# When will a Pipe Burst

## Main Question or Discussion Point

I want to know when a pipe will burst i have attached a img wear the out side of the pipe has 1000 psi around it the inside should be lets say 25 pounds higher, does this mean i am putting 25 psi on it or 1025 psi. thanks for yalls help

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Your concern is in the difference in pressure.

jack action
Gold Member
Not an expert in the field, but I would consider the hoop stress with 25 psi (acting tangent to the pipe) added to the compressive stress with 1000 psi (acting radially). It seems to me that even if the pressure differential was 0, if the surrounding pressure is high enough, the material will deform and break just like putting dead weight on a flat surface.

Thanks for both of yalls help, if I understand jack action correctly the psi rating of the pipe is one thing but the pressure at which the material the pipe is made fails is another. I am looking into some poly pipe, how would I go about finding out this fail point for this product and is there a name for this fail point. It is confusing to me because there is a burst psi rating and that is what most people want to talk about I am just trying to educate myself before I talk to these pipe manufactures.

Also another concern I have is the tensile strength of the pipe I plan on running 1000 feet of the pipe straight down. The pipe weighs 1.38 per foot, the inside diameter of the pipe is 2.004, the weight of the fluid inside the pipe will be 9.0 ppg. The capacity of the 1000 foot of pipe would be 655.4 gallons. 655.4 x 9.0 ppg = 5898.6 lbs. Do I have to account for the weight of the fluid in the pipe?

jack action
Gold Member
The way I look at it, if you «unroll» the pipe lengthwise, you will end up with a rectangular flat piece with 1000 psi on one side and 1025 psi on the other. I can't believe that this is, stress-wise, the same as having, say, 100 psi on one side and 125 psi on the other.

If your pipe is suspended, like your drawing seems to show, the stress caused by the weight of the pipe will have to be considered if it is large enough. That stress will decrease as you go down the pipe length.

The weight of the fluid wouldn't be relevant, as your system seems to be vertical and the pipe has an open bottom end.

If you are worried about the pipe bursting, then, as Pkruse said, you are concerned with the difference in pressure between the inside and outside of the pipe in question.

As Jack_Action said, putting too much pressure on something will cause it to deform and probably fail. However, I doubt you'll find many applications where you will cause the structure of a pipe to fail due to high combined internal/external pressures, with low or null differential, over failing at fittings and the like.

As for your other concern, the fluid will not pull appreciably on the pipe for you to worry about tensile strength. However, you should certainly take care to stabilize the run of pipe. Fluids are dynamic, and you don't want to let a 1000 ft run of pipe go unsupported. You will, however, have to take the weight of the water into account for sizing supports, assuming there is an elbow or something which the weight of water will push against at the bottom of the 1000 foot run.

edit: if your pipe is open at the end, then the water weight will have virtually no effect on the tensile stress of the pipe. I wouldn't worry about that beyond sizing vertical supports.

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