Use of long bolt flanges - fire protection 2

[JBernardi]

I have gotten conflicting opinions about the use and protection of long bolt style flanges in a chemical plant. One calls for the flange to be wrapped to prevent/decrease the amount of leakage in a fire situation. The other calls for leaving the flange open as the wrapping can cause corrosion. What experience have you had?

 

[bernoullies123]

No specific experience with such, but I was sent an email from my company's HSE department about the use of long bolts and the consequences in a fire. (I cannot find the presentation, I must deleted the email)
The wrapping may lower the temperature locally to the bolts and should help but with all wrappings you may be susceptible to CUI.

Here is a case study in China and their countermeasures for such.

http://shippai.jst.go.jp/en/Detail?fn=0&id=CC1300006&

 

[Devious]

No specific experience yet but I would think if you wrapped a flange similar to cladding on piping insulation, the wrapping would be outside the bolt circle so your risk should corrosion occur would be rather low. There would be ample opportunity to visually inspect for corrosion and you could put material between the flange and wrapping similar to clamp-on pipe shoes.

 

[SJones]

See attached.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[JLSeagull]

Can someone clarify what is meant by "long bolts"?

This is the second mention of long bolts that I have seen or heard within the last week. What is this about? Is this issue about long bolts such as non-flanged wafer style valves installed with through bolts? If so the solution is to prohibit wafer valves in hydrocarbon service.

 

[donf]

JLSeagull,

Don't know where the term originated, but yes, it is about wafer style components (not just valves, but also flow meters, etc.)

Donf

 

[bcd]

So to answer the question, yes, both are correct. During a fire, long, exposed bolts around the outside of a wafer-style component will heat up first, causing the bolt to loose strength. The remaining piping and gasket loads cause the bolt to stretch and the gaskets will leak profusely. Normally, the only way to get the components to pass the fire test standards is to insulate around the exposed bolts so everything heats up more evenly.

If my choice, I would push back against the "insulation causes corrosion" response. If not generously painted exposed bolting will corrode. Option is to use expensive non-corrosive materials. Paint the bolting then apply insulation is the most cost effective solution. If money is no problem, then only use lug-style components where the bolting shorter and is not exposed.

 

[JLSeagull]

Most wafer style valves and flow meters are also available with a single flange or double flange. Tap screws threaded into the body are much better than long through bolts. Avoid or prohibit wafer style components in hydrocarbon or toxic service.

 

[JBernardi]

I do appreciate the comments and information that has been posted. I have been involved in a training class, so have not had time to respond before this. Thank you very much.

 

[JKoenders]

Does anybody know what makes an acceptable fire-protective wrap for a flangeless/wafer component? Are there companies that fabricate/install a product for this specific purpose, or is it something I can simply ask a general piping and vessel insulation contractor to make up?

I asked our usual insulation contractor if it's something they do, and the answer was effectively "no", but he offered that they could make a removable steel mesh blanket with ceramic insulation within, but pointed out that there is a lot of liability when something needs to be fire resistant.

CCPS published a Safety Beacon on this matter - see attached.

 

[JKoenders]

... and I also wanted to add that our facility started phasing out wafer-style butterfly valves some time ago. We now only use lug-style butterfly valves. The best solution for this problem is to avoid using long-bolt style devices in flammable service. We do, however, still have a handful of other wafer-style components in flammable service, such as flow meters and check valves, which I would like to have properly fire-protected.

 

[rneill]

Try 20 gauge 316 SS wrapped around the flanges and strapped on with 0.5" x 0.020" 316SS bands.

The idea is the this will hold fluid around the bolts in case of leakage and the bolt temperature can't rise above the boiling point of the liquid

 

[JKoenders]

Seems to me that the wrapping must have an insulation effect. If liquid has escaped the flange, then the bolts have already been heated to the point of expanding. The goal is to insulate the bolts to prevent them from expanding and releasing any product in the first place.