Replacing a Well Pump with Many Unknowns 2

[Leisuretime]

Hello all,

I've been tasked with specifying and planning the installation of a new well water pump, and would like to garnish some opinions from those who have much more experience than I. We had no design data on the original pump and limited information on the piping network. The piping network is simple (only 2 users), but there are several unknowns about the pump and well that give me pause before moving forward. The well pump in question is pictured in the attachment.

Background Info:
The well pump's primary function is to feed a small elevated atmospheric storage tank (15' above grade) during plant operation, which in turn is the suction for 3 pumps. The well pump's secondary function is to feed a fire hose used mainly for washing down surrounding areas when the plant is not in operation (3 pumps from primary function are not utilized during this time). The motor on the well pump is 15HP. I had reasonable access to the entire piping network and was able to identify a demand range (40-100gpm) based on plant data from the 3 downstream pumps.

This is where things get gray. The well itself is old enough to not be listed on the state geologic survey (prior to 1985, this was not required by the state where the plant resides). I assumed the well LLL based on state hydrologic data for the area (25'), added 4' (to account for NPSHr for the new pump), and generated a system curve to use in specifying a new pump.

Questions:
I opted for a VTP as the replacement pump. I think the original pump is a VTP, but am uncertain (came to that conclusion based on the discharge arrangement of the existing pump, and in reading that this is a common application for a VTP). Do you guys have any thoughts on what type of pump the existing one is based on the picture?

I also do not know what the pump-to-well interface looks like. I've seen various well pump mounting flanges or bracket connections across the internet, and am hesitant to assume a standard connection based on the age of the well. The last thing I want to do is procure a replacement pump that doesn't interface properly with the well. I don't think I can avoid breaking up the buildup around the pump until I can see the well-to-pump interface. Does anyone have any suggestions on how to best break up the buildup shown in the photo, without risking damage to the existing pump? Or perhaps an alternative suggestion?

To go along with an unknown well opening diameter or details on the well head, I also do not know the depth of the existing well. I'd like to think my assumptions for LLL and pump NPSHr would keep me out of trouble (hoping the original designer made similar assumptions before digging the well), but a little more certainty that the replacement pump won't bottom out in the well would be nice. Right now I'm hoping there is an access port on the well head that I can use for verify depth with a long rigid object. Would this be feasible, and if there is not an access port, what would you recommend? Do well heads typically provide a means for measuring total well depth, as opposed to just water level?

Thanks in advance for your time and thoughts

 

[bimr]

You might consider contracting with a well driller to install a brand new well with a submersible pump.

From the picture that you provided, it does not appear that this system was properly maintained. You may be better off with a new well.

 

[Leisuretime]

Preaching to the choir on the maintenance aspect.

As much as I'd love to go with a new well and pump, I doubt that's in the cards unless I can prove to them that the existing one cannot be used or refurbished to point where it could be used.

Do you have specific concerns regarding the condition that makes you want to replace it entirely instead of at least investigating its reuse?

 

[LittleInch]

Looks like a hiding to nothing trying to replace this pump, but understand the resistance to doing what is correct and thinking they're going for cheap.

first off, get everything removed from the area and brush / power jet / scrape off as much of the gunge as you can.

Although it would likely be buried under that brown crud, any sight of a pump data plate would be very useful.

The pump well connection will probably be some sort of flange foot, but size and connection would all be specific to the pump. Do you know what the well bore actually is?

The pump has a look of a vertical pump alright. The end connection could easily be a bearing flush for the lower bearings, but not easy to say for definite.

Why is it being replaced?

I do agree with bimr though - I think you'll burn lots more time and cost trying to get this old thing out with all sorts of risks and issues about unknown information when you could just get another one.

This is a bit like turning up with a 20 year old car covered in oil and gunge and then saying - can I fit a new engine and gearbox, but ??I don't know engine size, model year or mountings. In theory, yes, but practice....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DubMac]

Definitely a VTP. Column pipe on the pump is usually the same diameter as the discharge pipe, 4" in your case. The column pipe is most likely threaded at that small diameter as opposed to flanged, and could possibly be 6" since that is many times the minimum size offered. The pump bowls will be the same nominal size as the column (4" or 6").

Unless you do find a nice big inspection hatch, it will be tough to determine the depth of the setting with any confidence with your pump installed. Not sure why this is so critical at this point. You will eventually need to accurately measure the well depth and water level once the pump is out. Column/lineshaft assemblies are priced in 5' long sections and adding a few sections won't have much impact on overall unit cost.

I would suggest using the "green and red axe" (cutting torch) to get the existing installation apart; doesn't look like those bolts are going to spin very easily with a wrench.

