Published Pump Data 3

[PUMPDESIGNER]

Would like input on experiences with published pump performance data. Tell me what your experience is good or bad. Specifically, do you see a trend of increasing variation or decreasing variation from published data?

REASON - We believe there has been a sudden rise in the last 2 years of variations that even surprise the manufacturers. In one instance the manufacturer admitted that they changed the casting process but not the shape of the impeller. Even they were not aware that the casting process had a dramatic affect on pump performance. In that instance the curve flattened out considerably, there was 18% less head at shut-off and 40% more power required at one performance point. In another instance pumps that we have been using for years have suddenly started to overload by about 10% when we always have impeller trims incapable of overloading the motor or using the service factor at every point on the pump curve.

We have documented our pumps for years and we know when something has changed because we use the same pumps over and over. We are also very careful to check site conditions for possible causes.

We believe that we see a trend where many manufacturers are not aware that manufacturing process changes are changing performance considerably.

Thank you. Richard Neff
Irrigation Craft

 

[d23]

PUMPDESIGNER:

The API specifications for &quot;head and flow&quot; on our pumps is to be within +- 5% of our published curve. If your talking about building a pump that can develop 10,000 feet of head this number can be a concern depending on the IPR of a well. Every pump we build is tested before delivery. We know what to expect from our pumps within <1% even if changing stage batches. It is quite seldom that I depend on a catalog curve for my designs. We are willing to provide actual test results to a customer before building a pump to support the design decisions. Our customers (at least mine) also get the test results of the pump we deliver.

When casting stages the blocks or tool you use for the cast will wear out over time changing the product or stage. A manufacture will use the 5% variation so new tools won't be required for each cast.

For larger industrial type pumps you should be able to get test data from your manufacture to aid in designs.

 

[BobPE]

Richard:

I have seen lots of errant problems from the catalog to the field. The latest one I am now working on was a pump that was made by a leading manufacturer. Upon investigation (since the pump failed in the field) I discovered that it had no serial number. As it turns out, it was made from parts that the contractor had around the shop. Don't get me wrong, it was all the same parts that would be in the specified pump, but the factory did not know it existed. Other problems I found are too many to list. It is a rising problem because it seems that engineers are not checking the pump upon installation and I personally think it stems from the engineers general lack of knowledge of just how to performance test a pump. It is always easier to find the problem after the pump breaks it seems.

I am very tough on pump manufacturers, and yes I have found &quot;casting changes&quot; that were not reflected in their catalogs. It seems that all the good pump makers have been bought up by companies more concerned with profit that appeasing the engineers taht specify their stuff, and it's our fault.

BobPE

 

[d23]

PUMPDESIGNER

This would be after the fact and something you’re probably quite familiar with, but we have used epoxy coatings to improve efficiencies on some pumps. We do publish or flag our coated stages so fluid/coating compatibility can be checked. Most of the improvement seems to be with head and flow by reducing friction. For a given installation if the actual pump operation is close you may be able satisfy your customers needs by coating the stage(s) rather than replacing it. I’m not trying to justify any manufacture, but this may offer a possible “price effective” option for you somewhere down the road.

BOBPE is exactly correct. Customers typically only want the low price and manufactures always want sales. Wouldn’t it be nice only to work with customers that are willing to pay a little extra for quality and only deal with manufactures willing to tell you that your application is beyond there capability.

In your case it seems you have a close working relationship with the manufacture. That should at least help you some.

Good Luck

 

[PUMPDESIGNER]

d23 - I suppose we should be more specific. I can live with 5% head flow data, but definitely not an ounce more. However it would be hard to live with 5% on power or NPSHr, but I don't think you were referring to those with the 5%.

d23 - Based on your statements I do not believe your company would have a problem because of all the testing. But I believe that companies building repetitive production units are the problem. Testing is not done at all until someone like nasty old BobPE or myself comes along scratching our overloaded head in dismay.

d23 - I am curious if you know the answer to this question. I ask this because of limited ability to test in the field. If the surface roughness of an impeller is changed (made smoother) such as by a coating, is the result a simple improvement of efficiency as you state, but does the shape of the curve change? If so then the problem is much more complex and would require complete re-testing and documentation.

