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What is the purpose of anchoring a transformer that weighs 15,000lbs?
2

What is the purpose of anchoring a transformer that weighs 15,000lbs?

What is the purpose of anchoring a transformer that weighs 15,000lbs?

(OP)
I look at the work we are performing and just wonder why do we have to anchor such a big heavy piece of equipment?
Do utilities anchor transformers to their concrete pads?

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

Earthquakes are very good at moving heavy objects.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

Quote:

Do utilities anchor transformers to their concrete pads

Not always done in times of old, but it is generally a requirement today due to seismic concerns, as David pointed out.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

(OP)
Actually the point of my question is that we've anchored many transformers down on a concrete pads. Our Client, has found in the manufacture's literature that the transformers should be anchored a specific way.

We had a reason we did what we did, as the concrete pad wasn't wide enough to do it as it was shown. So you guys are saying an earthquake force comes along, enough force on its own could move a 15,000 dead weight...and those anchor bolts are going to hold that down?

I'd like to know how they determine the size, strength and where those bolts gotta be placed in order really know that.

It all comes down to money, such a trivial thing will end up costing $1000s to fix. It always does.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

This reminds me a bit of the contractor who thought that, because my Main Battle Tank weighed just shy of 65 Tonnes, there was no point in lashing it onto the low loader. The subsequent picture made page 7 of the Sun.

A.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

I had a problem understanding what you needed a Main Battle Tank for. Then I saw the (Military) after your nick. Never thought of that before.

OK that bolts could help ride through a mild earthquake. But the tougher ones?

OP: What are the typical magnitudes of your earthquakes? Ours are 1. mostly absent and 2. infrequent and 3. below 2 on the Richter scale. We had one around 30 years ago. Then I thought it was the neighbour's wife that hit the barn door (outhouse, 50 m away) with the tractor again.

If you are in a similarly geologically quiet zone, you may get away with the installation as-is.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

Yes, that is what we are saying. The design engineer will specify a particular seismic zone and that determines the horizontal and vertical forces that the transformer must withstand. The civil engineer designs a pad with sufficient mass and reinforcing and the transformer designer determines an anchoring system that will withstand the specified forces. If you install it per the manufacturer's specs and it fails, then shame on him. If you do it your way and it fails, guess who is to blame? Seismic forces can destroy structures that are orders of magnitude more massive than a transformer. It seems trivial until the earthquake happens.


http://www.iitk.ac.in/nicee/wcee/article/13_1605.p...

http://www.asce.org/uploadedFiles/Institutes/Techn...

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

After the earthquake, the power company is going to want to use that transformer immediately ... NOT wait 6 months for a replacement to arrive..

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

(OP)
I read an article on line that said the strongest earthquake ever in this area was 3.4 the Richter scale. I lived through a 5.4 a few years ago and can honestly say that I didn't have to move even my 10 lb coat rack back into place or my 200 lb couch.
Again we did anchor these transformers firmly to the concrete, but we went through some other tabs on the base that we were told are there to attach the transformer to shipping pallets. we will end up changing it I'm sure and eat all the costs. 15000 lbs in a footprint of about 3' x 7' oh and about 21 huge underground primary and secondary feeders are attached to this thing...I'm still having a hard time believing this.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?


Definitely it is better to anchor the base of transformer to foundation esp in earthquake prone areas. It is not a good practice to leave alone as the tank base can slide even under slight tremors.

The standards for Seismic design of Transformers are covered in the following:

IEEE Standard 693-2005 Recommended Guide for design of substation
IEEE Standard C57.114-1990 Seismic Guide for Transformers &Reactors (withdrawn in 1996)
IEC TS 61463 -2000- Bushing seismic Qualifications
IEEE Standard 1527 –2006 Recommended Practice for the design of flexible bus work in seismically active areas.

The above standards do cover about anchoring:
Quote
4.2 Foundations. The transformer and all interconnected equipment should be placed on a monolithic foundation so as to reduce differential movement due to the design earthquake. Provision should be made to accommodate expected differential motions between equipment mounted on separate foundations but which are interconnected. Provision should also be made for interconnected equipment mounted on the same foundation but having differing frequency content. Lastly, consideration should be given to the interaction of underground conduits and the foundations. Foundations should withstand all forces resulting from the design earthquake in the vertical and horizontal directions simultaneously. A comprehensive soil survey is recommended to determine if any unusual conditions exist at the site that would warrant special design considerations for the foundations.
4.3 Anchoring. It is recommended that transformers be anchored by welding the base to structural steel members embedded in or firmly anchored to a concrete foundation. Size, location, and type of welds should be shown on the manufacturer’s drawings. All welds must conform to applicable AWS specifications. AISC weld allowables should be used. However, the one-third increase in weld allowable stress due to earthquake loads should not be permitted. If bolts are to be used, size, strength, location, and materials should be shown on the manufacturer’s drawings. The size and strength of the anchor bolts should be determined by bolt material allowable stresses. However, the one-third increase in bolt allowable stresses due to earthquake loads should not be permitted. It is recommended that mild ductile steel, such as A36 or A307, be used, and that design philosophy such as stated in the article, “Design of Threaded Anchor Bolts” by John G. Shipp and Edward R. Harringer, Engineering Journal, AISC, in the second quarter of 1983, be followed. The length of embedment and the type of bonding to that portion of the anchor system within the foundation should be determined by the user and should be greater than the strength of the bolts attaching the equipment to the foundation. Consideration should be given by the user to any unequal distribution of dynamic earthquake loadings on the anchor bolts. All anchor systems must withstand the forces resulting from the design earthquake. (from 1990 IEEE standard)
UNQUOTE

