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Foundations for Pumps

07/02/2013 8:22 AM

I'm just looking for opinions on a matter. Please read it out……..

The company where I am working, we are doing an expansion in two phases. And what I am in charge of is the cooling water.

Phase 1: we are increasing our cooling water to 6000 GPM on (2) 200 HP pumps and with Phase 2: adding a third pump. Bringing it to 9000 GPM. The weight of these pumps is 4000 lbs each are on a 26" x 98" steel base.

I am installing these pumps under our cooling tower outside, (will be putting a temporary steel building over the pumps)

Where the pumps are going, it's is on asphalt, so I was putting out RFQ to have the asphalt removed and put a concrete pad under these pumps.

I briefed out plant engineer about this, he asked why I'm doing this, since this is only temporary and just put them on the asphalt secure it with stell post driven into the ground so it would not walk and concrete around them. My reply was,

  • Asphalt is soft and I want a stable foundation
  • And since our down time for this phase is only (2) days to integrate it, we will require at the minimum one week to do anything on phase 2 with the pumps for a shut-down. Otherwise it would be at the very least 1 week down time, (2 weeks minimum to put the pad in reality for phase two). And by putting in a solid foundations we can just work around the pads as we put the building up around the cooling towers. And concrete around the pads of the pumps and we can keep the process running.

Now our plant engineer is very familiar with this, has been working there for 20 years and is in my opinion very competent. So I thought with his workload, I'll give him a chance to think about it, then ask again only earlier in the day.

When I asked, again, the answer is to set the pumps on the asphalt, putting in and concrete around them.

Well, now's the time to make a decision, I have RFQ's out for the pad, and the owner of the company will be will be wanted the justification on this, and since I'm going against our plant engineer. I'm just pulling information together for this and thought I'd also get some opinion here also.

If you have anything to add, I would appreciate it.

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#1

Re: Foundations for Pumps

07/02/2013 10:14 AM

If I were you I'd make a strong argument for the temporary concrete pad, as the existing asphalt will not hold up to the load + any vibration imparted from the pumps should that happen due to an unbalance condition.

You don't tell us where you're located, but if your area experiences fairly high daytime temps the asphalt will become very soft.

Ask him if he wants broken pipes and a failed coolant system anytime during the two weeks?

Besides, if the new temporary pad is 26"x98"x8" that amounts to 0.45 Cubic Yard of concrete...the cost, even with rebar or welded wire mesh + demolition + new construction + labor + equipment costs is minimal and IS cheap insurance against failures.

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#3
In reply to #1

Re: Foundations for Pumps

07/02/2013 10:46 AM

Thanks Capt, I was hoping you respond

We're located in Wisconsin,

If I were you I'd make a strong argument for the temporary concrete pad,

Well its the down time that cost us. the cost of putting in a solid concrete permanent is nominal.

Because on a crack pipe from settling, will shut the whole plant down.

The cost of the pad is nothing compared to the over all project......and frankly I am surprised at the resistance.

(If I had the chance for a do over, I Never would have brought it up at the status meeting and just did it.)

The pad itself I have RFQ's out for all three pumps 12' x 14'.

But what I was looking for, and what the owner likes is factual numbers. Not so much as down time costs, he knows that, but more so the material properties of asphalt. But my justification is that the risk is too high that would force down time.

An example. the weight of just one pump.

Pump Base
length( 98")8.17ft
width (26")2.17ft
sq/ft17.69sq/ft
lbs/sq ft226.06Force on the Asphalt.

And I am looking for the properties of asphalt if there are any, just to reinforce my position. To also satisfy the plant engineer. I do have to work with him, and he is who I answer to.

and Frankly, I am surprised of the difficulty. We are the worlds largest manufacturer of this food ingredient. and even at this time, this plant goes down 2 times (2 days) a year for inspection and maintenance. And that has to be planned well in advance. operating 24/7.

Things like this, I would do it, and asking for forgiveness later. but for this, its going to require some schedule changes..... so, now my option are narrowed.

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#2

Re: Foundations for Pumps

07/02/2013 10:25 AM

My 2 cents for practicality (& Capt Moosie↑is the civil Engineer, NOT me):

  1. Anything temporary is going to be more permanent than you think,
  2. Sounds like you trust your guy, & he's seen the drawings & knows the site,
  3. I'd just form up a slab on top of the pressure washed asphalt if it was sound so I didn't have to redo all the nicely compacted base AND the drainage was good. Pin the mesh through the asphalt with bar or pipe as suggested to key it to the ground, & now you have a quick, flat & level (Hopefully!) base. Just run a bead of urethane around the asphalt/ concrete join to prevent water infiltration between the layers.
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#5
In reply to #2

Re: Foundations for Pumps

07/02/2013 11:04 AM

Anything temporary is going to be more permanent than you think,

That's what I have experience also, but here where I work, built and DEMO is pretty common. Expansions is pretty ongoing.

