give maximum space

give maximum strength

withstand pressure inside boiler ,

resist intense heat in fire box

non-coking bituminous coal

brown coal

pulverised coal

coking bituminous coal

horizontal

vertical

inclined

both horizontal and vertical

one-half

one-third

one-fourth

two-fifth.

serve as storage of steam

serve as storage of feed water for water wall

remove salts from water

separate steam from water