A line drawn on the chart in lieu of the mean high water line or the mean water level line in areas where either may be obscured by marsh, mangrove, cypress, or other marine vegetation.

Related Terms

RESTRICTOR

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

DIELECTRIC STRENGTH

A measure of the ability of an insulating material to withstand electric stress (voltage) without failure. Fluids with high dielectric strength (usually expressed in volts or kilovolts) are good electrical insulators. (ASTM Designation D 877.)

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.

CARBON RESIDUE

Coked material remaining after an oil has been exposed to high temperatures under controlled conditions.

REFRIGERATOR

A device to transfer heat from a low temperature to a high temperature medium.

ADSORPTION

Adhesion of the molecules of gases, liquids, or dissolved substances to a solid surface, resulting in relatively high concentration of the molecules at the place of contact; e.g. the plating out of an anti-wear additive on metal surfaces.

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.

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.

GRID RHUMB LINE

A line making the same oblique angle with all grid meridians. Grid parallels and meridians may be considered special cases of the grid rhumb line.

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