Chock blaster
The chock blaster is used for automatic cleaning of fluegas pipes in the boiler.
A 1" chock blaster is used for boilers below 80 kW and a 2" blaster is used for boilers larger than 80 kW (mounted in batteries for larger boilers).
Note that the chock blaster can't replace manual cleanings of the boiler, but it can extend the periods between these cleanings, when you have to stop the boiler to clean the flue pipes.
