Repair of Galvanized Silos

Aurizon's suggestion is likely a good compromise.

Consider the corrosiveness of both the environment and the silo contents. If those are mild, a simple repair of good brushing/blasting followed by cold galvanizing compound may suffice. The zinc-rich paint is a higher level of repair. Even higher still would be spray-galvanizing.

Also think about future inspection. If you can empty the silo periodically, you can see how well your repairs hold up, and then progress to a higher level if needed.

What was in the silos when they, "were exposed to fire for some time"?

Where are they?

What is the environment?

Wet?

Dry?

Humid?

What does your engineer have to say about repair?

Do you have an engineer?

NO?

You should get one if you don't have one. A local one would be nice. Someone who could perform an evaluation of the damage and recommend a repair.

Otherwise, divine intervention may be your best hope.

Of topic? Of topic????

You are kidding me, right?

What's off topic about questions and advice????

Yemen is a war zone, isn't it????

This might have been one of those prefab silos, made up of those sections of galvanized corrugated steel that is erected locally with ladders etc.

Sadly these things are easier to build than to take apart to get to the area where the heat oxidized or boiled off the zinc, leaving a naked, rustable steel surface in the inevitable water used to douse the fire.

There might have been a dust exposition, followed by a fire, or a fire in a wooden base structure??

Stored grain and or sileage needs galvanized steel - it is quite moist and thermal cycling causes wall condensation.

I stand corrected.

It seems that OP is an engineer with "12 wheat silos of 10000 tons capacity" in his charge, based on his thread from 10/24/2009.

Large silos indeed. It might have been a lightning caused fire. Corrugated iron, even if galvanized, would be a bad lightning conductor, since it would have a tortuous high inductance path and this would lead to numerous out-fork strikes to nearby people or structures - which any lightning consultant would advise. High metal thing are good attractors of lightning, unless liberally studded with air points that are well grounded.

Perhaps OP will advise us?

Silage has too much acid to be galvanized, that would need glass lined silos such as A.O. Smith Harvestors.

It most likely be a grain silo.

You might be right, I know maple sap can not be allowed to contact galvanized steel or the zinc dissolves and ruins the taste. It may well be the same for sileage = lining needed.

I believe leaching is the culprit. We make liquid smoke (which is a oil), and the most important part is the brix.

And as far as liquid smoke being oil, oil does have a acidic pH.

(has nothing to do with this thread, just thought I'd mention it.)

There is wheat inside and fire in silo from month before

We are in Yemen in south of Saudia Arabia and it very humid whether .

Our engineers do not have experience in this field .

1. Remove the wheat. Dispose of all fire damaged wheat.

2. Remove the scale and burned coating, both sides. (light sand blast OK)

3. Coat the metal with liquid zinc coating, both sides.

4. Weld zinc coated steel panels on both sides of the burned metal silo over the coated sections. (Use a certified breathing mask to wed the zinc panels)

5. Coat all exposed welds with liquid zinc coating.

6. Do not use the silo for 14 days.

If you're gonna wed a zinc panel, definitely wear a mask. Make the zinc panel wear one, too.

Repair of galvanized metal is not simple. First sand blasting is too abrasive. It will do more damage than good. Even the heaviest of metals are stripped using plastic beads sprayed like sand in a blasting technique. Then damage can be minimized and repair can proceed using thin film spray coatings.We do this on a regular basis, stripping metal for thin film coating.

Abrasive blasting using sand media i.e. sandblasting has been illegal in Australia since at least the early 80's (and I assume in many other countries) as it can cause silicosis. As has been said elsewhere, there are plenty of other blasting mediums to choose from which will provide a better and safer result.

OP is in Yemen. I doubt that Yemeni laws regarding silicosis are very strict, if they exist at all.

We are talking about Yemen. A very poor country!

Yemen ranks 151st out of 177 countries on the human development index.

They have plenty of sand there. They don't have OSHA or health laws like other countries and they don't have money for much of anything.

This forum is notorious for over complicating things, making suggestions that do not fit the circumstances of the OP and not stopping to think about what the OP may have to work with.

OP can't just order 50# of plastic blasting media or even ground walnut shells or baking soda.

Not to dump on you specifically, but we need to consider what is to hand for the OP. Not what we in fully developed countries CAN do.

Of course that doesn't make it ok....

but the infrastructure in these country's are more then likely non existent. Unless you visit the black market,.... But who knows.

I should have added that apparently nobody reads individual posts, either.

#10

"There is wheat inside and fire in silo from month before

We are in Yemen in south of Saudia Arabia and it very humid whether."

I am like everyone one else, I start at the top and comment, then read on and comment.

I do this instead of reading all the comments, because when I come across something I like to add, If I continue reading, I'll forget it.

ditto!

Other idea if it's possible, rivet and seal some stainless steel plate patches over the damaged sections, would eliminate the welding/zinc painting etc..

Sand Blast (or use the Sponge Jet) and metallize.

Suggest you follow the provided advice on removing the oxidation and re-coating all surfaces with zinc rich coating then wait for several days before refilling the silos with grain.

If you can afford the cost, it is possible to purchase a two-part epoxy coating that if applied properly will greatly improve the silo's ability to resist oxidation by providing waterproofing and by preventing direct contact of the grain with the silo walls.

I suggest you also consider that wet grain can suffer from spontaneous combustion so ensuring the silo(s) are waterproof is critical.

A simple aeration process that circulates air from the bottom of the silo(s) up through the grain and out through the top of the silo(s) can help keep the grain dry and prevent fires.

I think the fire is the issue on the structure and if its structurally sound, more than the corrosion.

Not having a picture of it, would you consider just leaving it as it is, at least on the inside.....

The out side of it, that can just be galvanized painted. (link as an example) No prep work. Just painted.