Help with crimping

[RF Lighting]

I've fitted thousands of crimps. I've never seen a failed one fitted by me or any one else.

Crimps are fine, and it seems the only people who dislike them are people not in the industry who have no actual real world experience of using them.

 

[EFLImpudence]

I've fitted thousands of crimps.

On solid conductors ?

 

[JohnW2]

I've fitted thousands of crimps. I've never seen a failed one fitted by me or any one else.
Crimps are fine, and it seems the only people who dislike them are people not in the industry who have no actual real world experience of using them.

You may be right but, as I said, I would want to see some good evidence before I was personally convinced. However,as I keep saying, I accept that to be a personal thing, and that I'm seemingly in a minority.

As for experience, I do have some experience of trying to use them (experimentally) - and those experiences merely strengthed my concerns, particularly in relation to electricians who (unlike you, it seems) only use crimps occasionally.

Kind Regards, John.

 

[RF Lighting]

I've fitted thousands of crimps.

On solid conductors ?

Hmm good question. I'd guess that 40% would be on solid conductors, but still thousands on each type of cable. Solid, stranded and to a lesser extent fine wire too.

 

[JohnW2]

Hmm good question. I'd guess that 40% would be on solid conductors, but still thousands on each type of cable. Solid, stranded and to a lesser extent fine wire too.

Everything I've heard and read seems to suggest that crimping is much more reliable with stranded conductors. Indeed, my understanding is that, using serious heavy-duty kit, it's one of the established (and well tested) methods of joining very large stranded cables. The uncertainties (at least in my mind) relate to crimping solid conductors with simple hand tools.

Kind Regards, John.

 

[milliamp]

After a discussion, crimps v screw joints, a work mate and I set out to prove which was the stronger. A jig was set up and a pull applied either side of each joint.
The screw terminal joint pulled free with only 15kg load.
The crimp joint held beyond 40kg.

The only failures I have seen are the result of poorly prepared cables, not far enough into the crimp.

 

[EFLImpudence]

The crimp joint held beyond 40kg.

The same question as above. Was this single solid conductors?

I agree that they are good for stranded conductors but, as I have said before, I maintain that crimps are not designed or intended for single solid conductors and as such do not comply with 526.3(iv).

 

[sparkwright]

I have seen failed crimps on pubs and factories (where wiring is often done badly) and obvious DIY attempts.

Other failed joints have been where two or more wires have been inserted in one end, and where the wrong size crimp has been used.

Other failed joints I put down to the wrong type of crimping tool used.

 

[pjo123]

Interesting debate

Well I've spent £50 in total including heat shrink stuff, I hope it's not money down the drain. I brought it as people were saying that to do it right I shouldn't use junction boxes but should crimp instead.

Screwfix out of stock so wont get crimper until tomorrow afternoon, then I shall have another play.

 

[JohnW2]

I agree that they are good for stranded conductors but, as I have said before, I maintain that crimps are not designed or intended for single solid conductors and as such do not comply with 526.3(iv).

Same here. I'm sure it's been wheeled out before but, just to remind everyone, the NASA Workmanship Standards (here) explicitly prohibit the use of crimped joints for solid conductors:

Crimping of solid wire, component leads, or stranded wire that has been solder-tinned, is prohibited.
NASA-STD-8739.4 [4.3.4]

Kind Regards, John

 

[EFLImpudence]

including heat shrink

Solder

Make physical joint by making hooks on the end of the wires to be joined and squash tight then solder. Stagger the joints.
You can still use the heatshrink, small on individuals, no need to do the CPC, then large over them all but don't for get to put it on first.

 

[pjo123]

Only thing that concerns me with soldering, is the heat shrink is a lot thinner than the plastic surrounding the cable.

I have a box of various sizes but it doesn't give any indication for it's suitability to be used for mains cable.

Or to put it another way, I presume the blue and brown plastic the copper cable is in, is that thick for a reason?

I presume it's bog standard electrical multicore fluxed solder, think I have a huge roll of the stuff that still has lead in it somewhere.

Thanks

 

[EFLImpudence]

You could use two pieces on the single wires (one first then another) or wrap with self-amalgamating tape before the heatshrink.

Staggering the joints, as well as reducing the thickness of the finished cable, does also leave one of the original wire's insulation next to each joint.

 

[crystal ball]

I agree that they are good for stranded conductors but, as I have said before, I maintain that crimps are not designed or intended for single solid conductors and as such do not comply with 526.3(iv).

Same here. I'm sure it's been wheeled out before but, just to remind everyone, the NASA Workmanship Standards (here) explicitly prohibit the use of crimped joints for solid conductors:

Crimping of solid wire, component leads, or stranded wire that has been solder-tinned, is prohibited.
NASA-STD-8739.4 [4.3.4]

Kind Regards, John

I served my time in an industry working to MOD standards and the crimping of solid coductors was prohibited, I have never crimped solids due to this

 

[bernardgreen]

The screw terminal joint pulled free with only 15kg load.
The crimp joint held beyond 40kg.

You need to repeat the experiment but allow time between crimping and testing for the copper to cold flow ( change shape ) from areas of high pressure in the joint to areas of low pressure and the overall pressure on the copper has reduced as a result.

The time required will depend on many factors and could be as long as a year or more. To prove a crimp joint is safe to be hidden in a domestic situation one should wait maybe 20 years before testing.

If a cold weld has been formed during the crimping process then the joint no longer relies on pressure alone.