Fusible Link Failure

[Footer]

Came in today for a show in our small space. During a client walkthrough for another show in our larger venue, we went to run our firewall out and it did not move (firewall comes in every night for security purposes). After looking into it further, one of the fusible link s in the "cut the rope" system split apart. There is no sign of fire or heat. The link was closest to the deck. I don't have a picture of the failure, but it looks like the solder tore from the inside of the link. Has anyone seen this before? Rigging install/inspector types, is there a lifespan for these things? Is it something we should add to our maintenance cycles? The wall was already in when it broke so we did not have a false trip situation, but its not something I want to see again, especially during a show.

 

[derekleffew]

FromStage Rigging Handbook by Jay O. Glerum, page 263:

...Second, the solder on these devices deteriorates with age. Fusible links have been known to open and lower the curtain at inappropriate times. The manufacturer recommends replacing them annually. It is a good idea to have some spare fusible links on hand. ...

Replace yearly? Yeah, we know that's not going to happen. I'd also like to see a substantiation of Mr. Glerum's quote.

See also UL 33.

 

[gafftapegreenia]

A thought: perhaps the daily opening and closing of the fire curtain decreases the lifespan of a fusible link?

 

[avkid]

A thought: perhaps the daily opening and closing of the fire curtain decreases the lifespan of a fusible link?

Should it not be designed for that exact circumstance?

 

[Sony]

I've been told by a couple people the average lifespan for a fuseable link is about 3 - 5 years depending on who you ask, usually after 3 - 5 years they cannot be guaranteed to hold anymore. It was recommended to me that we should replace them every 3 years.

 

[Footer]

A thought: perhaps the daily opening and closing of the fire curtain decreases the lifespan of a fusible link?

Nope, the fusible link is in the emergency release system/cut the rope system. When that system releases, it free wheels the clutch releasing the wall. A dash pot on the arbor slows the wall its last 6' of travel. Daily operation does not touch this system.

 

[venuetech]

I have had this problem on two fire curtains. Both of them had the flat style that i believe were load rated for something like 20 pounds. I ended up replacing them with higher load rated links. That had the same 165 deg. temperature rating.

McMaster-Carr

the #6 style has the solder in compression as long as the solder is solid it will not seperate. imho it will last much longer and is less likely to fail without cause.

The flat styles all put tension directly onto the solder. that style failed with time in my case, as the load was very close to the rating.