Old Schaefer pump and Franklin Electric motor review

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Hatsuwr

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Alright, last long post from me for now.

Franklin Electric told me that this pump and motor are not repairable, which is kind of odd since they sell repair parts and it's all a fairly basic design. There are some minor differences between this pump and motor from 2007 and their current versions, but for the most part they are exactly the same. I would've expected a bit more improvement over 15+ years, but it seems to be a good design, and it's nice to have repair parts still available.

A parts catalog from 2018 is archived below. Without more information, I'm assuming it applies to my components. They all line up from what I have observed: https://web.archive.org/web/2018061...0940/m2172_pump_replacement_parts_catalog.pdf

Pump

The pump is a Schaefer Legend Tri-Seal series, model 7LD05S4-2W230, order 93720710. It's 7 stage and rated for 7 GPM.

Not a whole lot to say here, since I wasn't able to get it apart without risking damage. It seems probable that it unscrews by rotating the bottom clockwise but it didn't come loose with an amount of torque that I was comfortable with while planning on reusing it. All I would expect to do anyway is remove any debris or buildup that hopefully shouldn't be present, so I'll leave it alone for now.

Here's the parts diagram and list:


pump_parts_diagram.png

pump_parts_list.png


And here's the performance information. My water level is around 130', so it looks like I can expect around 9 GPM at 0 PSI and 4 GPM at 60 PSI, minus frictional losses. Ouch.

performance_curve.png


Motor

The motor is a Franklin Electric Super Stainless series, model 2445059004, rated for 0.5 HP at 230 V.

Here's the parts diagram and list:

motor_parts_Page_2.jpg


The design uses upper and lower radial bearings and a thrust bearing on the bottom. All appear to be graphite. Only two things stand out to me regarding its construction and potential repair.

First, all of the listed replacement components between the old and new parts catalogs are identical except for the thrust bearing assembly. The newer one looks like it went from two to three pads, and what seems like a more integrated design. As far as I can tell, the thrust bearing rating has been and remains at 300 lb, but newer versions of the motor consume more power in their operation. If I had to guess, I'd say that this design offers better thrust bearing at the expense of increased frictional losses.

I contacted Franklin Electric to try and get one of their newer bottom end bell kits that contains the thrust bearing (part #305974922), but they would only refer me to distributors, none of which were able to get the part.

thrust_bearing_differences.png


Second is the fill fluid. Information here isn't exactly clear, but as far as I can tell, the smaller motors like this come with a fill fluid of 10% propylene glycol in water, while the larger ones are 50% PG. A document relating to more serviceable motors, but with the same HP rating as mine, gives hints that they might be refilled with something closer to the range of 20-30% PG. If this is an intended difference, it could be meant to increase the viscosity of the fluid after the motor has undergone some wear and clearances have expanded.

There are claims that a mechanism exists to allow filtered water to enter the motor from outside to make up for fluid losses. I couldn't find any mechanism for filtering, other than what would be accomplished simply by having to pass through the seals around the shaft. I assume they are just describing equalization of a pressure differential caused by submerging the pump, not anything more active. There is a diaphragm on the bottom that should probably keep it sealed during the temperature changes during normal operation, so I don't expect full fluid changeovers during normal operation, and my motor seems to confirm that.

The fluid in my motor was contaminated with wear particles though. I assume it was mostly graphite. I had some thoughts that suspended graphite particles could help decrease future wear, but I couldn't really get any useful information from Franklin Electric about this (or any related questions for that matter.) I decided to just replace it, and I will be going with a 20% concentration of PG.

But then there's the question of additives. As far as I understand it, there should be very little wear on the bearings outside of the startup of the motor.

When running, a film of fluid should be protecting the bearing surfaces. As long as the viscosity of the fluid is high enough, there should be little to improve in this regard. Adding PG will increase viscosity, but at the cost of increased frictional losses, heat generation, and heat transfer. I really don't have anything concrete to go off of unfortunately, so my 20% is just based on what I could find of the manufacturer's practices.

