|The Pump Guy visits and ethanol processing plant to address some pump problems and does his best Sherlock Holmes imitation.|
The greatest detective in literary history asserted that observation and deduction were a science that could be developed and exercised to remarkable heights. In “The Greek Interpreter,” Sherlock Holmes and his brother Mycroft (another private-eye, though retired) astound Dr. Watson (Holmes’ assistant) with a superb demonstration of observation and deduction while they sit comfortably in a London pub.
Mycroft spoke first. “This is an excellent place to study mankind. Consider the short, tanned fellow with his hat pushed back, carrying several packages. He’s coming towards us now.” Sherlock, Mycroft and Dr. Watson peered into the street through the window at their booth.
“An old soldier, I perceive,” said Sherlock. “And recently discharged from service,” remarked Mycroft.
“I’d say he served in India as a non-commissioned officer. Royal Artillery, I fancy,” said Sherlock. “And a widower, with a child.” added Mycroft.
“Children, my dear boy, children,” said Sherlock. Seeing Dr. Watson gaping with astonishment, the two detectives explained.
“Surely,” said Sherlock, “it’s not hard to say that a man with that bearing, expression of authority, and sunbaked skin is a soldier – more than a private – and is not long from India. You see, India is the only sunny place where England currently stations troops.”
Mycroft added, “It’s obvious the man is recently discharged from the service. He still wears his ammunition boots. He doesn’t have the stride of a cavalry officer. Yet, he wears his hat on one side, as is shown by the lighter skin on that side of his brow. He is in the artillery. His weight doesn’t support work as a trench soldier.”
Sherlock continued the observation. “Then, of course, his complete mourning shows that he has lost someone very dear. The fact that he is doing his own shopping looks as though it were his wife who died. He has been buying things for children, I perceive. There is a rattle. One of the children is very young. His wife may have died in childbirth. The fact that he has a picture book under his arm shows that there is another older child to be thought of.”
Amazing? For sure! Impossible? No! Especially when you consider that this piece of observation and deduction was actually performed by Dr. Joseph Bell, a professor of surgery at Edinburgh University in Scotland. Dr. Bell inspired Arthur Conan Doyle to create the fictional detective Sherlock Holmes.
These preceding paragraphs illustrate my work as a pump consultant. (I don’t just teach pump courses.) The “Pump Guy” observes and deduces, aided with over 40 years of experience as an industrial maintenance practitioner.
Recently, I had the occasion to address some problematic pumps at an ethanol processing plant in the upper Midwest. I recalled reading Sherlock Holmes. And while my performance did, by no stretch of the imagination, approach the heights that only the inimitable private eye could attain, it was, nonetheless, rewarding. Beginner’s luck, I presume.
Joe F., a supervisor at the ethanol plant, met me at the luggage carousel in the Minneapolis airport. We loaded my stuff into a company pick-up and started a two-hour trek into northern Iowa.
Joe dodged the potholes with his left hand. His right hand was busy shuffling two plastic cups. A diet soda was in one cup. The other cup held Joe’s tobacco-chewing spit. Both cups bounced and wobbled in the two console cup holders. I was worried Joe might drink from the wrong cup. I moved my computer bag away from splash range.
Joe signed me in at the guard shack. The afternoon guard bummed a wad off Joe and the two of them talked and spit as I watched the safety video. Then we went to Joe’s office to talk.
Joe said they were beset with mechanical seal failures on five sister pumps. They had installed 16 cartridge seals on five centrifugal pumps in the past year. The pumps were all ANSI spec, same model and brand, moving industrial water with the same suction and discharge pipe diameters. They were not parallel pumps because the discharge pipes went in different directions, as the plant was built eight years ago.
Probing a bit, I learned that only one pump was eating seals. The seals on the other four pumps had run for over a year with no leakage. But one pump had eaten 12 cartridge seals in the last year. That accounted for the 16 seals.
It was pretty clear to me that this was a pump problem, especially since the pumps were “identical” and all of them handled cold, relatively clean water.
