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August 24[edit]

How strong does a pipe of water have to be.[edit]

In order for it to stand the force when the water freezes to ice, and the pipe won't crack?

The freeze-thaw cycle of water, when water becomes ice, it's density goes down, and so the volume goes up, it expands.

This is why potholes form in the winter, when water becomes ice. So this force-expansion of water to ice is strong enough to crack steel pipes and concrete. I wonder if a tungsten-pipe can withhold the force of water freezing to ice. Thanks. 12.130.157.65 (talk) 12:14, 24 August 2017 (UTC).[reply]

It's too hard to think about this as force and stress. The forces generated by ice can be very high. Instead think about designing a pipe which can absorb the dimension change of the ice, and so the strain. This might involve using a weaker pipe, that is also more elastic, or else by adding an additional expansion reservoir to the system, such as an air chamber or even a piece of crushable foam. Andy Dingley (talk) 12:22, 24 August 2017 (UTC)[reply]

Yep there already is, tygon tubing is a type of rubber pipe that can expand with the water as it becomes ice without cracking. 12.130.157.65 (talk) 12:53, 24 August 2017 (UTC).[reply]

But the common approach to this problem is pipe insulation.--Shantavira|^{feed me} 12:55, 24 August 2017 (UTC)[reply]

Or heat tape. --Jayron 32 13:14, 24 August 2017 (UTC)[reply]

Or leaving your faucets dripping (provided it doesn't get too cold). shoy (reactions) 13:40, 24 August 2017 (UTC)[reply]

If freezing would occur, you only have 4 basic choices (they may combine, though)

0)freezing is prevented, one way or another (insulation, heating, antifreeze additive...).

1)enough of the water find its way elsewhere, so volume do not change in the section of the pipe.

2)the pipe increase volume by ~10%, meaning it increases radius/diameter/perimeter by ~5%.

3)the pipe is "strong" enough to apply the pressure required to make some sort ice, different from usual ice (Ice_Ih), with higher density than water.

options "0" and "1" obviously are not the kind you have in mind, but it is the kind that plumbers practice.

option "2" is what fellow refdeskers talked about; the pipe do not require special "strength", it requires elasticity.

option "3" is doable, it requires high pressure, in the 100s MPa (= 1000s of atm) range, that industrial process routinely achieve, meaning you'll find them just your usual search tool with "high pressure pipe" keywords. This way I found 8mm diameter (1.6 mm inner diameter), stainless steel, water pipe, standing pressure >10000 bar, 426°C > temp > -198°C (note this is far below 0°C). You don't need tungsten nor titanium. Note the small inner diameter: since deformation is a % of original diameter, a smaller inner diameter means a smaller absolute deformation, easier withstood by the pipe.

bottom line: stainless steel can do it, copper certainly too. It can be done, but is NOT in practice in common plumbing, so it is probably too much expensive

Gem fr (talk) 15:00, 24 August 2017 (UTC)[reply]

"Stainless can do it" is far from a simple assertion. Ask any plumber!

First of all, how is this stainless pipe made? Continuous drawn is expensive, welded is ice-burstable in diameters that are credible in plumbing.

Mostly though, how is stainless pipe joined? For typical UK plumbing, copper would be soldered or (slightly less commonly) joined with compression fittings. Stainless is joined with compression fittings, O-ring fittings or very rarely by silver soldering. If compression fittings are a problem for a UK winter in copper, because they pop out endwise, stainless compression joints are a nightmare. The surface hardness of the pipe means that there's even less grip from the compressed olive than on a copper pipe. Andy Dingley (talk) 15:07, 24 August 2017 (UTC)[reply]

Come on, "any plumber" do not usually work high pressure. I said stainless steel can do it because i did find sellers of stainless steel pipe that can do it, period (and you could, too). This is however and obviously not common plumbing, but industrial, expensive, piping -- and of course this kind of piping wouldn't exist if there were no joints, soldering, valve, tap etc. that are also required with it. Who said it would be easy or practical? not me. Just imagine the flow you'll get from a 1.6 mm inner diameter pipe, instead of the ~10x radius usual copper pipe... Gem fr (talk) 15:40, 24 August 2017 (UTC)[reply]

