L/R and S/R Elbow 2

[pimeng12]

Dear all,

Does anyone can explain where is the 90 DEC long radius elbow and short radius used?
or where I can find references about it?

Thanks.

 

[C2it]

Both can be used anywhere in a piping system, provided that relevant criteria are met.

By industry convention a long radius bend is 1.5x nominal diameter and a short radius bend is 1.0x nominal diameter. A short radius bend will cause more pressure loss and will attract a higher stress intensification factor than the other, but it takes up less space. It is also less readily available in the huge range of diameters and wall thicknesses. Your choice.

 

[pennpiper]

Go here

http://pipingdesigners.com/phpBB3/viewforum.php?f=1

and use the "Search" feature to check for issues you are interested in.

It is really a big help.

 

[pennpiper]

More on Elbows:

Elbows (Ells):

An Elbow is a piping fitting used for changing direction. There are five basic versions of elbows. The first and by far the most common is the 90° long radius Ell. The second is the 45° long radius Ell. The third is the 90° short radius Ell. The fourth is the long radius reducing Ell. The fifth version is the long radius 180° Return Bend. The basic Butt-Weld Ell is manufactured in 90° or 45° configurations as a standard. However for special order and extra cost, the large sizes can be made in other degrees of turn.

The standard Butt-Weld elbows (90°, 45° and 180° ) can be altered to meet any special angle needs of a piping system. Elbows like pipe can be flame cut or machine cut to the required angle. The rough end is then ground or machine beveled to the proper angle for welding. There is normally no harm to the fitting when this is done.

The terms "Long Radius" and "Short Radius" are important to understand. "Long Radius" means that the center to end dimension is one and a half times the nominal pipe size.

Example:
Nominal Line Size (and Center-tend of short radius Ell) Center-to-end of long radius Ell
4" = 6"
10" = 15"
14" = 21"
20" = 30"
24" = 36"


"Short Radius" means that the center to end dimension is equal to the nominal pipe size. This means that the center-to-end for a 4" short radius Ell is 4", for a 10" Ell the center-to-end is 10" and so on.

The long radius Ell is the default standard. All elbows shown in a system are assumed to be long radius 90° Ells unless noted otherwise. This means that the designer must call out any and all exceptions to this rule. If the Ell is a 90° long radius Ell then the elbow symbol is all that is required. However, if the Ell is a 45° Ell then the designer must add the notation "45° Ell" next to the elbow symbol. If the Ell is a 90° short radius Ell then the designer must place the notation S. R. next to the elbow symbol. Also if the elbow has been trimmed to any odd angle this too must be noted next to the fitting.

As stated above the 90° long radius Ell is the default standard and is the most used. The designed should use the long radius Ell at all times unless conditions exist that force another choice. The short radius 90° Ell should only be used when tight space does not allow the long radius. The 45° Ell is normally used where a simple offset is required for some purpose. The 180° Ell is used mostly by equipment manufacturers to form heating or cooling coils. Return Bends are not normally required by the piping designer unless there is a requirement to fabricate a complex configuration.

The purpose of the 90° long radius Reducing Ell is to do the job of an elbow and a reducer. (Reducers will be covered later.) As such this Ell is made with one end of one size and the other end one or two line sizes smaller. The using of the reducing Ell is not cheaper; it only takes less room. The "long radius" dimension for the 90° long radius reducing Ell is based on the size of the large end.

 

[zdas04]

Pennpiper,
You were doing fine until you got to

"Long Radius" means that the center to end dimension is one and a half times the nominal pipe size.

It may be that you just took a language short cut that is crystal clear to you, but clear as mud to me. The definition (as you would expect from something called a "radius") is "The radius of the arc along the centerline of the fitting, with the center of the arc 1.5 times the nominal diameter of the pipe away from the centerline of the pipe". So a LR 90° bend in a 6-inch pipe will conform to an arc with a center 9 inches from the centerline of the pipe. The outside diameter of the bend will be Nominal *1.5+ OD/2, for 6-inch pipe the outside is 6*1.5+6.625/2=12.3125 and the inside of the bend will be 5.6875.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[pennpiper]

David,
While you are technically absolutely correct, surprisingly enough you have taken something that should be very simple and made it sound very complicated.

This surprises me because normally your comments/responses are very helpful and easy to understand.

 

[zdas04]

Describing geometric shapes in words is never easy. I wasn't about to take you to task for shortcutting the description and then leave out words myself. Hope I do better next time.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[BigInch]

What would you be doing, if you knew that you could not fail?

 

[pimeng12]

Thank you for all of your responses. It really help me.