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Power/ Utility Pole

Power/ Utility Pole

Power/ Utility Pole

(OP)
I am in the process of detailing some power transmission poles that bring power from the road into a substation yard for a new facility. My question is, does the electrical contrator usually field drill the holes in the pole for the connections of insulators and other hardware?   

RE: Power/ Utility Pole

As opposed to...?

RE: Power/ Utility Pole

(OP)
...as opposed to me detailing out the holes for the the hardware/insulators etc. on fabrication or shop drawing of the pole.  

RE: Power/ Utility Pole

(OP)
davidbeach:
These are dodecagonal or 12-sided steel poles anywhere from 45' to 60' tall.  

RE: Power/ Utility Pole

Holes and flanges in steel poles are usually done at the shop before finishing.  I'd use flanges for suspension insulator connections instead of holes and eyebolts.
 

RE: Power/ Utility Pole

All that hardware goes onto brackets welded to the poles or on to mounting pads provided with the pole by the manufacturer.  Nothing is just drilled into a steel pole.

RE: Power/ Utility Pole

In the rare case in which the structures are wooden, the holes are usually field drilled. As others have stated, for steel structures (or steel components used on wooden or concrete poles) the holes are installed at fabrication.

Often, steel structures will be specified with flanges that have a series of pre-drilled holes for various hardware spacings. Utilities standards departments will have established specifications to suit their construction types. The crews will pick the closest holes that fit conductor elevation and spacings.  

RE: Power/ Utility Pole

Don't drill holes in steel poles unless approved by manufacturer.   

RE: Power/ Utility Pole

(OP)
thanks fellas....you'll notice the (Structural) next to my name. Apparently the hardware details I have are for wooden poles, not steel, as they should be. If the hardware details are wrong, it means our Electrical engineering consultant has his head buried in his ass.  

RE: Power/ Utility Pole

(OP)
dpc:
see my first post...I am detailing and having the poles fabricated...I am the manufacturer.  

RE: Power/ Utility Pole

(OP)
By the way...just so i know...
What would be the big deal with using thru-bolted hardware on a steel pole? What are the concerns here?  

RE: Power/ Utility Pole

OK -that wasn't clear to me, I guess.   

RE: Power/ Utility Pole

I would imagine that steel poles are designed with stress reviews and possibly heat treating that can go haywire when you start drilling holes in them.  Same as truck frames - you shall not drill them(truck frames).

Keith Cress
kcress - http://www.flaminsystems.com

RE: Power/ Utility Pole

(OP)
itsmoked:
As the design engineer of the poles I can assure that drilling a several small holes will be of no structural consequence whatsoever. Even holes drilled in very heavily loaded building beams/frames are for the most part totally ignored in the design process so long as they are not drilled in an area of high stress or are unusually large (something other than bolt holes).     

RE: Power/ Utility Pole

(OP)
itsmoked:
Sorry, I wasn't trying to get indignent on you, but it sure as hell sounded that way didn't it!!!

RE: Power/ Utility Pole

Quote:

By the way...just so i know...
What would be the big deal with using thru-bolted hardware on a steel pole? What are the concerns here?
Through bolted hardware is OK and is often done with post insulators.  It is generally less expensive to fabricate the pole with flanges where appropriate, however, rather than using thru-bolts.  Field drilling holes can be done if the finish is repaired, but is more expensive than having the holes drilled by the fabricator before finishing.  Repairing the finish with zinc-rich paint is usually acceptable to stop rust, but it if you can predict where holes are needed, have the fabricator drill them.  

You might want to include threaded holes for ground connectors if any equipment needs grounding or if the poles need connected to a separate grounding electrode.
 

RE: Power/ Utility Pole

(OP)
jghrist:

Thank you.
Makes damn good sense.
First good answer.

My main concern was drilling the galvanized pole afterwards and having to make repairs.

The biggest problem I have here is I am a Structural Engr who is designing and detailing the poles (working directly for the owner....everything done in house).
Laying out power transmission lines is not my thing. We have required pole heights, line elevations and hardware details from our Electrical consultant, but i am not comfortable with laying out the hardware locations on the detail drawings. I have completed it, but still dont have much confidence in it. My thinking was that if i left the poles blank I could have the contractor work directly with the Electrical Engr consultant and be sure the hardware locations were correct.  

RE: Power/ Utility Pole

Practice within your expertise.  

RE: Power/ Utility Pole

I agree with nonsinusoidal.  If the electrical consultant will not give you a drawing showing where to drill the holes and install flanges (with hole sizes), then leave it all blank.  I would never expect the pole fabricator to determine how to frame the pole.
 

RE: Power/ Utility Pole

(OP)
nonsinusoidal (Electrical) 3 Sep 09 20:33  
"Practice within your expertise"

So, designing a pole for line tension loads, ice, wind etc. is not the expertise of a Structural Engineer? Should I consult a "Pole Engineer". Can you do it for me?. I am well within my expertise here and I by no means expect the fabricator to do anything but EXACTLY what I put on the drawing. If my electrical "expert" wasn't a jagoff, I wouldn't have to worry about it. I'd detail the pole showing attachemnt points and have him review it.   

RE: Power/ Utility Pole

I don't think nonsinusoidal was questioning your structural expertise.  If you don't have expertise in framing transmission poles (figuring out exactly where to put what), however, you need to get someone who does or leave it up to the field to do.
 

RE: Power/ Utility Pole

Obligation of an Engineer:

"As an engineer, we all shall participate in none but honest enterprises. When needed, our skills and knowledge shall be given without reservation for the public good.  In the performance of duty and fidelity to our profession,we shall give the utmost."

I am not questioning your expertise! I was just suggesting for you to exercise what you are an expert at?..........  

RE: Power/ Utility Pole

Typically the Transmission Engineer (could be Electrical, commonly Civil) details how the post insulators, or insulator brackets, or davit arms are attached to the pole.  *Somebody* has to be responsible for the design, right?

I've never seen it (the transmission design) left up to the installer, or the pole manufacturer.

Field drilling is common if something like a crossarm for a distribution circuit is attached to the same pole.  Even then there should be a design standard, and a work package from the estimator/designer.

What is the transmission voltage for this line?

RE: Power/ Utility Pole

Quote:

What would be the big deal with using thru-bolted hardware on a steel pole? What are the concerns here?

Do you mean field drilled at some random point through the pole? Now, I'm no structural engineer, but my understanding is that these things are hollow. Just running a bolt through the middle and placing it under tension (dead ending a conductor, for example) and the pole could squash like a beer can.

In my experience, attachment points for significant loads have to be properly reinforced (the odd street light is probably OK). At least that's what my structural people have told me.

RE: Power/ Utility Pole

It is a very common practice for steel poles, galvanized or weathering steel, to be field drilled for some or all of the holes.  Thru-bolts are the most common type of connection.  The design of those connections is often over-looked, which is a mistake.  It is generally recommended that holes be drilled in the center of the flats and that flat plate washers, say 4x4x 1/4 or thicker, be used to span the width of the flat.  Bolt shear, bearing at the bolt hole, over tightening of bolts and pole crushing due to unbalanced loads are the primary concerns.

ASCE 48-05 is currently under revision with some cautions regarding these issues.

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