seeking suggestions for a stainless grating project I have been asked to build....

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Hi forum members,Aside from my bread and butter maintenance and repair welding, I get called on to build items for clients from time to time.  One of my clients is a commercial laundry.  They are expanding and are putting in some new equipment and are in need to cover a 7' x 3' rectangular concrete drainage pit with some type of stainless steel grating.  Stainless is a must as they operate in a very corrosive environment due to the laundry chemicals involved in their trade.  I was thinking 316 grade ss.What I have in mind is to frame the concrete pit with some type of "s" bar (so it will have two lips to work with) one leg will hang on the surface of the pit and the other leg will provide a "shelf" for the stainless grating either prefabricated or built by me depending on what I find on the market near me.  If I find no such shape, then I plan to take a ss angle and weld a piece of flat bar to it thus forming a second leg on it to form an "s" shape as described.  This is to avoid having to anchor the framework to the sides of the concrete pit by just having it sit in place.  The grating will be subject to normal foot traffic of a handful of workers who will be working this new equipment and going back and forth over the grating during their normal work routine operating the machinery.  The idea also is to have it built in segments so that they could be removed when there is a need to go into the pit.I have a few questions that I hope others who have been down this road before me might answer:1) Is such an "s" bar shape readily available by metal suppliers or is this considered a custom shape?2) What about stainless grating or "catwalk" material?  Is this stuff an off the shelf item or is it custom order?3) Would some  heavy gauge (1 1/2" x 9 gauge) expanded ss (non-flattened) work just as well?  I could just build a rectangular base out of inverted angles (with the leg up and horizontal) to act as a base for welding the expanded metal to.  This could sit on the "S" bar's lower "shelf".Any thoughts would be appreciated.  My only concern with having the frame rest on the surface is that it might prove to be a tripping hazard for the crew as they go back and forth over it during the work day since it would not be flush with the ground but be raised 3/16".Thanks for any feedback.TonyLast edited by therrera; 10-21-2013 at 04:13 AM.Reason: correct some grammar....
Reply:I would be in agreement as to a bit of a tripping hazard with the raised lip. Perhaps a formed 11 ga "Z" would help. There is fiberglass bar grating available, but I am not sure as to its resistance to chemicals. You might want to research it.
Reply:I build pit covers such as this reasonably often.  Typically they are built with two pieces of angle one forms the top edge and the other forms the support for the grating. The piece that forms the top edge is set flush into the concrete and has nelson studs set at 45 deg angles. The other piece is stitch welded to this piece.Obviously they are installed when the concrete is cast. Is there a reason other than simplicity that you do not want to anchor a support frame to concrete ? If this item is getting inspected you will need it to be flush with the floor. Welded grating has a twisted wire which holds every thing together it is pressed into the slats and welded. This wire sits proud of the slats so if the grate is already sitting above the floor the wire will be even higher.brad
Reply:Would it be better to anchor a piece of angle iron inside the opening for the grating to rest on? This way you would not have a trip hazard.
Reply:Here is a link for SS bar grating http://www.mcnichols.com/products/gr...ainless-steel/
Reply:316SS might not be the best material for your project.  316SS is good in many corrosive environments, but has poor performance when exposed to Chlorine-rich corrosives.  A laundry would likely use lots of bleach, which contains lots of Chlorine.  Might be worth checking with your customer to find out just what chemicals the grate would be exposed to.A better choice would be a Duplex Stainless steel, like 2205.  It's about the same cost as 304SS, if you can find someone that stocks it.  If you're building a custom grate, you might be ordering enough bar or flat stock that the cost would break even to special order what you need.  You'd also need the right TIG or MIG filler metal, 2209.You can buy Duplex SS material and filler metals from Rolled Alloys, Copper & Brass Sales (Thyssen-Krupp), Carpenter Stainless, or Outokumpu.http://www.rolledalloys.com/alloys/d...inless-steels/They need a little more care in welding, like keeping the interpass temp below 250F.  But for a grate, I wouldn't think this would be a problem.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Sorry, I forgot to mention an idea about your design.  Fabricating a Z from angle or flat stock makes good sense to me.  I would stay away from using expanded metal.  Too much flex unless you really build a tight grid of support bars underneath it.  Flat stock turned on edge is what they use for pre-manufactured gratings and stair tread.  That's what I'd use to build the entire grate.  Check your local building codes for any requirements on spacing between the bars and load capacity in a commercial environment.  Even if it only has foot traffic on it now, that might not always be true in the future.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Thank you all for the suggestions and ideas.  I will go the approach of anchoring to the walls of the pit.  You are right, now that I think about it, any time I've seen metal work on concrete walking areas, it is always flush with the surface.  Even if the tripping possibility is minor, it still exists and I'm glad that you pointed this out to me.  Regarding the type of Stainless: I was not aware of the need to prevent chlorine corrosion specifically.  You bring up a good point.  I think along those lines, I might consult with some technical source related to the commercial laundry industry that could suggest which grade is commonly used.Guess what??  I just got off the phone with my client and brought these issues up with him as I had already told him of my approach.  He agreed about making it flush with the surface.  He also added that they don't use chlorine so that would not be an issue, so it simplifies the selection of material grade.Thanks for the links.  I'll post the finished product pictures.Tony