra-
tion of phosphates in the water to 30-50 p.p.m. in order for complete reaction of the phosphates with
the calcium hardness entering the boiler through the feed water.
Hardness
•
The hardness of water is caused by calcium and magnesium ions which will vary greatly throughout the
country depending on the source of the water.
• In boilers the hardness of the water can cause the formation of scale and sludge or mud.
• The hardness must be removed in the makeup water to the return system.
• Total hardness should not exceed 50 p.p.m.
Oils
•
Every effort should be made to prevent oils from getting into the boiler water. Oil causes foaming or
combines with suspended solids to form a sludge which can cause the overheating of boiler plates. If oil
does get into the boiler, the boiler should be taken immediately out of service and thoroughly cleaned.
STEAM BOILER BLOW DOWN PROCEDURE TO REMOVE SOLIDS
• Blow down can be done in the evening after burner has been shut down and water has settled
• Open boiler blow down valve for 30 seconds, then close.
• Open float type low water cut off or feeder blow down valve for 30 seconds, then close.
• Now go back to the boiler blow down valve. Open and close the valve quickly, three times
• Repeat this procedure with the low water cutoff or feeder valve
• This should rid the boiler of most precipitated solids