Pyro Cable

R1CH-G · Mar 2, 2011

Just a bit of history first. The following occurred in what is classed as a bunker in the military sense of the word, and all works were carried out to JSP military regs.

Cable used was 2H10 orange sheathed pyro (low smoke zero halides). Cables was potted and glanded and insulation resistance readings taken (500 volts on Fluke 1652) and came back at >500 MegOhms. This cable sat there happily for over 4 months until I got a call saying the DB had gone bang!!

On inspection, the pot was blown to bits! The only thing I can put this down to was dodgy compound and tracking.

Anyone out there who could suggest any alternatives, because for the life of me, I can't work this one out!

millwall ken · Mar 3, 2011

olly w said:
Joint Services Publications. JSP 375 Vol 3 Chapter 3 Electrical...

But as far as I remember they always stated IAW BS7671 so how the cable was installed badly I don't know?

Thanks, knew it was Joint Services something........ Would these be the same clowns who hold Service Records and send Emails saying you're sacked?

R1CH-G · Mar 3, 2011

johnboy6083 said:
could it be air in the pot, sealed in by compound, and then charged by the conductors?

It shouldn't be, I filled the pot in the prescribed manner - you never really know though, could be an air bubble - worth bearing in mind!

olly w · Mar 3, 2011

The JSP's only came out in about 2006 and the electrical sections were based mostly around BS7671 where they actually quoted the specific regs, then as the regs got updated it started changing to IAW.

Before then it was SRP's (Safety Rules and Procedures) for which each service had their own set.(Navy, RAF and Army)

DurhamSparky · Mar 3, 2011

Would these be the same clowns who hold Service Records and send Emails saying you're sacked?

no that will be career managers located at the Joint Personal Admin dept in glasgow!! (p.s old service records are held at relevant service HQ archive dept)

olly w · Mar 3, 2011

DurhamSparky said:
no that will be career managers located at the Joint Personal Admin dept in glasgow!! (p.s old service records are held at relevant service HQ archive dept)

And kept for 100 years, along with all the other out of date military equipment that is no longer needed but keeps civil servants in jobs for stock taking purposes.

UNG · Mar 3, 2011

Only time I've seen this happen the pot had not been completely filled with compound at the time the only reason I could suggest was condensation had formed in the air pocket thus causing a short