TACK WELD
A light weld whose function is to hold parts in proper position, but not to transfer heavy loads.

TANK
The completed vessel assembly of a tank car, consisting of (2) heads, a number of ring sections, and one or more nozzles.

TANK ANCHOR
On underframe tank cars, the structural arrangement at the bottom center of the tank that provides a means for attaching the tank to the center sill.

TANK BAND
On underframe tank cars, the steel straps that pass over the tank at each cradle (bolster) to help hold the tank on the underframe cradles.

TANK CAR
A railcar, the body of which consists of a tank for transporting liquids or compressed gas. Tank cars may be pressure or non-pressure design and are often equipped with special equipment to enhance their usefulness for handling specific commodities.

TANK CRADLE
On underframe tank cars, the underframe structure, at the center of each truck, on which the tank sits.

TANK HEAD
A circular, curved and/or elliptical pressed end sheet of a cylindrical tank.

TARE WEIGHT
As applied to a carload, weight of the car exclusive of contents. See Light Weight.

TARIFF
A schedule of rates charged, together with governing rules and regulations.

TELL TALE
See "Fixed Tube Gauge."

THERMOMETER WELL
A small diameter pipe, closed at the bottom, that extends into the tank from a mounting on top. Various temperature sensing devices can be inserted into this pipe to determine the temperature of the tank contents.

THROAT
The shortest distance from the root of a fillet weld to its face.

THROUGH TRAIN
A train which does not stop at all stations on its route.

TIH
Toxic Inhalation Hazard.

TON MILE
The movement of a ton of freight one mile.

TONGUE & GROOVE
Refers to a gasketed connection where the gasket is placed into a circular groove on one surface (nozzle flange or saddle) and a tongue on the mating surface (valve or fitting) fits into the groove thereby compressing the gasket as the joint is tightened.

TOP COAT
Refers to the last coat applied on a multiple coat paint or coating system.

TOP FITTINGS
Refers to the top unloading valves and other fittings mounted on the top of some tank cars.

TOP OPERATED PLUG VALVE
A bottom outlet plug valve whose operating shaft extends to the top of the car thereby removing the un-loader from a position under the car. (aka: Outside Valve Operating Mechanism (OVOM)

TOP OPERATING PLATFORM
The platform that provides a working area and access to the manway and fittings located on the top of a tank car.

TOP STYLE SAFETY VALVE
A safety valve whose spring(s) is located above the valve seat thereby isolating the spring from the commodity. This valve is used to protect the spring from corrosion or where interior cleanliness is of prime importance.

TOP UNLOAD
An assembly of valves used to unload a tank car from the top.

TOP WALKWAY
On cars equipped with end ladders, the walkway extending from the end ladders at each end of the car to the centrally located top operating platform.

TORQUE
Refers to the rotational force applied to tighten threaded fasteners (bolts and nuts) or the force applied to valve handles to open or close the valve.

TRAIN LINE
The continuous line of brake pipe extending from the lead locomotive to the last car in a train.

TRD
Tentative Release Date

TREAD
The surface of a railcar wheel that contacts the top surface of the rail.

TRUCK
The complete assembly of parts, including wheels, axles, bearings, side frames, bolster, brake rigging, springs and all associated connecting components, the function of which is to provide support, mobility and guidance to a railroad car.

TRUCK BOLSTER
The main transverse member of a truck assembly that transmits car body loads to the side frame through the suspension system. The ends of the bolster fill loosely into the wide opening in the side frames and are retained by the gibs, which contact the side frame column guides. Truck bolster contact with the car body is through the truck center plate, which mates with the body center plate and through the side bearings. See Bolster Gibs.

TRUCK CENTERS
The distance between the truck center pins on a single car.

TRUCK MOUNTED BRAKES
An air brake system whose cylinder(s) are mounted on the trucks, thereby eliminating the need for mounting rods, levers, and a slack adjustor directly to the underside of the car. Generally used to provide clearance under the side.

TRUNK LINE
A railroad line operating over an extensive territory.

TRUST PLATE
A metal plate, decal, or stencil, applied to the side of a railway car to identify the trustee (usually a bank) holding ownership to the equipment.

TT
Tank Test.

TUB
The assembly of a tank ring and a tank head.

TURNBUCKLE
A mechanical device with a threaded eye bolt at each end, used to tighten tank bands.