Some questions about conduit's vertical sweep

[rongyuer_2001]

I'm a very junior designer, I met some issues about conduit's vertical sweep. Now I need to simulate an algorithm to calculate all kinds of Sweep, especially for vertical sweep.I attached a very simple case about vertical sweep, could anyone give some real cases, real design cases or real construction cases are better.
Or some references....


Many many thanks!

 

[Smart $]

I'm a very junior designer, I met some issues about conduit's vertical sweep. Now I need to simulate an algorithm to calculate all kinds of Sweep, especially for vertical sweep.I attached a very simple case about vertical sweep, could anyone give some real cases, real design cases or real construction cases are better.
Or some references....View attachment 8227


Many many thanks!

Uncertain what you are asking for. A sweep is a pre-fabricated bent section of conduit. A vertical sweep is simply a sweep installed in a vertical orientation. The term loosely means having a radius. Long sweep elbows refer to those made with a longer radius. There are some standards that apply here in the U.S., so perhaps you can elaborate on what information you are seeking...

 

[GoldDigger]

...so perhaps you can elaborate on what information you are seeking...

My guess is that he is interested in the length of the conduit section for a particular horizontal and vertical offset and radius, the sort of thing that would be needed to fabricate the sweep section with a bender.

 

[Smart $]

My guess is that he is interested in the length of the conduit section for a particular horizontal and vertical offset and radius, the sort of thing that would be needed to fabricate the sweep section with a bender.

Well we'll have to wait on that... but that is why I pointed out that sweep usually refers to pre-fabricated bent sections... and that info should be obtained from either the appropriate standard or the manufacturer.

BTW, he may also be asking about info for multi-shot fabricating of 'long sweep' radius bends... ???

 

[rcwilson]

Or he may be looking at the issue a lot of my beginning designers face. They design a 4 foot radius bend on a conduit buried 18" deep in concrete and wonder why it came out of the floor at an angle instead of straight up.

Worst case was a 230 kV, 1800 kcmil cable that had an 9'-12' minimum radius, buried only 4 feet deep due to the solid rock and interference with piping. Cable missed the dead end structure and transformer at each end.

 

[GoldDigger]

Worst case was a 230 kV, 1800 kcmil cable that had an 9'-12' minimum radius, buried only 4 feet deep due to the solid rock and interference with piping. Cable missed the dead end structure and transformer at each end.

So just what do you do in a case like that? Blast? Design to have most of the bend above ground? Do an offset bend or a mostly horizontal bend and come in from the side? The world wants to know.

PS: It may just be an optical illusion, but the OP's drawing looks like the conduit is not entering the box vertically.

 

[rcwilson]

So just what do you do in a case like that? Blast? Design to have most of the bend above ground? Do an offset bend or a mostly horizontal bend and come in from the side? The world wants to know.

Cables had to be vertical as possible to fit the pre-manufactured stress cones/ terminators with no forces or weight hanging on the termination or the warranty was void. The contractor had to raise the transformer end terminations by extending the lattice work support structure enough to fit in an S bend in the cable. They added some gimbal mounted clamps to secure the cable in that shape. Fortunately, the transformers did not have enclosed 230 kV termination boxes (oil-filled or SF6) and just had ACSR jumper cables through the air from the top mounted HV bushings to the cable terminations? air terminals. There was enough clearance to handle the extra height, just needed longer jumpers. We were also fortunate that there was enough cable sticking up to provide the needed length.

The solution at the switchyard end was to relocate the structure more in line with the conduit which allowed the bend to finish above ground and line up vertically. That end was skewed in more than one axis before the fix.

The original design solution would have been to blast deeper to slope the conduit down deep enough before starting the upward sweep, or to design the termination structure and surrounding structures so the conduit bend could come out of the ground at a 45 degree angle and finish the sweep in the air with suitable cross brace anchor points.

Many installations of this type of cable don?t use conduit and direct bury the HV cable in a trench with thermal backfill.
They also get plenty of room at the terminations.