FP Cable Is Not Always Suitable

[shanky887614]

As an apprentice I was given scrap ends to make off, After a while and some intense inspections of my efforts I was allowed to use potting compound. The first end I made off that actually went into service made me a very proud puppy spark.
Afaik it's still there to this day.

your gran kids might get the chance to rip it out while complaining its better than what they are replacing it with you never know

 

[trev]

Well so far we're one from three and it looks like it's staying that way. Grandson will not be a spark if I've got anything to do with it.

 

[tazz]

No point in testing until you have potted the gland......this will be another learning curve, testing the insulation with one reading..then testing 24 hours later, with another reading. Full marks, for taking the time to practice and post your results. In the next few years, when industrial projects need installing and renewing...The quick course guys will be left to their house bashing, whilst others will be back in the thick of it.

 

[Dcf]

A decent effort.
when doing it for real remember and put the compound in from one side only of the pot.
keep the compound clean and free from bits of swarf etc.
i wouldn't blow in the pot as mdj suggests I would give it a tap and make sure it's clean myself
like all black arts practice is the key

 

[trev]

Blowing in the pot is potentially bad news. You could have bits of swarf in there which could blow up into your eyes.
Tappy tappy is much better.

 

[shanky887614]

Blowing in the pot is potentially bad news. You could have bits of swarf in there which could blow up into your eyes.
Tappy tappy is much better.

to be honest I didnt blow into it, I wiped conductors first to get rid of most of it then tap.

I didnt touch compound either, I used the wrapper and overfilled it from one side to stop the formation of any air pockets

 

[davesparks]

Beware of a tiny thread of brass/copper swarf which can sometimes appear in the pot as you screw it onto the cable.

Also pop the megger on it before you put the compound in, and then just before you crimp it, and then after you crimp it. this was you have a chance to correct things before you crimp it and get to the point of no return.

 

[stevethesparks]

The reason I was taught not to blow in a pot is because the moisture from your breath can dampen the mineral - of which would be sealed in with the compound.

 

[tazz]

Shanky...are you using a cutting compound or oil when cutting....if you find this messy, old trick from an old sod...is use a candle, just as good, less mess and saves you joist blade

 

[trev]

The reason I was taught not to blow in a pot is because the moisture from your breath can dampen the mineral - of which would be sealed in with the compound.

While it's a possibility the likelyhood of it happening is fairly low

 

[tazz]

The reason I was taught not to blow in a pot is because the moisture from your breath can dampen the mineral - of which would be sealed in with the compound.

LOL, would soon dry out

 

[trev]

Shanky...are you using a cutting compound or oil when cutting....if you find this messy, old trick from an old sod...is use a candle, just as good, less mess and saves you joist blade

Or a tiny dab of vaseline

 

[shanky887614]

Shanky...are you using a cutting compound or oil when cutting....if you find this messy, old trick from an old sod...is use a candle, just as good, less mess and saves you joist blade

course not, I used an old musicians trick and put a bit of oil from face on first

 

[tazz]

course not, I used an old musicians trick and put a bit of oil from face on first

LOL....well if it saves you blade, go for it

 

[shanky887614]

LOL....well if it saves you blade, go for it

the blade itself had a lot of oil on it when I recieved it, tbh I tend to use 3in1 oil for everything even though I know I shouldn't.

the blade will soon get coated it that after it has been cleaned.

 

[tazz]

Joist blades, ware very quickly, if you use oil, wax or compound anything is fine...but nothing will result is 3-4 cuts, then some really bad snagging and a lot of swearing.

 

[micknew]

The reason you shouldn't blow dust etc out of a pot is because your breath contains moisture which will lower the IR test, obviously.
The moisture will never dry out after the seal is fitted, because it cannot escape.

 

[ipf]

Joist blades, ware very quickly, if you use oil, wax or compound anything is fine...but nothing will result is 3-4 cuts, then some really bad snagging and a lot of swearing.

Use a T bar, then, and a ringing tool....not an alarm for when you've stripped the right amount, by the way

 

[trev]

The reason you shouldn't blow dust etc out of a pot is because your breath contains moisture which will lower the IR test, obviously.
The moisture will never dry out after the seal is fitted, because it cannot escape.

You're going to blow on it (if you're daft enough) for a second or two, this will not give the insulant much moisture at all, any moisture it absorbs will disipate almost immediately.
How much residual moisture is in the air around us at any given time?

 

[ipf]

The reason you shouldn't blow dust etc out of a pot is because your breath contains moisture which will lower the IR test, obviously.
The moisture will never dry out after the seal is fitted, because it cannot escape.

