Page 85 - Boiler_Operators_Handbook,_Second_Edition

70 Boiler Operator’s Handbook

heater) and the inlet to the stack. at a later date will prove the boiler wasn’t abused while
Sometime in the future you should be applauded waiting for a load.
for taking readings of shell or casing temperature. The Acceptance tests vary. ASME PTC-4.1 the “Steam
best way to do this today is with an infrared camera that Generating Units” power test code provides three
is calibrated to accurately indicate temperatures. There means of testing a boiler for acceptance. However, a test
are contractors that provide an infrared survey service in conformance with that test code is an expensive prop-
that could be used. There are less expensive methods osition requiring continuous documented operation of
including use of an infrared thermometer or as simple as the boiler for a period of 8 to 12 hours. It’s justified for a
holding a thermometer against the casing or shell with a boiler designed to generate more than 60,000 pounds of
piece of insulation. That last method has to be described steam per hour but not for a small 50-horsepower boiler
along with the recorded data because the insulation that only generates 1,700 pounds per hour. There are
does restrict heat flow and produces a higher tempera- other simpler and acceptable means for testing boilers;
ture than actual so the same method must be used for the important element is having established one accept-
comparison at a later date. I have detected consider- able to owner and manufacturer before the boiler is pur-
able differences in the temperatures of casing surfaces chased. In the unlikely event the boiler fails to perform
on water tube package boilers and recommend taking the manufacturer is then committed to make it right.
several measurements of those surfaces. I also insist that For small boilers, I always recommend testing for
new water tube boilers be fitted with insulated drum one hour at each load point and, with that exception,
head covers and their surface temperatures should be testing using the “heat loss method” of PTC-4.1. That
recorded as well. If your boiler (new or not) isn’t fitted way you have a formal acceptance test but not the ex-
with insulated drum covers measurements of the drum pense of long runs. It shouldn’t require any overtime
head surfaces should suggest an early modification to because you should allow it to settle for half an hour
your new boiler to include them. before each test to establish test conditions, and you can
Photographs of the flame in the furnace for each do six a day. On a boiler with two fuels that would mean
fuel as well as each load can be used for comparison in no less than four days just running acceptance tests. I al-
the future. I carry a piece of blued glass to reduce the ways wonder what some engineers were thinking when
light intensity when photographing a fuel oil or coal they said the start-up should take a couple of days, it
fire because my camera is typically blurred when photo- takes more time to check operation and tune the boiler
graphing flames of those fuels. than it does to test it.
If the boiler is fitted with automatic controls your A final acceptance test when a boiler is field erected
recorded data should include each controller’s set point is very important. A contractor can build a boiler wrong
(whether manually set, fixed, or remote), process vari- and many have. What about the boiler that is factory
able value and/or percent, and the controller’s output tested? I would still run an acceptance test of the final
signal, normally in percent. installation. The cost of a boiler is a small fraction of the
cost of fuel it will burn in its lifetime; on average—ten
Acceptance Testing times the price of the boiler each year. A small differ-
The final step in start-up of a new boiler should ence in performance can represent a considerable sum. I
be the performance of an acceptance test. Data should actually estimate the cost of a 1% difference in efficiency
be collected and recorded at the firing rate where ef- for a particular installation and use that value, with the
ficiency is guaranteed by the manufacturer and, if it is a vendor’s knowledge, in evaluating boiler offerings.
modulating boiler, at no less than three other firing rates Other start-up activities that may be associated
(maximum, 75%, 50%, and 25% being common). All data with a new plant are covered in the following descrip-
collected should be carefully recorded and stored in a tions.
binder for future reference. If it is a new plant the per-
formance of all equipment should be documented at the
various firing rates. Occasionally a plant is started when DEAD PLANT START-UP
there is no place to use the steam and no way to perform
the test until other installations are in place. The install- All personnel working on the site within the boiler
ing contractor then requests a delay in testing until a plant and equipment rooms should be notified of the
load is available. When that occurs collect data at firing plant startup so they are not surprised and more impor-
rates which can be handled. Nearly identical readings tantly not injured as, the system comes up to tempera-