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ML
normally open (with a pipe plug in the "A"
port), has two positions, is four-way, is sole-
noid-controlled and hydraulic-piloted, and
has a spring return.
Without reading the symbol, the only thing
that might be identifi ed by looking at the valve
is that it is solenoid-controlled. Not knowing
the valve's fi ve attributes would make trouble-
shooting much more diffi cult.
A valve often is installed on a machine
simply because it looks the same as the original
valve. If even one letter or number is diff erent, it
must be discovered before the valve is changed.
When one plant replaced a valve that had a
single number diff erence between the original
and the new valve, it resulted in eight hours of
downtime at a cost of $12,000 per hour.
If your maintenance crew is not trained on
these four things, they likely will do the best
they can when an issue occurs, which usually
means changing parts until the problem is
solved. Frequently, many parts are changed
and the machine is fi xed, but no one learns
anything. By properly training your main-
tenance personnel, you will spend less on
equipment parts, reduce your hydraulic-related
downtime and enjoy a safer workforce.
ML
About the Author
Al Smiley is the president of GPM Hydraulic
Consulting Inc., located in Monroe, Georgia.
Since 1994, GPM has provided hydraulic
training, consulting and reliability assessments
to companies in the United States, Canada, the
United Kingdom and South America. Contact
Al at gpm@gpmhydraulic.com.
A commonly used directional valve
The hydraulic symbol for a
directional valve
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