Confusing pipe elbow radius

[lummz]

I just got a tender where i among others ordered some pipe elbows. On the pipe elbows it said 3D and i thought, "hmm that must be wrong because i want 1,5D bends (1,5 times the diameter)". However now that I've done some googling I realized that the pipe standard (ISO 5151) says that 3D elbows has a 1,5D bend (1,5 times the diameter), and a 5D elbow has a 3D bend (3 times the diameter).... Why in the world does someone name the pipe elbows to 3D and 5D when it is so easily confused with the radius of the pipe...

So my question is what does the name 3D and 5D refer to?

 

[robyengIT]

You are a bit confused. Check here

http://www.crp.co.uk/UserFiles/Documents/Dimensional Table CRP.pdf

 

[zdas04]

The specification for an elbow lists the distance from the center of one leg to the face of the other leg. That dimension is the same for all pressure classes (i.e. it is independent of wall thickness). For standard radius elbows this is 1.5 times the nominal diameter. This can be confusing. 6-inch pipe has an OD of 6.625 inches. The distance from the center of the pipe on one leg to the face of the the other leg is specified as exactly 9 inches. For a long radius elbow it is 3D or 18 inches.

When you go to SI it isn't quite so pretty since the SI equivalent of "nominal" is "DN" which rounds the conversion from inches to mm to 25 instead of 25.4. This means that a 10-inch (250 DN) short radius elbow has a dimension of 15 inches [381 mm] from center on one leg to the face of the other leg instead of 375 mm.

ASME B16.5 further complicates this by listing distances for flanged fittings instead of the raw fitting without flanges welded on. The information is all there, but it can be a challenge to dig out.

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

 

[lummz]

Hmm, i'm not exactly sure you understand my confusion.
If you look at the dimension table that robyengIT posted is says that a DN50/2" 3D elbow has a radius of 152mm (3 times the radius).

But if you look at this:

http://www.sagarfitting.com/buttwel...fitting/ansi-asme-b16.9-3D-buttweldelbow.html

There it says that a DN50/2" 3D elbow has a radius of 76mm (1,5 times the radius).

And if you look at this:

http://www.bendtechgroup.com.au/images/downloads/dn_1336623906_80558412.pdf

There, on page 5, they call a DN50 elbow with 76mm radius 1,5D


I figure that the most "right way" is the 2nd link where a DN50 3D elbow has a 76mm radius. But what does the name 3D come from, that is my question. What does the "3" and the "D" in 3D refer to?

 

[zdas04]

I'm not sure what you are talking about. In the first link a 2-inch "Long Radius" (which everyone considers the "standard radius") is 76 or 2*2"*1.5*25.4. The 3D radius is 152 mm. In the second one they seem to have generated their own dimensions and use DN * 1.5 for long radius or 3.0 for 3D radius. I've never seen that before. A DN 50 long radius elbow has a radius of 76.2 mm and a 3D elbow has a bend radius of 152.4 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

 

[Krausen]

I'm not familiar with ISO, but under ASME B16.9 a standard elbow radius is 1.5D, which is also considered Long Radius ("LR"). These are the most common elbow fittings. A 3D radius elbow is more of a specialty fitting and is NOT the same as a Long Radius (LR) elbow. 3D elbows, along with 5D elbows, are specialty fittings that should not be confused with standard LR (1.5D) elbows. There are also Short Radius (SR) specialty elbows that have 1D radiuses (I know, radii) if I remember correctly.

 

[LittleInch]

Your iso code refers to air conditioners

The sagar site says 3D elbow is 152mm

Your post makes no sense I'm afraid. 3D means 3 D median radius.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

The Differences Between Bends and Elbows

Although the words bends and elbows are often used as synonyms, there are some differences. Bend is a term for any offset of direction in the piping while elbow is an engineering term. Elbows have limitations to angle, bend radius and size. Most angles are either 45 degrees or 90 degrees. All other offsets are specifically pipe bends. And while elbows have sharp corners, bends never do. The most basic different between a bend and an elbow is the radius of curvature. Bends have a radius more than twice the diameter, and elbows have a radius of curvature between one and two times the size of the pipe’s diameter. All elbows are bends, but not all bends are elbows.

http://www.benditinc.com/uncategorized/9-facts-about-5d-bends/