In The Trenches
others came on the job. Always be
vigilant. Look and see where and how
problems can occur. Can something
tip over? If so, where will it fall and
what will happen? Are the wheels
locked? Is the power off? Are you
sure? What could happen if you drop a
tool when working over some equipment? Is there high voltage or high current near where you are working? I'm
sure you've heard the saying, "Drive
defensively." It applies to everything
you do, as well. "Work defensively."
Whenever I work on household
wiring, I always do checks with a
voltmeter and then with my hand. I
figure it's better to get a shock when
I expect it, rather than unexpectedly. I
touch the wire with the back of my
hand, rather than with my finger tips.
This is because, if there is current
present, the shock will tend to
contract the muscles. If the wire is in
front, I might close my hand on it. By
keeping the wire behind my hand, I
eliminate that possibility.
use make your product a danger? Can
common, abnormal use be a problem?
From just after World War II until
the AC-powered transistor radio was
developed, many (most?) table
radios were the "All-American Five"
type. That is, they had five tubes and
no power transformer. The transformer was probably the most expensive part, so eliminating it was very
cost effective. This design forced one
lead of the AC power to be connected
directly to the metal chassis. Since
the AC plugs of the time were not
polarized, there was a 50-50 chance
that the hot lead would be connected
You certainly have the right to
risk your life and health as you see fit.
You can sky dive, race cars, or enter
a boxing ring. However, you do not
have the right to risk anyone else’s
without their knowledge or consent.
This seems painfully obvious; however, engineers are sometimes placed in
situations where this is not obvious.
Suppose you are asked to find
ways to reduce the manufacturing
costs of hydraulic hoses. You
determine that substituting a cheaper
braid will provide a cost savings.
However, at low temperature, there is
a greater chance of hose failure under
pressure. A trade-off — it happens all
the time. Your company goes with your
recommendation, but, a few years later,
there is an airplane crash because your
hydraulic hose failed at high altitude,
where the temperature was very low.
Now, things are complicated.
It is important to think about how
your product is going to be used when
you are designing it. Are any common
failure modes dangerous? Can normal