Steam boilers

Scotch fire tube marine steam boiler

The single-ended return tube Scotch marine boiler consists of a cylindrical boiler shell of large diameter and short length, provided with two or more furnaces in corrugated fire-tubes. Each furnace ends in a combustion chamber, surrounded by water. The gases pass through a bank of flue-tubes from the combustion chamber to the smoke-box at the boiler front

The Scotch marine fire-tube boiler contained a large quantity of water, about six times more than a water-tube boiler, and was therefore slow to steam up and to change the output capacity. Due to the Scotch boilers stiff construction it required also a long steaming up period to avoid leaks caused by thermal expansion of the material.

The double-ended Scotch fire-tube steam boiler

These types of boilers were normally used in ships with many Scotch boilers. Space was saved even though two stokeholes were required. Normally a pair of furnaces shared one combustion chamber.

When the furnace door was open, cold air could hit the combustion chamber's opposite wall and cause tube leakage. To prevent that, a high baffle of firebrick was installed in the middle of the combustion chamber.

Twenty-four double-ended Scotch boilers with three furnaces at each end and five single-ended boilers with three furnaces were installed onboard R.M.S. Titanic. Electrically operated stoking indicators were used in the stokeholds to prevent that opposite furnace doors were open at the same time. These indicators also helped to minimize the total number of simultaneously open furnace doors.

Many old steamships are still sailing with this type of boiler, some of the with new-built old fashion Scotch fire tube marine steam boiler.