6 replies to this topic

[irene]

hello,
i would just like to ask what is my target in a water pipeline design from a water well to a storage tank and from the storage tank to a faucet. i already have a layout of the pipeline. do i need to get the power required by the pump? how can i select the suitable pump? is there a rule of thumb for the height of the support (eg. trusses) for the storage tank? I'll appreciate much if you'll lend me some help. thank you very much!

irene

[johnsonn239]

irene,

There is not a lot of information given here but I'll give a general angle of attack for pump selection. First because you are pumping from a water well you could probably look at a submersible or self priming pump as your first choices. Second you need to come up with a head calculation for your pump. If you have access to a Crane Technical paper 410, it will explain exactly how to go about making this calculation. This reference will help you caluclate the needed power of the pump and your next step would be to obtain a pump performance curve. You can find pump curves at pump manufactures websites like Goulds(centrifigal pumps) or Tri Clover(positive displacement pumps) etc.

If you know your max flow rate of water and the TDH(Total Dynamic Head) calculated using the Crane Technical paper reference, you can determine, using the pump curve, what pump is right for the job.

Another aspect of designing this piping system is obviously the nominal pipe size that is needed. The suction and discharge pipe sizes are usually suggested on the pump performance curve.
FYI. The discharge pipe size will never be larger than the suction pipe size for it is more likely to cause cavitation.

johnsonn239

[Art Montemayor]

Irene:

Welcome to our Forum.

Please refer to the attached Excel workbook with a schematic drawing of what I think is your water supply system. This sketch is the most accurate and precise method to convey engineering basic data and definition of what you are trying to work with. Your verbal description – like anyone else’s – falls short of telling us a lot of details that can easily and accurately be noted on a schematic or Flow Diagram.

You have large deficiencies in your query. Allow me to point out where you have engineering communications problems that prevent us from helping you right away:

1. You fail to tell us exactly just what it is that you are working on and what the problem is. Without a detailed explanation of what you have before you (it could be a project, a class problem, a personal question, or a formal class assignment) we are unable to know just what it is that you need or lack. If you are to function as a future professional engineer, you must learn and dominate the art and skill of communicating correctly, accurately, and precisely. Otherwise, people working for you and those supervising you will not be able to understand what you need or what you are planning to do. A failure to communicate precisely and accurately is not acceptable in engineering – at least not when you are working with and/or depending on other engineers to work with you as a team effort. Therefore, please tell us what you have as a problem or as an objective – concisely and in detail.

2. What pump are you referring to? Again, we don’t have even a slight idea of what your system looks like. You haven’t told us. That’s why I’m taking a guess and drawing the Excel sketch to show you how to better communicate with engineers. You probably mean the main deep well pump. But you could also have an additional pump from your storage tank to the domestic supply - if the tank isn’t elevated sufficiently. We simply don’t know. It is your obligation to tell us all the details if you are to expect a serious, engineering response to your needs.

3. We don’t know if you are required to specify the pump’s horsepower. That is your knowledge and you haven’t shared that information with us. How can you expect us to know what your Scope of Work is, if you haven’t told us? If you don’t know what a Scope of Work is for a project, please tell us immediately. This is vital information that is a pre-requisite for any project of job involving an engineering solution or effort.

Your Forum Profile – like that of most Students who come to this Forum looking for help – does not tell us who you are, where you are from, or what grade you are in. Without this background information, it is very difficult to address what we know to be your real needs. Without knowing, for example, your level of engineering education, we can really mess you up by discussing subjects you haven’t been prepared to understand yet. A Scope of Work is just such a subject. An engineering Schematic Drawing or Process Flow Diagram is yet another similar subject. I have to assume that you know what I’m talking about because I’m reaching out to try to help. But we really can’t spend days guessing at what you need as help. We need your help in order to help you. I am taking all this time and effort to explain to you - and to all other students reading this - in order to avoid this kind of wasteful and time-consuming procedures that only serve to cause mixup and misunderstandings of what the real problem (and answer) is.

Look at the Excel sketch and put any remarks or comments on it that you think are pertinent and are part of the Basic Data. If you don’t know what Basic Data is, tell us. But don’t give up. This Forum is made for helping you – not just for criticizing you.

I hope the weather is good in Makati City and around Manila and that you will respond with some needed Basic Data to allow us to help you out.

