Returning to school this fall, my English Composition teacher asked all of us in the class to write a journal-form essay based on our summer experiences.
Late May 2023
On my first job near a quaint little town by the river, my new boss was excavating for the foundation of a new library. I was placed on the sidewalk above the dig site and tasked with lifting rainwater out of the lower level, a vertical distance of over 40 feet. Of course, I failed miserably because the operators didn’t realize that, even under ideal conditions, a self-primer can’t lift water that high, regardless of their size and age.
Because pumps don’t speak English, and most people don’t speak “pumpese,” I couldn’t tell them the reasons why the application wouldn’t work. I kept trying to telepathically suggest they read the instruction and operating manual, but the impeller brain waves weren’t getting through the hard hats.
Finally, they called a local pump technician for assistance and they pointed out to the operator that, even in a perfect world, the maximum obtainable lift would be 34 feet. That perfect lift would be at an elevation near sea level, and the water would be near 33 F (1 C) to reduce the vapor pressure. Since the jobsite was nowhere near that perfect world, my maximum lift limitations were closer to 24 feet.
The pump technician explained about net positive suction head and the eternal pump enemies of friction and vapor pressure. The operator repositioned me at a lower level and I happily pumped rainwater for the next few days. I must say, I don’t really care for all the mud, debris, frogs and trash coming through my impeller eye, but knowing it was fully expected of me, I did my job.
June 2, 2023
The contractor moved me to another site with a new operator. This time it was a simple dewatering mission on an underground utilities job near an avant-garde bar over by the mall. They have the best hot wings in town. Well, you might have guessed what happened because I failed miserably … again.
The operator knew I was a self-primer but didn’t realize I needed to be primed the first time. There was no water in my priming chamber, so I couldn’t get the prime started. I kept thinking they would realize that I am a pump and not a compressor, but again my telepathic powers were lacking. Luckily, one of the crane operators noticed, and after some time, they were able to come over and explain that I needed to be primed. It took a while to find a bucket, funnel, wrench and some clean water, but we finally got me primed, and I was pleased to pump to my impellers content all the rest of that day.
Later that night, some people tried to steal me from the jobsite, but luckily my trailer pintle hitch was locked with an anti-theft device.
Late June & Early July 2023
The next six jobs went very well. There was one time the fuel ran out on my engine through no fault of mine.
They got me refueled and restarted before the water level got too high. Luckily, one of the members on the crew was a farmer with diesel engine (tractor) experience, so they knew all the tricks on how to vent the injectors.
July 14, 2023
I won’t forget this date for a long time. It was a Friday, and I was looking forward to having the weekend off. Plus, there was no rain in the forecast. The regular operator was off for the day, so I was assigned a new one. The supervisor wanted some water removed over where they were running the new 138 kilovolt (kv) oil-filled underground electric supply. The operator did most everything right, except they didn’t realize they needed to be concerned about proper submergence. For the uninitiated, submergence is the vertical level of liquid from the suction line up to the surface.
I require a certain amount of submergence based on my flow rate, or the angular velocity of the liquid entering the suction will create a vortex all the way to the surface, and I am, excuse the pun, stuck sucking air. I hate pumping dual-phase fluids. While compared to other centrifugal pumps, I can handle fairly large percentages of air entrainment, but it is not my favorite thing to do. I don’t like making the slurping noise any more than the operators like hearing it.
The backhoe operator realized what was happening and dug a parallel and deeper sump adjacent to the trench. The extra vertical distance of just a few feet, combined with cutting back on my throttle (speed) a little bit, was all that was needed to mitigate the submergence issue.
The good news is I got the rest of the weekend off, but on a sour note, a family of chipmunks moved into the engine compartment and started chewing on the control system wires.
July 25, 2023
I got moved to another site on the other side of town for more trench dewatering work. This time the job was for a high-speed fiber optic cable. I was hoping for better internet speeds on my side of town (I love to stream the Pump Channel), but it seems like it’s always someone else getting the higher speeds. The good news is the operator chased the chipmunks out of the engine compartment. That day and the remainder of the week all went well.
Mondays are typically not good days on construction sites for some reason, and this day was no exception. I had been moved around quite a lot the previous week and my suction hose connections were getting loose. When I couldn’t prime after five minutes of operation that morning, the operator did the correct thing and turned the engine off.
Then, the operator called the pump technician for advice. They said the symptoms sounded like there was a leak in the suction line. The operator argued they could not see any leaks. The technician replied that, on a suction lift, the leak would not be an egress leak, like water leaking out, but an ingress leak, like air leaking in.
This is because the suction line is at a lower pressure than ambient. They suggested the operator wrap some plastic and duct tape around the flange joints and see if that corrected the issue. The operator used a contractor trash bag for the plastic, and sure enough, the first flange they taped up was the one with the air leak. I was able to prime right away. The bad news is the operator didn’t realize the bag and tape trick is supposed to be temporary. I sit here today with the bag still taped over the line like a bad tattoo.
September 2023
I had a great summer, and while I worked hard, it was also a good teaching/learning experience. As fall and winter approach, I just hope the contractor remembers to drain the water out of my priming chamber before it freezes and cracks the casing. I hear that’s how Uncle Harry passed away.
Summary
George may be a hypothetical and personified pump, but the problems and issues encountered are real. Pumps don’t speak English or any other common languages spoken on this planet. It is incumbent on the responsible operator/owner to learn the language of pumps. It really just boils down to some basic science that is not hard to learn.
Do you want or need more explanation of what was creating these issues? Please refer to these previous Jim Elsey columns for details.
References
10 Common Issues With Self-Primer Pumps (September 2015)
Submergence (April 2016)
Air Entrainment (December 2017)
Vapor Pressure (April 2018)
NPSH Part 2 (Lift Condition) (August 2018)
Rethinking the NPSHA Matrix (October 2021)
Priming Time (two parts; September and October 2022)