| Author | Message | ||
     Just_ziptab |
How much pressure would be attained in a 30 foot pipe,3 inches in diameter that was full of 98°water(no air) and was heated to 171°? I'm thinking way over 1,000 psi. I ask because it was enuf to blow apart a 400 WOG brass ball valve at it's threaded joint that connects it's two body halves together. | ||
| Hex |
PV=nRT? Delta T? | ||
| Hex |
What material was the pipe made out of??? | ||
| Hex |
Here's my nephew's answer (doesn't answer your question either...) I think pv=nrt is for an ideal gas and doesn't hold so well for things like a superheated liquid with no steam (assuming that 98 and 171 are in Celsius. Given that everything else is in British units, that is well below the boiling point if in F... ) You can determine how much energy it took to heat it (I.e energy stored) from, say, 0 C (1 joule per cc per deg C as long as it is liquid, have fin converting that to British units!) and divide that by total volume (calculating from 98 to 171 gives you pressure change), I think (not sure, but the units work). Depends a lot on if that is C or F temperatures, as in C you need to see if it will just convert to steam before bursting, too (doesn't sound like it!) I dunno off hand. Try google? Tired now, good night! | ||
| Just_ziptab |
The pipe was simple schedule 40. The temperature is in F° and it really had tallow in it,not water,but I figure water would be easier to to use as a factor. The pipe was heated beyond what we needed because an external heat trace went ballistic. Just something that went wrong at work the other day in a transfer pipe. (Message edited by just_ziptab on October 29, 2009) | ||
| Oldog |
We have seen this in chemical feed lines at plants that were built by my employeer If you have a copy of machineries hand book look there, If I get a chance I will check, in the past it was liquds trapped in a pipe between 2 valves, or a ball valve and a good check valve, in the case of a check we drilled a small hole in it or scratched the seat, minute leakage rate but enough to prevent what you are describing, in our case the valve was a 3 piece stainless ball valve and the pipe split open | ||
| Drfudd |
this is a more complicated question than what it seems. first you need to know the thermal expansion of water, I have no idea what tallow is so I'll use water. which is ~250x10^-6/K you need to convert the temperature differential of 73F into Kelvin or C. which is 22.7 K. volumetric expansion is delta V = V original times coefficient times temp diff. so delta V = 6.129 cu inches. now you need to know the compressibility of water or bulk modulus which is about 3.12 x 10^5 PSI = differential pressure / (delta volume/initial volume) where as differential pressure = E times (delta volume/initial volume) = 1770 PSI so its alot. that is assuming Tallow is similar to water, which it probably isn't, and also assuming you had no air volume in the cylinder at all, and also assuming the schedule 40 pipe didn't deform, which depending on the material it may or may not. Also assuming the temperature increase didn't expand the pipe, which it does, its assuming a lot of things really. hopefully that answers your question, I work with pressures all day long at work we have a 3000 psi air line in the building, very small and thick. we also have a few high pressure test units that can reach 20,000 psi, it uses water because water is the easiest to compress to high volume since its largely incompressible, but in reality it isn't since I just showed that. (Message edited by dr.fudd on October 29, 2009) (Message edited by dr.fudd on October 29, 2009) | ||
| Xbmacon |
http://en.wikipedia.org/wiki/Tallow Tallow is a rendered form of beef or mutton fat, processed from suet. It is solid at room temperature. Unlike suet, tallow can be stored for extended periods without the need for refrigeration to prevent decomposition, provided it is kept in an airtight container to prevent oxidation. Rendered fat obtained from pigs is known as lard. Industrially, tallow is not strictly defined as beef or mutton fat. In this context, tallow is animal fat that conforms to certain technical criteria, including its melting point, which is also known as titre. It is common for commercial tallow to contain fat derived from other animals, such as pigs or even from plant sources. ------ That being said, properties would be different than water I would assume. (Message edited by xbmacon on October 29, 2009) | ||
| Brinnutz |
42 | ||
| Sleez |
thermal expansion of tallow; ml/g Deg C 7.26 X 10^-4 Handbook of food science, technology, and engineering, Volume 1 By Yiu H. Hui | ||
| Vtwinbuell |
One missing piece of information to the calculation. How far below the top of the water was the valve? Assuming celsius and the container was sealed at 98 degrees at atmospheric pressure of 0 psig. Also assuming the water was heated evenly. If the pipe was vertical and the valve was at the bottom, making a 30 ft difference, then the answer is the pressure that water boils at, at 171 degrees(about 118 psia or 133 psig) plus about 16psi for the depth of 30 feet. So the answer is 133 + 16 = 149 psig plus or minus a few psi, real life never matches calculations exactly. The valve had a problem, it should handle far more pressure than that, I'm sure it looked like a lot more than that with all the steam that would have been created by the superheated water. reference: http://www.engineeringtoolbox.com/boiling-point-wa ter-d_926.html Sorry if I lost anyone. John | ||
