# Understanding Bend Categorization

• princessme
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...It's actually pretty simple. The bend radius is the distance from the fitting's "outside" diameter to the "inside" diameter of the elbow. So, in this case, the bend radius would be 3.0d.It's actually pretty simple. The bend radius is the distance from the fitting's "outside" diameter to the "inside" diameter of the elbow.

#### princessme

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?

princessme said:
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:

SteamKing said:
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:

Alright, I understand about the 1.5D and 3D definition. How about the D/d ratio?

princessme said:
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.

SteamKing said:
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?i...considered in terms of the bend angle&f=false

princessme said:
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.

princessme said:
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:

don't get stuck in the piping when they are being pushed thru the system by compressed air.

SteamKing said:
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:

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?

princessme said:
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.

I think that D is used for the outside or nominal diameter.

xukaus said:
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.

## What is the purpose of bend categorization?

Bend categorization is an important tool used in scientific research to help understand and classify the different types of bends or curves that occur in various structures, such as proteins and DNA. By categorizing these bends, scientists can better understand their function and potential impact on the overall structure and function of the molecule.

## How is bend categorization performed?

Bend categorization is typically performed using specialized software and algorithms that analyze the shape and curvature of a molecule. These programs use various parameters, such as angle, radius, and direction, to classify the bend based on its characteristics. The results are then compared to a database of known bend types to determine the most accurate classification.

## What are the different types of bends that can be categorized?

There are several types of bends that can be categorized, including hairpin bends, kinked bends, and helical bends. Hairpin bends occur when there is a sharp turn in the molecule, while kinked bends result in a more gradual curvature. Helical bends, on the other hand, involve a bend that follows a helical pattern.

## Why is understanding bend categorization important?

Understanding bend categorization is crucial for gaining insight into the structure and function of molecules. By accurately categorizing bends, scientists can better understand how they affect the overall structure and function of the molecule, and potentially how they contribute to diseases or other biological processes.

## Are there any limitations to bend categorization?

Like any scientific tool, bend categorization has its limitations. It relies on the accuracy and completeness of the database used for comparison, and can be affected by variations in the molecule's structure or environmental conditions. Additionally, certain types of bends may be difficult to categorize due to their complex or unique characteristics.