Bend geometry

  • Thread starter princessme
  • Start date
  • #1
35
0

Main Question or Discussion Point

I'm quite confused on how bends are categorised. Some would refer it to 1.5D or 3D bends for instance, while some will use the ratio of the bend diameter (D) to pipe bore (d).

I somewhat understand the two separately, but couldn't go about how to convert between the two. Can someone help me understand them better?
 

Answers and Replies

  • #2
18,091
7,510
Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
 
  • #3
SteamKing
Staff Emeritus
Science Advisor
Homework Helper
12,798
1,666
I'm quite confused on how bends are categorised. Some would refer it to 1.5D or 3D bends for instance, while some will use the ratio of the bend diameter (D) to pipe bore (d).

I somewhat understand the two separately, but couldn't go about how to convert between the two. Can someone help me understand them better?
The nomenclature "1.5D" and "3D" refers to the radius of the bend of the fitting to the nominal diameter D of the fitting. AFAIK, D is not the bend diameter.

Below, find a sample table of ANSI fittings:


1023504149_511.jpg

 
  • #4
35
0
The nomenclature "1.5D" and "3D" refers to the radius of the bend of the fitting to the nominal diameter D of the fitting. AFAIK, D is not the bend diameter.

Below, find a sample table of ANSI fittings:


1023504149_511.jpg

Alright, I understand about the 1.5D and 3D definition. How about the D/d ratio?
 
  • #5
SteamKing
Staff Emeritus
Science Advisor
Homework Helper
12,798
1,666
Alright, I understand about the 1.5D and 3D definition. How about the D/d ratio?
Well, what about it? Your original post wasn't too clear on that.

I think that D is used for the outside or nominal diameter, while d is used for the inside diameter in some cases. Most piping catalogs include a diagram which lays out the key dimensions of the fitting. OD and ID are used for the respective diameters so that their meaning is unambiguous.
 
  • #6
35
0
Well, what about it? Your original post wasn't too clear on that.

I think that D is used for the outside or nominal diameter, while d is used for the inside diameter in some cases. Most piping catalogs include a diagram which lays out the key dimensions of the fitting. OD and ID are used for the respective diameters so that their meaning is unambiguous.
Please refer to the link below, section 1.3.4.2. I'm quite confused about the bend geometry here as compared to the regular 1.5D and 3D ratio.

https://books.google.com.my/books?id=TBmjBQAAQBAJ&pg=PA9&lpg=PA9&dq=pneumatic+design+bend+geometry+is+considered+in+terms+of+the+bend+angle&source=bl&ots=C7G7tnU3AF&sig=gZUS4J0d12Q3lRA0bsVxrOAgxKo&hl=en&sa=X&redir_esc=y#v=onepage&q=pneumatic design bend geometry is considered in terms of the bend angle&f=false
 
  • #7
SteamKing
Staff Emeritus
Science Advisor
Homework Helper
12,798
1,666
I'm sorry, but for some reason, this link isn't working for me. Can you provide an alternate means of viewing this page?

EDIT: Nevermind. Got it working.
 
  • #8
SteamKing
Staff Emeritus
Science Advisor
Homework Helper
12,798
1,666
It appears this reference is discussing design rules for designing things like pneumatic conveying systems, which don't use regular steel pipe designed for pumping liquids, for example. That's one reason bend radii are so large, for example D/d = 24:1. In the latter case, it appears that the bend radius D = 24 × d, pipe diameter.

The bend radii are very large so that the pneumatic carriers:


slider-2-grouped-version.png


don't get stuck in the piping when they are being pushed thru the system by compressed air.
 
  • #9
35
0
It appears this reference is discussing design rules for designing things like pneumatic conveying systems, which don't use regular steel pipe designed for pumping liquids, for example. That's one reason bend radii are so large, for example D/d = 24:1. In the latter case, it appears that the bend radius D = 24 × d, pipe diameter.

The bend radii are very large so that the pneumatic carriers:


slider-2-grouped-version.png


don't get stuck in the piping when they are being pushed thru the system by compressed air.
Okay, I get what you meant. For instance, I'm using 3D elbows (in the general context), so how do I interpret it in terms of the D/d ratio?
 
  • #10
SteamKing
Staff Emeritus
Science Advisor
Homework Helper
12,798
1,666
Okay, I get what you meant. For instance, I'm using 3D elbows (in the general context), so how do I interpret it in terms of the D/d ratio?
Then the bend radius of the pipe or conduit is going to be so many times the bore of the pipe or conduit.

For example, D/d = 24:1 means the bend radius D = 24 × Pipe diameter d.

It's not clear how pneumatic conduit is made: If a piece of straight conduit is bent to the required radius or what.

For fluid piping, there are standard sizes of elbows and other fittings made to match the nominal diameter and wall thickness schedules of straight piping. The bend radii of these elbows is either 1.5 × nominal diameter, the so-called "short radius" elbow, or 3.0 × nominal diameter, the so-called :long radius" elbow. Anything else must be specially manufactured for liquid piping systems or fabricated by bending a length of straight pipe.
 
  • #11
1
0
I think that D is used for the outside or nominal diameter.
 
  • #12
SteamKing
Staff Emeritus
Science Advisor
Homework Helper
12,798
1,666
I think that D is used for the outside or nominal diameter.
The attached reference in Post #6 clearly mentions D as being the bend radius of the pipe.

This is pneumatic piping rather than fluid piping, so the pipe bore and nominal pipe sizing is different from fluid piping. Pneumatic piping is typically light gauge metal or plastic material, unlike fluid piping, which is constructed from heavy walled metal to withstand high pressure service.

That's why the bend radius to pipe bore is given as a ratio, like D/d = 24:1. :smile:
 

Related Threads on Bend geometry

  • Last Post
Replies
4
Views
7K
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
2
Views
882
  • Last Post
Replies
4
Views
3K
  • Last Post
Replies
4
Views
958
  • Last Post
Replies
1
Views
760
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
5K
  • Last Post
Replies
0
Views
2K
  • Last Post
Replies
4
Views
5K
Top