Whilst not a solution, the issue seems to be poorly designed/faulty catering equipment or the manufacturer underselling how much current they pull. Your solution sounds grand, although beggars belief it requires that much kit to simply supply a couple of bits of kitchen equipment. Only thing I can think of is that you are removing the (presumably) 13A fuse in the plug that is, notionally at least, protecting the appliance flex.

 have had a similar problem with commercial deep fat fryers where the plugs burn out or melt. Perhaps the plugs need to be withdrawn and cleaned every few weeks. Today's value engineered carp just can't cope with the full 13 Amps. Much commercial catering equipment is designed to be supplied by a 15/16 Amp supply. I would do what is necessary to ensure reliable operation. Failed cooking equipment equals lost profits.

Z.

depending on your labour rates, you may like to consider if it is worth to buy in something like this

https://www.distributionzone.com/Products/Lighting/IEC309-Commando-Splitters/PCE-ST-Anton-Power-Distribution-Box-32A-1pH-N-E

splash proof and as seen on the floor in tents at all trendy pop festivals. Makes for a more "plug and play" solution.
Mike.

Are the plugs also burning out, or just the sockets? I infer from the OP that the appliances come with moulded plugs, so if they can withstand 13 A for any significant duration, why not the sockets?

It is also possible that the appliances are being used beyond their duty cycle. With everything on, my commercial combination oven can pull 3 kW, but the instructions specify that it is to be for not more than 5 minutes at a time.

"13A" sockets are odd beasts. The standard only requires the entire unit to be able to supply 13A - so a total of 13A for a double, not 13A each so 26A - and then only for certain ambient temperatures (max 25ºC average over 24 hours comes to mind) and even then not necessarily continuously for extended periods.

There has been trouble with 13A sockets overheating with near 13A loads on for many hours - e.g. when used to charge electric vehicles. There are now "EV" variants which are supposed to be better at supplying the full 13A for many hours at a time.

MK used to rate their sockets at 13A per outlet - so 26A for a double - but the design has changed over the years and the old statement seems to be missing from newer specifications. Generally things seem to be a lot more stamped steel rather than milled brass and soft plastics rather than hard UF - things aren't what they used to be...

So there are perhaps a number of options before going down the industrial socket route...

1. If the sockets are doubles, replace each with two singles.

2. Try "EV" marked single sockets

3. Try to position where the ambient temperature might not be quite so high (just a bit further from the fryer etc, or just around a corner, if the flex length allows)

or if you do go down the industrial socket route (which might not be bad idea anyway if the walls need regular washing down) and need to provide lower overcurrent protection you can get sockets in an enclosure that also contains a small DIN rail - so you can add MCBs/RCCBs/RCBOs to suit.

  - Andy.

An alternative approach that I have used is to modify the appliance.

Fit inside the appliance a couple of HRC fuse holders with 16 amp fuses. Fit a single 6mm flexible cord HOFR or other suitable type and supply this from a single 32 amp ceeform plug and socket.

This works excellently IME. 32 Amp plugs and sockets stand up well to heavy loads, and in this case are probably only loaded to 26 amps and not to 32 amps.

Even simpler is to omit the fuses and simply connect both the original inputs internally to a single 6mm flex and then to a 32 amp plug. This is in my view poor practice as the appliance is now protected  by an OCPD of more than twice the intended capacity.

Suggest that any replacement appliances be the type fitted with one 32 amp plug and not the two times 13 amp type.

Something like this perhaps https://www.screwfix.com/p/mk-masterseal-plus-ip66-13a-1-gang-weatherproof-outdoor-unswitched-socket/41160#product_additional_details_container

Should stop water and most grease getting in there. Could get a double socket with BS7288 RCD per plug, so two doubles per appliance. 

Might be best way to go if appliances are in warranty.

I had similar issues at a pub carvery, which has now closed down because it needs to much spent on it and gastro pub that went bust.

The pub carvery had a three phase deep fat fryer which was replaced with some table top fryers, which were definitely over worked.

From experience I can say the Commando sockets are not indestructible and had urgent calls to replace both single and three phase sockets and plugs. 

Not certain that the product linked to would help.

The problem is not primarily the ingress of water or grease, it is the inability of 13 amp plugs and sockets to withstand full load other than briefly. A water resistant type might be more vulnerable to heat build up.

If it is the sockets that are burning out I would make sure they are single outlets. Also anecdotally I have had more success with the unswitched sockets, like the MK K780