Pipes banging in boiler

[craig1]

Hello,

I have a wall hung boiler which after half an hour after being fired

up a hissing noise occurs, then the pipes at the boiler vibrate and bang.

I then switch off the system, then switch it back on and the

vibrating/banging has stopped and runs ok. any ideas how to prevent the

banging when first switched on?

Thanks!

 

[ChrisR]

It's overheating. Possibly dicky thermostat or pump, or sludge/scale.