| Fast1075 |
The valve failed from hydraulic pressure caused by the expansion of the fluid...there was no head space...expansion overpressured the valve...the failure pressure of the valve should be at least 3 times the safe working pressure... There is no way that the air (if it had head space) could expand enough to fail the valve at the temperatures encountered. I work in refrigeration...we periodically see rupture failures...invariably caused by hydraulic stack... | ||
| Jramsey |
The volumetric expansion of liquid tallow is linear with temperature and is 3-4 times that of water. No wonder the valve failed. | ||
| Hootowl |
I'm pretty sure Sched40 PVC is not rated for that temperature. That could be the cause of the failure. CPVC is rated for higher temps, and is commonly used for hot potable water piping. Regular PVC is not. | ||
| Alchemy |
It wouldn't be sheep tallow would it? | ||
| Skinstains |
6 | ||
| Fast1075 |
He didn't specify the material...I assumed it is schedule 40 steel AKA black iron pipe. Rolled, welded mild steel. Get some self regulating heat tape...it is expensive, but is failure proof...self limits to around 90 degrees farenheit...depending on type selected. (Message edited by fast1075 on October 29, 2009) | ||
| Just_ziptab |
Yeah,I didn't clarify. It is steel pipe used to transfer beef tallow from tank to tank and will see maybe 60 psi in operation. The pipe was a horizontal run between tanks and has automatic, pneumatic operated ball valves($900.00 each!) and centrifical pumps(like an automotive water pump,only bigger).They are computer controlled to transfer tallow via tank level sensors. Max tank level could be as much as 190 inches if the valves closed on a fully full tanks. Pretty neat home grown system for ten tanks that temper and cool the tallow to our needs. It has a total capacity of about 300,000 pounds.......and the pipe work is way over built for what it does. We were blowing out 4 bolt flange gaskets and I told "them guys" something was very wrong.Dudes,your either turning close the ball valves too early while the pump is still running and trapping dead head pressure or the heat trace is expanding the cool tallow and making a hydraulic bomb........or both. Nobody would believe me till the manual safety ball valve was closed for the evening. I missed seeing it blow by about a minute. Splatter zone was about 30 feet. We were using the high priced stainless armored self regulating heat trace and it wasn't getting hot enuf when the weather cools down..............plugged pipes on occasion. Went to another style of heat trace(expensive again)(240 volts) that requires a thermocouple to turn on or off the heat trace.What happened was the thermocouple was exposed to ambient air because the insulation wrap wasn't finished in testing the whole system. The thermocouple "thought" the pipe was too cold and poured on the heat. They wrapped it yesterday and the temp is now "controlled". I added a 8'x3" capped stand pipe to a tee in the system to absorb the expansion yesterday too. No blowouts today. I knew I could count on you guys here to show your talents to my non Buell question. What a great and diversified group! | ||
| Hootowl |
I'm in the plastics biz, so that was the first thing I thought of. Narrow thinking strikes again. | ||
| Gohot |
I like Pie. apple pie.....  | ||
| 99savage |
Got my "Mark's" out - Can't find a coefficient of cubic expansion (1000a''') for Tallow BUT found for: Olive oil= 0.41 and my favorite Rapeseed oil = 0.50 which are WAY different than: Water = 0.115 oils expand a LOT more than water have to go out - will attempt the cyphering when I get back} | ||
| Petereid |
You should ask Erik.....he knows everything and has a little time on his hands these days  | ||
| Just_ziptab |
On my other hand,we had a dry transfer pipe that was not put into service yet,just pressure tested with air to look for leaks in the welds. It's flange gasket also started to leak. The flange bolts were loosened and it spewed tallow out for a bit.The 65 foot feed line to it had so much pressure from the same cause that it leaked past it's closed ball valve seat.Yeah,I'm thinking 1,700 could do that. Oh well,the system has been "proofed" way beyond it's design intent. | ||
| 99savage |
Raining & did the ciphering Might have made an algebraic mistake but my logic is good. If the pipe was made of infinitely strong material the pressure would have exceeded 38,000lb/in^2 Did it on a spread sheet - if anybody wants to drop me a PM - will send a copy - feel free to throw rocks at it | ||
| Skinstains |
7 | ||
| Just_ziptab |
I'm thinking we should probably put an alarm on the system that reads pressure and shuts down the heat trace if it sees beyond what is normal. You just know that someday the thermocouple will fail and send the pressure to the roof again. You guys are pretty damned crafty with your understandings of formulas\calculations..............all I got to work with........ is to apply common sense and logic from different experiences............  |