As you can see there are two practices –weld the base of transformer to the anchored plate on foundation (popular in US) or use M24 or M36 Foundation bolts on either (longer) sides of transformer. Bolts are taken from the roller frames mounted on rails on foundation.(one or two bolts from each frame). This is found popular in Japan (where they experience maximum number of minor tremors)and also followed in India.

Another point to remember is higher the load, less g it can tolerate!


RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

Once saw an oil-filled 115 kV circuit breaker rip itself clean off its concrete pad, shearing all its'hold-down' bolts in the process, due to the mechanical forces generated during a relatively close-in slow-clearing electrical fault. Miracle the tank wasn't ruptured...

Reason enough?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

(OP)
Crshears,
Is there anything in any standard that requires anchoring a transformer for the express purpose of keeping it intact during a fault? It's much more likely than a 8.0 earthquake yet I don't recall ever seeing anything like that.

As I pointed out, an earthquake would be an extreme rarity. I used to work for a chemical company that has and still does have on every drawing "Minimum Essential design is the requirement" and is the company policy. And another thing they had in their specs I always remember..."do not design for catastrophic failure". Doing either costs money. And money is not an unlimited resource. The money you spend unnecessarily could have been perhaps used for something much more beneficial. This won't be that big a deal but just thinking this way is what bothers me.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

OK, your chemical company can go out of business following an earth quake that does too much damage, or ride on business interruption insurance until they can get their feet back on the ground. Do you want your local power company to take the same approach?

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

You, an electric engineer working with power transformers, are trying to "argue the Code" (for structural earthquake standards in your particular area) because "the transformer is very heavy" ....

Don't do it.

In this case, the solution is simple, not actually very expensive in the big scheme of "providing power after an earthquake", and straightforward.
Look up the Code,
Understand the relevant parts of the Code,
and, finally, Follow the Code.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

(OP)
This is maybe the most successful chemical company in world history. They didn't say do bad engineering.. They said do what is required no more no less. That approach is exactly why they are successful.
A power company or a chemical company would probably be criminally negligent if they didn't design to seismic standards in San Francisco. I'm not arguing that.
This is a no risk seismic zone. But a generic detail is ruling the day and trumping a reasonable installation and changing it will just add cost to the project. The problem is this mentality doesn't just show itself once like here...it's all over the place. And America wonders why it can't compete.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

A few years ago, a quake south of Memphis rattled houses as far north as Chicago.

A quake in Charleston broke chimneys across the Atlantic seaboard.

We were woken up by an earthquake across the border in Alabama from a quake that was felt over in South Carolina.

A nuke power plant in Virginia was shutdown by a quake there.

There is an active fault down the St Lawrence River bed with regular earthquakes.

Where do you think is a non-seismic zone in the US?

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

(OP)
I concede I don't have all of the seismic data memorized for the USA.
Where these transformers are anchored in 4 places are within 6" of where the mfg says to anchor, through the same gauge steel at the 4 corners.
The pads were not designed or installed by us and the underground conduits were not installed perfectly. The pad left maybe 5" on each side in the long direction - not much. In order to get the transformer to fit over the duct banks it had to encroach on this 5" leaving even less room and no room to anchor as per the mfg detail. And that's how things are in construction.
So what would you do? I guess we could have them remove the xfmrs, bust out all the duct bank, send it back to engineering and have them redesign the pads and bust all them out too. we must get it exactly per a generic detail to plan for an earthquake that hasn't ever happened because those anchors will save the day.
Or perhaps we could stand back a say what do these anchors really do? And will it really make any difference if they were moved slightly? Call me crazy.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

Have you considered asking your structural engineer to:

1) Evaluate the manufacturer's design;
2) Evaluate your as-installed design; and
3) If the former is superior to the latter, engineer the difference?

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

I'm confused. You seem concerned with the financial burden you (your company) will shoulder by fixing the installation yet you are posting that you were not responsible for the engineering or installation of the transformer base. So, why would you have any financial responsibility to fix it? Take a technical response back to the owner explaining how the pad is bad and won't accept the proper anchoring and make the person who improperly installed the pad responsible for the expense of fixing it.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

Yeah, that, what Lionel said.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

Yeah - What Lionel said above: Have the company that put in the bad pad pay for a simple - BUT ADEQUATELY DESIGNED! - "adapter pad" between the anchors in the concrete pad and an "acceptable" location on the transformer body/frame/side tank walls.

