Piston Valve to Screw Propeller

A small single or double piston which reciprocates in its cylinder past ports which are in the circumference of that cylinder. It is a slide valve with curved face and seat, and is balanced.

The distance that any given point in the screw would move in the direction of the axis if turned through one revolution in a solid fixed nut.

The distance between their centres.

(See Pillow Block.)

The cylindrical piece of equal diameter which, reciprocating in a pump cylinder through a stuffing box in one head, forces the fluid out past the delivery valve by displacing it in the cylinder.

A circular valve with a conical face and seat. It moves in the direction of its axis. There may be one or two on the same stem.

An opening in a valve-seat leading to the interior of the cylinder, or to the exhaust passage.

(See Foaming.)

A sudden increase of speed of a marine engine due to the propeller being lifted wholly or partly out of the water when the vessel is pitching.

The confined space between two cylinders of a compound or triple expansion engine into which the smaller discharges, and from which the next larger draws its supply.

The amount a bar of metal of one inch area of cross-section will be reduced in size at the point of fracture when broken in a testing machine.

A valve fitted to a circulating pump to permit a part of the water to return to the injection pipe to relieve the load on the pump.

An automatic valve attached to a cylinder, pump or line of pipe, which opens when the pressure exceeds that for which it is set.

The apparatus for changing at will the distribution of steam to the engine to make it run either ahead or back.

(See Screw Propeller.)

An arm or lever attached to a shaft that vibrates only, receiving or transmitting motion from its outer end.

One that vibrates only, not making complete revolutions.

The supports on which a boiler rests.

An apparatus attached to a steam boiler or pipe for relieving it automatically of any pressure in excess of that for which it is set.

A small vessel connected with the interior of a steam boiler into which a sample of the hot water can be drawn to determine its density.

In the engine-room it means a decomposition of a lubricant into a lather like substance.

Steam whose latent heat is sufficient to maintain it in a gaseous state. When saturated steam suffers any loss of heat, some of it will be condensed.

A term referring to the proportionate amount of saline matter held dissolved in the water in a boiler.

Mineral matter from the water in a boiler which has settled on and adhered to the heating surfaces.

A submerged propelling wheel. It is virtually a section of a screw of two or more threads or helices, each blade representing a thread.

Left-hand Screw Propeller. A propeller which revolves from the starboard to the port side during the upper part of its revolution while the engines are working ahead.

Right-hand Screw Propeller. A propeller which revolves from the port to the starboard side during the upper part of its revolution while the engines are working ahead.