Do cartridge fuses deteriorate with age?

[jenkinsrichard]

I have a 13 amp fuse in an extension socket, both socket and fuse being at least 35 years old. After severely heating up the fuse and socket the fuse blew, eventually.

There's nothing actually wrong with the 2700 watt electric fire which was plugged in at the time, but even if there were, I would expect the fuse to blow without heating up and blackening the surround.

Is this normal? Should I replace all my fuses with new ones every few years to avoid possible fires?

Regards, Richard.

[Station X]

I had a similar thing happen with a plug, supplied by the manufacturer, attached to a 3kW Fan heater. It didn't just take out the plug, but the metal faced wall socket as well.

I fitted a decent MK plug and it's been fine ever since.

[Nickthedentist]

Richard's does look like the fuse itself was the culprit though, and it's a proper, certified one rather than a market stall special.

Or do you think that the damage to the red plastic fuse carrier was actually caused by the plug?

Either way, it seems that our plug/socket system has always struggled with continuous loads near the 13A maximum rating, whatever the brand.

[Station X]

Originally Posted by Nickthedentist

Either way, it seems that our plug/socket system has always struggled with continuous loads near the 13A maximum rating, whatever the brand.

That's very true, with a heavily loaded plug you can feel them getting hot and when you pull out the plug the pins are very hot indeed.

I have known cartridge fuses in consumer units die of old age, but there was no visible damage.

Looks like the damage caused by the OP's fuse was down to it overheating rather than rupturing.

[GMB]

I think it most likely to be heat from ageing fuse clips. I have had that happen so many times. If I was writing the product regulations I would not deem 13A plugs as being suitable for more than a couple of amps!

[fetteler]

Originally Posted by GMB

I think it most likely to be heat from ageing fuse clips. I have had that happen so many times. If I was writing the product regulations I would not deem 13A plugs as being suitable for more than a couple of amps!

Seconded!

Steve

[petertheorgan]

I agree

[The Philpott]

Many of the plugs/extension sockets/distribution boards which use the red plastic cassette for fuse insertion, do have quite poor fuse clips, not good for 10-13 amp loads
Possibly just a rogue fuse in this case.?

Dave

[Radio Wrangler]

All fuses age. The closer to their rating they are run at, the faster the ageing. Heating and cooling affect the crystalline structure of the wire. Switch-on surges count, too.

The rated current of a fuse is the current at which it will take 1000 hours to blow.

So an old fuse in an extension cable blowing isn't a surprise, especially if it's seen heavy loads in those 35 years.

But as someone said earlier, check the tension of sprung connections. 13A sockets also go soft and heat goes up the brass pins quite efficiently.

David

[G6Tanuki]

I've seen quite a few fuses/fuse-carriers/13A plugs fail in similar ways - often you can _smell_ them! [the bakelite and plastic gives-off a sort of 'fishy' smell when it gets hot].

There are lots of cheap - and some not-so-cheap - 13A plugs whose fuse-clips are nowhere near up to handling a 13A load continuously. In particular, plugs where the fuse-clips are riveted to the live-pin/terminal - often the riveting isn't exactly good.

There used to be 13A plugs where the live pin and terminal were both solid brass - from memory they were Crabtree - which seemed to survive rather well. For heavy loads I still prefer the old BS546 15A round-pin -plugs/sockets and the blue industrial "Commando" connectors.

[ms660]

Got to say there's no way I would connect a 2.7kW load to a standard mains outlet socket except to make a cup of tea.

Lawrence.

[HamishBoxer]

I have had a packet of glass 20MM fuses go open without ever been used, I think we have had this brought up before.

[broadgage]

Very small fuses might spoil in storage due to oxidation of the very fine wire, or they might have been defective in the first place and this not noticed until put to use.

I doubt that 13 amp plug fuses would suffer thus.
Almost certainly the reported failure was due to poor contacts heating up under heavy load. I have observed many very similar failures of fuses/fuse holders in plugs and trailing sockets.

I agree that most designs of 13 amp plug and socket are not suitable for a long hour full load.
This is reflected in appliance designs, very few modern appliances use more than 10 amps other than briefly.
Tumble dryers and space heaters are generally a maximum of 10 amps these days, partly I suspect to avoid warranty claims for melted plus.
Immersion heaters are often a full 13 amps, but SHOULD NOT be connected via 13 amp plugs.
Kettles are often a full 13 amps and are fine in view of the short term use.
SOME washing machines use 13 amps when heating the water, but not for long due to the small water volume used by modern machines.

[GMB]

I think the problem with the fuse clips is that once a tiny bit of heat is generated it heat-treats the metal making it less springy and so the process quickly escalates.

[G6Tanuki]

Originally Posted by GMB

I think the problem with the fuse clips is that once a tiny bit of heat is generated it heat-treats the metal making it less springy and so the process quickly escalates.

Exactly! The heat anneals the clips, making them less-springy so the grip reduces, the resistance rises, more heat is generated...

[jenkinsrichard]

The fuse fits very snugly when re-inserted.
Heat appears to have radiated from the fuse cartridge body itself, not just from the metal ends.

[Radio Wrangler]

That sounds like the fuse wire itself going crystalline.... a bit like a dry solder joint. Its resistance goes up.

David

[Herald1360]

The screw connection block to the line busbar looks as though it's been hot- loose screw or poor riveted connection to the fuse clip?

I don't trust those multiway socket strips for more than about 5A total load!

[duncanlowe]

That's a properly old four way strip. I still have a couple somewhere. Back when they were new, I remember some of them being used for plugging in heaters, and they weren't really up to the job. It was quite common for the strip to get quite hot and discolour /distort where the heater was plugged in.

[Lucien Nunes]

Often, when a plug, socket or fuseholder fails through prolonged overheating, there is a visible focus at which much of the heat was generated during the failure process. As mentioned above, the effect of heat on contact resistance through accelerated oxidation and loss of spring temper can cause one particular point of contact to go into runaway. Here, the dissipation does look more uniform, with a significant contribution from the fuse element itself.