2 replies to this topic

[Felina]

Hello,

 

I have been asked with the following question regarding the design of a pumping system for a potable water pipeline, and I have several questions which I hope can be cleared.

 

Here's the question:

 

The pipeline is to transfer bulk water supplies from the treated water tank, at the outlet of a new treatment works, to a service reservoir about 35 km away. The water levels in the treated water tank vary between +31.0 and +35.0 mAD and the delivery level at the service reservoir is +116 mAD. (see attachment)

 

The project is to be developed in two phases. In Stage 1 the maximum flow requirement is 75 Ml/day. In Stage 2 this will be doubled to 150 Ml/d. The client has specified that he must be able to transfer any flow up to the maximum at each Stage.

The preliminary design report carried out by the client’s engineer recommended a minimum size of pipe of 1200 mm and the Terms of Reference specify that the pipe shall be cement-lined ductile iron, and be capable of passing the maximum flow with a possible roughness of 0.6 mm.

 

I am also attaching the longitudinal profile given.

 

Here are my considerations for the solution:
 

- I would install two reservoirs: one at the very beginning and another one at the first higher pic of 149 in order to make sure the velocity established is fulfilled.

 

- In the first reservoir I am planning to install 3 horizontal centrifugal pumps in series (would need some help on getting pump catalogs!)

 

- On the second reservoir, I would put the reservoir at least up to 165 m above the pic to enable gravity forces to come out.

 

- Since it is an open tank system, I would use variable speed valves at the beginning and close valves right before the last reservoir to prevent surge problems, although I am not sure about it.

 

- In order to draw the gradient line, according to the designing made, I have taken into account the first elevation of 31 and the system head calculated on this first part, and the same applied to the second.

 

My main question arises of the whole justification of the system designed, since I find it hard due to the lack of information given to, for instance, justify the pumps duty and the different protections needed.

 

Any help or tip on that would be really appreciate it.

 

Best Regards

 

Walt.

Attached Files

•  Pipeline Longitudinal Profile.pdf   91.08KB   37 downloads

Edited by Felina, 06 January 2014 - 03:20 PM.

[Art Montemayor]

Walt

 

No one on our Forums – to my knowledge – is capable of reading your mind.  Therefore, if you don’t write out or explain your algorithms in your calculations, our forum members (especially the professional ones) will not spend a second on trying to figure out what you mean or intend by your calculations.  I strongly recommend to you (and to all other engineering students) to fully explain your calculations – step by step – or write out the algorithm that your calculations follow.  When submitting your calculations to a peer for checking or (worse) submitting your calculations to a client as product, you must fully explain and communicate what it is that you are calculating and why.  This is a requirement of all engineers who expect to be compensated for their calculation efforts.  You must make it easy for the reader to understand what it is that you are doing (calculating).  Contrary to what you think, your spreadsheet IS NOT easier to understand.  Some of your curves have no explanation as what they are supposed to depict.  Additionally, it is customary to draw your system curve on top of your pump performance curve(s).

 

Do not simply “cut and paste” a problem given to you for resolution.  We don’t know where your “Figure 1” is to be found.  You don’t tell us; and it isn’t listed in the workbook submitted.

 

Some of us don’t have an idea of what “mAD” means.  I think it means meters above sea level – but that’s a guess.  Why don’t you simply communicate correctly by defining all special terms you use?  No one is obligated to know your favorite acronyms or abbreviations.  What is a “pic”?

 

Instead of using a bunch of verbiage and composition to try to describe what you mean, simply draw sketches or drawings of your proposed water transport system in the form of a Process Flow Diagram (PFD) or Piping and Instrumentation Diagram (P&ID).  You are going to have to do this before it is all over anyway.  A drawing speaks a thousand words.

 

I hope this helps you clear up a lot of basic data and information that is needed.  You state you have several questions; yet you only list one.

 

[Felina]

Sorry, I made some modifications now, I hope it is clearer.

 

Regards

 

Walt