EBME Forums Forums Maintenance Technical Assistance Moulded Mains Plugs

Where equipment is supplied with a mains lead, in our Trust, we are routinely changing the moulded mains plug for a MK Toughplug. This has its origins in the early days of moulded mains plugs when quality control was an issue.
We are thinking it may be time to change this practice.

Question. Does anyone else change moulded mains plugs for a high quality discrete mains plug?

Moulded Mains Plugs single choice
	Yes
	No
Votes accepted starting: 01/01/70 1:00 AM You must vote before you can view the results of this poll.

Over recent years we've seen far fewer problems with moulded plugs than discrete plugs.
I wonder how many of you out there remember how often you found loose wires when checking a plug or how many times you ended up re-wiring one to a decent standard?
Even with a strict control of equipment entering the site we never managed to work out where all the rogue mains leads appeared from, I reckon that they must have been breeding in a dark corner of that little store cupboard at the back of Admissions or something!

Yes, my own policy would always be to replace those moulded plugs. If your PM procedure says “check the integrity of the mains power plug” – well, how can you with a moulded type (x-ray)? How can you be sure that the earth is not hanging in on a single strand?

I note, however, that so far the poll indicates that most disagree. I must say that I’m not surprised by that.

Not too sure about the MK Toughplug specifically, though. Any chance of more details on that one, Hufty? A link to the RS catalogue, perhaps, so we can all take a look?

... how about http://www.t2technical.co.uk/acatalog/Plugs_fusesetc.html ? I guess that's the one!

I must admit I like the MK Toughplug BS1363A, especially before those plastic rivets were used to hold the terminals inside the plug. They do tend to break. The threaded terminals are much better than screw-terminals generally found on inferior mains plugs. Sad but true.

MK Toughplugs are not what they use to be. They have reverted to inserting wire in hole and screwdown like other manufacturers, rather than the terminal posts. I also think moulded plugs are less prone to fluid ingress and fiddling with generally. As for the earth conection holding on with the single strand this should be picked up with the eath bond test.
I have had instancies of poor quality moulded plugs in the past but Medical Companies usually supply quality leads these days. We pay for them in the cost of the product.

Lee says “As for the earth connection holding on with the single strand this should be picked up with the earth bond test.”

Surely this depends on the test current used? I doubt that many people pass 25 amps down the protective earth these days!

Not quite Lee and Geoff, in fact it was this observation that helped cause the change from our in-hospital bonders using 25 amps to using around an amp only. It was found that a strand or two could carry the high 25-amp current from the early safety testers, which made a mockery of the "bonding" part of the test of course. That is why it is important to open the plug-top on each PM and, on initial commisioning only of any equipment, take off the covers and confirm that the earth bonding lug is secuerly fastened and most important of all, that any paint from the metal it is bonded to has been removed down to bare metal before the Protective Earth wire has been attached - not an uncommon thing to find.

Yes, Nick, but a bit difficult to do with a moulded plug!

Geoff, there may be a few who still pass 25A in their tests, maybe others could comment on their interpretation of IEC601 testing?
We supply moulded plugs with some of our equipment, but other type needs re-wiring from a German Shucko.
Philip