Thursday, July 29, 2010

Compound lighting foundation size

I am sending up the following three images on compound lighting pole foundation details to fulfill a request by a friend earlier today.

Image 1 – The overall diagram of a five-meter lighting pole

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About the author:

He was supervising a construction job of several pumping stations at a remote location in the countryside.

The project was worth just above ten million (I think that was what he told me a few months ago), so the budget for the supervision team was not that high.

Being a little bit out of the way, not many engineers would be interested to fulfill the vacancies for the resident engineer posts with the salary the engineering consultant could afford to pay.

However, the construction works still have to proceed and the project still need to be completed and delivered on time. No main contractor would want to risk any possibility of delays especially in a design-and-build or a turnkey contract.

As usual, the best solution in this sort of situations is to employ just one resident engineer to supervise both the electrical parts of the work.

This way the salaries meant for two resident engineers (i.e. for electrical and mechanical resident engineers) is paid to just one making the vacant post much more attractive.

That was the kind of post this friend of mine took and he got a pretty good offer to supervise a relatively small jab.

Naturally there is a problem, however. He is a mechanical engineer who needs to look after all the electrical works also.

He needs a friend’s help now and then to ask for some free professional advice.

That was what happened today. He needed to advise the electrical contractor on the size of the foundation for the compound lighting pole.

Image 2 – The blow-up view of the foundation for the 5 meter compound light pole

There not much that I need to elaborate on this concrete foundation. It’s just a simple plinth with the size of 500mm x 500mm x 900mm.

Notice the mounting bolts and the high impact PVC pipe cast into the concrete.

This image above shows just one uPVC pipe sleeve. Normally you would want at least two sleeves: one to the left and one to the right because cables to the light poles are usually looped in and out from the previous pole and then to the next pole.

So the image above if for a pole that is on the end of the loop.

Observe also that the dimensions of the concrete base are sized at bit larger than the base plate or the bearing plate of the steel pole (See Image 3 below).

Image 3 – Bearing plate dimensions

This is to give enough clearance around all the mounting bolts so that there is enough strength of the concrete to withstand the load imposed to each of the bolt.

The size of the foundation above is actually one of the standard practices that I know for the light pole height shown above and you should have nothing to worry about.

Of course the type of the soil is a major factor. So if you have doubts just call the light pole supplier or just ask the civil engineer. This is just a simple common issue for them, so you should be able to get an immediate confirmation.

I have been using this size in all my projects and never had any problem.

See you again the next time.

Copyright Compound lighting foundation size

Friday, July 23, 2010

Site fabricated electrical trunking

What will be the problem if an electrical contractor fabricates the electrical trunking at the construction site? Why do I make an issue of this matter?

Picture 1 – Electrical trunking already installed at a new building under construction

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About the author:

Majority of Clients and Consultants that I know specifically state that all electrical trunking and the related accessories should be factory-manufactured and should preferably be obtained from the same manufacturer.

This means that all parts and pieces that make up an electrical trunking installation should purchased as finished products from factory.

Observe from Picture 1 above that one of the electrical trunking has been bent. That was to make room for something else that would be installed there later (it was not yet installed at the time this picture was taken. I am not yet very sure myself what that something is… which reminds me that I need to check it out soon).

The point here is that now and then electrical trunking need to bend and turn around things and other services and equipment along their path inside a building.

Because of that, we need the angle pieces of the trunking.

However, fabricating an angle piece from a straight trunking piece is the most economical alternative for many electrical subcontractors. That is why many of them usually try very hard to use this alternative rather than buying them ready-made from factory as specifically required by the Contract Specifications.

I was once faced with a contractor who just bulldozed their way and installed the site-fabricated trunking bends for eleven of the twenty floors of an office building.

The contractor thought he could play hardball and force me to accept and approve the installation.

Too bad he lost the battle in the end and he had to spend all the manpower and the extra “factory-manufactured” materials to redo the trunking installation.

The worst thing was that all the wiring had already been installed.

The three pictures below show a trunking bend being fabricated by the electrical worker at a construction site that I was involved in.

I rejected these works also and the rectification work should be done by the electrical subcontractor. The contractor knew I would not accept this sort of quality, but he thought he was smart I guess.

Why such a big fuss over this matter?

Because the site fabricated trunking accessories are almost always of very poor quality. The finished product usually produces very sharp edges all over the piece.

The sharp edges cut into the insulation of the wiring cables during the cable installation. When the insulation is damaged all over the place along the length of a cable, then it is no longer a good cable no matter how much you paid for it.

Wiring cables that have been damaged in this way not only become a maintenance headache to the operation people after just a few years, they are also dangerous and can cause deadly electrical accidents.


Picture 2 – 45-degree trunking bend

Picture 3 – Sharp edges of the trunking bend

Picture 4 – Site workbench where the trunking “accessories” are “manufactured”

That is all the time I have for this blog today. Visit this post, Electrical installation pictures, to see more pictures of electrical installations.

There are other posts that I have sent a few months back about electrical trunking installation. You need to browse around this blog see them. I will put their direct links to this post in a few days for the readers’ convenience.

One last note: I wish to apologize to my regular visitors for being away this past few weeks. I know this blog has been getting regular visits from quite a number of readers.

The last few projects that I have been involved in have been taking too much of my time and energy, too much more than I would normally like to spend.

I also wish to thank the readers who have left messages. If you like these pictures, visit again.

I, however, will not be answering messages yet on this blog because I think this blog has not yet enough contents.

Not only that, once I start answering your messages, then I would feel very guilty when I cannot spare time on them.

Again thank you for visiting. I sincerely hope that pictures and other information that I put up here are useful to you all.

See you again soon.

Copyright Site-fabricated electrical trunking