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| Larry Bachus
(a.k.a The Pump Guy)
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Did
you know that the instrumentation technician is a better friend to the
Pump Reliability Engineer, than the vibration analyzer or the
Computerized Maintenance Management program? I believe this to be true. Let me explain ...
Pumps-mated-to-electric-motors
are the most popular piece of industrial equipment in the world. Most
instrumentation is installed onto equipment fed by pumps. Sometimes a
process engineer wants to know the fluid velocity, flow, or pressure in
a pipe. A pump normally generates that velocity, flow, and pressure.
And sometimes the pump contributes to the temperature in a chemical
process. When the temperature, velocity, flow, and pressure are not
what they should be, it normally indicates that the pump is in stress
and headed for failure. And folks, that's why the instrumentation tech
is reliability's friend.
The
industrial pump is a relatively simple device when compared to a V-8
engine or a refrigerator. Pumps are only slightly more complicated than
a butter knife. The shaft and impeller assembly is the only moving
part. And most of what we call “pump problems” actually originate
outside the pump.
Let’s
consider pumps and gauges. Pump manufacturers use the term “head” in
feet for fluid force. Maintenance people use the term pressure in PSI
for fluid force. The conversion factor 2.31 separates the two terms.
For
water, head divided by 2.31 is pressure, and pressure multiplied by
2.31 is head. If the liquid is not ambient water, then the liquid’s
specific gravity (sp.gr.) must be factored into the formula.
[Head (ft.) / 2.31] x sp.gr. = PSI
[PSI x 2.31] / sp.gr. = Head in ft.
For
example, most communities have an elevated water tank that supplies
water pressure to the neighborhoods below the tank. Let’s say the level
of water in the tank is 200 feet above a kitchen faucet in one of the
homes. What is the water pressure at the faucet? 200 ft./2.31 = 86.6
PSI.
There
would be about 87 PSI of water pressure at the kitchen faucet because
the water in the supply tank is 200 feet high. Let’s say a pump is
designed to develop 70 feet of head. 70 ft./2.31 = 30 PSI. There should
be 30 PSI of differential pressure across this pump. This means if the
suction pressure gauge reads zero PSI, the discharge gauge should read
30 PSI (30 PSI diff.). If the suction gauge reads 55 PSI, the discharge
gauge should read 85 PSI (30 PSI diff.). The pump is at its optimum
design point at 30 PSI of differential pressure. As the pressures move
away from 30 PSI (observed on the gauges), the maintenance rises on
that pump.
| Process pumps need gauges installed, otherwise the operator has no reference point to determine the system's health.
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If
you walk around your plant and look at the pumps, you’ll see that most
pumps don’t have pressure gauges on the suction nozzle. Thus, the
operator has no reference point. You wouldn’t cook a pizza without a
timer and temperature gauge on the oven.
Why
don’t the pumps have gauges? Some would blame the instrumentation tech.
But instrumentation takes instructions from the production engineer. So
why doesn’t the engineer order the instrumentation tech to install
gauges on the pumps? Why does no one train the operators to read the
gauges once they’re installed?
Every
day there are mechanics and operators standing next to pumps without
gauges. The operator has absolutely no idea if the pump is healthy or
sick. Before long, the pump becomes a high maintenance item.
And
someone will say, “Maybe we should buy that $50,000 CMM program.” And
someone else will say, “Let’s buy that $80,000 vibration analyzer.” I
would say, “Why don’t you go buy a set of gauges for $200 and train the
operators?” Duuuhhh!!
As
a pump consultant, I see too many pumps without gauges. I see gauges
where the needle has fallen off the stem. I see gauges where the cover
glass is fogged ... or broken. All pumps should have suction and
discharge pressure gauges installed. The gauges should be calibrated,
clean, and adequate for the service. Operators should monitor the
differential pressure. The pump is sick if the differential pressure is
too high or too low. This ain’t rocket science!
Larry Bachus, founder of pump services firm Bachus Company Inc., is a new columnist for Flow Control magazine.
He is a pump consultant, lecturer, and inventor based in Nashville,
Tenn. Mr. Bachus is a member of ASME and lectures in both English and
Spanish. He can be reached at larry@bachusinc.com or 615 361-7295.
For More Information: www.bachusinc.com
Get Hands-On Training at the
PUMP GUY SEMINAR
Oct. 21-23 - Houston, TX
REGISTER NOW!!!
ATTENDEES RECEIVE:
Complimentary Companion Text - Discounted Hotel Rooms - Free Parking - Complimentary Food & Bev Service.
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Larry
Bachus (a.k.a. "Pump Guy") demonstrates the principles of NPSHr vs.
NPSHa at his Aug. 18-20 Pump Guy Seminar in the Chicago area.
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Larry Bachus (a.k.a. "Pump Guy"), a regular contributor to
Flow Control
magazine and a widely recognized expert on pumping technology, recently
presented his Pump Guy Seminar in the Chicago area to an eager crowd of
pump users. Here's what some of the attendees had to say about this
training event:
- “I
attended your seminar this week in Chicago, and it’s already paying for
itself. Your seminar
taught me about concentric reducers on suction
lines and horizontal elbows on split case pumps, which will be quite
helpful on several plant system designs I’m currently working on.” - “Just
a brief note to say ‘thank you’ with regards to the Pump Guy Seminar. I
thought the seminar was very informative and entertaining as well. I
wish to thank you for all of your efforts with the seminar on behalf of
the attendees. A good job well done!"
- “The course was everything I expected. I needed this information 30 years ago, but it’s never too late.”
- “This course holds tremendous value for anyone involved in the design, operation, maintenance, or purchasing of pump systems.”
- “The information I’ve learned from this seminar will most definitely help my understanding of pump issues at work.”
- “For
my line of work, this seminar was dead on. It met my needs fully. Best
money my company has ever spent for a training course.”
- “The
monetary price for your shared knowledge and ability to bring pump
design back to the basics was worth every penny. Thank you for making
your seminar attendees look good with our colleagues.”
FOR MORE INFORMATION & TO REGISTER
FOR THE PUMP GUY SEMINAR, CLICK HERE.
KEY SEMINAR TOPICS INCLUDE:
•
Basic Pump Principles
•
NPSH
•
Cavitation
•
The Affinity Laws
•
Work & Efficiency
•
Pump Classification
•
Pump Curves
•
System Curves
•
Shaft Deflection
•
Pump-Motor Alignment
•
Bearings
•
Pump Packing
•
Mechanical Seals
•
Pump Piping
For a sampling of Larry's latest "PUMP GUY" columns from
Flow Control magazine, see:
•
"Cheat Sheets: Energy, Work & Power"
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"Cheat Sheets: Unwritten Pump Rules"
•
"Cheat Sheets: The Affinity Laws"
FOR MORE INFORMATION & TO REGISTER
FOR THE PUMP GUY SEMINAR, CLICK HERE.
If you have any questions about the PUMP GUY SEMINAR or need help registering, please contact Matt Migliore at 610.828.1711 or Matt@GrandViewMedia.com. |
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