NDM
National Railway of Mexico.

NEEDLE VALVE
A small manual valve used where fine regulation of the working fluid is required. This type of valve is used on fixed tube gauges.

NET LEASE
A lease whereby the lessee assumes responsibility for all maintenance, administrative, and tax services required for the use and operation of leased property.

NET TON
Equal to 2000 pounds.

NET WEIGHT
The weight of only the contents of a railcar.

NFL BEARING
A railcar wheel roller bearing designed not to require periodic field lubrication.

NINC
Acronym for a non-insulated and non-coiled tank car.

NITROGEN PURGE
The process of replacing a portion of the air inside of a tank with dry nitrogen, mainly to minimize moisture formation and/or the subsequent rusting of the tank interior prior to the first load.

NOMINAL CAPACITY (OBSOLETE TERM)
The approximate load carrying capacity of a railcar measured to the nearest 1000 pounds. Not to appear stenciled on any cars after 12/31/96. See Rule 70 in AAR Field Manual.

NON-COILED
Refers to a tank car that does not have heater coils.

NON-DESTRUCTIVE TESTING
A test procedure that does not destroy or otherwise limit the utility of the object being tested. An example is the x-raying of tank welds.

NON-INSULATED
Normally refers to a tank car that does not have any thermal insulation covering the tank.

NON-PIPED
Refers to a tank that does not have interior heater pipes.

NON-PRESSURE CAR
A tank car built to DOT specs 103, 104, 111 and 115. Reference 49 CFR Part 179, Subparts A, B, and D. The test pressure for non-pressure tanks is either 100 PSI or 60 PSI.

NORMALIZED
A heat treating process mainly utilized to improve the properties of shell and head plate.

NOZZLE
A cylindrical structure generally welded to a tank along its top centerline. The function of a nozzle is to provide access to the tank interior and/or a location for mounting fittings.

NTSB
The National Transportation Safety Board part of U.S. Dot, which investigates all transportation accidents.

NYCOPAC/WABCOPAC BRAKES
The proprietary name for truck mounted brakes manufactured by New York Air Brake Company and Westinghouse Air Brake Company.