With use of Benson boiler the main difficulties experienced in the La Mont boiler, the formation and attachment of bubbles on the inner surfaces of the heating tubes of boiler are resolved. The attached bubbles reduce the heat flow and steam generation as it offers higher thermal resistance compared to water film.
Benson Boiler
- In the year 1922 Benson argued that if the boiler pressure was raised to critical pressure of 225 atmospheres, the steam and water would have the same density and therefore the danger of bubble formation can be high.
- Natural circulation boilers require expansion joints but these are not required for Benson as the pipes are welded. The erection of Benson boiler is easier and quicker as all the parts are welded at site and workshop job of tube expansion is altogether avoided.
- Benson boiler parts transportation is easy as no drums are required and majority of the parts are carried to the site without pre-assembly.
- The Benson boiler can be erected in a comparatively smaller floor area. The space problem does not control the size of Benson boiler used.
- The furnace walls of the boiler can be more efficiently protected by using small diameter and close pitched tubes.
- In Benson boiler superheater is an integral part of forced circulation system, therefore no special starting arrangement for superheater is needed.
- Due to welded joints Benson boiler can be started very quickly.
- Benson boiler can be operated most economically by varying the temperature and pressure at partial loads and overloads. The desired temperature can also be maintained constant at any pressure.
- Sudden fall of demand creates circulation problems in this boiler due to bubble formation in the natural circulation boiler which never occurs in Benson boiler. This feature of in-sensitiveness to load fluctuations makes this boiler more suitable for grid power station as it has better adaptive capacity to meet sudden load fluctuations.
- The blowdown losses in this boiler are hardly 4% of natural circulation boilers of same capacity.
- Explosion hazards are not at all severe as it consists of only small diameter tubes and has very little storage capacity compared to drum type of boiler.
During starting of this boiler, the water is made pass through the economizer, evaporator, superheater and back to the feed line through starting valve.
During starting of this boiler, first circulating pumps are made to start and then the burners are made to start to avoid the overheating of evaporator and superheater tubes.