What is the best wire termination method? 1

[EdDanzer]

We have manufactured an air amplifier with electric controls. This unit is used near large coal fired boilers and is subjected to temperatures up to 150° F and a wide range of vibrations. The incoming wire is #16 stranded and the control wires are #18 and #20. The #18 and #20 wires have pins crimped on the end, the #16 is just stripped and inserted into Entrelec M 4/6 standard terminal blocks. The problem is the connections keeps coming loose.
What other termination options should we try?

 

[felixc]

M4/6 is screw clamp. Perhaps it gets loose because of temperature gradients, in addition to vibrations. Still it is surprinsing that such connections go loose.

You may want to try spring clamp terminal blocks. They will maintain a constant pressure on the wires. But if there is a lot of vibrations, it may not be enough.

If you can contact a local rep from this terminal block company (Entrelec isn't crap), he may have something better to suggest for your application.

 

[ScottyUK]

Weidmuller-Klippon make the melamine RSF3 and RSF4 terminals which are designed to be used with a lipped blade terminal. The design incorporates a spring which maintains electrical contact even if the clamp screw loosens under vibration. They are an excellent design which very rarely gives a bad joint. You must ensure that the electricians use the correct lug on the cable to get maximum benefit. I think this was developed in conjunction with the old CEGB in the UK to overcome the problem of terminals loosening over time.

If you are doing an installation which will be installed and left alone, the screwless sprung type referred to above are good. Maintenance guys hate them if they have to make frequent disconnections and reconnections and the conductor in use is stranded, but I've found them to be reliable if left undisturbed.



-----------------------------------

Start each new day with a smile.

Get it over with.

 

[jmartin931]

From a maintenance mans standpoint, might I suggest soledering the connections. Granted this does make it more difficult to re-do things, but in retrospect I also like it better when I don't have to constantly retighten loose wires.

 

[EdDanzer]

We have found that the wires break just past the solder faster than clamped or crimped connections. One solution that is expensive but seems to help is shrink tube, tape, or silicon a ways up the insulation from the crimped connection.

 

[rmw]

It just occurred to me to ask what the wire material is? Initially I assumed it was copper, but then it occured to me that it might just be aluminum, which has its own set of issues with cold creep in wiring termination situations.

rmw

 

[EdDanzer]

The wire is stranded copper. The connections in the block are plated steel.

 

[GOTWW]

I see them advertising in electronics mags,what would appear to be a super-compressive bonding technique that basically fuses the conductor and connector into a honogeneous entity, basically can not tell the wire from the connector, or the wire becomes the connecter, it is not clear, and have'nt investigated it. Plus I believe that the high compression grounding system connections are as good or bettr than the exothernic welds now dayes.

 

[advidana]

contact cadweld and see if they can help.

 

[billinj]

At my company, we insist on crimped terminations. Whenever we must terminate to a clamp-type terminal, we always use crimped ferrules on the wire. They provide the reliable electrical joint with the wire as expected of a crimped termination, and are much less likely to slip out of the clamped terminal. Ferrules are readily available from AMP and other suppliers.
-Mepman

 

[felixc]

As billinj says, a crimping ferrule can help in providing a better mechanical joint when stranded wire is used. Your remark about the stranded wire breaking just after the solder indicates that the environment has a lot of vibrations. This is no good for whatever termination that you can use. Is there any way to attach the cable assembly to the chassis somehow near the terminal block. This will reduce the amount of vibrations at the junction between the cable and the terminal block, and in addition the resonant frequency of the shorter section will go up, hopefully high enough so that the frequencies of your system will be out of range of the one of the secured cable. I think your problem is also of resonant frequency.
Felix