ECN Forum Forums General Topics of the Trade General Discussion Area Risers

Can't seem to get the link to work but look for slip risers under electrical. to have a look at one
Ob

When they first went to PVC risors for UG around here both PoCos required a 90 deg sweep 24" below grade. When it became obvious that over time the ground settling around the 90 pulled down on the pipe and caused damage, they prohibited the use of the 90 and instead required just a straight pipe at least 24" below grade with a slack loop of conductor where it entered the risor.

They are not legal here. We do a GRC 90 up, then GRC up the pole.

IMHO (stress the H) a riser should be GRC.

We run 3" pvc from transformer/pole to meter socket with this thing at the riser. They were having guys not straping well and then not back filling right. The meter sockets would pull right off the building. Now we have These things, but there is no place to leave slack for the cable?

Ob

mxslick,
While I am not a fan of PVC because of the physical damage issue, I watched the same thing happen to a 4" rigid steel riser with 4 500 kcmil conductors. Both the conduit and the conductors "vaporized".
Don


[This message has been edited by resqcapt19 (edited 12-23-2006).]

There are some areas along the coast where PVC is used but its more an issue with the GRC not lasting long in the salt air.

I share your opinion on the physical damage issue, especially since PVC is much more likely to get damaged by a "love tap" from a passing truck than rigid steel. I'm almost willing to bet that a tap from a truck is waht started the fault in the video.

But to be fair, I will concede that nothing is gonna stop a fault on a POCO feed from burning through whatever pipe it may be in. Unless through dumb luck the transformer's primary fuse is either weak or was sized to open under a secondary fault.