problems crimping with yellow crimps, 6mm.

[HappyHippyDad]

This is only the second time I have had to crimp 6mm cable. I remember the first time a couple of years ago I had problems. Again this time the connection just pulled apart in my hands.

After looking through the forum I can see that others have had the same problem specifically with yellow crimps. 1mm and 2.5mm seem to crimp perfectly well (again seen in other threads), but with 6mm there is a problem.

The reason for this thread is because other threads point to the crimp or the crimping tool being the problem. I have a CK crimping tool which has good reviews and crimps 1mm and 2.5mm very well (I have tested these in a vice), so I believed the crimp to be the problem. I was about to buy some SWA crimps as other threads point to these being good quality. However, my red and blue crimps were bought from the same manufacturer as the yellow so it didn't really make sense that it was the crimp at fault.

I've just been in the shed crimping 6mm in a number of different ways and think I have found the problem. With red and blue crimps you have the crimp flush with the crimping tool when you crimp. I assumed it would be the same with yellow, however the crimping tool is wider for the yellow crimps meaning that when you crimp you are crimping the entire half of the crimp (perhaps even slightly over), meaning that you are crimping down on the piece of metal that sticks out in the middle of the crimp and I think this must be stopping the crimping tool from crimping properly.

The top crimp (see picture) was crimped with the yellow crimp (outer part) flush with the crimping tool and just pulled out easily. With the other two I slightly pushed the crimp into the crimping tool so that the central piece of metal would not be disturbed (you can see that the bottom 2 crimps have a bit in the middle still raised whereas the top one doesn't). I could not pull either of these out when placed in a vice.

Correct crimping is so important I thought I'd mention my little test. I tested the 2 ways each with 5 crimps and it was the same with all of them.

 

[HappyHippyDad]

Because you can see when the conductor is properly inserted and can see that the crimp is properly located in the crimp die. Plus the standard uninsulated crimps have a thicker copper tube than the metal of the insulated.
I've stripped the insulation off of a few insulated crimps to have a look inside and they don't inspire confidence.

How can you see? You cannot see inside so I'm guessing you mean where the conductor enters the crimp, but that would be the same as an insulated crimp? I'm talking in relation to butt crimps.

 

[Marvo]

I just think that compression crimping with the insulation in the crimper is just going to inherently give inconsistent results. I was taught as an apprentice that indent crimps were never to be used on MV terminations, only hex. I can't specifically remember why but they were considered more reliable. Also I have a small hand operated hydraulic hex crimper that has crimping dies going down to 16mm and up to 185mm so it's just easier for me to use it on any crimps in that size range, for 16mm and under I have a ratchet type indent crimper that is regularly calibrated, we pull-test lugs or ferrules as well and they pass with good results.

I think technology, materials and techniques have probably evolved somewhat since I was taught so I guess if they sell insulated crimps for 6mm then it should be okay to use them but with uninsulated lugs especially you can better visually check the result of crimping.

 

[davesparks]

How can you see? You cannot see inside so I'm guessing you mean where the conductor enters the crimp, but that would be the same as an insulated crimp? I'm talking in relation to butt crimps.

You can see by looking at it, you can see that all strands of the conductor have entered the tube and you can see that the conductor has gone all of the way in to the tube. Plus you can see that the crimp die is correctly positioned on the tube.
With an insulated crimp you cannot see the metal tube to know that the crimp die is correctly located, or see if there are any imperfections in the tube.

Plus, as you have noticed, the length of the insulating tube isn't quite standardised between manufacturers. So if you have crimps from the same manufacturer as your crimpers then you probably won't come across the issue you highlighted in your OP, however using crimps from another brand could be part of your issue.

With an uninsulated crimp and a hex crimper it is much simpler to do a test crimp and see if it is all ok before making the connection. Cutting through the test crimp to view the cross section of the crimped joint allows you to see if it has been made correctly or if there is a problem, a good crimp will compress the conductor fully, a bad crimp will leave gaps between the strands of the conductor.