BobPE- If I was in the business of hiring engineers to design projects I would hire you in 1/2 a second, and also pay you for full site supervision and sign off. If anyone ever asks me for help I will surely send them to you. I identify with your situation Bob because when you are the &quot;only one&quot; complaining it makes life harder. Richard Neff
Irrigation Craft

 

[d23]

PUMPDESIGNER:

Due to the design of our impellors they are next to impossible to completely de-burr so coating offers me one possible means of reducing friction. Coating cannot fix the problem that you referenced (18% head, 40% BHP.) A lot of the specification sheets I receive will require an absolute minimum flow and dp. If our historic pump test gets me within 1 percent or so of their requirement I may offer the customer coating as one possible option or solution to prevent over sizing.

In very strict terms you are absolutely correct about coating changing the stage geometry. When we coat a stage it will change all that you mentioned, BHP, head & flow, NPSH etc… Testing or retesting is required. Due to our stage design the amount of change we experience is very minimal, but it is there as you suspected.

Coating was only offered as one possible idea if the pump performance is close and you need a minor improvement.

For me to have instant access to pump test clearly means that I live a very sheltered life!

 

[PUMPDESIGNER]

d23 - You sure do live in a sheltered place.

I have dreamed of having enough cabbage to build and sell automated test stations. I am convinced that if manufacturers had the ability to quickly and efficiently test they would test more often.

Hook a pump up, push a button, go get breakfast. An hour later download the logged data. Verify test parameters remained within HI standards, paste the data into an Excel template.

1.5 hours - Pump tested, certified, and published. Richard Neff
Irrigation Craft

 

[Kawartha]

PUMPDESINGER,

It's very refreshing to have someone start a thread and continue to work with the responses. I find that 2-way communication is very helpful in resolving relatively complex problems.

I just want to add that I recently specified some high head, low flow, radial impeller, ANSI type pumps for a small BFP application. This design utilizes the Barski type impeller (straight radial vanes).

Performance was close to quoted curves, but the pump BHP ended up being about 25% higher than quoted. The resolution to the problem was that the supplier (a major North American pump manufacturer) supplied a 40 hp motor (at no charge), to replace the existing 30 hp motor.

What was most disturbing about this case is that we included a non-witnessed performance test in the specification, and the test results indicated a maximum pump BHP requirement of 28 bhp.

Never did get a reasonable explanation from the vendor.

 

[d23]

Kawartha, All

A few years ago one of my competitors tested a four year old pump of mine so it could be re-ran into a well simply due to the location of their test bench. The impeller/pump came out of a well that has over 5% H2S. After a four year run stage or pump degradation is expected. The impeller of this particular pump is a mixed flow 4”+- OD and the Q at BEP was 120 GPM. Due to the small OD a new pump would have an expected efficiency of about 68 percent. The test my competitor provided for a four year old pump claimed 82 percent efficiency on my used pump. When I pointed out to my customer the test discrepancy he laughed at it, ha ha funny! This is the same test bench my competitors test most of their &quot;new&quot; pumps with. I’m sure you realize my sales get killed due to low efficiency. Like BOBPE stated sales are everything.

For any test one thing you may want to ask or require from a manufacture is the date of the last calibration and what third party performed it. Do not accept in-house calibrations, we don’t.

Another thing to consider about testing pumps is do they test used equipment at the facility/bench you have testing your equipment? PUMPDESIGNER and I both agree that I live a very very sheltered life, but we absolutely will not test or repair used equipment and new equipment at the same facility. We won’t even store used or new parts at the same facility, not even the same state or country as the case may be. Contaminating test fluids or parts negates reliability of any possible test.

I am just now beginning to realize how sheltered my life actually is (thanks Richard!!!!) As engineering firms when you design pumps do you include specifications to cover the problem(s) identified in this post? In most cases my customers do. I’m not asking this to point blame I’m just wondering how a manufacture can talk their way out of your problems.

Another question is what is it worth to you or your customer to purchase equipment that performs within one percent of quoted design? As engineering firms you want perfection, but I have to believe that the only thing your customers want is low dollar! Our real problem or mission is to teach the words ethics and quality to our customers!!! If you can teach me how to do this I would be eternally grateful!!!!

