Poor pump reliability

[NurseryPump]

Hi. We are having issues with low reliability on a vertical turbine pump used for irrigating nursery stock. We had a failure the other day requiring is removal. It moves 700gpm at 640TDH with 290ft of column and an open lineshaft.

Upon removal it was found that the bearings in the pump had failed and wiped out two bearings above it in the column. This well has previously had issues with lineshaft breakage due to failure of cutlass rubber bearing failures due to lack of sufficient prelube. After that failure vesconite lineshaft bearings were installed to provide greater dry running durability. The pump failed after that in a similar way to this time taking out the pump bearings and bearings above it. The discharge head was leveled and the number of bearings doubled by going from 10ft column sections to 5ft to increase rigidity.

At this point we believe our root problem is the amount of sand and iron being pumped is causing premature failure of the bearings in the pump. Is there a way to improve pump reliability in these conditions short of having a new well drilled? We have gone from needing an annual overhaul to making it slightly over two years.

Thanks

 

[JS_]

Larger line shafting would of fixed rigidity of 10ft joints, but not the lube requirements.......

Grease packed pump bearings and oil column for the line shafting.....

 

[Artisi]

Cutless rubber bearings should haver been sufficient, sounds more like lack of pre-lube was the problem for the line shaft bearings. What material are the turbine bearings?
Are the replacement line shaft bearings fluted or solid? - if solid the sand could now be the problem.


It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[NurseryPump]

Pump bearings have been bronze each time. The vesconite bearings on the spiders have straight flutes vertically down not spiraled like cutless rubber.

 

[Artisi]

A few pictures mighy help.
Have you looked at cutless rubber for the turbine bearings?
How much sand is entering the well, have you considered lifting the pump a few feet?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[ashtree]

Sand in the well is often a sign of over pumping or poor well design. Do you absolutely have to pump that fast.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[JJPellin]

Artisi is right. Cutless rubber is the best material option for well water with sand. You probably need to get a well company in to bail the sand out of the well. You should run pre-lube water down the column to lubricate the bushings prior to start-up if the pump has been down for more than 24 hours.

Johnny Pellin

 

[Valvecrazy]

As has been said the Cutless rubber bearings are best for sand. You will need rubber bearings in the pump as well instead of brass. Pre-lube is important. I prefer a foot valve on the turbine pump, as that keeps the bearings submerged and lets the pump start with some load. Always best to solve the original problem if possible first, which would be the sand. Bailing might help, but there are other ways to develop a well like blowing with air that might be better. A high speed bailer is best if you have steel casing. High speed bailing causes enough suction to collapse PVC casing, which is why it works so well to get the sand out. Over pumping the well can also make sand.

 

[NurseryPump]

Pre lube is being used from 500gal tank prior to starting. Bearing failures are occurring below static level.

Top two picture shows an intact bearing. Bottom two are just above the turbine and have been worn completely away.

 

[Valvecrazy]

If only bearings below the static level are failing, then your pre-lube is fine and most likely failure is due to sand. Brass bearings will not hold up in sand. Use rubber bearings all the way through. I have used a high speed bailer on wells like this, and a 200' deep well can make 65 yards of sand which is replaced with 65 yards of gravel pack. Spent more developing the well than drilling it, but have perfectly clean water and no pump failures in 30 years.

 

[TenPenny]

You might need to consider an enclosed lineshaft version, where the shaft and bearings are contained in a tube with separate lubricating (water or oil); in most cases it's water, but obviously you want water without the sand, so this may not be practical.

Or, you might have to consider a submersible, you'd still have bearing issues in the bowl assembly, but that would eliminate all the lineshaft bearings. Depending on the well size, if it's a 12" well, a 200 hp submersible would fit I would think.

These are just off my head without knowing any specifics or thinking too hard about it.

 

[EdStainless]

What is the fluid level drop when pumping? Are you over drawing the well? Is it gravel packed?
Are you getting more sand that you used to? What has changed?
I'll also suggest the use of rubber bearings all of the way down.
How near the BEP are you running?
There are some inlet separation schemes out there. You might look into that.

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P.E. Metallurgy, consulting work welcomed