WWTP - Galvanized Steel 1

[bpstruct]

I am working on a wastewater treatment plant and I currently have galvanized steel I-beams shown to support some of the grating and diamond checker plating covering a coarse screening structure. The environment will be corrosive, especially in this part of the plant. I have used galvanized steel in some of the other plants we have designed, and it hasn't been questioned. It is being suggested to switch to aluminum on this project. I had then, as I do now, concerns about long term serviceability of galvanized steel. However, it seems that most metals exposed to this environment will require maintenance over time.

My question is whether aluminum outperforms galvanized steel substantially in these kinds of environments. H2S is expected to be an issue.

 

[dik]

It can... depends on the WW byproducts. My preference is HDG. Maintenance is essential and with aluminum and alloys, you have to be careful with any concrete contact due to alkalynity. HDG is generally tougher for a hostile environment. Aluminum is generally more costly.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Rabbit12]

We don't use any HDG steel. In the most severe corrosive environments we use FRP grating and supports.

 

[dik]

Sorry... FRP is best for corrosive environments... had my 'blinders' on...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[bpstruct]

How do you design FRP I-beams? I'm not familiar with those. Is there a guide?

 

[Rabbit12]

https://www.creativepultrusions.com/default/assets/File/DMV5R11.pdf

Here is a link to the design manual I've used.

 

[JedClampett]

You have three choices on FRP member design:
[ul]
[li]You can totally delegate the design of the area to a FRP manufacturer.[/li]
[li]You can use the tables linked to design the shapes.[/li]
[li]Or mix the two above (give sizes, but make the supplier submit their own calculations).[/li]
[/ul]
I've done them all. What I don't like about FRP is it gets worn due to foot traffic and frays due to UV exposure (I'm in Phoenix, so UV).

But back to the subject, we use a lot of aluminum in this situation. It's pretty resistant to H₂S damage, plus it's well referenced in codes. I also use HDG, but not in raw sewage channels.

 

[dik]

Jed... for what we miss in UV, we make up for in snow.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[rowingengineer]

We use aluminium in these types of situations, frp is ok, but getting product for heavy jobs is difficult. Isolation washers and inserts to all connection of dissimilar materials is normally required.

 

[Rabbit12]

Jed, good point about UV. I can't think of a place we've used FRP outdoors.

 

[dik]

Wascally Wabbit:
Just went through the manual listed... it's pretty good...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik