Exercise 3. Make up a dialogue of your own based on the one given below. A.: If all the stored air is lost how can the engines be started?

A.: If all the stored air is lost how can the engines be started?

В.: In most cases a small emergency compressor is provided, driven by a very small oil engine that can be started by hand After a small amount of air is pumped up an auxiliary engine can be started and air pumped up to start the main engine.

A.: How much starting air capacity should the tanks have?

В.: The usual requirement is enough to start the engine 12 times. A better rule is to provide at least 35 times the volume swept through by one piston for each main engine.

A.: Describe the preparations for starting the engine.

В.: Jack the engine to see that it is clear for running, start lubricating oil pump and see that oil reaches all bearings, open by-pass valves in fuel oil lines to injection valves and pump oil through by hand to clear out all air and fill the pipes with oil, open stop valves in starting air and injection air lines, give cyl­inder lubricators a number of turns by hand to get some oil into the cylinders, start jacket cooling water pump and see that the propellers are clear. If means for heating the cylinders are avail­able and the weather is cold, warming up should be started in time to have all the cylinders hot before starting.

A.: Why should the bearings of a new engine be gone over after 800 to 900 hours of running?

В.: То take up looseness due to the initial wearing in.

A.: Why will a piston sometimes run without trouble at nor­mal load and drag or stick if the load is increased?

В.: Because the clearance in the cylinder may be sufficient at normal load but when overload causes all parts to become hotter the increased temperature of the piston causes it to expand more and reduce the clearance.

A.: What is the effect of too much or too little clearance be­tween a cam and its roller?

В.: Too much clearance causes late valve opening, early clo­sure, decreased lift and noisy operation. Too little clearance causes early opening, late closure, increased valve lift and may pre­vent complete closure.

A.: What are some of the common troubles experienced with fuel measuring pumps?

В.: Leaky suction and discharge valves, due to grit in the oil or to particles of dirt or lint becoming caught under the valves; pump becoming air bound; incorrect clearance between suction valve stems and tappets; leaky plungers, and change in timing, due to looseness in the operating gear.

A.: Why is it desirable to have thermometers so located that separate temperature readings of the cooling water discharge from the cylinders can be taken?

В.: If merely the temperature of the common discharge from all cylinders is taken, a single cylinder jacket may become air bound and the flow of cooling water through it stopped altogether without giving any indication at the common outlet.

A.: What are the effects of too many or incorrectly placed oil grooves in a bearing?

В.: The bearing surface is reduced and the oil escapes from the bearing without spreading over its surface.

A.: What is a common trouble with the cylinder lubricating system?

В.: Excessive feed of lubricating oil into the system, causing collection of gum and carbon in the ring slots and leakage of black oil into the crank pits.