Sizing Propane Gas Lines 3

[supaman79]

Guys,

Can you size propane gas lines the same way as you wouls for natural gas? I can't find a propane chart for propane gas in the Gas code. Can anyone help?

 

[Montemayor]

supaman79:

You determine the size of propane lines the same way lines for any compressible fluid are determined. I presume you are referring to tables or nomographs developed for natural gas specifically, and these are prepared from the same method I just mentioned. This, of course, is assuming you are sub-sonic, and the calculated pressure drop is less than 10% of the inlet pressure. This the Darcy Formula and can be found in classic engineering design books such as Crane's Tech Paper #410 and Cameron's Hydraulic data.

Don't use the natural gas tables, graphs, or nomographs for sizing propane lines. It's the wrong application.

Don't forget to check for sonic flow and don't exceed the 10% rule I mention above. Good luck.

Art Montemayor
Spring, TX

 

[supaman79]

Crane's Tech Paper #410....is that the name of the text book? Also what would a typical pressure drop be for gas/propane per 100'

 

[CRG]

If this is for a commercial building or residential structure:

Take a look at the International Fuel Gas Code.

402.5.1
~ system shall be designed to either accommodate or prevent LP gas vapors from condensing into liquids.

If your are planning to design system to prevent LP gas vapors from condensing into liquids, look at Table 402.3(24) for multipliers to be used for 0.6 SG gas tables when the SG of the gas is other than 0.6.

CRG

 

[Montemayor]

Supa:

As you previously stated in thread 378-99935, you only have an AS in mechanical engineering, and you’re working on the rest (you still don’t have Fluid Dynamics under your belt). I’m going to assume you have a real world design problem in front of you and offer the following comments:

1) If you are designing a Propane gas line, you should have several courses (especially Fluid Dynamics) and some field experience in your background. No serious engineering fluid design should be done by simply taking a figure or value from a table without documenting the source and the credibility of that source. That’s why going back to basics and employing the classic Darcy equation with its applicable caveats is the formal way to go. But you can’t begin to understand what I’m pointing out if you don’t know who Darcy was and what his formula represents. There is a basic, fundamental problem here that puts a halt on the operation.
2) The correct engineering algorithm for determining the size of a gas line (natural gas, propane, chlorine, etc.) involves identifying the pressure of the gas in question and limiting the pressure drop to 10% (or less) of that figure. If you don’t do this, Darcy’s equation doesn’t apply.
3) You have other parameters that you usually have to consider, such as the maximum tolerable average velocity; this value is obtained from empirical experience or experiments.
4) Follow the outlined procedures clearly given in Crane’s Tech Paper #410 (which can be obtained through the internet); study this booklet as seriously as you can. All the information to allow you to understand the principles of Fluid Dynamics are in this booklet. That is why it would be more fruitful and practical for you to successfully complete a Fluid Dynamics course -at the very least before attempting to understand Crane’s Tech Paper or the Propane application.
5) Professional engineers don’t simply employ values taken from tables, graphs, or nomographs to solve problems. We employ Logic, experience, academic study & learning in science and mathematics, and our portfolio of prior problems resolved (successfully & unsuccessfully). That’s why we always state our basis and reasons for our solutions. Otherwise, we have no reason to believe each other on our solutions.
6) A “typical pressure drop” for a Propane gas pipeline depends on a lot of factors as I’ve mentioned above. To give you one without specifics would be analogous to giving you a blank check; I wouldn’t know what or how you would use it for.

I would love to resolve your problem, were I in your place; however, you’re the one who has to do it and all I, or any other professional engineer, can do is counsel you on how to go about it. I believe you understand that I wouldn’t work the problem for you by giving you the answer. That’s not what we do here. We merely give free advice. And my advice is to take that Fluids course (& maybe a few more) and find out about Reynolds Number, friction factors, choke flow, compressible and non-compressible flow, Newtonian and non-Newtonian fluids, viscosity effects, dimensional analysis, etc., etc..

I hope I’ve been of some help, although I believe your hands are tied without the Fluids course in your background.

Best of luck.


