7 replies to this topic

[formula.crazy]

Hey guys,
Firstly, I'm a little dyslexic. I'm not a student, I'm a production supervisor with little knowledge of process calculation. I have many questions but they're all simpler than the topics in this forum.
I'm looking for answers in how to do the calculation and what steps to take.
Plenty of answers online are in imperial units and when i try to do the same for SI units I'm getting all the wrong answers.


Please guide me to solve a problem like this,
For water supply. At the end of a 2 inch line I'm getting one bar pressure, whats the flow rate im getting?

The source pump delivers 25m3/hr with 60m head.
What size piping should i use?


Please give in SI units only, i am totally unfamiliar with imperial units. Other than pipe size which i only work in inches.

My home PC dosent have ms Excel, alot of help files here are Excel. how do i use it?

Thanks,
FC

Edited by formula.crazy, 02 November 2012 - 01:37 PM.

[Art Montemayor]

Forumula:

Don’t feel dyslexic. If you are production supervisor in a processing or similar plant, you could probably teach us all a lot of practical solutions to everyday problems.

Advice from an old engineer:

• Get your home PC capable of taking on the latest Windows version 7. This is a necessity if you are serious about resolving these issues you have with calculations.
• Once you have a capable, updated PC, go to http://katmarsoftware.com and make sure you buy a copy of Katmar’s latest UCONEER program. This is THE only serious conversion program that I have found to date. With this program you can convert any units you desire to whatever units you want.

With your updated PC you will be able to download every Excel workbook on this Website – and others on the Web. You will also be able to employ our Forums to seek answers to specific queries or problems you are facing – using Excel workbooks to transmit or receive answers to calculations.

As for your above 2 questions:

Question #1
We can’t tell you the water flowing at the end of a 2” pipe without you telling us more information than just pressure of one bar. We need the differential pressure across the pipe in order to apply the appropriate fluid flow equation.

Question #2
The recommended pipe size for 25m³/hr (110 gpm) of water flow could be a 2” or 3” pipe. This I know from field experience. You can verify this by employing the average design velocity of water flow (5 ft/sec = 1.524 m/sec) to the calculations as follow:

(110 gal/min) (1ft³/7.48052 gal) (min/60 sec) (sec/5 ft) (144 in²/ft²) = 7.058 in²

This calculation states that a pipe with 7.058 in² of flow area will give the recommended water velocity. From the pipe tables, we see that a 3”, schedule 40 pipe has a cross-sectional flow area of 7.393 in². I would use a 3” pipe.

Note that the appropriate conversions used in the above calculation all came from the handy Uconeer program. That’s why I always recommend it.

[Ahsan67]

@Art Montemayor
can u please guide me regarding the velocity in the pipe as in the above calculation it was used as 5ft/sec.from my calculation i see found that it can go up 8ft/sec that is 70% of it's erossion velocity, please also help me in understanding velocity coeff , what velocity coeff should be used to find erossion Velocity

[Art Montemayor]

Ahsan67:

After 52 years in engineering, I know (and have always used) a mean liquid design velocity of 5 ft/sec – unless instructed otherwise, or in the case of a slurry or suspended solids. I see no reason for designing for “erosion” – unless solids are involved. But this example has no mention of solids.

I don’t know what you mean by a “velocity coefficient”. Are you referring to API 14C or another “recommended practice”? If so, please be specific and spell it out clearly. I can’t read minds. After having designed, led, and managed many projects in many countries, I know that a design value of 5 ft/sec is a very reasonable number to use when not given any more specific basic data. When you give an experienced engineer un-specific, un-detailed basic data, you are going to obtain only general, good judgment type of answers from him/her. You certainly are not going to get a specific answer involving erosion.

[kkala]

In addition to above posts, some relevant notes probably useful.
1. For liquid pipe sizing (=define proper diameter) in general, you can look at pipe sizing criteria, http://www.cheresour...d-line-sizing/. (1ft/s=0.3048 m/s and 1 psi/100 ft = 0.226 Bar/100 m).
2. Concerning other queries by formula.crasy:
2.1 Assuming centrifugal pump of suction pressure=0 Barg, flow rate will be 25 m3/h if discharge pressure is Pd=6 Barg (water sg=1). Which means pressure difference in whole discharge line (by frictional pressure drop and static elevation) = 6 Bar for 25 m3/h, if it ends to atmosphere (pressure=1 Bara=0 Barg). If Pd is lower, flow rate will be higher than 25 m3/h according to pump performance curve.
Studying liquid flow in pipes from a book on Chemical Engineering (e.g. by McCabe-Smith-Harriot, or Coulson-Richardson-Sinot, etc), will help to clarify such matters.
2.2 You could buy older versions of MS Office quite cheap (e.g. from e-bay, etc). I use MS office 2000, which can use the converter of .xlsx or docx files. But first look into Open Office, http://downloadhaus.com/open-office/, which is free.

Edited by kkala, 14 November 2012 - 02:35 AM.

[Ahsan67]

Art Montemayor

Sir first of all thanks for your kind attention and reply, i have got just 11 months of experience in an EPC(Oil & Gas) company working as a trainee process engineer. i was referring to API 14E which suggest the below formula for finding the erosion velocity

Ve= C/sqrt(em)

C = velocity coefficient
sqrt = Square Root
em = mixture density

this formula uses velocity coefficient(empirical constant) as C = 100 for solid free fluid, C =125 for intermediate fluid and so on, i wanted to know about erosion velocity in this case will this criteria be considered or not to specify the line size ?

Regards
Ahsan

[Art Montemayor]

Ahsan:

I thought I was very clear in my response to your query, but I sense now that I failed in explaining myself to you.

The topic of this thread is about a flow of water. Since the OP (original poster) does not give detailed specifics regarding the quality of the water he is dealing with, we have but one choice and that is to treat the query in a general, non-specific manner. That is the way I responded, using a general, accepted water design velocity of 5 ft/sec.

Now, you bring in API 14E into the thread and try to apply it to the topic at hand. My response was – and remains – that you cannot apply an empirical equation that relates to another, totally different application: the oil and gas industry.

The reason we have – and apply - API 14E is because crude oil, like any resource found in nature, is a mixture of many things that can cause damage when forced to flow in the manner we want it to. Sand, for example, is a common abrasive found in crude oil as it rises to the surface for recovery. That is why API developed empirical relationships that now form recommended practices when dealing with crude oil and gas. However, here we are not dealing with crude oil nor gas. How can you introduce the subject of erosion in this thread when we have no basis for believing that the water fluid being discussed has an sand, solids, or particles that could cause erosion?

If you want to discuss API 14E, that is fine. Simply start a new thread with that as a topic. I can add a considerable amount of process engineering experience in that respect and even contribute spreadsheets I developed for applying API 14E and the so-called erosion velocity.

I hope that I have addressed and responded to your query in a constructive manner.

[kkala]

A notice about formalities: Author of post No 7 apparently wrote dash in the text, converted into "–" when the post was published. In one case dash was correctly attributed though.
I have also observed that upper symbol of key 7 (on the main keyboard side, not on the right side of it / US type keyboard), meaning "and", is converted into an irrelevant symbol. But it remains if written in quotation marks "&".
Similar examples could be seen in other posts, creating "words" rather illegible or hard to understand.
Some symbols of http://rmhh.co.uk/ascii.html are returned on the text by using the relevant code, other symbols are not. And when the text is posted, symbols correctly returned may be converted to irrelevant ones seen on the published post.
Explanations in the long term how to avoid such problems would be useful, probably to be contained in the pinned "how to use BB code in posting messages".

Edited by kkala, 15 November 2012 - 03:25 AM.