Time limit for removing steel fireproofing for repairs?

[Liam Nesson]

Hi All,

I realise this might not be the correct location to ask this question, but maybe other engineers have run into a similar problem.

We are currently preparing to carry out structural steel repairs to the base of a furnace in a petrochemical facility. To complete the repairs we need to remove the fireproofing. Is there any guidance on how long the fireproofing can be removed for, 2weeks, 2 months, 2 years? Maintaining fireproofing throughout seems unrealistic. I know for temporary conditions, say a temporary foundation to dress a tall vessel before you crane it into position, can be designed for reduced wind and seismic loads. These reductions are based on duration and must take into consideration some level of risk. I am hoping there is something similar for fire rating.

The ideal repair process is as follows:
1. Remove a small portion of fireproofing
2. Test material thickness
3. Provided engineered detail and reinforce, if necessary.
4. repeat steps 1-3 possibly 5-10 times (this may take some time)
5. Removing all fireproofing at once is not possible as the steel is heavily corroded and we are concerned the concrete fireproofing may be providing some form of lateral restraint to the steel. Therefore we open a small section then repair and keep moving along.
6. All steel will need to be cleaned and painted at the end once strength requirements are satisfied.
7. Repair Fireproofing.

 

[phamENG]

Will the furnace be taken out of service? If not, I'd say no. You can reduce seismic and wind loads on temporary structures because they're driven by probabilities of occurrence of random natural phenomena. You're talking about predictable thermal loading of a structure by a man-made heat source. It's either going to be exposed to it or it isn't. This is a case for engineering controls, not probabilistic modeling.

 

[r13]

You should coordinate with the plant operation and maintenance managers to determine timing and duration allocated for the tasks, as they are the most knowledgeable on the equipment and structures in the facility, and ultimately responsible for the success and safety of all operations/personnel. I recall workers been buried inside of furnace by falling liner materials due to violation of safety rules.

 

[Liam Nesson]

Thanks for the responses!

I realise furnace base may not be the correct term as this implies part of the furnace itself, we are looking to repair the structure that supports the furnace. This is a structural steel frame fireproofed (concrete fireproofing) for an event in which the furnace would go on fire, or a hydro carbon pool fire would occur below. I have referred the client to a fire engineer, however I am trying to find any other information that I can.

PhamENG
Most likely the furnace will be operating. I presume furnaces themselves only go on fire every now and again , this is why I was leaning towards probabilities.

retired13
Again my question has misled, I will not be repairing the furnace itself or any internal liners.

What if the structure wasn't supporting a furnace, but was part of a building structure support system. How would you determine the amount of time that the fireproofing can be removed for?

 

[r13]

In general, you can only work around a furnace supporting structure during a scheduled outage, the length will vary depending on maintenance needs. I don't think there is limit on how long the steel can be kept exposed, but limited by the time given by the plant. So you need to have your plan drawn up, get in touch, discuss and modify your plan accordingly.

 

[HTURKAK]

.........1. Remove a small portion of fireproofing
2. Test material thickness
3. Provided engineered detail and reinforce, if necessary.....

Dear Liam Nesson ,
As far as I understand, you will perform destructive testing for fireproofing to see the remaining thickness of the supporting structure.

I will suggest you; conduct INCOTEST (INsulated COmponent TESTing) and see the remaining thicknesses of steel profiles and perform calculation to determine the remaining strength of the supporting structure.

Most probably, some of them will be heavily corroded while some of them could be still intact.

Regarding the heavily corroded ones , provide scaffolding to support temporary the furnace then make the necessary repair. I will suggest the changing of the columns with new ones rather than strengthening.

The following picture depicts collapse of an old spherical tank during hydrotest.

 

[Liam Nesson]

retired 13 and Hturkak, thank you for the additional comments.

At the moment we are trying to determine the extent of corrosion and can then determine a path forward on repairs / replacement of the support structure.

 

[dik]

You can check to see if there are additional measures that can be implemented to mitigate the fire proofing removal.


Dik

 

[Agent666]

Mitigate the risk, to run with dik's suggestion:-

Why not prop the beam with temporary fire rated support frames or columns for the duration of the works. Prove that under fire conditions if the worst happens that the loads settle into the new columns and design check beams and propping accordingly.

 

[JLNJ]

Since this isn't building-code related there are no hard and fast rules. It's a matter of the risk tolerance of your client. Once the client calls the shots, you avoid (or at least greatly reduce) your liability.

 

[dik]

In some jurisdictions it could be code related...

Dik

 

[r13]

My advice is not to overly obsessed with code provisions, in a live plant, there are many real hazards to be concerned with, lend your ears and pay attention to the plant representative, and ask questions.