Question on NEC 2005 article's 334.24 bending radius

Status
Not open for further replies.
S

stcalle

Member
In the 2005 NEC, article 334.24 refers to chaper 9 table 2 for deciding the bending radius for RMC. My question is on table 2 in chaper 9. There are two columns titles
1) one shot and full shoe benders
2) other bends

Can someone explain what these two titles are referring to?
From what I can see the first column is a more stringent requirement, but I do not understand in what cases you would want this.

For background, I am looking at this table in reference to wanting to calculate sidewall pressure during cable pulling.

thanks
 
this would be an example of an other than full shoe bender I would think

gg508-516.jpg

with a hickey the radius is tighter than a full shod bender??
 
thanks for the reply. Could you give me a little more information on that picture you posted? are you saying that piece of equipment is considered the "other bend" from the table? If so, then would you be able to show me an example of "one shot and full shoe benders" bend?

also, what is the difference between these two types of bends? Pros and cons to either?

any additional information would be appreciated.
 
A single shot is a bender or bender shoe that allows you to bend a 90 in one shot. The radius is determined by the shoe.

A multi shot bend is a several bends to make one bend. The radius is determined by the number of ?shots? and the distance the ?shots? are apart.

For example if you need a 90 with a 16? radius.

1) Multiply your desired radius by 1.57 (? of pie) to come up with a ?developed length?. 16 X 1.57=25.12?
2) Determine number of shots. More shots=smoother bend. Lets use 5 degrees in this example. 90 degrees divided by 5 degrees=18 shots.
3) Determine distance between ?shots? Developed length divided by number of shots. 25.12? divided by 18?=1.396?
4) Mark the conduit with 18 marks 1.396? apart.
5) Place conduit in appropriate bender (hydraulic multi shot or Chicago type) and bend 5 degrees at each mark. After 18 shots at 5 degrees each you will have 90 with a 16? radius.

This is a simple example and of course doing the real thing requires the proper know how and tools. This method also allows bending concentric bends. Bends that fit inside each other while maintaining the same spacing. By adding the spacing between conduits & OD of conduits to the first radius you can calculate the radius of the next pipe.
Like the others mentioned the hickey is an example of a multi shot bender. It usually takes more than one shot to make a bend.
I would post some pictures but I am not to good at it and it would take me all night. Maybe somebody else could post some pics of bender types I mentioned.
 
Status
Not open for further replies.
Top