Centrifugal pump technical bid evaluation.

[zipped]

Hello Friends
I have very little experience in technical bid evaluation. This question has haunted me several times.
My doubt is, if one has to evaluate a bid for 3 centrifugal pumps offered by 3 different vendors. What all parameters do an engineer consider/check to select the best pump among the three.
Step wise or priority wise solution would be appreciated.

Regards

 

[KiwiMace]

I think these are the major points below. You might shuffle the priority based on your particular demands or add other criteria.

1. Technical - does the submitted pump meet the technical specifications of the bid. Flow, head, type, configuration, materials, pressure rating, standard complying, motor power, efficiency, coupling, seal type....

2. Schedule - Can it be supplied in time for your project.

3. Service/Maintenance - Is the vendor nearby, do they offer 24/7 support and parts, do they stock common parts or whole assemblies, are they competent and reliable, does the plant have 200 Vendor A pumps and this will be the first Vendor B? Do they factory test?

4. Price.

 

[Artisi]

Assuming the bids meet flow, head, materials etc etc as already stated above, the most important consideration is pump efficiency.
You don't say what size these units are in terms of installed power, large units can use thousands of dollars worth of power over a year and 1 or 2% difference in pump efficiency can cost more than the initial pump purchase in a very short time period.

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.)

 

[zipped]

Thanx KiwiMace & Artisi
From your replies, can it be implied that the pump which is designed to work closer to its BEP is best to select?
My query is more related to technical aspects. Suppose an engineer of an EPC company has to do this.
Assuming that all 3 pumps meet process criteria s, delivery date.


@Artisi: Nice quote.

 

[TenPenny]

Typically, it's the end user or the EPC who determines what factors are more important.

Efficiency is, or should be, one of the top considerations
MTBF data, reliability should be high on the list
If an existing plant, interchangeability with existing population is sometimes considered.

 

[cvg]

you might also get / check references. Anybody can quote low and promise to meet the specs and schedule, but can they really deliver the goods?

 

[GPRnD]

I'd say as long as the selected pump is in the range of 80 to 110% of BEP that is sufficient. Closer to BEP matters less than overall efficiency and sufficient NPSH margin.

Hydraulic Institute has a pretty decent book covering a lot of these issues. It is called Optimizing Pumping Systems. In the interests of full disclosure I did contribute some material for this book, but I don't get any commission from sales .

 

[GPRnD]

I'd also add that the weighting for the criteria you use depends greatly on the type/size of pump you are evaluating.

For example selecting a pipeline pump, efficiency is so important I'm sure some pipeline engineers would happily sell a close family member if it got them another 0.5% efficiency.

However on a refinery process where NPSHa is at a premium, efficiency is often sacrificed to select a slower running pump with lower NPSHr.

So if you hpost more information on the specific application we can probably provide better guidance.

 

[PumpSmart]

zipped,
First, are those pump/motor mfg on your preferred vendor list?.
Because some users would like standardization and does not like to have around to 30 pump mfg in their plant and like to have the best reputation mfg pump as possible.

Second, do you have any techical specification? if so you should evaluate if they meet all data and criteria.
If your specification is light, you should take care.
In small, and medium water system is understandable to check efficiency.
But for API refinery process, critical chemical/mining process, criogenic, nuclear, slurry mill circuit, etc, etc, you should go for reliability/quality (more than efficiency).

3.Thrid, Local Pump mfg Service is very important if
-pumps are critical.
-pump service is difficult and generate heavy duty loads.
-service is new in this plant and there is no previous experience.

4, Price: You should evaluate initial price or TCO price,
and indicate penalty to vendors if they does not meet delivery required.


i hope this helps

 

[DubMac]

Before you get into evaluating hydraulic performance requirements; flow, head, eff., NPSHR, ......

you better FIRST be sure that the pump fits the application.

What features are the most critical to the application? If you have a heavily abrasive solids service, you better have materials and clearances at the top of your list, efficiency not that important. If you're pumping water in a municipality, materials aren't as critical; efficiency is king. High temp service? volatile/toxic fluids? super low NPSHA?

You need to decide on which STYLE of pump fits best: centrifugal or PD?, overhung or between brgs.?, vertical, horizontal? API,ANSI,general service??

Once you have an idea of the best style pump for your service, decide on what mechanical design features are most important to the service: Materials?, volute/impeller style?, bearing design?, shaft deflection?, wear rings, running clearances, fits and tolerances, sealing details/sealess, etc.

Assign relative value to and prioritize the features required by the service and then rank the candidates by WHAT FITS THE SERVICE BEST.

THEN do your hydraulic evaluation using the same methodology.

 

[stanier]

When doing your hydraulic evaluation check for pipe losses when new and when old. If using thermoplastic pipes check the inside diamter using both maximum and minimum wall thicknesses. The plot your duty poit on the curve offered and make sure that the points fall within the range of best efficiency points (BEPs). These may be 90 to 115% of the BEP.

Refer

http://www.mcnallyinstitute.com

for information on pumps.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[stanier]

Zipped,

A good start point is your pump data sheet. Put all the parameters specified and requested into a spreadsheet. Compare all the submitted responses to each parameter. Then have the mechanical/electrical/process engineers make a call on compliance with standards, specification and contract.

Feed the non conformances back to Procurement for them to negotiate price for compliance.

Any non compliances that you cannot accept will rule out a supplier.

Consider one supplier for the plant as this makes spares holding/maintenance simpler. In fact you could negotiate the supplier holding the spares or providing maintenance. You may be able to select a series of pump models. Although not ideal gives improved economy in spares. this is particularly so for slurry pumps.

Also i suggest getting the preferred supplier'sd software and selecting the pump yourself. They are not infallible.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/