How a Submersible Motor/Pump Works

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How a Submersible Motor/Pump Works

Postby Pumpmd » Thu Mar 09, 2017 12:45 pm

Kevin,

Franklin pumps have floating stage assemblies so very little down thrust is put on the motor thrust bearing. Each stage has it’s own bearing area for thrust.

We see frequent premature pump failures from the use of various flow restrictors and my suspicion is that they do not open and close properly causing over circulation of water in the pump. I don’t know if fluttering restrictors could be part of the problem causing a hammering of the impellers up and down in the stage assembly. Poor performance and pump shavings and debris after a year to 18 months of use is not uncommon and the problem goes away when the valves are removed from the system. I have no idea how many work properly as we only get the calls for failed systems.

I hope this helps answer your questions.

Thanks,
Bob J
Water Systems Service Engineer


From Pentair: SignaSeal staging system incorporates a harder-than-sand ceramic wear surface and a floating impeller design - which together literally pulverize sand and small debris. This proven feature reduces lock-ups, dry-runs, and abrasive wear.

Floating Stage Design is engineered to transmit forces away from the motor bearing and through the pump housing. This reduces premature wear and misalignment.

Fully-Enclosed Shaft Bearing creates a pressure zone that prevents sand & water from entering. Eliminates wear and misalignment.

Wear Ring forms a seal between impeller hub and suction cap for low friction and no unwanted recirculation of water.
Corrosion resistant 300 grade stainless steel discharge for durability in aggressive water.

From Franklin: Tri-Seal floating stage system. This stage system further improves efficiency and protects against wear when pumping abrasives (sand). Tri-Seal pumps are unconditionally guaranteed against sand locking in abrasive well conditions for one full year.

Hex rubber bearing and ceramic shaft sleeve allows sand and abrasives to pass through, virtually eliminating shaft wear and upper bearing failures.

Improved hydraulic performance for deeper set depths at all horsepower and flow ratings.

Floating stage design allows for maximum efficiency while minimizing the downthrust load that is transferred to the motor. Floating stage design allows impeller to float independently.

Noryl® diffuser and disc with 300 Series stainless steel thrust and eye seal protection for durability and abrasion resistance.

Celcon® impeller provides high performance to increase pressure output while reducing system losses from friction
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Re: How a Submersible Motor/Pump Works

Postby Pumpmd » Thu Mar 09, 2017 1:03 pm

"Floating impeller" or "Floating Stage"

Pumps have impellers that are not secured to the pump shaft. They can slide up and down on the shaft. The bottoms of these impellers actually touch or drag on the diffuser. The marketing gimmick is that the "floating stage" takes all the load off of the motor thrust bearing. While it certainly does this, now each impeller drags on the diffuser below it during down thrust conditions. This produces more heat at low flows and more wear on the impellers. Plastic impellers grinding against plastic diffusers causes more wear than if the impellers did not touch the diffusers. Throw in a little abrasive like sand, and they wear even faster. However, the Celcon or Delrin plastic they use is suppose to be self lubricating. It will last pretty good. But the deeper the pump is set or the more back pressure it has, the harder the impellers drag on the diffusers. Pentair and Franklin are the only two I know of that make a "floating stage" design. The Pentair has been around for a long time, except that it doesn't drop in amps as much as a "floating stack" design. Franklin changed the old Jacuzzi "floating stack" design to the "floating stage" design, and Franklin claims they do not last when used with a Dole valve,CSV, or any kind of restriction under 5gpm. This includes constant pressure systems on homes that use low flow rates.

A "floating stack" design has all the impellers locked to the shaft and the whole "stack" can float up and down a little. The whole "Stack" is held up by the motor thrust bearing and the impellers do not touch the diffuser at all. The Kingsbury type thrust bearing in the motor is made to handle downthrust in lbs. There is a film of water between the thrust shoes and plate, so nothing touches which makes a completely frictionless bearing. (Theory) Letting the thrust load be handled by a Kingsbury frictionless bearing will allow the pump to spin easier. This produces less heat and lower amp draws(drops amps lower than "normal operations" stamped on the motor), especially at low flow rates where downthrust increases.

Some pumps like the Goulds have plastic impellers, but use the "floating stack" design so the impellers do not touch the diffusers. Any pump with Stainless Steel impellers like the Grundfos cannot use the "floating stage" design, as Stainless Steel dragging against Stainless Steel diffusers is not self lubricating and would lock down quickly. However, the Kingsbury thrust bearing does a much better job of holding downthrust than plastic impellers grinding against plastic diffusers. (Theory) There is also more tolerance between the impellers and diffusers with the "floating stack" design, which allows more room for debris to pass through without causing damage.


When water is just used for a house, the difference in amp draw between these two designs at low flow rates will not make much difference in the electric bill. But with a heat pump or irrigation system the lower amps from the "floating stack" design can make a big difference.
Last edited by Pumpmd on Thu Mar 09, 2017 4:22 pm, edited 1 time in total.
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Re: How a Submersible Motor/Pump Works

Postby Pumpmd » Thu Mar 09, 2017 2:16 pm

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