Shunt locks

[9651]

Evening all

 

Shunt locks 

 

Can't find anything about a "graded" shunt lock 

 

We don't fit them, (well I have but donkeys years ago) but have one on a current takeover 

 

Presume this calls up Does this calls up an existing BS4737 standard or something in 50131? I can't seem to see anything about locks though

 

BS8243 permits a shunt lock for completion of setting -  but wondering where we are in terms of component grade?

 

Many thanks