Art Montemayor
Spring, TX

 

[supaman79]

Montemayor,

Thank you for your detailed reply that you had just written. That must have taken some time out of your day to reply to question that's pretty basic to you. I know now that a fluid dynamics course is holding me back from answering alot of my own questions. On top of that, I appreciate you keeping me in check by having me research and think like a jr. engineer should. I would never want someone to simply come on here and just give me the answers to my questions, that would just hurt me for the future. Thanks again and I hope we can talk soon.

 

[Montemayor]

Supa:

Thanks go to you for the courteous attention and the consideration that this is all done for your benefit. Most of us on this Forum do this because, as one astute and wise engineer (Katmar) stated, "we love to solve problems". Helping out young engineers is one type of problem - but that's all it is: a problem, and one that can be resolved easily when the young engineer is willing to listen and take advice. We all have had to do this in order to accumulate the mileage and scars.

You've got the right attitude, and that's a jump start that'll put you competitively ahead of most of your colleagues when you obtain that BS in Mechanical Engineering. Good luck and hang in there.


Art Montemayor
Spring, TX

 

[CRG]

Art Montemayor, I consider myself a professional engineer and so does the state where I practice. I use tables, graphs, or nomographs to solve some problems in contrast to your comment #5 above.

I use the gas tables in the International Gas Code for sizing low pressure (0.5 psi to 5 psi) piping for gas appliances in homes and commercial buildings. I also use tables and graphs to size sanitary waste and vents for residential and commercial buildings. The department of public safety requires compliance with this code in my area. The code does allow the use of alternate means of sizing, which I use under non-typical design conditions.

In contrast, for many other types of flow calculations for piping systems, I use many of the methods outlined in Crane’s Tech Paper #410.

There are economics and experience involved in deciding the best approach to solving a problem. I too appreciate your comments Art; however, I disagree about the use of tables, graphs, etc for problem solving. The real point I believe is to know when to pull out your calculator and when to pull out a table.

Supaman79, without knowing the particular application, I would also recommend that you consider problems associated with low temperatures and condensing gases. Under some circumstances, even with low pressure gas, very high pressures can arise if the gas condenses and then warms in a blocked in pipe segment.

CRG

 

[supaman79]

I definately agree with you CRG.....I used to be under a P.E. and it was standard practice to use Mass. Gas Code to size a natural gas line.

1.) Find the longest run x 1.5 (for fittings and equipment)

2.) Add the total MBH for the job

3.) Then follow the chart to your calculated distance and max. mbh for the specified pipe size.

But in Montemayor defense, as engineers it's good to have an understanding of what you're working with, and not to rely on charts and graphs. I agree with both of you strongly (not like my opinion is as good as yours haha). My application is very simple, I'm piping to (4) Propane Unit Heaters in a warehouse, approx. 200' to my furthest unit. One question that now comes up is since I started working at my new company, we like to use propane over natural gas, what are the advantages? Cleanliness...price...effeciency?

 

[Montemayor]

CRG:

With all due respect to your standing as a registered engineer, I reply to your statement that infers that I am against the use of tables, graphs, etc.. I take this opportunity to respond solely because I can categorically state that I have never said or written any such thing.

I refer you to my statement #1: “No serious engineering fluid design should be done by simply taking a figure or value from a table without documenting the source and the credibility of that source.”

I believe the meaning of my statement is perfectly clear and stands in line with what you state also: “I also use tables and graphs to size sanitary waste and vents for residential and commercial buildings. The department of public safety requires compliance with this code in my area. The code does allow the use of alternate means of sizing, which I use under non-typical design conditions.” What you state is exactly what I have said about professional, registered engineers: we always document and reference our work – we have to. We both agree on the same issue, from what I can read. However, you don’t seem to believe that we both agree.

I don’t believe you read through all that I wrote and have taken some of what I said to mean that I don’t employ or recommend the use of information or data in the form of tables or graphs. This is not true, and I want to make sure that everyone who reads what I wrote does not interpret or assume it as such. The format in which data or information is given is not what is important when used as input to an engineering problem. The authoritativeness, authenticity, credibility, and accuracy of the data is what is of prime importance – and it should be documented or referenced to the reader. Otherwise, it is useless and not credible. As professional engineers we owe that to our clients and people who rely on our solutions. That, in specific language is what I was saying and recommending to a young engineer who asked me to pull a figure out of the air. I hope I have succeeded in explaining my position on this matter.


