




#65131  04/26/06 04:32 AM
Re: Concentric or Segmented bends

Member
Registered: 11/28/01
Posts: 77
Loc: Indianapolis, IN, USA

The math is pretty simple. The more bends the smoother the bend, especially on large radius bends. Be sure to use some type of "antidog" device. Also, be careful rounding off the #'s. Small things tend to add up.
From Greenlee's conduit book: 1. Decide on # of bends/segments per 90 (90/15 = 6 degrees per bend.
2. Pick centerline radius of inside pipe's 90 (36").
3. Find developed length  radius x 1.57 (36" X 1.57 = 56.52")
4. Find distance between bends by dividing the developed length by # of shots. (56.52" / 15 = 3.77" between bends).
Next step is to find the radius of the second pipe. Suppose all pipes are 2" rigid w/2" spacing btw. pipes.
1. If the second pipe is the same size, add O.D. plus centertocenter spacing, then add that to the first radius (2" rigid = 2.375 + 2" + 36" = 40.375" radius for second pipe).
2. Find developed length  radius x 1.57 (40.375" X 1.57 = 63.39")
3. Find distance between bends by dividing the developed length by # of shots. (63.39" = 4.23" between bends).
4. Repeat steps 1,2, & 3 for every pipe (if the same size and spacing).
To find the radius increase when pipe sizes vary, add the two outside diameters of the pipe, divide answer by 2, then add the space between bends. This gives you the increase in center line radius of the next larger bend.

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