Flame Arrester Materials of Construction 2

[Fzob]

Hi to all.

I need to replace a 6" flame arrestor due to corrosion. The MOC is Hastalloy C, and costs about 30K to replace. Repair is not possible due to the extent of corrosion. The vapors it is exposed to are a combination of wet HF and HCl, is low concentration (approx 1% to 5%) and ambient temp. Of course most of the balance is flammable gas.

My question is this; are there any flame arrestor designs that are corrosion resistant and made out of a coated or non metallic material?

Thanks in advance

 

[JimCasey]

Coated or nonmetallic material would defeat the purpose of a flame arrestor. The wat a Flame arrestor works is to cinduct the heat out of the fuel/air mixture faster that the heat is liberated by combustion. Hence the flame will not propogate through the element and it is "arrested". Nonmetallic materials are inherently less conductive than metals and coatings are nonmetallic.

Hast-C is pretty corrosion-resistant, but you might look at monel or titanium as alternates. Both are used in applications where they are required to resist corrosion from free halogens.

Plan 2 is to change the type of flame arrestor. If the original unit has a crimped ribbon-type arrestor, those are efficient but the ribbon is very thin and there is not much material to be corroded. An alternate construction is the stacked disc type where a stack of discs with a hole in the middle are assembled with thin spacers between each. THere is a blind disc at the end of the stack. The discs tend to be more robust (1/16" inch thick) so there would be more material to withstand corrosion.

 

[Rocco8]

Try and scrubb out the acid gases prior to going through the flame arrestor. The combination of wet HF and HCl is a very difficult gas stream to contend with corrosion wise. The alloy ALX6N might be considered but I don't think anyone makes a flame arrrestor in this material. If all else fails consider an explosion isolation valve to replace the flame arrestor.

 

[TrevorP]

Sounds like you probably need a detonation arrestor rather than a flame arrestor. In essence, a flame arrestor should only be used on an end of line application (or within a few metres of it) - e.g. on a storage tank. In line applications require a detonation arrestor. Check it out with your supplier, and make sure you get the right type. It could be overlooked, especially if your focus is on getting the material of construction right.

 

[PAN]

Fzob,

-Do you have valves in this line? What is the body and trim material?
-Do you also have corrosion problem in other portions in this line?

 

[rolledalloy]

I would not suggest AL-6XN for a flame arrestor application. Its high molybdenum content is good for aqueous corrosion, but above 1000F it leads to embrittlement of the alloy. We suggest AL-6XN be used to a upper temperature limit of 800F to be safe.

 

[Rocco8]

If a flame arrestor reaches 450°F throughout the unit the flame front on the front face passes through. So temperature would not be an issue. Rolledalloy thanks for the temperature information. In general a secondary action of an inert purge is required to snuff the flame. An air purge can sometimes be used to move the HC concentration below the LFL extinguishing the flame.

 

[krossview]

Fzob

Check out Tornado Technologies as an arrestor vendor as they use aluminum ceramic beads for flame cell material, which are resitant to oxidation and corrosion. You will need to contact them the about the use of Hastelloy C or other alloys for construction of the body and flame cell housing.

Also check out plasma coati as there are companies out there who do some great work in coating CS with exotic alloys. This may be a more cost effective way to go.

Krossview

 

[erdie]

You may want to check out

http://www.protego.com

for this type of application. I have had some experience with specifing a detonation arrester that utilizes a PTFE element. It really solved a tremendous corrosion problem at a vitamin e facility.

So, to answer your question, yes there is something out there that is non metallic that you can use.
good luck!!

 

[erdie]

PS. They really don't promote this very well on the web and may be hard to find, so if still interested let me know.

erdie