We walked to the maintenance shop to see the failed seals. Joe offered a wad to the shop foreman. My suspicion was reinforced when I observed that all the failed seals exhibited the same evidence. Considerable chipping on the outside diameter of the carbon face suggested excessive vibration. I allowed the information to sink in.
As the three of us ruminated (mine was mental), something clicked in my mind as I recalled Sherlock and “The Greek Interpreter.” It was time to visit the five sister water pumps. As we walked through the plant, Joe pointed 40 yards ahead in the distance and said, “Those are the pumps over there.”
“And the fourth pump on the right is the problem!” I commented. Joe’s chew fell to the ground leaving a line of wet, brown drool on his white shirt. Joe stopped walking and exclaimed, “How the _&#@ do you know that from this distance?”
I responded, “Though the pumps and pipes are ‘identical,’ the motors are not. That fourth pump has a larger motor. It suggests one of two motives. That’s either a two-pole motor (3,500-rpm), or it’s larger because the pump is running on the right extreme of the curve. But, I can’t see that from here.” We walked.
Standing over the noisy pumps, I shouted, “The other pumps are running at 1,750-rpm. This fourth pump is on a 3,500-rpm motor. It’s larger than the others, and making more noise.”
Joe inserted another wad. With his attention diverted, I touched the offending fourth pump with my right hand and the fifth pump with my left hand. There was a noticeable difference. Joe tugged my shirt sleeve and led me away from the noise toward the shade of a fire-hose shack.
Joe asked, “What do you know about a pump by looking at the electric motor?” I answered, “The Affinity Laws state that flow changes proportional to the change in speed. Twice the speed generates twice the flow. The same laws also state that power changes by the cube of the change in the speed. Twice the speed requires eight times (23) the power to drive the pump. This fourth motor is larger, probably for more flow. And this fourth pump and motor are making all the noise.”
Now, any pump or seal manufacturer will tell you that shaft runout should not exceed two thousandths of an inch (0.002”) on a mid-frame ANSI pump. That figure includes a safety factor, because they know that in the real world, four and five thousandths runouts are common. At twice the speed and eight times the power, this poor pump shaft is experiencing severe runout (maybe 0.040”) and vibrations, which supports the chipped and broken seal carbons.
I led Joe back to the sister water pumps. This time we both put our fingertips onto pumps one, two, three and five, noting the noise, heat and vibrations. A circle of mechanics and workers (the audience) had gathered around us.
Then Joe touched the casing of number four pump. Although pumping the same cold water, the number four pump was notably hotter. And, sure enough, the vibrations were excessive on number four. And I said so.
An onlooking mechanic raised his eyebrows and commented that the word “excessive” was a relative term. I shot back that he was absolutely right. The vibrations on pump number four (with the larger motor) were excessive relative to the level of vibrations in the other sister pumps.
I stretched my novice luck with another deduction. “This pump eats bearings too!” Joe’s eyes fixed on the ground, in silence. He didn’t deny it.
We returned to Joe’s office and sound insulation. Joe asked, “What can we do?” “There’s a lot we can do,” I said, “but not today. It’s already 5:18.”
Joe took me to the hotel. The next morning, Joe negotiated potholes with his left hand for two hours back to the Minneapolis airport. We scheduled a return visit to the ethanol plant. As we bounced, the same two cups of diet soda and stale spit wobbled in the console cup-holders. Joe alternately reached for both with his right hand. I slid my computer bag away from splash range. True Story! Thanks Sherlock!
It is always possible to find the answer to a problem if we make a point to doggedly search for it and to constantly increase our knowledge. Bad Actor pumps don’t exist. Remove these words from your vocabulary. I wish you all a millionaire’s future and a rewarding professional career with pumps.
Larry Bachus, founder of pump services firm Bachus Company Inc., is a regular contributor to Flow Control magazine. He is a pump consultant, lecturer, and inventor based in Nashville, Tenn. Mr. Bachus is a retired member of ASME and lectures in both English and Spanish. He can be reached at firstname.lastname@example.org.