Bends less than 11.25 deg in rigid pipe
Bends less than 11.25 deg in rigid pipe
(OP)
What do you do for gentle bends (<<11.25 degrees) in a 3" rigid forcemain? I have a 1000 ft long arc that traverses 33 degrees total (radius is 1850 ft). If I use tangents and 11.25 degree elbows I'm going to blow my easement, but I have been advised that the pipe is too rigid to bend to match the curve.





RE: Bends less than 11.25 deg in rigid pipe
http://www.dipra.org/pdf/joints.pdf
RE: Bends less than 11.25 deg in rigid pipe
RE: Bends less than 11.25 deg in rigid pipe
RE: Bends less than 11.25 deg in rigid pipe
You should be able to get your radius in this manner.
The other way to deflect is to actually bend the pipe using blocking. 3" is a fairly small diameter pipe.
What is "rigid" PVC? I have not seen this terminology. 3" PVC pipe should be able to be bent to well under an 1850' radius without deflecting the joints, If I remember right.
RE: Bends less than 11.25 deg in rigid pipe
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
http://waterhammer.hopout.com.au/
RE: Bends less than 11.25 deg in rigid pipe
"A joint that is assembled per our recommendations will exhibit a gap, in which the beveled end of the spigot is stopped short of being fully bottomed out in the bell."
"...'s standard installation recommendations call for no axial deflection at the joint. This recommendation emphasizes the fact that any intentional change of direction should be accomplished through a fitting connection or by bending the barrel of the pipe rather than offsetting the pipe joint. "and later again in multiple locations:
"... does not recommend any deflection at the joint for any of our products."
"The pipe should be assembled above ground, in a straight line, then curved and laid in the trench. All curvature results from the bending of the pipe lengths. There is no deflection at the joint."
"Brace the bell while the spigot end is pushed under the gasket, so that previously completed joints will not be further inserted." And repeated:
"Lastly, there should be no axial deflection at the joint. Bending the pipe, rather than deflecting the joints, should serve to accomplish small changes in direction."
"... pipe does not meet AWWA C-111; this standard is for Ductile Iron Pipe."
"The joint design meets ASTM D 3212 performance testing requirements, thereby assuring a watertight joint that does not exceed an infiltration / exfiltration allowance of 25 gallons / inch diameter / mile / day."
With all this being said, it is my understanding field splitting failures of pvc pipelines, with and without eventual tapping involved, have incidentally been blamed (or explained away?) on the Contractor (or other installer) bending the barrel of the pipe. Go figure! [While I guess it could be argued a pvc sewer force main would not have as many required drilled holes or taps in the pipe wall(that are obvious stress concentrators)as a water distribution piping, pvc force mains can (as a practical matter) also can have some stress concentrations and also are possibly more subject to cyclical stress/fatigue issues, due to pumps cutting on and off etc.]
RE: Bends less than 11.25 deg in rigid pipe
It must be considered though that the physical properties, in response to a rapid pressure event, for a thermo plastic pipe are much higher than the publised steady state figures. So pipe burst is unlikely. However damage to the pipe will have occurred. The criteria to be most considered with PVC are surface defects when it comes to failures from cyclic events. Defects a are crack initiators. That is why the C ring test is so important.
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
http://waterhammer.hopout.com.au/
RE: Bends less than 11.25 deg in rigid pipe
It is an interesting point about bending the pipe versus the joints and the potential for failure, because the relocation will likely go through Limited Access ROW. In a LAROW the utility owner (a church with a low pressure pump station, ~ 25 gpm @ 30 ft) will have to take the risk that the forcemain will never fail or they will have to reroute around an Interstate/US highway interchange. (The existing FM is along the US highway and it's a new-build Interstate.) We may as a precaution "relocate" everything within the LAROW to ensure the construction quality (as existing plans give no confidence) and we will be adding ARVs, etc. as the 4,000+ ft line currently has one, about 400 ft from the lift station, and the manhole its in is full of water!