Startup friction is a bit different though, and here I can actually do some testing. In my testing, water showed a fairly small reduction in static friction between two objects, and propylene glycol did little to improve the situation. An additive for this purpose needs to have a few traits: soluble in water, long term stability at the normal operating temperature of the motor, minimal increase in viscosity, non-corrosive to the motor's internal components, and non-toxic. I believe polyethylene glycol fits fairly well for this purpose. Static friction was reduced by around 70% when I added ~20% PEG 3350 to a 20% PG/water mixture under a load of around 10 PSI. Something with a higher thermal conductivity would be nice, but I don't know what would be a better fit.

With all of that considered, I think an addition of 10% PEG would be an overall improvement. I wish I had the ability to better test viscosity, static/dynamic friction, and thermal conductivity to a greater degree, but I can't just now.
 

Valveman

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Yeah nobody repairs pumps anymore, they just replace them. The Pentek and Centripeo motors seem to be welded, and I can't get them apart without just cutting them open. I am glad they went back to three pads as the two pads was sketchy. Once any of the graphite has worn off the stick up height of the shaft is not high enough and the pump impellers will drag. Plain water is the best lubricant. The only reason they add antifreeze is for storage and shipping temperatures. Once the motor is in the well the fluid inside will get replaced with regular well water anyway.

If the bottom end bell of the pump is threaded, it will come off. Many are being crimped on these days and are not able to come apart. If threaded, put your pipe vice on the far end of the pump to unscrew the bottom end bell. Having the pipe vice too close to the threaded end will squeeze the threads and you won't be able to unscrew it. From looking at the eye of the first impeller in one of your pictures, I don't think there is anything wrong with the pump end and would test it instead of taking it apart. If the deadhead pressure is anywhere close to spec (129 PSI), it will be fine. But graphite in the motor is not a good thing and I would replace it.
 

Fitter30

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Can u repair a submersible pump maybe if the parts are available but should u. What is cost of pulling a pump, being down for a few days waiting for parts and hopefully having them all correct then not knowing if the pump repair is 100% sealed. It's one thing to repair a pump that u can walk up to another where it has to be pulled. With the cost of labor and down time think it would be a disservice to the customer.
 

Hatsuwr

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Too bad about the lack of repairs. I wonder what the most common mode of failure for these is. Considering the location, most failures probably won't be noticed until pumping has pretty much completely stopped. A lot of the failures I saw when researching had to do with the coils overheating, necessitating a stator replacement at minimum. I would think that most economical repairs (usually bearings) wouldn't have their need noticed until more damage had been done.

If I'm understanding this design correctly, when the motor is mounted to the pump, it lifts the pump impellers slightly, so that any thrust from them is transferred to the motor's thrust bearings. When those bearings wear enough, the motor no longer takes the thrust and that job falls to the pump itself, which is less capable in that regard and experiences quick wear.

I imagine quite a bit of early warning could be derived from a simple vibration monitor and ammeter.

Regarding propylene glycol, the AIM manual references it in regard to lubrication. It also has information regarding replacing the fill fluid with deionized water only, and as a result requiring a derating factor applied to the motor. This document also makes the claim that the PG aids in lubrication: https://www.scribd.com/document/525808359/franklin-motor-with-propylene-glycol
If they do actually have a different concentration for their different motor sizes, I can't think of a reason for this other than wanting the higher viscosity for larger motors.
 

Reach4

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Too bad about the lack of repairs. I wonder what the most common mode of failure for these is. Considering the location, most failures probably won't be noticed until pumping has pretty much completely stopped. A lot of the failures I saw when researching had to do with the coils overheating,
Motor cooling is the main advantage of a flow inducer sleeve.
 

Hatsuwr

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Yea I wouldn't run without one with a large pump-casing diameter difference, or with a top feeding well. Even if the motor doesn't directly overheat, the larger temperature fluctuations will increase wear.
 
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