my heating pipes are banging

[daimo]

i have a coal fire with a grant back boiler which works perfect for a few hours all rads are really hot and then the pipes in the roof space start banging so i run off the hot water to stop them but even with the tank cold they still give the odd bang why is this

 

[justlead1]

Probably that boiler is producing heat quicker than is can be dissipated via rads and heat exchanger / coil in cylinder.