Serrated or Non-serrated grating 1

[cajun0000]

Our Company is designing a seven story refinery open structure (no roof or walls) which has continuous handrails and stairs for means of egress. The question is whether the working surface requires non-slip surface. The IBC 1003.4 Floor Surface requires it to be slip-resistant, but it all leads to the question of whether this structure is occupied or un-occupied. There will be routine maintenance throughout each day. I know this must have been decided prior to now but can not find any defined answer. Thanks in advance for any help.

 

[SlideRuleEra]

Our electric generating stations have large areas of open structure with grating... all of it non-serrated. A number of years ago I discussed this with a technical representative from Ohio Grating. They offer both types. His recommendation was to continue using non-serrated:

Their experience is that actual "slip-resistance" of both products is essentially identical.

For a given grating size, non-serrated has higher load capacity. Serrated grating has the "scalloped" surface to created the serrations. The scallops reduce both moment of inertia and section modulus of the main bars.

We have continued to use non-serrated grating, successfully.

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[dik]

If exposed to exterior, or moisture, then use serrated.

Dik

 

[cajun0000]

I am leaning toward using the serrated grating, but our Construction crew is wanting non-serrated to save on cost. It is all exterior and exposed to moisture. The means of egress makes it very clear to provide non-slip surface for the "access to exit" for occupied structures. Does anyone know whether this type of structure is defined as occupied or unoccupied in accordance with IBC? Thanks again.

 

[canwesteng]

Use serrated and galvanized or the operators will hate you.

 

[MotorCity]

For that size of an operation, I would expect your client to have a standard or requirement for grating used at their refinery.

 

[JAE]

Use non-serrated grating everywhere and have all the maintenance workers strap on ice crampons or something - lots cheaper!



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[IFRs]

Serrated grating ALWAYS. Even in a slight misty it is much less slippery not to mention the light film of oil that will settle on it over time in any urban environment. Especially if alumimum or SS

 

[thaidavid40]

I don't think that the building code is directly applicable to refinery structures, but OSHA is. Most oil companies have their own internal specifications, or else rely on Process Industry Practices ("PIP") specifications and details for much of the everyday structural design. If your client's company has no preferred specifications, then you can defer to the PIP practices, or to API practices. We use mostly non-serrated grating around here (North Alabama), as we don't typically get a lot of ice during the winter. Since we don't know how to handle snow and ice in these parts, when ice is present on grating, there's often no one around to walk on it!
Dave

Thaidavid

 

[spieng89]

I used to walk around on such structures and appreciated it when serrated grating was utilized in wet conditions. Grating can become quite slippery. What's the difference in cost? For a seven story structure you would think the percentage of cost to use serrated would be minimal and help operations in the long run. In the end if you're still unsure, ask the techs using the structure as it's their livelihood at stake.

 

[PEinc]

I would use serrated grating if exposed to weather. A grating can have a ice coating that is unnoticeable. It's like "black ice."

http://www.PeirceEngineering.com

 

[dik]

but, with grating, more slippery... <G>

Dik

 

[PEinc]

That's for sure. I found out the hard way!

http://www.PeirceEngineering.com

 

[SlideRuleEra]

1. What's the difference in cost?

2. For a seven story structure you would think the percentage of cost to use serrated would be minimal...

1. Typical non-serrated for our stations: LL = 100 lb/ft², use W-19-4 (1 1/4 x 3/16) Hot-Dip Galvanized Steel (Approx. Weight = 9 lb/ft²)

From NAAMM MBG-531-09:

Therefore serrated: LL = 100 lb/ft², use W-19-4 (1 1/2 x 3/16) Hot-Dip Galvanized (Approx. Weight = 11 1b/ft²)

Cost of grating proportional to weight: (11 lb/ft² - 9 lb/ft²) / 9 lb/ft² = Approx. 20% additional cost per ft²


2. Don't know about a refinery. For an electric generating station, several acres. Estimated 6+ acres for our larger units.

Can see where ice may be a game-changer. Rarely a problem in eastern SC.
Hot-dip galvanized surface should help on non-serrated.

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[spieng89]

Cost of grating proportional to weight: (11 lb/ft2 - 9 lb/ft2) / 9 lb/ft2 = Approx. 20% additional cost per ft2

Additional 20% in material cost doesn't say much without looking at total cost of project. If total project cost is 10 million and 50,000 is material cost for grating...an extra $10,000 is not much if it reduces insurance claims and possible worker comps in future. My moto think cheap long term not short term.

 

[SlideRuleEra]

...if it reduces insurance claims and possible worker comps in future.

The "if" is the key. As a former "sophisticated" Owner's employee, I would ask for reasonable evidence, not professional opinion, before agreeing to the extra cost. Where is the evidence?

To my knowledge (I have looked), OSHA does not offer an opinion on superiority of serrated grating.

Have looked (actually performed a pdf search) through the 112 page Ohio Grating Catalog. The term "OSHA" is not mentioned even once. You would think that a manufacturer would advertise a clearly better product.

It's all about reasonable proof. If the evidence is there... go with serrated.

BTW, total project cost for a generating station is more like $1 billion. Six acres of grating (material only) about $4 million. Add $800,000 to that grating cost to switch from non-serrated to serrated.

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