Glossary

The empty space between the liquid surface and the top of the tank.

A graduated rod lowered to the tank bottom; the wet line shows liquid depth.

The total volume of a vessel measured in water gallons — how propane tanks are sized.

Propane vessels are filled to at most 80% of water capacity to leave expansion vapor space.

A cross-section with two flat parallel sides joined by semicircular ends; the shape of standard 275/330 oil tanks.

A dished tank end made of a spherical dish and a toroidal knuckle; the common ASME F&D head.

A dished head whose depth is one quarter of the diameter; standard on many pressure vessels.

The region of a circle cut off by a chord — the wetted cross-section of a partly filled horizontal cylinder.

How much volume one inch of depth represents; constant for vertical-walled tanks, varying for round ones.

The marketing size of a tank (e.g. 55-gal drum), often different from brim-full geometric volume.

Commercial measurement of fuel changing ownership — requires certified meters, not geometric charts.

Unpumpable liquid remaining below the outlet.

Vertical distance kept between liquid surface and tank top, especially in open tanks.

Measuring liquid depth (marine usage); same operation as sticking a tank.

Intermediate Bulk Container — caged plastic tote, commonly 275 or 330 gallons.

Gallons per minute, the standard flow-rate unit for fill and drain times.

Density relative to water; multiplying water weight by SG gives liquid weight.

See ullage; in pressure vessels, the gas-filled region above the liquid.

The curved transition between a tank shell and a dished head.

Filled to the absolute geometric top — usually above safe working capacity.

Petroleum industry density scale; higher API = lighter fluid. Diesel ~36°, heating oil ~32°.

A pressure vessel built to the ASME Boiler and Pressure Vessel Code — residential propane tanks are ASME vessels.

British thermal unit, the energy to heat one pound of water 1°F. Propane carries ~91,500 BTU/gal; heating oil ~138,500.

A cylinder with hemispherical heads — the maximum-volume head shape.

The reference point a measurement starts from; tank charts use the inside tank bottom.

A fixed tube through which a tank is sticked or sampled, keeping the stick path vertical.

Any concave tank end — ellipsoidal, torispherical or hemispherical — that adds volume beyond the cylinder.

A low pocket molded into a tank or tote bottom so it drains completely.

See 80% rule — the maximum propane fill leaving vapor expansion space.

The capped pipe through which a tank receives delivery; on buried tanks, also the sticking access.

Rainwater fitting that discards the first dirty roof runoff before water enters storage.

A buoyant arm or disc driving a dial — reads level mechanically, typically ±5%.

Height of liquid above a point; 1 ft of water ≈ 0.433 psi. Why overhead tanks make pressure.

The small transition radius between a dished head's crown and the tank shell — 0.06D on standard ASME F&D heads.

Litres per capita per day — the water-planning unit; IS 1172's norm is 135 lpcd.

The US standard for oil-burning equipment installation, including indoor tank placement.

The Liquefied Petroleum Gas Code — source of propane tank clearance distances.

Fraction of rainfall that actually leaves a roof as collectable water; ~0.8 for sloped roofs.

Industry name for a calibrated depth-to-volume table — what this site calls a tank chart.

The empty weight of a container; gross minus tare is the liquid weight.

Device on oil tank vents that whistles during filling and stops near full — the driver's audible gauge.

The boundary between wet and dry on a withdrawn gauge stick — the actual measurement.

Usable volume between practical full and the outlet — less than geometric capacity.

An underground bulk storage tank filled from intermittent mains, paired with an overhead tank.

The large spherical radius of a dished head's center section — equal to D on standard F&D heads.