pin termination loosening problems

[tuscan]

On my previous contract, I took issue with the use of round pins on cables being terminated into blocks that had flat clamping surfaces. Because these were in an area of constant low level vibration, problems with loosening and current carrying capacity were evident, due it seems to the small contact area. This was never rectified on a cost vs safety basis. However, I have now found a similar arrangement in some equipment supplied for a system requiring extremely high levels of safety integrity. I am trying to find any information/ investigations/standards which may relate to this. Does anyone know where I might find anything. I need it to make a strong argument for changing these.

 

[Ddons]

I find that a standard crimp pin, which you can purchase thru Allied Electronics/RS Online when crimped with the appropriate tool will not come loose when properly tightened. These are used extensively in Europe and we use them on all of our equipment, most of which originates in Italy and Germany.

Don Spiker

http://www.lewis-equipment.com

 

[tuscan]

Thanks for that Don. Can you tell me if this is a flat pin or one that will squash to some degree when tightened. The problem with the old design was that the pin was fairly solid and did not deform when tightened. This resulted in a relatively small effective contact area.

 

[Ddons]

This is a hollow pin thru which the conductor is passed, you then crimp the pin onto the conductor and it takes on a rectangular shape. They come in a single and dual conductor style. Thomas & Betts has many to choose from but prefer I prefer these from Altech

http://www.alliedelec.com/Search/SearchResults.asp?N=0&Ntk=Primary&Ntt=ferrules&sid=454935006003617F

Don Spiker

http://www.lewis-equipment.com

 

[ScottyUK]

Boot lace ferrules: they have a place (other than the bin) but not in high current applications. They are good for high density low current applications like PLC I/O. I would be most unhappy to see them in a power circuit. A proper formed lug is a better choice for terminals provided the correct lug is chosen.

The hook blade type shown in the bottom of the set of pictures on

http://www.etechcomponents.co.uk/subpics.asp?id=13&catname=Cable Connectors

shows a very high reliability type lug when used with the matching terminal. If the terminal screw loosens, a powerful spring holds the lug. It can not be removed without a tool because of the lip on the end which engages with the terminal. Weidmuller's RSF series of terminals is typical of the type designed for these lugs. They are popular for protection relay connections in the UK electricity industry and other hi-rel applications.


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Sometimes I only open my mouth to swap feet...

 

[tuscan]

Thnks for the replies, they were very helpful. Although the terminations are on low current control wiring, I still had an issue with possible loosening over time. I am glad that bootlace ferrules were mentioned because I have now found that our Engineering Standards state that these are to be used for this application. The supplied equipment does not meet this standard so I have a good case for getting them replaced.