The pressure rating dictates the thickness of the body of the flexible joint - depending on what type you are using. This is a manmufacturer's problem.
Length & temperature are used to determine the axial movement that will occur.
The expansion due to temperature is: -
delta (L) = alpha x D(t) x L
where delta (L) is the change in length due to a temp difference (metres)
alpha is the coefficient of thermal expansion
steel 11.9 x 10^^(-6)
PVC 7 x 10^^(-5)
PE 18 x 10^^(-5)
D(t) is the change in temp (degree C)
L is the original length (metres)
You will have to make an allowance (over & above) the thermal movement for the total length of the flexible joint, to allow for an axial misplacement.
Some joints (like the Straub coupling) will only take a max axial movement of (say) 15 mm without a cover plate (bridging the gap), & up to 65 mm with a cover plate.
First of all, contact all of joint suppliers & find out what is available & what is applicable for your pipe material, movement, temp range, fluid within the pipe etc etc.
Another thing to remember, flexible joints allow for an axial movement but some are VERY susceptable to a displacement at right angles to the axis of the pipe. Look carefully at the manufacturer's literature for ANY limitations due to misalignment etc.
It concerns me a great deal when I see someone outside a given discipline field ask a question about that field unknown to him and do it poorly. Then another person from outside the given field submits answers that may be wrong.
In the case we have here we have someone from the Electrical field (not Piping) who submitted a Piping question that is not clear in its intent and lacks any detail as to a real world Piping problem.
Then we have a person from the Civil field (not Piping) who proceeds to give Piping answers that may or may not be relevant. May or may not be relevant because we do not know what the real question is.
Swng (Electrical) Please explain what the problem is. Give us some background about the piping system. The size, the wall schedule, the material, the temperature, the configuration, what the pipe is connected to on both ends, etc.
BarryEng (Civil/Environme) Your information, although it may be correct, may not be right. Right for SWNG's problem and there is a difference. I suggest we should wait until we have more information.
There is nothing more dangerous and irresponsible than persons outside their given fields of expertise giving advice to others.
So sorry for unclear question from me,
You are say right I'm not mechanical eng. sometime make you annoy, in reality some time I face the problem with mechnical issues, I also guess you will face electrical problem sometime then you may be ask the question about electrical issues, for me it is normal.
my question is I was install the carbon steel pipe.
sch.10 the length about 100 meters. for compress air.
Do I need to install expansion or flexible joint. If yes how to install? every 50 meter or how to consideration about this matter.
I agree with Penn,
Please leave the issue to a piper.
Maybe he can eliminate the bellows(that is the best practice)
Is the air so hot You must use exp. joints?
To pennpiper
You said above 'There is nothing more dangerous and irresponsible than persons outside their given fields of expertise giving advice to others'.
I have designed hundreds of km of pipelines (in many countries) up to 2 m dia both below ground & above ground pipes (some over 40 m spans) & in many pipe wall materials (some buried pipes with surface loads of 250 T haulpaks). I have designed flexible joints for these pipes in steel & stainless steel. Recently I designed a 2 m dia stainless steel above ground pipe for compressed air at temperatures up to 90 deg C. I have also served on standards code committees for many pipe materials & methods of pipe design.
I'm curious - how did you come to your conclusion above, from my previous thread?
swng,
You wrote:
"my question is I (must) install the carbon steel pipe.
sch.10 the length about 100 meters. for compress air.
Do I need to install expansion or flexible joint. If yes how to install? every 50 meter or how to consideration about this matter?"
You did not tell us the size of this pipe. I would guess that being it is for compressed air that it is not larger than 2" NPS.
You did not tell us if there are any branches from this main line or if any what are their sizes, the quantity and spacing.
As for the use of expansion joints in this service I say NO! You do not need or want expansion joints in this line.
You did not tell us the temperature of the air but normally compressed air is relative cool. You did not tell us if this line is indoors or outdoors. If indoors then the line should remain relative cool and have very little expansion. If the line is outdoors and in an arctic location then it will tend to contract during real cold weather. If the line is outdoors and in a very hot climate then the line will tend to expand during the day from the heat of the sun and contract during the cool of the night.
This is not new, it has been going on in piping systems for a long time. Take a look at some of the other "cool" system piping already installed.
Any expansion or contraction of a piping system such as the one you have can normally be handled by a more flexible pipe routing. If there are any branches just make sure that there is flexibility build into each branch.
