Page 4 - Bosch The basis for production excellence

4 | Quality, precision and a sense of responsibility

Optimum boiler construction

thanks to more than 150 years of experience

Optimised design for modern steam supply

Modern steam boilers do not only have to work effi-
ciently, they also have to manage dynamic pressure
demands with a consistently high steam quality. When
it comes to dynamics, water content and steam space
are the factors most often taken into consideration,
although other factors are physically more relevant. Far Fig. 1
more crucial for the power reserve and the dynamics
with consistently high steam quality are the water
quality, the control quality and the height of steam
space. Bad water quality leads to a "turbulent" water
level and foaming. The risk of water entrainment is
thus increased.

The patented arrangement of the flame tube and the
passes of Bosch boilers (fig. 2) is ideal for a maximum Fig. 2
steam space at a low water content. At spontaneous
power peaks the water level inside the boiler rises Boiler design with passes lying side by side (fig. 1) and with
because of the increased amount of steam bubbles in optimised vapor space (fig. 2).
the boiler’s water. Here the height of the steam cham-
ber provides the highest safety for preventing a water
level caused emergency shut-down and for minimising
water entrainment. In addition, extremely fast reaction
to load peaks is reliably achieved by our intelligent
three-component control, pilot signals from large scale Diagonal stays instead of stud bolts
consumers and by avoiding preventilating (burner
start). State of the art design methods such as “design In other boiler designs the reversing chamber is fixed
by rules” and “design by analysis” (e.g. FEM) keep to the boiler end with stud bolts and there is no direct
tensions in the boiler low. connection between the flame tube and the boiler end.
During start-up of a boiler high forces occur between
Other advantages of the Bosch boiler design are: the warm flame tube and the cold boiler body. Stud
▶ Higher steam quality especially for dynamic bolts can distribute this force only punctually. This
requirements causes unfavourable stress peaks in their connecting
▶ Low water content allows faster heating from weldseams.
cold start condition
▶ Most compact design reduces required space, Other disadvantages of the stud bolt construction are:
radiation and downtime losses ▶ Stud bolts are more prone to flexural stress
▶ Lower flame chamber load and reduced NOX ▶ Frequent changes in temperature can lead to stud
emissions bolts being torn off