Freezing pipe physics

[Cap'n Refsmmat]

In my neighborhood here in Texas we have the water flow valves to each house above ground, apparently due to some building code. This means that, of course, the valves freeze over the winter and start leaking water everywhere.

 

So, a question: Suppose I were to take a very strong pipe and freeze the water in it. Would it break just as easily as a weak pipe would, since water will expand as it freezes regardless of its container, or would it withstand the force?

 

I was thinking two things could happen: the strength of the container would mean increased pressure on the water as it started freezing (since it would try to expand and fail), meaning more energy would be required to freeze the water and break the container; or, the freezing water would merely extrude itself along the insides of the pipe rather than breaking it.

 

Which explanation makes the most sense, or would each pipe break at the same time?

 

(We actually put a fake plastic rock over our valve to help protect it from the weather, and that seems to have saved us.)

[doG]

I seem to remember reading somewhere that the expansion force of freezing water exceeds 100,000 PSI....

[swansont]

Ice is going to have a value of Young's modulus that tells you how much force it exerts while expanding, or how much force you need to exert to keep it form expanding. The weak pipe breaks first.

[insane_alien]

you have a few options to combat this.

 

1/you have an infeasibly strong(and expensive) pipe and valve that can withstand such forces.

 

2/you have a pipe and valve made from flexible materials that can accomodate the expansion, downside is that they will have unacceptable performance when in normal use (valves will not be able to fully close).

 

3/ you use insulation.

 

as to your point about extrusion along the pipe, that is possible but frictive forces make the expansion very very slow. the pipe breaks before the pressure decreases sufficiently.

 

you would also suffer from very low water pressure when the thaw comes. turning on a tap would suck air in rather than let water out.

[cameron marical]

hmm. then a very strong pipe wich wouldnt break by the expanding water would also stop water from freezing due to the fact that it cant expand?

[insane_alien]

hmm. then a very strong pipe wich wouldnt break by the expanding water would also stop water from freezing due to the fact that it cant expand?

 

no, the water would still freeze it just wouldn't form normal ice. infact, theree are several types of ice that are denser than liquid water. these types of ice form in exactly the situations present in the scenario, high pressure.

[cameron marical]

but i thought that you cant compress water? well, you can, but it then gets to atomic changes and stuff, right?

[swansont]

but i thought that you cant compress water? well, you can, but it then gets to atomic changes and stuff, right?

 

 

That's liquid water, and nearly incompressible means that a very large pressure is needed for a very small reduction in volume (or, conversely, a very small increase in volume will drop the pressure dramatically)

[CaptainPanic]

http://en.wikipedia.org/wiki/Ice

Wikipedia shows a list of all known forms of ice. The ones that are described denser than water are formed at pressures above 300 MPa, or 200 MPa at very low temperatures.

 

300 MPa = 3000 bar

 

Ordinary pipes will not withstand such a pressure... so from a practical point of view, the answer is that the ice will expand regardless of the pipe you use.

Of course, pipes exist that can actually withstand this - you just don't want to buy them for normal houses.

 

I think the solution lies in allowing the ice to expand along the lenghth of the pipe, or to use flexible materials. I haven't investigated the solution for this post (just the properties of ice).

[swansont]

There's always the option that the water won't freeze completely if the pressure is sufficiently high. i.e. you form a small amount of ice and the pressure increases to the point that no more freezes. The phase diagram line separating solid and liquid has a negative slope, so water under pressure freezes at lower temperatures.

[Cap'n Refsmmat]

So basically you'd have to make it a bit colder if you wanted to freeze a stronger pipe?

[swansont]

So basically you'd have to make it a bit colder if you wanted to freeze a stronger pipe?

 

That may be required.

 

The weaker pipe breaks first because the water can freeze at a higher temperature and expand, while in the stronger pipe the ice takes longer to form because more heat transfer has to take place. It may break, too, depending on the conditions, but the strength definitely does matter. There will be conditions (identical for both pipes) where the weak pipe breaks, because the water froze, and the strong one does not, because the freezing was incomplete.

[alan2here]

I seem to remember reading somewhere that the expansion force of freezing water exceeds 100,000 PSI....

 

Therefore you could use freezing water to bend or destort things in industry that you want bending that are resistant to physical force.

 

Could take a lot of energy getting things cold enough.

[Kardia]

On the other hand, steel pipes (or cupper) get brittler (sp?) in low temperatures. It must be a really thick pipe to handle 100 KSI.

[north]

In my neighborhood here in Texas we have the water flow valves to each house above ground, apparently due to some building code. This means that, of course, the valves freeze over the winter and start leaking water everywhere.

 

obviously

 

but to help this , use a heater water line and wrap this heater line with some sort of insulation

 

So, a question: Suppose I were to take a very strong pipe and freeze the water in it. Would it break just as easily as a weak pipe would, since water will expand as it freezes regardless of its container, or would it withstand the force?

 

no

 

a weakness in any pipe , is a weakness period

 

I was thinking two things could happen: the strength of the container would mean increased pressure on the water as it started freezing (since it would try to expand and fail), meaning more energy would be required to freeze the water and break the container; or, the freezing water would merely extrude itself along the insides of the pipe rather than breaking it.

 

depends

 

look say you a foot of pipe filled with water and then allowed the water in this pipe to freeze , with no escape at either end . the odds are that the pipe will burst , whether it be copper or iron ( I know that copper pipe will , seen it many times ) iron hmm... maybe , maybe not , but the pressure would be enormous

 

now if the the pipe is open-ended the ice will expand as far as it can go , along the length of the pipe

 

Which explanation makes the most sense, or would each pipe break at the same time?

 

no

 

above

 

(We actually put a fake plastic rock over our valve to help protect it from the weather, and that seems to have saved us.)

 

the fake rock was just enough to protect the valve from the cold

 

by the way I live in central Ontario , Canada

 

what you describe is par for the course up here , nothing new!!!!

 

we can get too minus 20 , 30 and sometimes 40

Edited March 18, 2009 by north

[alan2here]

An open ended pipe would presumably due to the presure of ice expanding against ice and delay caused by not everything happening at once still result in some extra presure.

[north]

An open ended pipe would presumably due to the presure of ice expanding against ice and delay caused by not everything happening at once still result in some extra presure.

 

define " open ended pipe "

 

because really your not making sense

 

an open ended pipe , means to me that the ice will travel along the length of the pipe , and does so because there is no blockage along the length of the pipe , rather than expanding outwards , towards the sides of the pipe

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bascily if you use wrap insulation around your piping that is exposed to the enviroment , you should be fine

 

keeping the wind , especially , OFF your exposed pipes is essential

[alan2here]

define "open ended pipe"

 

...

 

An open ended pipe, means to me that the ice will travel along the length of the pipe, and does so because there is no blockage along the length of the pipe

 

Except there is more expanding ice in the way causing some presure against the walls of the pipe but not as much as in a pipe with closed ends (I guess like most real world pipes). Don't ask me to define something then emediatly go on to define yourself.

[north]

Originally Posted by north

define "open ended pipe"

 

...

 

An open ended pipe, means to me that the ice will travel along the length of the pipe, and does so because there is no blockage along the length of the pipe

 

 

Except there is more expanding ice in the way causing some presure against the walls of the pipe but not as much as in a pipe with closed ends (I guess like most real world pipes).

 

of course

 

 

 

Don't ask me to define something then emediatly go on to define yourself.

 

it just occured to me that .... upon further thought ....