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7 inch 90 degree elbow
- Thread starter mechbadem
- Start date
You'll have trouble finding 7-inch pipe too, but if you have some, you can do induction bends and get to 5D radius. I would say that that is your best bet.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
btrueblood
Mechanical
7 inch is not a standard pipe size, so you will need somebody to custom fabricate it for you. Why must it be seamless - this really limits your options?
racookpe1978
Nuclear
I'm wondering at what point he will find it cheaper to machine a 7 inch elbow out of 3x solid bars. You'd throw away a "lot" of chips, and would have to weld the three 30 degree sections together (30 degrees so the milling machine could cuut the interior adequately to approximate a true curve )
racookpe1978
Nuclear
Then again, a "seamless" machined pipe from sections could not have welds joining the three section together either .... 8<(
- Thread starter
- #9
Seamless is a dealbreaker here. our client will use them in a piping line while chatting with their inspector he told me that smoothness is very important for this project. I could also remember that from fluid mechanics. But, when i told him it is impossible to find he replied, italy, germany, egypt, czech republic everyone have it.
I want to ask you, my colleagues, this, it is possible to make a 7'' pipe from plate then fully RT it then bend it. in this situation maybe this type of welding and cold work would cause a lot of residual stress then we need to normalize it ( i am a freshmen mechanical engineer just got out of school and started working, if i sound ridiculous, forgive me
)
I want to ask you, my colleagues, this, it is possible to make a 7'' pipe from plate then fully RT it then bend it. in this situation maybe this type of welding and cold work would cause a lot of residual stress then we need to normalize it ( i am a freshmen mechanical engineer just got out of school and started working, if i sound ridiculous, forgive me
)
LittleInch
Petroleum
Are your really sure this is 7" nominal bore pipe? Not the ID of an 8" pipe?
Seven inch does not appear in any of the current ASME codes 36.10, 16.9 or API 5L as a standard size and I've never heard of it.
Perhaps just ask nicely for any suppliers your client has used in the past.
It is possible to make anything, but a one off cost will be huge as it either has to be machined from a solid block or made specially unless you happen on someone who makes this very odd size regularly.
Is this an existing plant / pipe or new design or what? what code does the pipe specification call up? what material is it made from? what wall thickness are you looking for? Is this a long radius elbow or a bend?
Perhaps you could get an 8" elbow with very high wall thickness to get your nominal ID of 7"
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
Seven inch does not appear in any of the current ASME codes 36.10, 16.9 or API 5L as a standard size and I've never heard of it.
Perhaps just ask nicely for any suppliers your client has used in the past.
It is possible to make anything, but a one off cost will be huge as it either has to be machined from a solid block or made specially unless you happen on someone who makes this very odd size regularly.
Is this an existing plant / pipe or new design or what? what code does the pipe specification call up? what material is it made from? what wall thickness are you looking for? Is this a long radius elbow or a bend?
Perhaps you could get an 8" elbow with very high wall thickness to get your nominal ID of 7"
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
I suspect that LittleInch is correct and it is not a 7" NB pipe and once you find the correct spec you will easily be able to purchase what you need.
But the point I want to raise is in regard to the requirement for "smoothness". The only advantage of seamless vs welded in terms of smoothness would be the weld seam on the inside. The cost of grinding and polishing that seam would be small compared with having custom units fabricated, and 7" is large enough to be able to polish inside easily. Do you have a requirement for very high hygiene standards? This is unusual in a relatively large pipe - it doesn't sound like a pharmaceutical plant.
If the requirement for smoothness is because of friction then you need to point out to them that the pressure drop caused by the change in direction through an elbow far outweighs the friction against the surface - and in any case the difference between welded and seamless pipe would be unmeasurably small.
Katmar Software - AioFlo Pipe Hydraulics
"An undefined problem has an infinite number of solutions"
But the point I want to raise is in regard to the requirement for "smoothness". The only advantage of seamless vs welded in terms of smoothness would be the weld seam on the inside. The cost of grinding and polishing that seam would be small compared with having custom units fabricated, and 7" is large enough to be able to polish inside easily. Do you have a requirement for very high hygiene standards? This is unusual in a relatively large pipe - it doesn't sound like a pharmaceutical plant.