Art Montemayor
Spring, TX

 

[CRG]

Art,

I think we agree on most points; excluding that I think supaman79’s problem is most efficiently solved with tables and not Crane’s tech paper. When all is said and done, it is the locally enforced plumbing/fuel-gas code that dictates the available methods employed for sizing appliance gas piping for commercial and residential applications. With the additional information that supraman79 gave, I think it is overkill to use anything except tables for this problem. Why would you not use the appropriate gas code tables for sizing appliance gas piping, and instead, use an alternate method?

CRG

 

[Montemayor]

CRG:

If we refer to the original post and the second one we see that no mention is made of the application being commercial or residential. Not until the 9th post do we learn that it is probably commercial. That is why I took the application to be a common industrial plant application. If appropriate industrial gas code tables for sizing industrial gas piping existed, I would certainly use them if they were available. But I would always document the source and fully identify it.

Art Montemayor
Spring, TX

 

[pmover]

my 2-cents worth..

i, like art & mainly due to my background, presumed the application was commercial (i.e. oil & gas industry); hence, requiring the use of industrial strength knowledge, practices, etc.

yet, crg presumed otherwise, whereas other techniques (not practiced in o & g industry - likely prohibited by some firms) are acceptable by some regulatory agency. this is likely done to allow the non-engr's conduct preliminary design or troubleshooting activities.

regardless of presumption, a prudent, skilled, and wise engr would practice & implement the fundamentals. probably the main difference between the two techniques is time spent in obtaining the results, which may be nearly identical.

i trust the original poster learned a valuable lesson and will exercise good judgement in the future.

good luck!
-pmover

 

[CRG]

Art:
Please accept my apology. I did not read your response carefully, and as such, I placed my foot squarely in my mouth. As I have stated above, I enjoy your responses to many of the questions posted in this and other forums.

Looking back at the original post, I mentally merged your comment, “Don't use the natural gas tables, graphs, or nomographs for sizing propane lines. It's the wrong application” and the first two sentences of your comment #5. I still can taste the leather in my mouth.

Pmover:
In my neck of the woods, the term commercial makes reference to HVAC/plumbing engineering for commercial buildings. Engineering work in the oil & gas industry is considered industrial.

I presumed little in this thread besides my memory being accurate regarding Art’s reply. I prefaced my first response to supaman79 with, “If this is for a commercial building or residential structure:” I did not see any other thread state, “if this is an industrial facility then ….”

You may be making an assumption stating that, “I, like art & mainly due to my background, presumed the application was commercial (i.e. oil & gas industry); hence, requiring the use of industrial strength knowledge, practices, etc.” I am not sure if you are trying to be humorous with a play of words or if you literally believe that industrial engineering requires some extraordinary knowledge. You do need to be able to read and think. The majority of my work experience has been involved with industrial design, specifically piping systems (gee, I wonder how I survived in this field of work without tasting leather often.) I have not noticed superior engineers in industrial design compared to the commercial guys. I have noticed bigger egos on the industrial design side. If you are being humorous, I need to lighten up.

Lastly, regarding your statement, “a prudent, skilled, and wise engr would practice & implement the fundamentals.” A prudent, skilled, and wise engr would be able to practice & implement the fundamentals; however, using fundamentals is not always the best method to efficiently ensure code compliance. Also, in our litigious society, I prefer to use the industry standard method for calculations. Typically, gas pipe sizing for small unit heaters in a commercial warehouse, is done using the gas tables in the mandated code for the jurisdiction, both by plumbers and engineers alike. Lastly, I am impressed that you might be able to run the pipe size calculations for this type of problem and verify that it meets the code requirements in a similar time frame than I can look up the size using tabled data in the IFGC or UPC.

 

[Montemayor]

CRG:

I don't believe I deserve an apology because I truly believe that we have never differed in our logic and thinking and, furthermore, you have never insulted my point of view. We merely discussed what we believed was a difference of opinion - and that is positive engineering communication. Whether our assumptions or bases were correct or not does not take precendence over the fact that we participated in a serious engineering conversation and, as would happen when done constructively, came to a logical engineering agreement. This is, in my opinion, perfectly in line with the concepts of professional engineering.

I, on the other hand, would hope you pardon my omission of stating my assumption that the application was an industrial one.




Art Montemayor
Spring, TX

 

[imok2]

Just ran across this if anyones interested:

http://www.regoproducts.com/linesize.htm