 

[PUMPDESIGNER]

Kawartha
Thank you for your compliment and response. So after you corrected that power problem, did you or your firm get paid extra for the telephone calls, letters, internal discussions, and the sheer exhaustion? I recently charged and got paid $1,000.00 fee for proving to a manufacturer that their pump was way off. Just sent them an invoice and grumbled a little. Not bragging, but if I had heard that 15 years ago from someone I might have more money now ... well in reality I would have lost it trying to build an automated test stand that no one would buy.

d23
You are at the core problem - ETHICS. Isn't that something they threw out of the course line-up at the Harvard and Yale business schools where all these genious MBAs and marketing execs come from?

d23 - Know the problem about losing sales to competitor's marketing crew, gang, or whatever they are called. I feel for you. But there is a great quote - &quot;Virtue be unkown unless it first be crushed.&quot; Stay the way you are, enjoy and let others enjoy your honesty.

d23
I have nothing against coatings, just don't need them often. Work only with clean water and such. Did electroless nickle a few times though.

d23
You are correct about testing, third party verification, and specifications for certified tests. I will mull your ideas over and see what I can do. My company manufactures skid mounted pumping plants. I pick a pump, test to see if the pump matches published data, then I put the pump into the line-up. That same pump gets ordered repetitively for years with only casual checks and no further testing. From the '80s until about 2000 we had zero problems. Last two years we are getting fried, and I am getting steamed. A person could say that I am guilty of not testing. But I do not think so. I supposedly have a teammate. I depend on that teammate. I cannot be looking back all the time. I try to find good teammates, and I did have some for years. No longer though. I am re-doing EVERY LAST PUMP in our line up.

Thank you all.
Richard Neff
Irrigation Craft

 

[d23]

PUMPDESIGNER:

One last thought:

Sales and ethics are taught in the same class. Regrettably the semester ends before you get to ethics….

 

[Kawartha]

PUMPDESIGNER,

I am with an Engineering Company, so when our client had problems with the 30 hp motor operating at about 38 hp output, they came back to us for assistance. We, of course spent several hours reviewing and checking the complete design, and could find nothing that explained the high pump bhp draw. As I mentioned, the pump was non-witness performance tested. This is a great lesson - if you really want a performance test, the only way is a witnessed performance test.

Your exactly right about the time, nuicence and frustration costs. But being on the consulting side, our client had to take the initiative in pursuing the supplier for compensation. As far as I know, they didn't pursue and additional compensation, and I don't think anything was offered. I should add that the supplier is probably the largest pump manufacturer in the US (possibly the World), and it seemed like they were doing the client a big favour in exchanging the motors.

The other thing I would like to say is that many suppliers have been, and will continue to experiment with sourcing their castings. Many manufacturers have tried Chinese, India, etc. castings, with many hitches. They will continue to do so. You can not assume that the pump parts (particularly casings and impellers)are made from the same patterns, at the same foundry or machined at the same shop. Even when these items are made with the same old patterns, the patterns wear until the manufacturer is forced to make a new pattern.

As you already know, you can not always depend on the manufacturer's curve, so you may have to allow slightly higher safety factors in selecting pump ratings. The other thing that you could consider is gauranteed operating points on the pump curve. If points are not observed during your tests, backcharge the supplier until they get it right.

Sorry for the long comment.

 

[dadfap]

Guys, I work for a mainly oilfield ESP manufacturer. We also sell ESP systems to the water well/ agricultural / utility water supply and mining markets.
Biggest differences I have noticed between the two markets are to do with &quot;GUARANTEED EFFICIENCIES&quot; as opposed to API tollerances.
This has proved a challenge for both myself and the company to get their heads around. I have managed though, generally by sitting and talking with the end users so that I understand a little better the differing markets.
Also, the water market requires a little more nursing from the sale to final commisioning / acceptance.
Whilst the oilfield manufacturers can do wonders for this market with our smaller OD equipment, generally higher tech products (I am sure that someone is going to give me heaps for that one) we do tend to charge more and therefor need to provide some more for that.
The dollar vs quality / performance point is well made. Personally, I would love to always supply what will do the best job, but both the specifications from the end user and their purchasing philosophy make this nearly impossible most times.
I am a great believer in fit for purpose engineering, although the end user does not like this approach as it makes his job of evaluating quotes and tenders all the more difficult.