PVC vs Rigid conduit in UG Duct Banks

[Lenz81]

I am currently on job and they require to use Rigid Elbows for UG duct banks ,when i ask for reason nobody seems to have answer , is there any code or reuirement on using rigid elbows ? Installating Rigid elbow is very time consuming specially in case of bigger conduits .
Thanks
Lenz

 

[infinity]

RMC elbows are sometimes installed to prevent elbow damage that can be caused by the pulling rope when PVC elbows are used. A metallic elbow in a run of PVC must be at least 18" below grade to the top of the elbow.

 

[masterinbama]

If you have ever had a rope burn through and either jam the pull or destroy the conductors you will use them all the time, even when not speced.