I await your reply.
 Deepwell_Water_Supply.xls   920KB   163 downloads

[irene]

hello,

Sorry for the lack of information on my first query.

It is actually a design problem given in our equipment design class. We are to lay out a design of the pipeline system from a deep well to a storage tank. From the storage tank, another pipeline will be designed to head the water to a faucet 3 feet from the ground. We were given a volumetric flow rate of 150 L/min, an outlet pressure of 1atm and a pressure to be maintained inside the pipeline which is 100 psi.

These are the requirements:
Calculations
Material of Construction
Pipeline design layout (top view and side view)

I have seen the excel sheet you’ve posted. It illustrates much of the design problem.

These are other information:
Distance from ground to water level in deep well : 17 feet (how deep more from the water level should I lay my pipe?)

With a rule of thumb I have seen from one of our references, I found out that typical water velocities range from 3 to 10 ft/s. Given the vol. flow rate, I calculated for the possible diameter of the pipe. For pump suction, it is 2 in nominal pipe size. For the pump discharge, it is 1.5 in nominal pipe size. Both are commercial steel. Is this a correct method of determining the pipe size?

Pipeline from the 1st pump to the storage tank would pass through the main road (how deep would be the excavation?)

I already calculated the diameter and height of the tank based on the vol. flow rate and storage time of 16 hours. The diameter is 16ft and the height if 20ft. With the capacity of the tank exceeding 90 m3, it should have concrete support. How high would that be? So that I can calculate for the final height and use it in the mechanical energy balance to compute for power requirement of pump.

I do not actually have an idea of what pump I am going to use. I thought that the power requirement would be my basis for pump selection. What really is the pump type suitable for this pipeline system?

After the storage tank, another pipeline would be designed to head the water to a faucet 3 feet from the ground. The pipeline would be laid on the ground after the storage tank since it would pass through classrooms and hallways. It will then be headed upwards by an elbow, 3 feet from the ground for the faucet. Do I still need to put a pump after the storage tank? I have asked several civil engineers here and they told me that if the tank discharge is higher than 3 ft, I need not put a pump. What is the principle behind this?

Being still a student, I really do not know what Scope of Work means. I’ll thank you much if you could tell me.

Being a busy student who doesn’t own a personal computer and only rents computers in internet café’s, I do not have much time to update my profile. But as I have found out that you, engineers to whom I consult, need it, I have already updated it.

Thank you very much!

Irene

[irene]

hello,
here is the excel sheet you've posted. I have already put my queries on it. thank you very much!

-irene

Attached Files

•  Deepwell_Water_Supply_with_corrections.xls   918.5KB   83 downloads

[johnsonn239]

Irene,

First off I calculated your tank demensions to be a little bit different. Using an arbitrary tank height of 20' I calculated your diameter to be 18' which gives you vol of 38,068 gal which would hold 37gpm(150l/min) for 16 hrs.

You said:"With a rule of thumb I have seen from one of our references, I found out that typical water velocities range from 3 to 10 ft/s. Given the vol. flow rate, I calculated for the possible diameter of the pipe. For pump suction, it is 2 in nominal pipe size. For the pump discharge, it is 1.5 in nominal pipe size. Both are commercial steel. Is this a correct method of determining the pipe size?"

I don't really know how you made your calculation for suction and discharge line size but I used an excel worksheet that does the calcuations you would do by using the Crane Technical Paper 410. I said the height to the top of the tower(delta Z) was 35ft(this is completely arbitrary and I am not sure what height water towers are usually at), and the vol. flow rate was 40gpm(gal per minute), the discharge pressure was 14.7 psia, and then I estimated the length of pipe, # of elbows, # of valves for both discharge and suction, and entrance and exit losses for the pump. With all of that I entered 2" suction size and 1.5" discharge size and got reasonable pressure drops. Velocities calculated were only 3.8 and 6.3 ft/s but that should be sufficient so our line sizes match up.

For your question about needing a pump after the tower, you need to specify what the distance is from the tower to the faucet. If there is only going to be 100' of pipe from the tower to the faucet then you won't need another pump, but if the pipe is a couple miles long then you might need an extra pump after the tower. You can calculate the pressure you will get from the elevated tank by using this equation: P = Patm + (desnity of water)(height of fluid). If the heighest the water can be is 18' in the tank and the bottom of the tank is 17' off the ground then P = 14.7psi + (62.4lb/ft^3)*(35ft)(ft^2/144in^2), P = 29.9psi. If the pressure loss in the pipe and the pressure loss due to 3' elevation to the faucet is less than 29.9psi then you don't need another pump.

