23.  Q. What are the advantages of radial stayed crown sheets?

A. They are easier to keep clean and cheaper to repair.

24.  Q. How are the inside and outside sheets of a fire-box secured at the bottom?

A. They are riveted to a wrought iron ring called a mud-ring.

25.  Q. Describe the ash-pan and its use.

A. It is a receptacle secured to the fire-box and usually provided with dampers to regulate the flow of air to the fire.  It collects the ashes that drop from the fire-box and prevents them from setting fire to bridges or other property along the track.  Engine-men must know that ash-pan slide and hopper bottoms are closed before leaving enginehouse.

26.  Q. What is a “wagon-top” boiler?

A. It is a boiler that has the fire-box end made larger than the cylindrical part to provide more steam space.

27.  Q. Why are boilers provided with steam domes?

A. To furnish more steam space and to obtain dryer steam and to provide a place for the safety valves, steam pipes, throttle valve and whistle.

28.  Q. What must be the condition of a boiler to give the best results?

A. It must have good circulation and be clean and free from mud or scale.

29.  Q. What is meant by “circulation” in a boiler?

A. Free movement of the water, so that it may come in contact with the heating surface and after being converted into steam be immediately replaced by a fresh supply of water.

30.  Q. What would be the effect if a “leg” of the fire-box became filled with mud?

A. There would be no water in contact with the fire-box sheets and they would quickly become overheated and mud-burned.

31.  Q. What would be the result if the fire-box sheets became overheated?

A. They would be weakened and forced off the staybolts and an explosion would occur.

32.  Q. Would it be advisable to put water into a boiler after the sheets had become bare and red hot?

A. No.  The fire should be killed at once.

33.  Q. What effect has the stoppage of a large number of flues?

A. The heating surface and draft are decreased by just that much area.

34.  Q. Why are boiler checks placed so far away from the fire-box?

A. To introduce the water into the boiler at as great a distance from the fire-box as possible.  This permits the water to become heated to a high temperature before it comes in contact with the fire-box and also improves circulation.

35.  Q. What part of the boiler has the greatest pressure?  Why?

A. The bottom, because it is subject to the weight of the water in addition to the steam pressure in the boiler.

36.  Q. What are the advantages of the extension front end?

A. To provide room for suitable draft and spark appliances.

37.  Q. What is the purpose of a netting in a smoke-box or front end?