Sounds like you trust your guy, & he's seen the drawings & knows the site,

That is just it, at times I rely on his expertise, but there were times where he was wrong and I was right. We both want it right. Also that's why I'll ask twice, in case the first time he was having a rough day. And I would do this for everyone, if I feel they did not give it full consideration.

I'd just form up a slab on top of the pressure washed asphalt if it was sound so I didn't have to redo all the nicely compacted base AND the drainage was good. Pin the mesh through the asphalt with bar or pipe as suggested to key it to the ground, & now you have a quick, ...... flat & level (Hopefully!) base.

That's how its currently planned........ and funny you mentioned hope......Hope is what I feel uncomfortable about....... the closest I done for hope at work is an educated guess.

That's why I like to get some physical properties of asphalt together and so I have something to hang my hat on. I do have a RFQ out to demo the asphalt and put in a cement foundation

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#9
In reply to #5

Re: Foundations for Pumps

07/02/2013 11:38 AM

What I actually meant was "hope" that the concrete guy did a good job & gave you a good platform for mounting the pumps. Just keep in mind that asphalt is a flexible, or at best semi-rigid membrane. At the PSF loading described- I've put lumber kilns on a slab over Styrofoam that well exceed that, and seen very nice roads done with concrete pour over asphalt base layer. So I take it your real question is should we not just make sure everything is good from the base up?

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#11
In reply to #9

Re: Foundations for Pumps

07/02/2013 12:00 PM

No, I'm having a RFQ for doing the slab, as soon as I get that. Then I have some solid numbers.

Still would like to know the material properties of asphalt..... I'm sure there are different grades, but just a base to would with to show the ductilbility of it.

If I did not have to do the logistic of other contractors, I would just do it. and then ask for forgiveness later...........but since, it would be hard to run under the radar, I can't.

What happens, is that if your caught after its done...... too bad, numbers are in and we saved money...or whatever..... and I'm sorry.......... when it works out positive, its quickly forgotten about.

But if its caught in the process of demo...... everything can come to a halt.

I did things on another item, that it was found out just prior to it being finished, and it literally kept hitting the fan, for 3-4 weeks afterwards. And only when positive results started to show, that it quieted down. But, if it would have been caught even a week sooner..... everything would shut down and we still be spinning in the mud, with should "done this or that" instead. Too many cooks.

Being a project manager, I give our shareholder's update status. not going into too much detail. I did it to this task, which I felt would not be a problem. Costs should be under $20,000.00 and that not even a fraction of 1% of the total project.

what's that about the 80/20 rule? .....

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#14
In reply to #11

Re: Foundations for Pumps

07/02/2013 12:22 PM

I've told you how I would do it. But I also sometimes do work for a small company called Imperial Oil, also known as Exxon or Esso. Their philosophy is- we can't afford not to do it right the first time. And your situation is starting to sound like that.

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#16
In reply to #14

Re: Foundations for Pumps

07/02/2013 1:17 PM

Exxon..... I heard of them....

And your comment:

"we can't afford not to do it right the first time. "

That is how I'm doing my justification.......

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#4

Re: Foundations for Pumps

07/02/2013 10:52 AM

Just my thoughts:

I tend to agree with CaptMoosie. I get very nervous around large pieces of rotating equipment, and I would not feel comfortable without your concrete pads in place. These are big heavy pumps, and even if properly balanced you can get enough vibration to cause them to shift on soft asphalt, even with steel posts driven into the ground, etc.

If you do decide to go the way of your plant engineer, you could consider using flexible pipe couplings to minimise the risk of damage to pipes and pumps, but this could cost more than putting in the concrete pads anyway.

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#6
In reply to #4

Re: Foundations for Pumps

07/02/2013 11:06 AM

We have flex pipe (Wire braided) on inlet and outlet of pumps.

its the eventual deformation of the asphalt from the weight that I'm concerned.

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#10
In reply to #6

Re: Foundations for Pumps

07/02/2013 11:45 AM

It's the deformation of the asphalt from the weight and vibration that would concern me aswell. The pump/motor unit can look after itself if it is mounted on a decent baseplate, which is most likely the case. The critical part is the pump/pipework interface. Too much movement and you could fracture the pipework, or exceed pump nozzle loadings which could damage the pumps. Flexible couplings will allow only so much movement, and you need to be sure you will be within these limits. Good luck.

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#12
In reply to #10

Re: Foundations for Pumps

07/02/2013 12:02 PM

exactly and thanks.......

Its the outlets that I'm concerned about. the inlet there can be quite a bit of movement the flex pipe will make up for it.. but the outlet which is going over head to the main there is not much movement to spare in the limits (they do not stretch).

