Expansion Loop Design 3

[Rigs01]

I am modeling an expension loop for steam distribution lines. What are the most fundamental steps that I need to take in order to complete a table of standard dimensions?

I have a Caesar II model that I intend to resize to generate different case scenarios and create a table. However, I'm not confident on using only the Allowable stress shown in Ceasar II.

How do I select Pressures and Temperatures in order to comply with ANSI classes?

thank you in advance

 

[BigInch]

Look at ANSI B16.5

http://www.engineeringtoolbox.com/ansi-flanges-pressure-temperature-d_342.html

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[pennpiper]

You did not indicate your level of training or your years of experience. However because you are asking this specific question it seems that you may be somewhat new ti the piping game.
How many "Tables" do you intend to create?
The variables include:
- Line size
- Line Material & Coefficient of expansion
- Wall schedule
- Line Operating Temperature
- Pipe Support spacing
- "L" Distance (Distance between Anchors)
- The available space for the "h" (height of the Loop)
- Extenuating circumstances

 

[MJCronin]

You state:

"What are the most fundamental steps that I need to take in order to complete a table of standard dimensions?"

What does this really mean...?

In any professional forum, it is always a good idea to clearly state the goal that you are trying to achieve.

When the poster is confused about his goals, or has little command of the language or syntax, we all have play the long and boring "eng-tips guessing game".

Are you trying to develop a standardized table of standard expansion loops for steam systems ?

This particular topic has been explored and explained by others some 50 years ago...

-MJC

 

[Rigs01]

Yes I'm new at this. Most of what I know is what I learned in school (Mec Eng).
Regarding all the variables, I have 3 pipe sizes, 2 schedules, one material, 2 heights H (available from manufacurer) and a conservative estimate of extenuating circumstances.

I intend to run models with different distances between anchors (L) and different distances between T-supports and guides (following existing patterns). And do this for each of the other variable that I'm considering.

I'm working on the first model, and what I don't know is if the allowable stress shown in Caesar II (after setting the material, the code B31.3, and the temp. and pressure) should be my guide for acceptable design.

And I also would like to know how to design according to ANSI 600, 900 and 1500 for saturated steam if I have the system pressures (and corresponding temperatures from steam tables).

thank you.

 

[BigInch]

You have to take the pipe and material catagory and cross reference that with the stress allowables for the temperature ranges you find in the code for that particular material.

I don't use Caesar, but I would think it already knows what those are.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Rigs01]

Thank you BigInch.
Now, if I consider a pressure of 1100psi for saturated steam, this corresponds to a temperature of 556 F. If I intend to use ANSI 600, entering the table based on my temperature, I would have these values
T1= 500 F, P1= 1200 psig and
T2= 600 F, P2= 1095 psig).

Should just interpolate to find the desig conditions as:
T=556 F, P=1141 psig ?
I appreciate the help.

 

[BigInch]

Yes I see that.

You can interpolate for allowable stresses between temperatures shown, but you CANNOT extrapolate for allowable stress past the lowest or highest listed temperature. Those are the absolute minimum and maximum temperatures in the entire temperature range for which a given material can be used.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[LSThill]

Attach may help you



L S THILL

 

[LSThill]

also loop lage

L S THILL

 

[Greg1920]

A high pressure steam system is very dangerous. Ensure that all the work you are doing is properly checked by an experienced engineer.

Usually your company would have a piping spec which is being used for steam systems. This piping systems would contain the maximum allowable working pressure and temperatures for the system. In Caesar you want to put in the highest temperature and pressure that your pipe will see.

As to what conditions will limit the distance between your loops in addition to stress you want to look very carefully and your anchor loads and displacements. Talk to your civil engineers to see what is the maximum loads they can handle on their pipe rack. Also make sure your shoes are long enough and strong enough to handle the displacements and imposed forces

Do not forget Friction. Even in a system where the anchor is balanced on each side you must assume at least a .1times static load frictional force per support from your loop to your anchor to take into account that the piping on one side of you anchor is going to slip first.

Also you must take into account possible slugging that will take place in the steam line. Condinsate induced steam hammer can cause the steam lines to fail and slugging can knock large lines off of pipe racks. Talk to your process engineers to obtain sizes and velocity of slugs and calculate loadings. Add these loadings to your anchor loads and talk to your civil guys again to ensure that they can design for these occasional loads.

There are quite a few more details to consider when designing steam lines and the consequences for failure are deadly. Again I will say ensure that your work is checked and remember that Caesar II is just a advanced calculator and does not ensure good engineering design.

 

[DSB123]

Greg1920
By your last remark " Caesar II is just an advanced calculator" it seems to suggest that if you know how to use the software this does not mean you are a Pipe Stress Engineer (joking). I like you consider these software packages as "tools" to aid the piping engineer but there are a vast number of people out there who think because they know how to use the "calculator" without the experience are proficient Pipe Stress Engineers.

 

[Hansito]

Rigs01:

Tables for loops is a very oldfashioned option byt it is very good that you try to provide preliminar information for the piping layout personal.

For me the main variables will be the structure dimension: if is a pipe rack, that will be the width and the lenght, the máximo loop leg will be similar that lenght , you can hanging around 1 meter or something like that.

You should define some porticals to group the loops.

Hot lines should be located at the sides to provide bigger leg and this way minimize the number of loops.

Anyway, independ on your previous steps, once you have the final layout with all loops you still need to reestudy all the lines individually. You always may be questioned about the quantity and dimension of loops, mainly quantity, so you need studies to show, these studies shouldn't show a very low thermal stress because this could suggest an overdimensioned number or loop dimensions.

I hope this add something to sevaral good answers to your consult I've seen from the other coleagues.

Remember estimate all the anchor loads and passed as son as you can to the civil/structure departmant as well.

REgards,
Hansito