Water Lubricated vertical turbine pump 2

[Cromaney]

Is it necessary for water lubricated vertical turbine pump line shaft bearings be immersed in water prior to starting the pump? I have a vertical turbine pump that is water lubricated and has experienced a failure in the “foot” check valve such that the pump column pipe drains down to the static water level after the pump is turned off. This exposes the line shaft bearings in the top 80 feet of the pump column to air. Prior to starting the pump the line shaft bearings are not lubricated for 5 to 10 seconds as the pump column fills with water. This pump could operate 3 to 4 times an hour during summertime water demands. Any input or experience on this subject would be greatly appreciated.

 

[Valvecrazy]

Yes 5 or 10 seconds of dry running will hurt the bearings. They make prelube systems that will dump a little water down the column pipe a few seconds before the pump starts. With out the foot valve you are now having to get rid of lots of air, and I’ll bet you have some real water hammer when the water finally hits the check valve at the top of the well. I am assuming you have a pressurized system since it comes on 3 or 4 times per hour. Which BTW that is about 100 times per day which is not good for anything, especially dry bearings.

As a matter of fact your foot valve probably failed from slamming 100 times per day. I have fixed lots of these with a constant pressure valve or CPV. This valve controls the flow from the pump and makes it start and stop at 5 GPM. This keeps the foot valve from slamming closed or flying open. Gentle closings and openings of the foot valve will make it last much longer.

Once the pump is started the CPV would vary the flow from the pump to exactly match the usage. This will keep the pressure steady about 10 PSI lower than the pressure switch off setting. The pump will run continuously instead of cycling on and off 100 times per day. This really saves a foot valve, as well as the motor, starter, pressure switch, and other things. Restricting the flow from the pump will lower the amperage, and it may not use any more energy than it does by cycling 100 times per day. If you use a lot of low flow, a smaller or jockey pump in the system would also help.

Either way, you are going to need to fix that foot valve.

 

[Artisi]

What size unit is it - how long does it stand between start ups - maybe there is no need for a foot valve - just incorporate a pre-lube system.

Valvecrazy - not CPV again - what did we ever do before you came along - I have sold and installed 100's of vertical inline turbine pumps from 4inch column to 24inch - column the longest being 500ft with pre-lube. Not one of them had a CPV valve - many have been in service for 20 years and more with just with normal maintenance.

 

[thewellguy]

The rule of thunb is that you do not need a prelude line if the static water level is 80' or less. HOwever, starting it 3-4 times per hour is outside the norm for the motors (you did't mention hp) of 4 per hour or 20 per day. Once the pump is on how long does it run for? How much water does it produce? Also 5-10 seconds seems long to get water to the surface, but without more info I don't know.

 

[Valvecrazy]

Artisi, I have also done hundreds of vertical turbines just the way you describe. Since I stared using the CPV over ten years ago, many of the old problems such as foot valves wearing out, water hammer, pump cycling, and many other problems, have gone away. I have used pre lube systems, soft starters, VFD's, standard pump control valves, and many other ways to control these pumps. The CPV is working better than anything I have tried.

I have been reading these post for years about the problems everyone is having with different type systems. I finally decided to log on and put in my two cents. I only deal with systems that pump cool water at a constant head or pressure. If this forum is all about the exchange of new and beneficial ideas, I have a few new ideas that really work. Some of them will seem unusual to many people but, they are well proven and nearly all involve using a CPV. I have found it really simplifies pump controls and makes systems very dependable. Hence the name Valvecrazy.

 

[Cromaney]

After discussing the water lubricating issue with a couple of pump manufacturer's they all agree that we need to either pre-lube the bearings with water prior to pumping and/or get the foot valve repaired. I found Valvecrazy's comments valuable and I agree that it would be useful to put some kind of volume control valve on the pump to regulate water discharge (i.e. a ClaVal) at the time of start-up and operation. Currently, the discharge piping has a air/vac valve and non-slam check valve so there is no significant water hammer during strat-up (w/o the foot valve). However, the concern is that there is something wrong w/ the foot valve that could cuase it to fail and send metal up through the impellers. My experience with foot valves are that at some point they will fail and start leaking. This one has been in the ground for about 15 years which is probably pretty good for this type of device.

 

[Slickstir]

You might take a look at Thordon bearings for the lineshaft. I've seen them be successful in dry start applications before. Some pump manufactures might shy away if they don't have experience with them though. However, you should be able to retrofit you pumps very easily.

http://www.thordonbearings.com/products/polymer.html

 

[Valvecrazy]

Those bearing look like they would help. Don't understand why the pump manufacturer would shy away. Must be something I can't see. If your going to pull the pump anyway, fix the foot valve. Then eliminate the cycling and the problem will go away.

A Cla-Val works much differently than the CPV. With the fully closing function of a Cla-Val, you can still have water hammer and the possibility of dead heading the pump. Not so with the CPV.