When pipes freeze, they do. Nor is this about pipe in isolation, it's about a plumbing system. A leak anywhere in that system is still a leak. Putting forward "use stainless pipe" as a solution to pipe freezing is not a practical solution, compared to typical low cost domestic plumbing. Not because the pipe will split, but because it's too hard to provide a freeze-proof joint onto such pipe, because of the hardness. There's a similar problem with titanium mountain bike frames. Supposedly 6/4 Ti alloy is "better" and stronger. However it's also so hard on the surface, compared to 3/2.5 Ti or CP Ti, that threaded fasteners won't clamp onto it, and your wheels can fall off! Andy Dingley (talk) 16:44, 24 August 2017 (UTC)[reply]

Then again, as I already said, it can be done, but is NOT practical. Plumbers don't use freezing resistant piping (including tap, joints, etc.) even though this kind of stuff do exist. Plumbers deal with possible freezing through insulation, expansion reservoirs, putting pipes where it won't freeze, etc. and they do this for some reason, don't they? One of these reason is, you usually want water to flow, and it stops if freezing occurs, so freezing is a problem even if piping resist. Gem fr (talk) 10:03, 25 August 2017 (UTC)[reply]

Yep, original poster here, and agree with Andy Dingley. I asked a Physics PhD, and he says "There's a lot of work on expansion force strength. From what I've seen, 25,000 psi - 110,000 psi depending on the state of water. I think regular pipe in your home can withstand 3,000 psi. Not even close." So not even close. 12.130.157.65 (talk) 15:35, 24 August 2017 (UTC).[reply]

I actually also agree with you PhD friend, we are talking about NOT ordinary piping, as would be obvious in my answer, and his range of pressure is just the same as mine -- actually not "mine", i took them from ice -- (25,000 - 100,000 psi = ~ 1,700 - 6,800 atm). But you asked if tungsten could do the trick, well, stainless steel can. Gem fr (talk) 16:30, 24 August 2017 (UTC)[reply]

Regarding #3, if the pipe is strong enough to keep the water from expanding and the pressure increases, couldn't you get below 0 °C and have the water remain liquid? Probably most effective if you started with the pipe "full" at 4 °C (temperature of maximum density of liquid water). It would be interesting to zoom in on the upper-left corner of File:Phase Space of Ice Ih.png, and to see temperature-vs-density graphs for the liquid and solid phases. DMacks (talk) 15:33, 24 August 2017 (UTC)[reply]

What is this "freezing pipes" you speak of? I have lived in Los Angeles my whole life and have never experienced a "freezing pipe". Maybe I should ask my neighbors who took a two-hour drive and went snow skiing on the fourth of July... --Guy Macon (talk) 15:17, 24 August 2017 (UTC)[reply]

I'm from Chicago, and we have cold winters. 12.130.157.65 (talk) 15:37, 24 August 2017 (UTC).[reply]

For some reason, some weird people live in places where the temperatures are obviously unfit for human habitation. (Fellow So Cal resident here.

) Although you guys in the LA area seem to be having a rash of exploding water mains lately. --47.138.161.183 (talk) 17:48, 24 August 2017 (UTC)[reply]

Hey! We have more important things to do than fix water mains and potholes. Why we sorta kinda have a high speed rail line from Madera, a tiny town 164 miles southeast of San Francisco ("Landmarks include the notable and historic Madera water tower and a fully operational drive-in movie theater") and an almond orchard on the fringes of Shafter, 19 miles north of Fresno. ("Home of the Shafter Modified Community Correctional Facility"). That's worth billion and billions of dollars, wouldn't you agree? --Guy Macon (talk) 20:54, 24 August 2017 (UTC)[reply]

Strength of materials is a much more complex theme then this one word "Strength" insinuates. Engineers need to study years to learn how to calculate "Strength of materials". One very important aspect is how brittle or elastic a material is. The elasticity is measured in elastic modulus and indeed tungsten has one of the highest elasticities and therefor would likely be very capable to endure the expansion forced upon it as pipe material, when i contains water that will become frozen. There are however some more aspects of "Strength" and other Questions that need to be checked (preferably by an Engineer) to offer a complete conclusion about "tungsten pipes". For example I believe the prize tag on your "tungsten pipes" would prevent most application ideas becoming real. --Kharon (talk) 01:23, 25 August 2017 (UTC)[reply]

Some pipes (notably garden hoses) have a criss-cross structure that improves flexibility, but might also allow for expansion. I have seen this type of hose left in the snow without bursting. All the best: Rich Farmbrough, 18:20, 25 August 2017 (UTC).[reply]

gelatin question[edit]