 

[rich.250]

In my opinion those CK crimpers are a load of junk! My new one went in the bin and out came the old draper expert one I brought 12 years ago lol.
Never had a bad connection with that one.

 

[Andy78]

In my opinion those CK crimpers are a load of junk! My new one went in the bin and out came the old draper expert one I brought 12 years ago lol.
Never had a bad connection with that one.

I have to say that my daily ratchet crimp tool is CK and I have never had a problem with it. Still tight and makes a good compression every time. It is nearly 10 years old however and I do feel that CK tools in general were of a better quality some years back now. I had a set of CK drivers that lasted for years with daily abuse. I also had a newer batch that all shattered under normal use.

 

[Simonslimline]

I have to say that my daily ratchet crimp tool is CK and I have never had a problem with it. Still tight and makes a good compression every time. It is nearly 10 years old however and I do feel that CK tools in general were of a better quality some years back now. I had a set of CK drivers that lasted for years with daily abuse. I also had a newer batch that all shattered under normal use.

Seems to be the case with more than just tools these days unfortunately.

 

[Lucien Nunes]

I wouldn't be surprised that the first crimp is faulty due to the indentations being too near the centre. Part of the width of the counductor crimp zone is wasted on the endstop as you say, the remainder is on the very end of the conductors where the strands are likely to splay and escape, or even be forcibly ejected as the tube becomes funnel-shaped at the edge of the crimp zone. I would liken it to the very end of a conductor pinched halfway under a choc block screw.

I do also share concerns about the mechcanical durability of yellow crimps and the current rating of a completed joint relative to the size of conductor. I would only use products from a proper manufacturer with published performance and dimensional specifications and approvals. For critical applications as per Darkwood and Davesparks I prefer uninsulated crimps with a hex die - mechanically stronger, more consistent and reliably gas-tight crimp pattern and easier to inspect for successful installation.

 

[Skimpy Wan]

What do you recon to this as it seems reasonably priced (maybe too reasonably priced)...

http://pages.ebay.com/link/?nav=item.view&id=291059818578&alt=web

 

[telectrix]

i'vegot those same ratchet cutters. cost £60.brilliant.cut right through SWA inc. the steel armour. ( i done up to 16mm) . can't comment on the crimpers except seen then at elex and they looked a good piece of kit.

 

[Andy78]

What do you recon to this as it seems reasonably priced (maybe too reasonably priced)...

http://pages.ebay.com/link/?nav=item.view&id=291059818578&alt=web

These style of hydraulic crimper regularly pop up on eBay for about the £50 mark, but I have no idea of their reliability.
To put them in context though, I used to use a set of a very similar style and construction and they were spot on. A company I worked for bought them for a switch room job they had on at the time. The difference was that those ones cost £900 for the set.

 

[Skimpy Wan]

May give them a go then. The seller seems to indicate that they are ISO registered which means that their traceable items etc.
I need a new ratchet crimper for 10 - 16 mm crimps (which are £40 on their own) so not a bad offer if they work okay.

 

[Andy78]

May give them a go then. The seller seems to indicate that they are ISO registered which means that their traceable items etc.
I need a new ratchet crimper for 10 - 16 mm crimps (which are £40 on their own) so not a bad offer if they work okay.

If the largest you are doing will be be 16mm then a hydraulic set are a bit overkill. Why not get something a bit mechanically simpler. Less to go wrong with them then, especially being a budget product.

6-50mm² Electrician Cable Wire Crimping Crimper Hand Tool Pliers Ratchet Crimp | eBay

 

[Skimpy Wan]

I did see those, but thought they maybe a little too flimsy.

Mainly I just need 10 / 16 mm crimper as the bigger boy the boss has, so I get those when required (but handy to have my own for a later date).

 

[davesparks]

I have the same pattern hex crimpers as that, but from a reputable manufacturer rather than ebay

 

[Marvo]

The hydraulic crimper I have is by Hellerman Tyton, can't remember what it cost but I've had it a good few years and it's seen some action without any problems.