Minor problem, done thousands with a short, sharp blow. Never straight after a brew, though :drool5:

 

[micknew]

You're going to blow on it (if you're daft enough) for a second or two, this will not give the insulant much moisture at all, any moisture it absorbs will disipate almost immediately.
How much residual moisture is in the air around us at any given time?

Quite a bit, try it.

 

[trev]

Quite a bit, try it.

The point is that as soon as you've stripped, the insulant is going to be absorbing moisture from the atmosphere. The tiny little bit from a short sharp blow is irrelevant.
I never blow on it but for a different reason

 

[ipf]

The point is that as soon as you've stripped, the insulant is going to be absorbing moisture from the atmosphere. The tiny little bit from a short sharp blow is irrelevant.
I never blow on it but for a different reason

Understandable.

 

[tazz]

The reason you shouldn't blow dust etc out of a pot is because your breath contains moisture which will lower the IR test, obviously.
The moisture will never dry out after the seal is fitted, because it cannot escape.

So what would you think the main content of potting compound is made of (oil & water perhaps), this is why ir readings are all over the place, until it drys out....!!

 

[stevethesparks]

So what would you think the main content of potting compound is made of (oil & water perhaps), this is why ir readings are all over the place, until it drys out....!!

It doesn't dry out, it cures. It certainly isn't made from water. Once sealed, how would it dry out, how many bottles of unopened water do you see drying out?
Its not like breathing on a mirror where the condensation dries almost immediately, the magnesium powder soaks up any such condensation and would be held there by said compound - as small as it may be. In my book, blowing into a pot is just a no go when making off micc ends.

 

[Guest77]

I am not lying if I say I have terminated thousands of ends, seriously thousands, and I blow the dust out of everyone, I rewired a childrens home 20 years ago in pyro and it is still working fine today lol

 

[Engineer54]

It doesn't dry out, it cures. It certainly isn't made from water. Once sealed, how would it dry out, how many bottles of unopened water do you see drying out?
Its not like breathing on a mirror where the condensation dries almost immediately, the magnesium powder soaks up any such condensation and would be held there by said compound - as small as it may be. In my book, blowing into a pot is just a no go when making off micc ends.

Never heard anything so ridiculous for a long time.....

If your hypothesis were correct, literary every pot ever made off, is sealing moisture into the cable from the time of termination.... Just how hydroscopic do you think the magnesium power is for gods sake?? Are you one of these people that think left unsealed for any amount of time, moisture will penetrate the the whole coil?? I'll give you a clue, it took years (around 6 years to be exact) for moisture to travel a couple of foot in a coil of MICC cable that got left at the end of the garden, semi open to the elements.

Some tap and some blow any mag dust or copper filings out of a pot prior to sealing, one things for sure blowing isn't going to matter one jot, and you can take that to the bank!!

 

[Guest111]

pyro was changed slightly in the early 80's I believe before this the filler was just a powder and it was common to have to leave about 2 foot spare for a termination especially outside as it did absorb moisture reasonably readily,however when it was modified a moisture repellant was added to the mag powder and it absorbed even less moisture,I think iirc that it was quoted as somewhere along the lines of less than 1 inch per week for open pyro in a damp environment and even then the application of a little gentle heat from a gas torch would soon dry this out,I think most of us that have worked with the stuff have blown out pots and not seen any problems.For me the most common cause of failure that I saw was the conductors touching within the pot,the best way to prevent this is careful alignment of the pot and seal and then after crimping to give a gentle pull on the conductors as this will ensure they have not been moved during crimping.

 

[Engineer54]

We were using MICC 240mm singles (Trefoil & N) with ultra high temp seals to supply the emergency power supply side of metro stationS (MTR) switchboards in Hong Kong. The humidity present underground during construction was almost unbearable. Like you would be working in a pair of shorts a hard hat and boots and that's it!! Sweat pouring off everyone, ....To my knowledge, not once did a problem arise from moisture entering the MICC cable during the termination processes, the tails of these cables all being in the region of around 600 to 800mm or thereabouts...

 

[stevethesparks]

I can only say I am a little surprised by the differing opinions. As said in my first post (#58) this is how I was taught, starting in the trade in 1972. Some things stick and this is one of them. Maybe phil d in post 78 has hit upon something that my early teachings stem from, who knows? Maybe its over the top twaddle?
I do admit to having a few blows myself in the past (strictly MICC you understand - nothing perverse), but not often and whether correct or twaddle I would still say it is good practice not to.
I don't think I suggested that the mineral insulation was anywhere near as absorbent as lets say talcum powder - as is isn't, but as said all down to good practice, and am a little surprised that E54 doesn't support that.
Either way, its not important, I haven't made an end off for a good 20 years or so now, but in my early days made them off in abundance. Should I come across an MICC installation before I retire, I shall try and refrain from blowing

 

[Engineer54]

but as said all down to good practice, and am a little surprised that E54 doesn't support that.

