Expansion vessel pressure?

[muckylugs]

Could someone tell how to repressurise an expansion vessel. I know the pressure it has to be and where to refill it what i need to know is does the boiler have to be empty when done or can it be done full but cold and is there anything else i need to know when doing this.
thanks in advance.
mucks.

 

[kevplumb]

you need to drain the boiler first
should be valves underneath but they have a habit of leaking if disturbed

 

[the boiler technician]

see my reply on "expansion vessel"
the boiler technician