A. The man-hole is a hole cut in boiler large enough to admit a man and is covered by a portable plate which can be fastened absolutely tight. Hand-holes are small holes cut in boiler in convenient places into which a hose can be placed and the boiler washed out and the mud and scale removed. Hand-holes are covered with portable plates which can be fastened absolutely tight.
Q. How can a boiler be protected from the cold?
A. By a non-conducting jacket which keeps off the cold, retains the high temperature of the boiler and prevents the radiation of heat.
Q. What materials are used for jacketing a boiler?
A. Plaster, wood, hair, rags, felt, paper and asbestos.
Q. How are they applied?
A. Wood is put on in long strips close together like barrel staves, fastened with hoops and usually covered with sheet iron. The other materials are put close to the boiler and held in place by sheet iron or canvas. They are sometimes put on with an intervening air space between them and the boiler.
Q. What is the use of air space?