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#7
In reply to #4

Re: Foundations for Pumps

07/02/2013 11:10 AM

Remember to write a memo to the plant engineer/manager so you can CYA thoroughly in case something goes terribly wrong. Keep a copy of that memo and any other correspondence regarding this matter at home, for safe keeping!

Just saying.....when the chips are down and your neck is on the line, the BossMan is always correct (in his mind), unless you can prove it in writing to his superiors!!!!!

Hmmmm large pucker factor here.........

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#8
In reply to #7

Re: Foundations for Pumps

07/02/2013 11:24 AM

email has been very prevalent with referenced calls, and it is actually easier read the email..

The plant engineer does have integrity and has proved it time and again and has stood up for me in defense.

plus the RFQ I sent out 2 1/2 month ago before withdrawing it when this first hit the fan. of which last week, I sent out again....... nice that I had all the info.

That's just it, this is my responsibility, and I have been already talked to about being a wild gun......... only to have documentation to show not only was I on top of the project, it saved money and time. kinda took the wind out of the sails of the verbal reprimand...... but I told then I'm spending as though its my money...... because it is my responsibility.

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#13

Re: Foundations for Pumps

07/02/2013 12:21 PM

I would forward a link to the Tacoma Narrows bridge failure to your plant engineer.

Here you go.... http://www.youtube.com/watch?v=j-zczJXSxnw

I'm sure he has done a detailed analysis of the pumps, considering the affects of piping construction and variations in the density of water and how this might lead to an excitation.....with all of his spare time and all .

He is gambling. There is a 90% chance he will be right and you will save a little money and a few days of down time. There is a 10% he will be wrong and the costs will be tremendous and downtime and loss of production will be enourmous.

If the pumps are driven by a VFD, he should start working on his resume now.

Mass is your friend.

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#15
In reply to #13

Re: Foundations for Pumps

07/02/2013 1:15 PM

I did the analysis, flows and pressure requirements for the process as well as the forces on the pipe due to flow........

He wanted Victaulic, and I did the forces on the piping and the required blocking on the piping was to restrain over 24,000 pounds of force on each elbow.......... I went with welded fittings on the critical and the straight runs with Vics.

What we do, no one wants anything to turn brown........ and we use each other as second checks......

your comment of " If the pumps are driven by a VFD, he should start working on his resume now."

Yes they are driven by a VFD.....I'm not following you on the problem of that.

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#17
In reply to #15

Re: Foundations for Pumps

07/02/2013 1:37 PM

Sorry...I was being to coy...I would be very concern about excitation of the pump at its natural frequency.

One of reasons the pump should be bolted to a slab is to ensure that there is enough mass to prevent excitation at its natural frequncy. The addition of the concrete bases drives the natural frequency of the pump/pump base combination much lower. If you use VFD, you will operate over a much wider range of frequencies and therefore increase the likelihood that you hit the natural frequncy of the pump. The best way to prevent this is to add copious amounts of mass, firmly attached to the pump base (i.e. using a large housekeeping pad). The soft asphalt is more of a fluid and will likely not contribute mass to the pump base - which will not provide protection against excitation.

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#18
In reply to #17

Re: Foundations for Pumps

07/02/2013 1:44 PM

Vibration, through a wide range of frequencies, will always occur and connecting the pump base to the asphalt should mitigate most of the movement.

Vibration at the natural frequency, however, will not be stopped by any mechanical fastener that you have selected and will lead to catistrophic distruction of the pump and connected piping....or perhaps even worse.

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#19
In reply to #18

Re: Foundations for Pumps

07/02/2013 1:57 PM

with the varying frequency that is something's that needed to be address more. its not that the speed will bounce around, but it changing with our production needs and weather.

The control will determine the speed based on the load that the cooling cells are seeing and production needs

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#20

Re: Foundations for Pumps

07/02/2013 2:20 PM

I have faced this in a similar situation. We bolted the pump to a 1/2" steel plate and bolted the plate to the asphalt. Lasted for around 5 years.

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#21
In reply to #20

Re: Foundations for Pumps

07/02/2013 4:42 PM

Curious, How big was the pumps?

The thing that I was also getting at, when we go to phase two, instead of taking the whole plant off line to demo'ing the pumps and put in the foundations...... we can keep the plant running.......

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#22

Re: Foundations for Pumps

07/02/2013 4:46 PM

Funny,

The owner stop in, and commented with excitement at the new pumps,

I started to mention about what I wanted to do with the foundations, didn't even finish ........ his answer.

do it......

so, ......... ah..... never mind.......

Thanks for everyone's prompt responses..... great resource here.

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#23

Re: Foundations for Pumps

07/02/2013 6:37 PM

Common sense won over for once! Hurray!!!!!

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