As the boiler heats up the water appears to surge in the flow pipe causing severe water hammer

Sounds like either air in pipes, or bad expansion tank, what is the pressure on the boiler?

Hi Me12day

This sounds like a STEAM BOILER... is that correct?

If this is a steam boiler then I'd ask you when was the last time you cleaned or "skimmed" the steam boiler?

Let me know more, OK?

Mark

Certainly does sound like a steamer. Too much water in the system will cause the same symptoms if I recall correctly.