If the requirement for smoothness is because of friction then you need to point out to them that the pressure drop caused by the change in direction through an elbow far outweighs the friction against the surface - and in any case the difference between welded and seamless pipe would be unmeasurably small.
Katmar Software - AioFlo Pipe Hydraulics
"An undefined problem has an infinite number of solutions"
In my fabrication design I specify that the longitudinal seam in ERW be located in the top half of pipe (I've had several MIC failures in the HAZ of ERW longitudinal welds) and the welders have the devil's own time finding the seam on most joints. Today's manufacturing processes make the longitudinal seam disappear. When I do a comparison of ERW and seamless I find:
[ul]
[li]ERW is less expensive[/li]
[li]ERW has much less ovality[/li]
[li]ERW has much more consistent wall thickness[/li]
[li]ERW gives me fewer welds that fail inspection[/li]
[/ul]
The only people I run into that insist on seamless are people who were burned badly by the crap pipe that came out of U.S. mills in the 1970s and early 1980's. That stuff was horrible and drove everyone to Japanese and European mills. When USX built the Fairfield plant in Virgina and Lone Star revamped their Texas plant that all changed and US pipe set a new standard that the rest of the world took 5 years to catch up to. Since early 1990's ERW has been a far superior product to seamless in every size where it is available.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
[ul]
[li]ERW is less expensive[/li]
[li]ERW has much less ovality[/li]
[li]ERW has much more consistent wall thickness[/li]
[li]ERW gives me fewer welds that fail inspection[/li]
[/ul]
The only people I run into that insist on seamless are people who were burned badly by the crap pipe that came out of U.S. mills in the 1970s and early 1980's. That stuff was horrible and drove everyone to Japanese and European mills. When USX built the Fairfield plant in Virgina and Lone Star revamped their Texas plant that all changed and US pipe set a new standard that the rest of the world took 5 years to catch up to. Since early 1990's ERW has been a far superior product to seamless in every size where it is available.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
- Thread starter
- #13
- Thread starter
- #15
LittleInch
Petroleum
Nice to get the info eventually - next time when you ask a question please provide all the info in one go - it makes it much easier to rule out some of the questions we've been asking you.... you still haven't said what the material is though.
This is 7" NB pipe alright (7.625" OD). I have found the odd reference to 7" pipe in some catalogues, but when you click on further links it then disappears. I've never seen or heard of 7" pipe before so I'm all out of ideas.
I can only suggest you keep on searching and if possible see if you can talk to the operators, find an old design and talk to the designers or even a material certificate for the existing pipe buried in the plant archives. Try a few pipe stockists - even if they don't stock it they migth know of a vendor who would do "specials", but brace yourself for the price....
It shouldn't be up to you to find this on your own - you've looked hard (I hope), asked a few people and now you need to go to your supervisor, not the client as he doesn't sound very helpful, and tell him your story.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
This is 7" NB pipe alright (7.625" OD). I have found the odd reference to 7" pipe in some catalogues, but when you click on further links it then disappears. I've never seen or heard of 7" pipe before so I'm all out of ideas.
I can only suggest you keep on searching and if possible see if you can talk to the operators, find an old design and talk to the designers or even a material certificate for the existing pipe buried in the plant archives. Try a few pipe stockists - even if they don't stock it they migth know of a vendor who would do "specials", but brace yourself for the price....
It shouldn't be up to you to find this on your own - you've looked hard (I hope), asked a few people and now you need to go to your supervisor, not the client as he doesn't sound very helpful, and tell him your story.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
- Thread starter
- #17
The OD works out to a number that could be a pipe OD (7.625 like LittleInch said), but the wall thickness of 5.6 mm (0.220 inch) if I extrapolate from standard tables it would be Sched 20 (for which there is no standard).
I did find one table with 7-inch, but it only had wall thickness for Sched 40 which is 0.301 in [7.6 mm], Sched 80 which is 0.5 in [12.7mm] or XXH which is 0.875 inch [22.2 mm].
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
I did find one table with 7-inch, but it only had wall thickness for Sched 40 which is 0.301 in [7.6 mm], Sched 80 which is 0.5 in [12.7mm] or XXH which is 0.875 inch [22.2 mm].
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
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