What's the nut on top of a gas supply bayonet fixing used for?

[Borderer]

I have a redundant gas cooker supply to cap, but wondered what the nut on the top of the gas supply bayonet fitting is used for?

 

[ShaunCorbs]

Picture ?

 

[Basher]

Presumably to allow the valve components to be assembled inside (during manufacture)
If you're talking about this sort of thing:

Gas Bayonet Socket

• BS669-1• For use with bayonet type cooker hoseThis product should only be installed by a Gas Safe registered engineer.

www.toolstation.com

 

[fowlerboi]

I expect it will be how they assembled the fitting.

In theory they are designed to be disconnected and gas tight. Realistically though I would get it capped. IT IS NOT SOMETHING A NON GAS SAFE ENGINEER CAN DO.

Guidance Note 65 to regulation 6(3) of GSIUR states:
“When an appliance is disconnected and open-ended pipework is left, the pipework should always be left sealed with an appropriate fitting. A self-sealing coupling, e.g. on a cooker connection, does not need to be capped-off, except where there is a significant risk of interference (such as by a child). However, it should be checked that any disconnected coupling is not leaking gas (see paragraph 68), and any wall- mounted connector has been installed in the downward mounted position to prevent dirt or grit getting into the self-closing seal.”

 

[ShaunCorbs]

Tesla Bayonet Cooker Hose Blanking Plug 1/2" (SBP12) - Unvented Components Europe, Unvented Cylinder System Spares, Spares for Hot Water Systems, Plumbing & Heating Parts

Designed to provide a secondary seal when the bayonet cooker hose is disconnected to prevent dirt and contaminant ingress. For use with bayonet sockets only. Manufactured to BS669. Features and Benefits Prevents dirt and contaminant ingress. Product Specification Code: SBP12 Size: 1/2″ Diameter...

www.unventedcomponentseurope.com