Does 240 bloom gelatin have more protein than 150 bloom gelatin or is it just that the protein bonds react differently to create a stronger jelly using the same amount? 202.124.205.26 (talk) 14:09, 24 August 2017 (UTC)[reply]

Wikipedia has a short article titled Bloom (test) that briefly discusses how the number is arrived at. --Jayron 32 14:22, 24 August 2017 (UTC)[reply]

But that article doesn't cover anything about the causality of different Bloom numbers. Andy Dingley (talk) 14:41, 24 August 2017 (UTC)[reply]

Here's one relevant detail: "Bloom number is proportional to the average molecular mass"[1] DMacks (talk) 15:08, 24 August 2017 (UTC)[reply]

...which is now in the article. DMacks (talk) 15:23, 24 August 2017 (UTC)[reply]

There will be no more of this. --Jayron 32 18:29, 24 August 2017 (UTC)[reply]

The following discussion has been closed. Please do not modify it.

seriously... RTFM! You just had to read gelatin to know, so you deserve a foot in your lazy ass more than an answer. Gem fr (talk) 15:28, 24 August 2017 (UTC)[reply]

That was rather unnecessarily rude towards a legitimate question. --Jayron 32 15:32, 24 August 2017 (UTC)[reply]

And that article actually doesn't seem to answer it. DMacks (talk) 16:00, 24 August 2017 (UTC)[reply]

"The viscosity of the gelatin-water mixture is greatest when the gelatin concentration is high and the mixture is kept cool at about 4 °C (39 °F). The gel strength is quantified using the Bloom test

Actually far from rude enough for the offense. How can a question be legitimate for ref desk, when the OP didn't even look at the obviously relevant article? Gem fr (talk) 16:17, 24 August 2017 (UTC)[reply]

The question excludes both temperature and concentration as variables by the definition of the Bloom test, so your answer here demonstrates that you either don't understand the question or didn't read the articles yourself. And there's no way "deserve a foot in your lazy ass" is anything other than an unacceptably personal attack. DMacks (talk) 16:26, 24 August 2017 (UTC)[reply]

you distort reality so much ("more protein", does that exclude concentration according to you?) that your personal attack against me is just funny. — Preceding unsigned comment added by Gem fr (talk • contribs) 16:43, 24 August 2017 (UTC)[reply]

He reminded you that directly addressing another person as a "lazy ass" is not acceptable. That's not a personal attack. You should stop doing things like that. Because what you did IS a personal attack. And you will not do it again. --Jayron 32 18:28, 24 August 2017 (UTC)[reply]

The issue with molecular mass makes sense as larger molecular mass polypeptides (proteins) have more opportunities for cross-linking. Generally, the process of "thickening", whether it is gelatin, starch, gums, gluten, or whatever, involves the formation of polymer cross links. Larger polymer chains means more cross-links. --Jayron 32 16:08, 24 August 2017 (UTC)[reply]

Light concentration of a lens with a plane side[edit]

Observing water drops on my skin I wonder what effect they have on incident light. Do the concentrate the light on a single spot? Can this be more damaging to the skin? — Preceding unsigned comment added by 31.4.139.201 (talk) 18:11, 24 August 2017 (UTC)[reply]

Yes it does concentrate light on a single spot, see here. You can calculate the focal length using the lensmaker's equation. --Jayron 32 18:27, 24 August 2017 (UTC)[reply]

No, they'll slightly concentrate the light, but not by much. They certainly won't focus to a point. The reason is that they're in contact with your skin. Their focal length might be short, but it is greater than zero. For the case here, the only concentration is between the incident flux on the curved surface and the emergent flux on the skin side, which is going to be little more than the geometrical surface ratio. A web site (like the linked on) showing some geometric optics should show what I mean - if the drop was slightly above the skin, it would be a different matter. Andy Dingley (talk) 19:19, 24 August 2017 (UTC)[reply]

The effect has been demonstrated for plant leaves, where hairs on the leaf hold the droplets above the leaf surface (see https://www.livescience.com/6017-water-drops-magnify-sunlight-burn-leaves.html) and there are claims that human body hairs can similarly lead to sunburnt spots (see https://www.sciencedaily.com/releases/2010/01/100111091226.htm) {The poster formerly known as 87.81.230.195} 90.202.208.101 (talk) 21:39, 24 August 2017 (UTC)[reply]