Hopefully I haven't confused you.
I'm not quite experienced enough to make a suggestion as to what the best kind of pump would be for this but I'm sure Art or somebody can make a good suggestion for you.

Let me know if I'm confusing or unclear in any of my explainations. I'm still a student as well and am trying to learn how to be more clear in my explainations.

Nic

[Art Montemayor]

Irene:

You have given us more information, but it is obvious now that you are not clearly expressing what you are thinking or what you are trying to think. Please pay particular attention to what I am about to say and explain to you. This has nothing to do with a different language or grammar. In any other language, your post would be just as confusing. You must first concentrate on what you are explaining in writing and then check your work to make sure it is clear, specific, concise, logical, and accurate. If you cannot explain your problem, you will never learn or understand how to resolve it – even when it is resolved for you. You must first concentrate on understanding your problem. Allow me to explain:

You state, “We are to lay out a design of the pipeline system from a deep well to a storage tank. From the storage tank, another pipeline will be designed to head the water to a faucet 3 feet from the ground.”
From this, I can only understand that you are to design the FIRST pipeline. I don’t know why you mention the second pipeline; I can only guess that someone else will design that one. Am I correct? Or did you fail to identify EXACTLY what you are assigned to design?

You state, “These are the requirements:
Calculations
Material of Construction
Pipeline design layout (top view and side view)”
What “calculations” are you referring to? Are these the hydraulic calculations or the structural, civil, pump foundation, piping, etc. calculations?
What materials of construction? –the pump? The pipeline? The structure? The tank? Do you understand now what I mean by specific and concise?

The correct pipe size is determined by the amount of pressure drop that you can tolerate as well as what you need for structural rigidity and robustness. It is NOT designed by assuming an average velocity. The recommended velocities simply are suggestions regarding what you should maintain within the pipe AFTER you have determined the correct size by using the Darcy equation.

At this point I have to presume that you are a university student and that you have taken sufficient Fluid Mechanics to understand what I am writing. If not, please tell us so that we can communicate in accordance with your preparation. That is what I meant as your background. We need to know who we are addressing and their level of preparation. Otherwise we are simply confusing you with material that may be over your head.

As an example of what a Scope of Work is, please read the attached document. In it, you will get an idea of where your project is lacking in communications and identification of what is required in order to reach a successful engineering solution.

You also state: “We were given a volumetric flow rate of 150 L/min, an outlet pressure of 1 atm and a pressure to be maintained inside the pipeline which is 100 psi.” This does not make any sense – primarily because it is badly communicated. As I stated, you have not given us an accurate description of what it is that you are designing. Is it one pipeline? Or is it two pipelines? You must communicate ALL the facts correctly. A water storage tank can be pressurized – this is sometimes done on some water supplies. However, Municipal water supplies seldom do this but instead they use atmospheric pressure tanks. That’s what I clearly showed and marked on my sketch. You failed to note anything on it and now you say that the pipeline is at 100 psi. Additionally, please always be SPECIFIC and state whether you mean gauge or absolute pressure. I assume you mean 100 psig. Is this correct?

How do you propose to have 100 psig in your pipeline? Again, refer to the importance of having a Scope of Work. Your lack of having a Scope is what is generating all these questions which are keeping us from helping you directly and quickly. Time and effort are being wasted in just asking questions – one at a time. This is not the way or manner that engineers are expected to work their projects. Accurate, specific and detailed data is required at the very onset of the project to enable quick, accurate and effective calculations and results.

I recommend you use the Excel sketch I supplied to accurately transmit your basic data and scope of work. You can use call-outs to pin point your information. If you do not have access to your own personal computer, this is going to be difficult, at best. I can turn-over a firm recommendation or reply in less than a day. If you have to wait in line at a computer café that doesn’t furnish Excel or your own storage disk, then this may take many days – especially if you don’t know how to convey or illustrate your project scope and basic data.

This is a very simple project to resolve and we could help you obtain a very good grade in whatever course you are taking, but you have to furnish the raw material – which is the basic data and the Scope. You also haven’t told us if there is a schedule or deadline for your project.

Await your response.
 Preparing_a_Scope_Of_Work.doc   68KB   120 downloads