CHAOS Report #9 - The Loose HEP Connection - June 21, 2014

Mechanical Liaison Officer's report by: Paul L. DeVerter II

DON'T SCRIMP ON THE CRIMP!

The moral of today’s story is to not scrimp on the crimping force that you exert when you are connecting your HEP cables to their lugs or other crimpable connectors. I am told that Amtrak has a practice in Chicago of requiring that all HEP cables be crimped to their lugs using a hydraulic crimping device. The only exceptions occur when there is a need to get a car out immediately and there is not enough time to obtain the device.  Hand crimpers simply do not exert enough force on large cables (particularly as large as 4/0) to ensure a reliable and secure connection. The use of universal dies, instead of the ones designed for heavy cable, are another source of faults.

Sometimes even a hydraulic crimper does not do the job, especially if the cable is not inserted completely into the lug, or if the operator is in a hurry and not paying sufficient attention to the task.  In the old days, it was common for connections to be made using solder. This has given way to crimping because crimping is easier, quicker, and not as messy. Another given reason is that many workers do not know how to solder large cables to lugs, and don’t want to have to carry torches and solder pots into the field.

The photograph shows a 4/0 HEP cable that has pulled loose from its lug in a splice. This was not a readily identified defect because the splice is in turn covered with a rubber sleeve and a couple of hose clamps.  It was only when this connection was tested by pulling on the 4/0 cable that it was discovered that the crimp had not been properly done, because it simply came apart.

If this were to happen in the field, the results could be catastrophic. The control cables for the Trainline Complete (TLC) safety circuit remain intact, so the exposed 4/0 cable would have been hot any time the HEP provided to the car/train was energized.  The failure of the crimp in a main 4/0 HEP cable does not open the TLC circuit, or any other curcuit breaker. The large amount of current available would have guaranteed a considerable arc display, and the result could easily blow a hole in the floor of a car, or any other object that the exposed end of the energized might have encountered.

In this instance the end of the 4/0 cable had been inserted into its lug with the use of a hydraulic crimper, which you can tell by the deformation of the lug on the right, but for some unknown reason the connection was not actually tight and secure.  It is believed that the cable simply had not been fully inserted into the lug.  One simple test you can make is to go to each of your connections and pull to see if anything gives way.  Ensure the power is off before you try this test! If you try this test with energized cables, you might not live to tell the tale.

In his article titled "Head-End Power" (PDF), published in Private Varnish issue #43, dated March/April 1992, Amtrak's Dick Bruss mentions the problem of poor quality crimps on 4/0 wire, which can be pulled apart by hand.

This is not a tutorial on how to mate cable, lugs and crimping devices, as there are way too many variables.  There are differences of opinion as to whether soldering is good or bad in situations involving vibration.  This is a suggestion that you grab a hold of your various (deenergized) HEP cables and give them a good pull to see it their connections are mechanically sound.

For those interested in further reading on this subject, I suggest Amtrak SMP 26002 "Inspection of 480-V HEP Trainline System. Section 9.1.9 (1) of this SMP addresses inspecting splices, although they do not specify tugging on a cable as a technique to verify the physical integrity of cable connections.

Paul DeVerter