Pyro Cable

[R1CH-G]

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!

 

[i=p/u]

probably ied

 

[R1CH-G]

probably ied

Not understandy...

 

[i=p/u]

im joking, you probably correct. no expierience

 

[sparky3366]

usually a good idea to use potting conpound instead of semtex...

 

[R1CH-G]

usually a good idea to use potting conpound instead of semtex...

Ah, note to self - don't use semtex

 

[Engineer54]

You wouldn't be the first to experience, what you call ''Dodgy Compound'' lol!!! Can also be old compound that's been on the shelve, past it's sell-by date. The only other thing i can think of in your case is moisture, but i would imagine the length you stripped back for a CU connection, the >500 meg and 4 months in service would justifiably nullify that possibility. ...lol!!!

 

[R1CH-G]

You wouldn't be the first to experience, what you call ''Dodgy Compound'' lol!!! Can also be old compound that's been on the shelve, past it's sell-by date. The only other thing i can think of in your case is moisture, but i would imagine the length you stripped back for a CU connection, the >500 meg and 4 months in service would justifiably nullify that possibility. ...lol!!!

Like I said, it's got me baffled. Only thing I could think of was dodgy compound. I wouldn't imagine that 2H10 pyro exactly flies off the shelves!

 

[DurhamSparky]

JSP military regs

hmmmm yeah i worked to them.. i suggest a rewire based on that fact alone!! lol...!

 

[R1CH-G]

JSP military regs

hmmmm yeah i worked to them.. i suggest a rewire based on that fact alone!! lol...!

You probably wouldn't be far wrong either!! JSP - BECAUSE WE SAY SO OK?????

 

[DurhamSparky]

yup!! JSP Testing of Circuits = BANG TEST!

loads of concessions and deviations as required lol...!

 

[johnboy6083]

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

 

[millwall ken]

You probably wouldn't be far wrong either!! JSP - BECAUSE WE SAY SO OK?????

Joint Services Personnel Military Regs?????????

 

[olly w]

Joint Services Personnel Military Regs?????????

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?

 

[R1CH-G]

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?

The cable wasn't installed badly - I know, I installed it!!

Thanks for the heads up on the IAW bit though. I didn't know that.

 

[millwall ken]

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]

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]

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]

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]

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]

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

 

[whats an rb4]

i would go for air pocket try as you might ya never really knw if it full

 

[Knobhead]

A small void in the compound. Aluminium oxide is a sod for drawing in moisture.