Once you do get the motor off and the discharge head loose, the entire pump should pull out easily. I'm guessing the motor is a hollowshaft version with the pump's lineshaft sticking up through the motor and hanging from a nut. Hopefully you can reuse the motor.

If you are going to select a new VTP pump, here are some of the considerations with configuration:

- discharge head: cast iron designed for hollowshaft motor ( most likely that is what you have existing). There is absolutely no reason to go with anything other than packing to seal lineshaft. Mechanical seals on a small water service pump like this are a complete waste of money and a maintenance headache. Unless your facility has ultra-strict requirements, go with packing.

- column assembly: Personally I would go with flanged column if offered at that small a diameter; makes disassembly easier, although threaded will be cheaper. Open lineshaft with rubber lineshaft bearings every 5'. Make sure lineshaft is sized properly for HP rating.

- bowl assembly: Cast iron bowls with bronze impellers and rubber bowl bearings. Really doubt there is a need for bowl wear rings but get them if offered at a reasonable adder. Under the bottom bowl you will need to decide some sort of screen or wire basket. The manufacturer will have those options.

Actually a good manufacturer or distributor will go through all of these considerations with you. There are a ton of very good VTP water pump manufacturers out there. You might look at National, Simflo, Aurora, Peerless (Grundfos now), etc.

 

[someguy79]

It's hard to tell what kind of pump that is specifically. It surely is a vertical unit, probably has a lineshaft of significant length, and I can't tell if it's centrifugal, mixed flow, axial (doubtful), turbine, or how many stages it might have.

Your picture shows a 4" discharge, but it looks like most/all of the flow ends up going through the hose. The size mismatch makes me wonder if this pump was originally set up to run several times the flow you've been getting from it.

As you may have figured, you aren't going to find out much more about this pump unless you;
- find some more info on the installation,
- clean up the existing installation and find identifiying marks/ID plate, etc., or
- take the thing apart.

What amount of down time is allowable for repair/replacement? With that much corrosion and sediment around the pump I would not be surprised if the mounting underneath is no good anymore. Plan a generous outage time to fix not just the pump, but the base too.

I agree with DubMac on the material choices, unless you have a lot of suspended solids or grit. If so, you might want some harder materials and wear rings.

It looks like you have a solid range of flows, and a strategy for getting well depth. With that you should be able to figure out a rated flow and TDH for a new unit.

 

[bimr]

It is difficult to guess the depth of the well and the water quality with the information provided.

Wells do not last forever. Periodic maintenance is generally required. Sometimes the wells have to be redeveloped. As part of this project, you should confirm that the well is producing water as it was designed to do.

Trying to fix the old well pump will be a nightmare. You will have to find some old timer who knows the particulars of the well pump. The well pump may no longer be a current model.

I would expect that there are more pump options and less expense associated with the use of a submersible pump.

Before designing this well pump project, I would review the application with a well driller that is familiar with the locale where the well is located.

With a new well and submersible pump, the project scope will be more defined and have less potential project risk. Risk equates to the potential for delays and expenses.

 

[Artisi]

So what is the question - far too many if's, but's or maybes and no actual data to make any recommendations?
The best solution is to remove the pump - if that is actually possible and take it straight to the scrap dealer.
Install a test pump and pump the well to establish flow, once this is established and the flow meets requirements, buy a new pump for installation. If the flow isn't suitable drill another well.



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.)

 

[Leisuretime]

Thanks for the information everyone.

To answer a few questions about the previous pump sizing - came to find out the fire hose is listed in our emergency action plan as an occupant hose, and NFPA requirements for such is the limiting factor in the design. Otherwise the current pump would have been ~10HP too big. The 2" hose in the background of the picture does carry all the flow, but it was likely just scabbed together by a shoddy maintenance crew in years prior.

We are planning a replacement only because losing this well pump would shut down our facility until we managed another water supply or got a trailer in. This is about being prepared to replace it when the time comes. The original idea was to have the replacement pump in hand and install it once the old one crapped out.

As far as downtime, it comes at a premium around here. I'd be shocked if they allotted me more than a weekend to do everything, unless I have a strong case for needing more (much more likely now). I've reached out to a few registered water well drillers in the area to get their thoughts and some pricing on a new well. It would certainly help to replace some piping too and get velocities back in check.

You guys have given me enough ammo to stand by a recommendation. Thanks again

 

[cvg]

at the very least you will need to pull the old pump before you can proceed. After pulling the contractor can run a camera down the well (probably after a lot of swabbing and flushing) and get a look at what you are dealing with. trying to engineer this thing without a good inspection and perhaps cleaning or test pumping before hand is a complete waste of time.