I would support any good practice that held creedence, unfortunately refraining from blowing out a MICC pot prior to sealing doesn't hold any credence for me. As i say it doesn't make one jot of difference...

 

[stevethesparks]

You may well be correct, but I would still say it is good practice as its always possible a little spit may follow.

 

[shanky887614]

You probably saw one of my first attempts Trev!! Got a right ear-bashing for it... no shroud, pot not straight and screwed on to far...

btw - I've a spare one of these if MDJ can't set you up...

Edit - didn't realize the pic was that big, i'ts only for 20mm pots

thanks for the offer of a spare potting tool guys, the local wholesaler's are very good and he has managed to get me one at a reasonable price.

£35 inc vat etc.

not bad considering I only spoke to him about it tuesday after 5pm

 

[Guest111]

thanks for the offer of a spare potting tool guys, the local wholesaler's are very good and he has managed to get me one at a reasonable price.

£35 inc vat etc.

not bad considering I only spoke to him about it tuesday after 5pm

just need a megger now.lol

 

[shanky887614]

just need a megger now.lol

is this a windup XD

 

[Guest111]

is this a windup XD

no you're better with a battery one,mind you I 've got a wind up one somewhere if that's what you want.lol

 

[shanky887614]

got my potting tool today so gave it another go

 

[Guest111]

have you meggered it yet?

 

[trev]

Take it to work and IR it mate, just out of interest.

 

[Silly Sausage]

Take it to work and IR it mate, just out of interest.

But in the meantime, plug it in at home and see if your RCD hangs on.

 

[shanky887614]

Take it to work and IR it mate, just out of interest.

I did take the other one to work and did ir it, got about 60Mohm.

to be honest I didnt cut any off coil or try to get any moisture out of it first before I made end of so who knows.

this one should have a lot higher reading?

it was a little odd because it fluctuated from 50mohm to > 299 at 500v. im guessing batteries in tester could be low because didnt get constant reading

 

[telectrix]

I did take the other one to work and did ir it, got about 60Mohm.

to be honest I didnt cut any off coil or try to get any moisture out of it first before I made end of so who knows.

this one should have a lot higher reading?

it was a little odd because it fluctuated from 50mohm to > 299 at 500v. im guessing batteries in tester could be low because didnt get constant reading

or there may be a slight bit of moisture there and the IR test is drying it out, thus readings will rise as you keep the tester on it.

 

[Engineer54]

Originally Posted by shanky887614
I did take the other one to work and did ir it, got about 60Mohm.

to be honest I didnt cut any off coil or try to get any moisture out of it first before I made end of so who knows.

this one should have a lot higher reading?

it was a little odd because it fluctuated from 50mohm to > 299 at 500v. im guessing batteries in tester could be low because didnt get constant reading

or there may be a slight bit of moisture there and the IR test is drying it out, thus readings will rise as you keep the tester on it.

The correct method of IR testing a new circuit/build is by applying the test voltage for a minimum of 1 minute... Most electricians, will if you're lucky IR test for 10 to 20 seconds. lol!!

 

[shanky887614]

The correct method of IR testing a new circuit/build is by applying the test voltage for a minimum of 1 minute... Most electricians, will if you're lucky IR test for 10 to 20 seconds. lol!!

thanks for that, I have never heard anyone mention that and nothing at college etc.

 

[Engineer54]

thanks for that, I have never heard anyone mention that and nothing at college etc.

Tut. tut!! They don't seem to be teaching much at all at college these days....

 

[shanky887614]

Tut. tut!! They don't seem to be teaching much at all at college these days....

they only teach the questions/answers that are in the exam now, only reason I didnt need any resists in final year was I studied off my own back online.

everyone else needed a resist or really struggled.

one question in jtl test was how deep is recommended for a bore hole for the average sized house.

no mention in revision books etc that we were supplied with etc and even tutors were clueless when I mentioned it after exam

 

[Engineer54]

Bore hole, ..bore hole for what??

 

[shanky887614]

Bore hole, ..bore hole for what??

ground source heat pump.

renewable crap in the new nvq

 

[telectrix]

thought a bore hole was where you put the father-in-law when you couldn't take any more of his verbal diorrhea.