Steps to Determine a Fire Resistance Rating?

1/13/2023

I’ve been reviewing standards to determine the equivalency between fireproofing thickness and the fire resistance rating.

This is for an industrial plant structure. I realize there are many factors but at some point I need a reference to determine what the rating is required to be.

What is the process to determine what the required fire-resistance-rating of a component needs to be?

In this case, it is for structural steel supporting columns of the open structure. The structure is composed of the main support columns and those supporting vessels, etc. The structure is about 5-6 levels tall. For simplicity I wanted to address the main columns starting on floor 1 where a pool fire may start. If I could find the standard / guidance for this then I can adapt for vessel supports, etc.

I’ve been through calculations and information from API 2218 to determine the fireproofing thickness for a certain hour rating. However, I have yet to determine or find the hourly rating requirement.

I’m assuming it will be 1-3 hours, for example, using API 2510 (LPG) as a guide with reference to UL 1709. It does specify a 1½ hour time rating which then gives a fireproofing thickness. Further, the fire protection requirements will come from a risk assessment of the system. I have to be able to give guidance to the risk team to help them come to suitable answers.

What can I use to provide a best answer to an hourly rating, hopefully, chapter and verse?

Thank you for your help in advance.

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5 Comments

James Stever Jr

1/13/2023 09:30:23 am

Check your applicable building code to find the code required rating and the reference standards applicable to the building code. Also check UL

Todd E Wyatt

1/13/2023 09:50:30 am

The Design Professional (e.g. Architect, Engineer) determines the Type of Construction (TC) of the Project based on the applicable Code(s) (e.g. 2021 IBC, 2021 NFPA 101 Life Safety Code).

Per 2021 IBC, the Types of Construction (TC) are identified in Chapter 6. There are (5) TCs :
Type IA/IB
Type IIA/IIB
Type IIIA/IIIB
Type IVA/IVB/IVC/IVHT
Type VA/VB

2021 IBC Ch 5 General Building Heights and Areas establishes the “limits to which a building can be built” per the Building Height, the Number of Stories, and the Building Area. These (3) “allowables” are determined by the Project’s Type of Construction (TC), the Occupancy Classification(s) (OC), and IF the building is protected by an automatic sprinkler system (ASPS) or not.

You state “This is for an industrial plant structure.” We’ll assume that this should be classified as a "Group F-1 Moderate-hazard Industrial" OC.
You state that the “structure is about 5-6 levels tall”. We’ll assume that it is (6) stories.
You do not clarify if it is protected by an ASPS so we’ll evaluate both possibilities.
You do not clarify what the Building Area is by individual story.
You do not clarify what the Building Height is.

If we start with Table 504.4 Allowable Number of Stories Above Grade Plane, a 6-Story “F-1” OC is limited to the following TCs :
ASPS (Yes) = IA, IB, IVA, IVB
ASPS (No) : IA, IB

Based on these (4) TCs, here are the minimum required Fire-Resistance Rating (FRR) of the “Building Components” :

IA (Noncombustible)
Primary Structural Frame = 3 Hrs
Bearing Walls (Ext) = 3 Hrs
Bearing Walls (Int) = 3 Hrs
Floor Const & Secondary Structure = 2 Hrs
Roof Const & Secondary Structure = 1.5 Hrs

IB (Noncombustible)
Primary Structural Frame = 2 Hrs
Bearing Walls (Ext) = 2 Hrs
Bearing Walls (Int) = 2 Hrs
Floor Const & Secondary Structure = 2 Hrs
Roof Const & Secondary Structure = 1 Hrs

I did not include Type IV since this is “mass timber”.

Using Type IA and Type IB, the “unknown” allowables are as follows :

Type IA
Building Height = Unlimited
Building Area = Unlimited

Type IB
Building Height = 160-feet
Building Area = Unlimited

Type IB appears to be the "least" compliant TC. The “Primary Structural Frame” which includes the columns would need to have a minimum FRR of 2 Hours.

Chuck Riforgiate

1/13/2023 10:41:27 am

The International Building Code in Section 722 provides a prescriptive method to calculate fire resistance ratings of materials and assemblies. This section also contains provisions that would permit modifications or changes to a tested assembly. Section 722 includes methods for calculating fire resistance for seven different construction materials: concrete assemblies, concrete masonry, clay brick & tile masonry, steel assemblies, beams, trusses and wood assemblies.

Ryan Hinson

1/13/2023 10:45:37 am

Does your client have their own design guidelines? Many do.

One petrochemical company I do work for, requires the following:
- "PFP materials shall be designed to provide a minimum of 3 hours of protection against hydrocarbon pool fires and 30 minutes against jet fires, appropriate to the hazard. The ratings shall be based upon assessment of substrates protected with PFP exposed to a hydrocarbon fire test or jet fire test procedure in accordance with ISO 22899-1."
- "Where the structural steel can be subjected to both a jet fire and a pool fire, the PFP system shall be protected for a minimum of a 30-minute jet fire and 3-hour hydrocarbon pool fire. The total fire duration shall be a minimum of 3 hours."

Another requires a minimum UL rating of 2 hours with the following statement, "Structural steel members shall have a UL 1709 certified design if applicable. If structural members do not have a UL 1709 certified design, an engineering analysis that demonstrates equivalent protection shall be provided to the Principal for review and comments."

If you do not have client guidance, I would start in API RP 2218 (2020) Section 4.2 and Tables 1 and 2 as you indicated. From there, fire scenario development based on realistic worst-case potentials specific to this facility/location is advised to determine the extents of the envelope(s) based on the hazard potential of the equipment.

What is the highest level where liquid may pool? What is supported on the racking within the determined fire scenario envelope? Is exposure to a jet fire expected in addition to/in lieu of a pool fire?

The selection of the fire resistance rating is explained further in API RP 2218 Section 4.2.5 and is based in part on severity and duration of the fire scenario previously developed in addition to any time delay prior to application of cooling streams and available durations.

In API RP 2218 Annex D Section 4, a rule of thumb comparison between building oriented fire-proofing tests like ASTM E119 and UL 1709 by one petroleum company reduces E119 ratings by a third while another's testing indicates a 15-50% reduction. Usage of UL 1709 is directed for GAPS 2.5.1.

Protection above 40 ft above the highest poolable level or or 40 ft away from edge of an expected spill is the starting point for liquid hydrocarbon fuels per Section 4.2.4 and Table 1.

The best direction I can find after briefly looking is EITHER:

The example given in API RP 2218 Section 4.2.5.1 for a moderate exposure where cooling can be applied in less then an hour, the equivalent of a 1½ hour UL 1709 rating is considered reasonable whereas, if emergency response is 1½ hrs away, a 3-hour rating is more appropriate.

OR

Conservatively, the first one I gave above from an actual petrochemical client.

Obviously, site/rack/structure/response-specific conditions must take precedence.

Good luck!

fire sprinkler companies near me link

6/17/2023 02:53:57 am

How Can I Tell If Something Is Fireproof? a lot of queries are brought up concerning how to calculate the needed fire resistance rating for components in a manufacturing plant. In order to determine the appropriate thickness of fireproofing for structural steel supporting columns, the author requests recommendations for relevant standards and reference materials. Reviewers applaud the author's research on API 2218, however they note how difficult it is to pin down the precise hourly rating required. It would be helpful if the article expanded on some points or linked to related material. However, the review provides a good place to begin for experts seeking information on how to evaluate buildings for their fire safety. Many people, in the future, will read this, I have no doubt.

Steps to Determine a Fire Resistance Rating?

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