The turnover resistance is what you require, not the "use of a hole on the side of the transformer" placed there for anchoring the transformer "as intended" ...

But, no, you do not have a ethical ability to decide "I am not going to anchor the transformer because it will be expensive ..." Unless you sign the insurance bill for your company.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

(OP)
The client is aware of the reason the anchors won't go in as detailed. It's obvious. When we first installed these transformers the doors wouldn't properly close on the high voltage air terminal chambers. And the reason was because the pads weren't perfectly level. But instead of shimming them up what did they say? We were at fault for not surveying the pads before we set them. So we took the transformers off the pads and those that did the pads came back out and leveled them.
See what I say of the mentality here.
It cost thousands for both companies. And gained what?
Arguing or suing a client who is paying you millions to do projects is impractical. You might win the battle but you will forever lose their business. So you do what they say. Blaming the other company won't work either. Been there done that.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

Well if you're not willing to force responsibility onto the party responsible for messing up the pad then you'll have to suck-it-up and just fix it yourself.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

(OP)
I can see those that poured the pads saying it was the engineering company's fault because the duct bank was sized too big and they didn't leave enough space to begin with. No room whatsoever was left to make any adjustments. The ducts would have had to be in there to the 1/10 of an inch for this to have worked out. I don't think people that pour these kinds of things are used to that kind of precision.
And then I can hear the engineers say it is the mfg fault for not making the termination chambers big enough. And then I can hear the mfg say it's worked for everyone else.

We haven't done this yet, actually thanks for your comments I will suggest it to tptb that we shouldn't have to take the hit for this.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

In the last years, our substations have been hit by significant earthquakes (e.g. in Aquila in 2006, PGA=0.675g and Emilia Romagna, PGA>0.3 g).
Some equipment suffered heavy damage and had to be replaced: 420 kV CBs were find to be the weakest point.
Our EHV/HV ATRs, which were not fixed to the ground, did not suffered heavy damages: only in one case 420 kV porcellain bushings, which were actually rated only up to 0.3 g, were damaged.
In fact active part of the transformer is designed to resist significantly higer mechanical stress durind transportation (often exceeding 0.5g) and during short circuits. Use of RIP bushing with silicon housing, will substantially reinforce the transformers, which however even without anchoring are probably the most robust equipment in a substation, if compared to CBs, CTs and VTs...

Si duri puer ingeni videtur,
preconem facias vel architectum.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

(OP)
FPelec,
I think you make an excellent point...that your transformers and all transformers are made to sustain minor vibrations just so they can be transported. The last transformers we bought were made in Europe. They travelled by truck, by ship, by rail and again by truck before they arrived on our site. Just think of all the jarring and vibration they went through traveling and during the multiple times they are lifted and sat back down. It would interesting to me to find out what the g scale equals on the Richter scale.
As a follow up on this...as I knew we would we are changing all these out. When you are fighting against a mfg detail you will lose every time. Even the NEC requires that you install per the mfg instructions...as it should be. Actually after a closer look we could have in most situations installed per that detail. We did have to deviate some as described but we did them all that way. Our major fault is that we didn't even look at the detail. Lesson learned for me even routine installations you've done a 100 times look at the mfg literature for installation. And any deviation you best get TPTB to buy in before you do it.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

The reasoning I would think that you anchor the transformers down is because of minor vibrations, such as those caused by big rig trucks, trains, or airplanes. I don't think that any one of those on its own would cause the transformer to vibrate off the pad, but over time you could find yourself looking at an outage caused by that has "magically" fallen off of its pad (assuming that it wasn't hit by a vehicle). I've observed a few un-anchored transformers that were very cock-eyed on the pad in a very low seismic area. The sum of a bunch of very small vibrations could cause the transformers to move off its pad.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

bdn2004, there is no precise equivalence between Richter scale and peak ground acceleration (g); however some rules of thumb apply. For instance the Italian standard CEI 75-16 "Environmental conditions appearing in nature - Earthquake vibration and shock" (there should be an equivalent IEC standard) reports some correspondances: 0.5 g are associated to Richter scales >7. See the attached files for further information.

Si duri puer ingeni videtur,
preconem facias vel architectum.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

bdn2004,

Consider specifying impact recorders for shipment. They will tell you the acceleration forces experienced.

RE: What is the purpose of anchoring a transformer that weighs 15,000lbs?

Read ASCE Manual 96 for a better understanding of substations (and transformers) for performance during seismic events. At a minimum, use .10g.
Travel forces of transformers from the manufacturer's plant to the final destination can be many times greater than the seismic requirements, but that only addresses the core/coils as the transformer is not dressed at that point.

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