HBr material compatibility

[Pneuking]

This is my first post, so I'll lay it out.
I'm working on a fusible plug that is installed in a cylinder. I've worked out that carbon steel 10 45 will be a suitable material for the plug itself. The issue is finding out if the meltable portion will be compatible with the gas.

Gas: Anhydrous Hydrogen Bromide or HBr.

Plug fill material. ROTO158.
Bismuth 50.0%
Cadmium 10.0%
Lead 26.7%
Tin 13.3%

The idea is that the plug holds the gas in the vessel under 600 psi max unless there is a temperature event at 158 degrees Fahrenheit and above. The design of the plug has been tested to the pressure with a variety of fill materials.

So, having a straight yes would be great, I'm looking to learn why it is or is not a proper fill material.

 

[moltenmetal]

I can't say with certainty that the answer will be an absolute no- but the consequences of it venting due to corrosion would be horrendous, so you need to get this right! Somebody who makes and packages HBr (i.e. the customer for this plug) should be able to tell you that answer based on testing and experience. I don't personally know if the tin, lead, cadmium or bismuth can produce the bromide and hydrogen under dry conditions at typical storage temperatures, given that iron apparently can't- otherwise the iron would fail too.

 

[Pneuking]

Exactly, the plug is designed to offer a slightly less catastrophic situation. The end users equip the vessels with a scavenging unit that mounts to the plugs. Whether a high temperature event, corrosion, or any plug event, the gas is piped of to a safe area.
How would I figure this out on my own? No chemical compatibility guides I've found have enough detail.
BTW, Thank You MoltenMetal for responding.

 

[EdStainless]

Given that the HBr behavior is similar to HCl I would be concerned.
the issue is that if there are any metal oxides then the reactions will form water on the surface, and then things get very corrosive.
Perhaps you could cover the plug with a very thin foil of Pt or Au, both are used as rupture disc materials in HBr service.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[Pneuking]

I have seen a plug used by another manufacturer of HBr use a SS plug that utilizes a Pt rupture disc. I was just reminded that this plug I'm working on will have a Tantalum rupture disc. Thin or not, with a melting temperature of 5463 deg F, how is that going to work. Its being used with success now, but I'm not clear on how it all works together. The fusible material melts at 158 F. I guess that would melt out allowing the rupture disc to flex enough to rupture, but the HBr would have to expand significantly before rupture occurred. The timing of the events would have to line up correctly for the plugs to react properly correct?

 

[moltenmetal]

Tantalum loses strength with increasing temperature just like all metals- and it loses it faster than you'd think given its extraordinarily high melting point.

Not exactly sure of the arrangement you're talking about: is the fusible plug upstream or downstream of the rupture disc, or are they in parallel?

If they are in parallel, either a high external temperature (due for instance to external fire) OR a high pressure resulting from externally applied overpressure during filling will result in a relief event- which would seem to be the safest option against the big risk- rupture of the cylinder itself. However, in this case, the plug material is directly exposed to corrosion and will need protection as mentioned- something such as PFA coating or plating with gold or platinum etc.- but only if those processes can happen at temperatures below which the plug melts! PFA coating is probably out for that reason.

If the disc is upstream of the plug, the disc protects the plug from corrosion until it ruptures, which it presumably will not do until the plug melts. However the system would no longer be protected against overpressure at room temperature- the unmelted plug would be in the way.

If the disc is downstream of the plug, you still have the corrosion concern as well as the cold overpressure concern.

 

[Pneuking]

Thank you for the explanation. The disc is upstream. Overpressure is controlled by another means. I was told that the users of the gas have been caught using a forced air kerosene type heater on the tanks to get every bit of gas out of the tanks! Thats just too close to the line for me!