Page 66 - Boiler_Operators_Handbook,_Second_Edition

Operating Wisely 51

these data are required to determine the heat ab- should be monitored at a frequency adequate to
sorbed by the steam. Reheater outlet temperature detect problems and any time a problem with wa-
also has to be monitored like superheater outlet ter chemistry is indicated.
temperature.
Testing: Regular testing such as testing operation of the
Softened water pressure: Comparing the pressures at the low water cutoffs on steam boilers should have a
inlet and outlet of the softener is a simple measure check box where, by checking the box, the operator
for determining the cleanliness and quality of the indicates he performed that operational test. An
resin bed. Higher pressure drop through a softener initial box, where the operator’s initials indicate
can limit the capacity of the makeup water supply. who did it is appropriate when more than one
person is on the shift. Most other tests, conducted
Stack gas oxygen: see oxygen infrequently, such as quarterly lift testing of a
steam boiler’s safety valves can be included in the
Stack gas combustibles: see combustibles operator’s narrative. Tests that should be recorded,
and their frequency, include:
Stack temperature: This list is in alphabetical order but
stack temperature is undoubtedly one of the most • Combustion analysis—Frequency is subject to
important data points to record. Monitoring stack State Environmental Regulations but should be
temperature is like monitoring a human’s tem- performed at least quarterly for boilers that op-
perature. Stack temperature is the most important erate continuously and any time the efficiency
indicator of boiler health so it should be recorded of combustion is questioned.
as frequently as possible. Stack temperature var-
ies slightly with load so load related temperatures • Flame sensor tests—each month for gas and oil
should be monitored to indicate scale accumula- fired boilers.
tion, fireside accumulation, baffle failures, improp-
er air fuel ratio and other problems. • Hydrostatic tests—for boilers, annually. For
unfired pressure vessels, bi-annually except for
Steam flow indication: If the plant load varies consider- compressed air storage tanks which may only
ably during a shift, say more than ten percent of be tested every five years. Note that these are
operating boiler capacity, recording the indication common time frames, your jurisdiction may
of steam flow consistent with the other data read- require a higher or lower frequency. For any
ings is desirable to maintain a correct relationship pressure vessel or piping system a test should
for evaluation. be conducted after the vessel or piping is
opened for inspection or repair.
Superheater outlet pressure: This pressure should be
recorded because, combined with the outlet tem- • Low water cutoff tests—each day for steam
perature, it is used to determine the amount of heat boilers, each shift for high pressure steam
added to the steam. Variations (relative to load) in boilers, semi-annually for hot water boilers.
superheater pressure drop can indicate superheat- Testing of the low water cutoff is imperative
er leaks or blockage that is otherwise undetectable. since fully one third of boiler failures are due
to low water.
Superheater outlet temperature: The damage associated
with an excessive superheater outlet temperature • Safety valve lift tests—each quarter for steam
requires constant monitoring of the superheater boilers operating at less than 400 psig, annually
outlet temperature. The superheater outlet tem- for hot water boilers.
perature combined with the outlet pressure is
required to determine the amount of heat added • Safety valve pop tests—each year for steam
to the steam. boilers and hot oil vapor boilers. Alternatively
record replacement with rebuilt safety valves.
TDS: The total dissolved solids content of the makeup, The boiler inspector normally governs the per-
condensate, boiler feedwater, and boiler water formance of these tests because many boilers