Page 48 - Boiler_Operators_Handbook,_Second_Edition

Operating Wisely 33

it weren’t for one simple problem. They can’t generate your shoes scraped electrons off the carpet which then
electricity using the carbon in the fuel. Any fuel cell us- collected in your body. When you reached for the door-
ing a typical hydrocarbon fuel like natural gas basically knob the electrons passed through your finger, through
burns the carbon. the air, into the doorknob. Another way mother nature
Whether it’s an engine, a gas turbine, a fuel cell, shows us how she handles electricity is lightning. In
or a very conventional steam turbine driving an electric those cases electric arcs form where the electricity just
generator you will eventually be operating one because flows through the air, just like the static spark off your
all plants will have them. So, … now’s the time to get an finger traveling to the doorknob.
adequate understanding of electricity. Those two natural examples imply that a circuit
I’m not going to use all the hydraulic analogies we doesn’t have to be like a circle (so the electrons can
engineers typically try to use because I think they are continue to flow around it) but the truth is that they are.
just confusing. Electricity is different but it isn’t a dark The electrons you dumped to the doorknob eventually
and mysterious thing that is beyond the understanding bleed through the door, hinges, door frame and into the
of a competent boiler operator. There are only two basic floor to get back to the carpet. The discharge of lightning
things you have to know about electricity and the rest is dumping electrons dragged to the earth by the rain
falls into place. drops back up to the clouds in the sky. Those rather fast
For electricity to work there has to be a closed cir- and furious discharges of electricity are not the kind of
cuit. A circuit is a path that the electricity flows through. thing we want to do in the boiler plant. Note that it’s
Break the circuit anywhere so it is not a closed path and called a “discharge” which means the electric charge is
electric current can’t flow through it. The second thing eliminated, at least until it builds up again. Once you’ve
is that there has to be something in that circuit that recovered from that spark between your finger and
produces electrical current. If electric current isn’t flow- doorknob you will not get shocked again, provided you
ing through the circuit the circuit isn’t doing anything. didn’t move around the carpet some more.
That’s it, create a circuit to make electricity work and A battery is like having stored electrons. The differ-
break the circuit to stop it. When the path is complete ence is a battery contains chemicals that react to replace
so current can flow we call it a closed circuit. Whenever the electrons when you start discharging it. You can dis-
there’s a break in it we call it an open circuit. To be fair charge a battery by running the electrons through a light
I should also explain that a “break” is typically undesir- bulb, as in a flashlight, or, as I sometimes do when car-
able whereas the “open” is a normal interruption in the rying some spares around, by shorting the battery. I do
circuit. that when the keys in my pocket manage to touch both
You pull the plug on the toaster that’s stuck and ends of the battery. I have some rechargeable batteries
belching black smoke while incinerating the last slice of in which the chemical process is reversed to restore the
bread that you planned on having for breakfast and you charge. A battery will keep restoring the charge until
opened the circuit. Actually, you opened it in two places, the chemicals all change then we call it “dead.” There’s
the plug does have two prongs. When you turn the light not much difference between a dead battery and a dead
switch off you opened the circuit. In most cases opening electrical circuit except that the battery just can’t pro-
a circuit consists of moving a piece of metal so there is a duce enough electrons to raise the voltage and a dead
gap between it and the rest of the metal that forms the circuit can have full voltage someplace.
circuit. In almost every case where we use electricity we It’s important to realize that an electrical circuit that
use metal wire and metal parts to form the circuit. Some- isn’t doing anything can still have a charge of electrons
times, as with the toaster plug, you can see the open. In stored someplace ready to surprise us just like when we
other situations, as with the light switch, you can’t see reached for the doorknob. The problem with electric cir-
the open because it’s enclosed in plastic to protect you cuits is they have the capacity to store a lot more electrons
and it. than our shoes can rubbing the carpet and it’s current that
When mother nature is dealing with electricity kills. The voltage you build up walking across the dry
metal is not a requirement. At some time in your life carpet is a lot higher than most electrical circuits, it takes
you had to walk across a carpet on a cold dry winter a lot of voltage to make electrons jump that gap between
day, reach for the doorknob and get surprised by a your finger and the doorknob.
spark jumping from your finger to the knob. We call that You’ll recall there was this earlier chapter on
static electricity but there wasn’t anything static (as in flow? Electricity is no different. You control the flow
standing still) about it. As you walked along the carpet of the electricity, those little electrons have to flow for