Maximum pressure in a rubber pipe

[nixy]

TL;DR Summary

What maximum pressure this silicon pipe would withstand? ID=1mm, OD=4mm

What maximum pressure this silicon pipe would withstand until blowing up? ID=1mm, OD=4mm, no cord or anything like that in the pipe, pure clear silicon.

 

[Baluncore]

Welcome to PF.

Silicon metal, or silicone a polysiloxane.

https://www.researchgate.net/post/Silicone-Tubing-Working-and-Burst-Pressure

 

[jrmichler]

Not completely relevant, but here is what happens when a piece of flexible vinyl tubing is used in a water line. Pressure is whatever their well pump puts out, probably about 40 PSI. They said it's been working for a month. I really do not understand why it continues to survive. Picture taken last month in a local greenhouse.

 

[nixy]

Thank you both. According to the formula in the link burst pressure should be around 70 bar (1000 psi) for my pipe. For the 1" PVC pipe in the picture it should be around 20 bar (300 psi).

(corrected the number, thank you)

 

[Baluncore]

According to the formula in the link burst pressure should be around 70 bar (300 psi) for my pipe.

That surprises me. I would expect about 50 psi. I think you are out by two orders of magnitude.

PS; 70 bar is closer to 1000 psi.

 

[nixy]

Thank you, corrected the psi figure above. I'm using the formula from the link above. Do you think it's wrong?

 

[Baluncore]

Do you think it's wrong?

I suspect the grade of the silicone material may be different to that specified.
I often work with several thousand psi in hydraulic circuits, so I wonder why, if the figures are right, all the hoses have not been replaced with un-reinforced silicone.

 

[nixy]

Are yours 1mm ID / 4mm OD or significantly different?
Then I guess working pressure should be, say, 1/10 of the burst pressure as a safety measure.

 

[Baluncore]

Steel lines for pressure measurement are closer to 1mm ID / 4mm OD.
High power requires that high pressure be multiplied by high volumetric flow, which needs bigger diameter lines, which have lower maximum pressure specifications, and bend less around corners.

If a balloon is inflated at a fixed volumetric rate, the radius rises with time. The pressure inside the balloon falls due to the change in curvature of the membrane. I wonder if there is a similar effect on rubber tubes.

A different situation occurs when the pressure is gradually increased, with no regulation of volume. There will come an applied pressure where the membrane stretches faster. That would define the burst pressure of a rubber balloon.

I don't know how the PV of spherical balloons compares to the PV of long cylindrical balloons, or clear vinyl tube, CVT.

 

[jrmichler]

In Post #4, the OP is apparently confusing vinyl with PVC. Vinyl tubing is NOT PVC pipe. The photo below shows three pieces of vinyl tubing and two pieces of PVC pipe. Vinyl tubing is not rated for pressure, while PVC pipe is.

Also, The Engineering Toolbox.com lists maximum operating pressure of 1/2" PVC pipe as 358 PSI, and 1" PVC pipe as 270 PSI. That's at 70 deg F. They also show the temperature derating for various types of plastic pipes. Note that PVC loses significant strength at only 90 deg F.

The question was raised about silicon vs silicone in Post #2, and not answered. Note that many materials are available in different grades, as alluded to in Post #7. Given the number of different types of metal and plastic tubing, the OP really needs to verify exactly what material and grade of tubing they really have in order for us to give useful advice.

 

[nixy]

I guess it's the same effect as with inflating balloon with gradually increasing pressure (see the picture).

Unless I'm (and Wikipedia is) mistaken Vynil == PVC (when talking about pipes). It could be coloured or clear, harder or softer, with or without additions. Could also be pressure rated.

Obviously I am talking about rubber not metal as per the subject.

 

[Baluncore]

I guess it's the same effect as with inflating balloon with gradually increasing pressure

Should the pressure rating for that balloon be the 1.023 atm peak, or the final lower 1.008 atm burst pressure of the bigger balloon.

 

[nixy]

On the shown image around 1.023. However that's a great question indeed... After all it bursts at 1.0008.... so that should be the bursting pressure

Here it shows a different curve with bursting pressure going off the chart.

 

[Lnewqban]

... Unless I'm (and Wikipedia is) mistaken Vynil == PVC (when talking about pipes). It could be coloured or clear, harder or softer, with or without additions. Could also be pressure rated.

This link shows different rated pressures according to tube material:

https://www.mcmaster.com/products/tubing/id~1mm/

 

[nixy]

This link shows different rated pressures according to tube material:

https://www.mcmaster.com/products/tubing/id~1mm/

I've entered details for the above pictured PVC pipe under pressure and got 15psi. Sounds about right. If it's indeed used with 40psi that'd explain the severely swollen shape. Still well below burst pressure and it will survive for some time.