Burnham MPC - Manual (Page 67)

67
The pH should be higher than 7 but lower than 11.
Add some appropriate water treatment chemicals,
if necessary, to bring the pH within the specified
range. With this lower level of protection, care must
be exercised to eliminate all of the free oxygen in
the system.
5. Boiler is now ready to be put into service.
G. fREQUENT WATER ADDiTiON
IMPORTANT
IF, DURING NORMAL OPERATION, IT IS NECES-
SARY TO ADD WATER MORE FREQUENTLY
THAN ONCE A MONTH, CONSULT A QUALIFIED
SERVICE TECHNICIAN TO CHECK YOUR
SYSTEM FOR LEAKS.
A leaky system will increase the volume of make-up
water supplied to the boiler which can significantly
shorten the life of the boiler. Entrained in make-up
water are dissolved minerals and oxygen. When the
fresh, cool make-up water is heated in the boiler the
minerals fall out as sediment and the oxygen escapes
as a gas. Both can result in reduced boiler life. The
accumulation of sediment can eventually isolate
the water from contacting the cast iron. When this
happens the cast iron in that area gets extremely hot
and eventually cracks. The presence of free oxygen in
the boiler creates a corrosive atmosphere which, if the
concentration becomes high enough, can corrode the
cast iron through from the waterside. Since neither of
these failure types are the result of a casting defect the
warranty does not apply. Clearly it is in everyone’s best
interest to prevent this type of failure. The maintenance
of system integrity is the best method to achieve less
makeup water.
h. OXYGEN cORROsiON:
WARNING
Oxygen contamination of the boiler water
will cause corrosion of iron and steel boiler
components, and can lead to boiler failure.
Burnham’s standard warranty does not cover
problems caused by oxygen contamination of
boiler water or scale (lime) build-up caused by
frequent addition of water.
There are many possible causes of oxygen
contamination such as:
a. Addition of excessive make-up water as a result of
system leaks.
b. Absorption through open tanks and fittings.
c. Oxygen permeable materials in the distribution
system.
d. Suction at pump and valve seals.
In order to ensure long product life, oxygen sources
should be eliminated. This can be accomplished by
taking the following measures:
a. Repairing system leaks to eliminate the need for
addition of make-up water.
b. Eliminating open tanks from the system.
c. Eliminating and/or repairing fittings which allow
oxygen absorption.
d. Use of non-permeable materials in the distribution
system.
e. Isolating the boiler from the system water by
installing a heat exchanger.