Gaps or holes at the bottom of the floor timbers by the keel that allow water to flow fore-and-aft.

Related Terms

RESTRICTOR

A device for producing a deliberate pressure drop or resistance in a line by reducing the cross-sectional flow area.

COMPRESSOR

A device which converts mechanical force and motion into pneumatic flow power.

CORROSION INHIBITOR

Additive for protecting lubricated metal surfaces against chemical attack by water or other contaminants. There are several types of corrosion inhibitors. Polar compounds wet the metal surface preferentially, protecting it with a film of oil. Other compounds may absorb water by incorporating it in a water-in-oil emulsion so that only the oil touches the metal surface. Another type of corrosion inhibitor combines chemically with the metal to present a non- reactive surface.

DEMULSIBILITY

The ability of a fluid that is insoluble in water to separate from water with which it may be mixed in the form of an emulsion.

HALF-TIDE BASIN

A lock of very large size and usually of irregular shape, the gates of which are kept open for several hours after high tide so that vessels may enter as long as there is sufficient depth over the sill. Vessels remain in the half-tide basin until the ensuing flood tide before they may pass through the gate to the inner harbor. If entry to the inner harbor is required before this time, water must be admitted to the half-tide basin from some external source.

GROUND LOG

A device for determining the course and speed over the ground in shallow water consisting of a lead or weight attached to a line. The lead is thrown overboard and allowed to rest on the bottom. The course over ground is indicated by the direction the line tends and the speed by the amount of line paid out in a unit of time.

GULLY

1. A small ravine, especially one cut by running water, but through which water flows only after a rain. 2. On the sea floor, a small valley-like feature

HALF-TIDE LEVEL

A tidal datum midway between mean high water and mean low water. Mean sea level may coincide with half-tide level, but seldom does; the variation is generally about 3 centimeters and rarely exceeds 6 centimeters. Also called MEAN TIDE LEVEL.

HIGH WATER STAND

The condition at high water when there is no sensible change in the height of the water. A similar condition at low water is called LOW WATER STAND

ANTI-WEAR ADDITIVE

Improves the service life of tribological elements operating in the boundary lubrication regime. Anti-wear compounds (for example, ZDDP and TCP) start decomposing at 90° to 100°C and even at a lower temperature if water (25 to 50 ppm) is present.

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