PTFE modified Firesafe property

[aldocigna]

In my refinery many PTFE modified gaskets (Garlock Red Gylon type) are used in H2SO4 piping. Recentely many PTFE lined ball valves are used too.
I want know your opinion and your experiences about the firesafe property of this material inside the Alkilation plant and inside the pipeway outside of the plant

Thanks
Aldo Cigna

 

[gerhardl]

Flange gaskets for piping joints and / or valves? Seat or stem gaskets for valves (and what type)?

'Gaskets' compatible to your liquid and temperature (PTFE,FKM) will in a fire melt or burn at a certain point (depending on fire development).

If the normal inforced are not compatible, there could be that neiter certified firesafe gaskets or firesafe tested /certified valves exists in the market suitable
for your process.

Remember that firesafe tests for valves actually involves
a complicated and costly test where you actually test with fire and burn out the valves, and that you afterwards have to test with pressure against minimum leakage requirements.

You therefore have a difference between a firesafe certified tested component, and a certified designed component. The design is similar to other components already tested, but that particular type, size or pressure class (whatever) is not tested istself.

If you do not find components that qualify in either aspect all fire-resisting estimates for a product will then at best be a non-qualified guesstimate, with at best a doubtful juridical backing, should the worst happen.

In this case my advice is to look at the total fire and accident protection for pipeline with sourronding buildings, areas etc with emergency shut-downs, relief, fire- and explosion preventing devices.

 

[aldocigna]

I've found in the Klinger internet web site the PTFE gasket type Top-chem-2000. It's an API6FA firesafe certified gasket. Perhaps it is a possible solution.

I've found in the EngineeringValves internet web site some firesafe certified metallic ball valves with a PTFE metal renforced seat

Perhaps, in the same way, could be possible find a firesafe certified fully lined PTFE ball valves. Do you know some ones?

Thanks very much

 

[aldocigna]

Does someone know a commercial type of fire-protection split bolted shell to protect some ptfe internal lined metallic bellows or ptfe fully lined metallic ball valves?
Dn100 and DN200

Thanks
Aldo Cigna

 

[hacksaw]

what metal temperatures are you expecting for the fire rating

 

[aldocigna]

i don't know it
The ptfe lining have to remain under 200°C max
the protection should be like api 6fd firesafe std

 

[hacksaw]

acid is pretty corrosive at high temp and non-flamable compared to the fluids in the alky unit,i understand your design spec for fire safe given the HC, but you are working with an acid plant, different rules apply as a rule, electrical safety issues excepted.

good luck

 

[aldocigna]

The problem is relative to pipeway where many hydrocarbons pipeline run near the acid pipe. In the last year we had a very big fire that destroyed all pipeline. But the problem is inside the alkilation plant too where there are many light hydrocarbons products
We have one H2SO4 regeneration plant but in that case there is no problem for fire
At first the piping specification previewed asbestos gasket (Garlok 400) for this service but now actualy we use PTFE gasket and packing and PTFE lined components. The garphite products (Gasket for example) are not usable in H2SO4 service >95%

 

[hacksaw]

the problem is understandable, but even welded pipe (no gaskets at all) is rapidly destroyed above 200C when it contains acid.

 

[joeswoes]

If a fire breaks out around Teflon lined valves, very corrosive and worker-unfriendly fumes will emit and the lined face which is sealing against the gasket will go away. Worrying about the gasket is a waste of time. You either get corrosion resistance with a valve that will disintegrate in a fire, but is inexpensive, or you put in an API-607 qualified valve of suitable metallurgy to the sulfuric acid and bolt it up with spiral wound gaskets. Spend the money now or later, I guess, we all face that one.