Page 226 - Boiler_Operators_Handbook,_Second_Edition

Maintenance 211

cooler, and the ones on the compressor head, clean so generator regularly you may find you need a UPS (un-
they reject heat the way they’re supposed to. It’s better interruptible power supply) on your controls to keep
to replace a coalescing filter a little early than to put it them from dropping out and doing stupid things (some
off until it’s too late, once oil gets past that filter and into set up by the logic designer) like restarting everything
the system it will take what seems like forever to get rid in manual. Actually I prefer a UPS on all electronic and
of the oil problems. microprocessor based control supplies because the UPS
If your pneumatic controls do get gummed up isolates the controls from the line and will protect the
with oil you or a contractor will eventually have to clean controls from surges and power line noise. It’s like put-
them or replace them because the oil gets gummier as it ting an oil-free compressor with a dryer on a pneumatic
dries and collects little particles of dust to really goo up control air supply.
the controls. If you simply ignore that problem you’ll Today there’s a lot of UPS systems designed for
soon discover that efficient operation is impossible be- computers that can handle the normal control system
cause the controls will always be hanging up. Hopefully load for a boiler. Putting one of those on your boiler con-
I’ve put the fear into you and you will never fail to keep trol power supply will be well worth the little bit they
an eye on the oil removal system to ensure it’s working. cost.
What happens, however, when you inherit the Logging readings not only allows an evaluation
problem? Say you just hired on in an old installation and of the continuing performance of the plant (see boiler
discovered all the controls are spitting out oil, what do logs) but also provides indications of instruments and
you do? The first thing I would do is try to convince the controls losing calibration or operating inconsistently.
owner to replace the controls with microprocessor based Maintaining local instruments like pressure gauges and
hardware to eliminate all the problems with the old thermometers provides a reference for your control and
pneumatics. Failing that I would watch the systems for instrument indications that can be used to identify prob-
a while without changing anything. Some of the older lems and schedule control and instrument tune-ups.
pneumatic systems can work on oil or water; the old ra- You may be allowed to do the instrument calibra-
tio totalizer seemed to be able to. I would hesitate to do tion yourself. With the proper training, tools, and by
anything about the oil getting into the system until I had carefully following the manufacturer’s instruction man-
a better understanding of how it affects everything. The uals it’s possible for an operator to maintain a calibra-
expense of all the oil added to the compressor may help tion schedule during his normal shift. That is not only a
convince the owner to upgrade but that’s not the reason big saving for the employer in contractor’s costs it will
to let it go on; fresh oil flowing through the instruments help keep fuel and power costs down as well. I know, it
will flush them and limit gumming up. sounds like I’m trying to keep an operator moving every
Situations where the controls work anyway should minute of his shift with no time to rest… I am.
probably be left alone, the only thing you can do is keep I did everything including polishing brass to make
good records of the costs associated with the problem my shift seem to go faster. Just sitting there listening to
to give the owner a justification for replacing those con- the plant gets boring and makes the time pass slowly.
trols. Switching a system by adding coalescing filters or Count your plant instruments, transmitters, controllers,
other oil removal devices could result in system failure etc. and multiply by four hours then compare the result
because the oil remaining in the instruments will gum to the 2,000 hours you normally spend in the plant (not
them up. counting overtime) and you’ll see that it’s not that big
Keeping the control devices clean, free of dust and a deal. Many plants are manned around the clock so
dirt, oil and grease is the most important thing you can there’s over 8,000 hours to share operating and main-
do. Electrical and electronic, including microprocessor tenance time. You’ll have at least three other people to
based controls are subject to dirty power supplies as take their share of the work load.
well. No, not real dirt, power with harmonics, spikes Tuning firing rate controls isn’t always something
and all those other things that do dirt to electrical equip- an operator can do. There’s a certain amount of skill and
ment. experience required to do it without blowing the boiler
Whenever a contractor tries to hook up a welding up. You can do it if you you’ve had hands on training
machine in the plant make sure a connection designated under the watchful eye of an instructor and that instruc-
for welding machines is used. Be certain any welding tor tells you that you have an aptitude for it and can do
lead is not run over or around control cabinets or con- it. I’m not confident that I can put enough guidance in
duit containing control wiring. If you test an emergency a few paragraphs of a book to guide someone through