SADDLE
The mounting flange welded to the tank bottom, to which the bottom outlet valve is attached.

SAFETY APPLIANCES
Any one of several specific components required on railway cars, the functions of which are directly related to the safety of train crew members and other persons whose duties require being on or around the equipment. The design, location, and proper maintenance of safety appliances are strictly regulated by the Department of Transportation. Safety appliances on cars include hand brakes, handholds, ladders, uncoupling levers, sill steps and safety railings.

SAFETY CHAIN
A detachable chain sometimes mounted across the access openings on top operating platforms.

SAFETY MAN
An individual used when another person enters a tank to ensure safety.

SAFETY VALVE
A device used to protect against an accumulation of excess pressure in a tank car. Usually held closed by a spring, which is forced open when pressure in the tank rises above a predetermined level.

SAFETY VENT
A safety relief device mounted on top of a tank car consisting of a frangible disc held in a housing. Used only on cars carrying nonflammable products or products that do not give off flammable vapors. See "Frangible Disc."

SAMPLE LINE
A device permitting the sampling of the product in a loaded tank car. This line is also known as a "test tube."

SAND BLAST
See "Blast."

SANDWICH™ CAR
A super insulated tank car whose inner tank is supported solely by urethane foam insulation, thereby eliminating most of the metal heat loss paths from the inner tank to the atmosphere. Class AAR 206A or DOT 115A.

SAV NOZZLE
Siphon and air vent nozzle. The top nozzle on nonpressure tank cars upon which the top unload valves and other fittings are normally mounted.

SAW
See "Submerged Arc Welding."

SCORE
A narrow deformation, caused by mechanical means, wherein parent or weld metal is upset and relocated.

SCREWED
Refers to valves or other fittings whose end connections consist of pipe threads.

SECURITY SEAL
A device used to indicate whether or not a closure has been opened. Typical examples are: wire, cable or metal band.

SEAL
A general term used to describe any device used to close off completely, to prevent leakage or to secure. Typical examples of seals found in railroad car work are: air brake valve gaskets, rubber washers in air hose connections, manway gaskets, and packing in valves.

SEAT
In mechanical systems, a term used to describe a specific location or surface on which another part rests and often depends for proper operation, such as a valve seat.

SEQUENCE NUMBER
Also known as an order number; set by the sales office for each 21 message (CF) entered during the year.

SERPENTINE SYSTEMS
A tank car heater system with only one possible passage or route from inlet to outlet. Can be used with either steam or liquid heating medium.

SERVICE PORTION
One of the three parts of an air brake control valve.

SERVICE EQUIPMENT
Equipment used for filling, sampling device, emptying, venting, vacuum relief, pressure relief, heating if internal to the tank, lading temperature measurement, or measuring the amount of lading within the tankcar.

SET PRESSURE
The pressure, measured at the valve inlet, at which a safety relief valve is set for start-to-discharge.

SHIELDED METAL ARC WELDING
An ARC welding process utilizing coated metal electrodes. The heat of welding vaporizes the coating thereby forming a protective atmosphere around the molten metal.

SHELF COUPLER
A special coupler, required on some cars designed for transporting hazardous commodities, having top and bottom "shelves" case integral with the head to prevent vertical disengagement of mating couplers in the event of an excessive end impact. Shelf couplers are fully compatible with other standard AAR couplers. See "Head Shield."

SHELL FULL CAPACITY
The maximum volume of a tank, not including any required outage.

SHELL PLATE
The steel or aluminum plate used to fabricate tank car tanks.

SHIM
A thin piece of steel used for leveling, raising, or otherwise locating a larger part to a precise position.

SHIPPER
The person or company that ships goods. The consignor.

SHOP TRUCKS
Device used to move a car in the shop to various locations setup for that particular repair or function.

SHOP TURNAROUND TIME
Begins when the delivering railroad sets a car in at the shop and ends when the car is offered to the railroad on the outbound track.

SHOPS (REPAIR VS. NEW)
Repair shops address existing equipment and new shops produce new equipment.

SHOPPED
The action of temporarily taking a car out of service for repairs or inspections.

SHOT
A blasting material consisting of spherically shaped particles of steel or iron. See "Blast."

SIDE BEARING
Usually blocks or rollers located on top of the truck bolster in retaining cages approximately 2 feet either side of the center of the bolster's center bowl. They are in line with the corresponding car body's structural side bearing plate and function to control car rocking and rolling. Constant contact side bearings use resilient components to keep the side bearing on the truck bolster "constantly" in contact with the car body structural side bearing plate without requiring the specified gap between them.
 

SIDE BEARING CLEARANCE
The AAR specified vertical space between the truck side bearing and the body side bearing.

SIDE FRAME
The heavy cast steel side member (one of two) of the conventional rail car truck.

SIDE FRAME KEY
A short steel retainer bolted to the bottom of a pedestal type side frame to prevent roller bearing assemblies from becoming dislodged from the side frame pedestals.

SIDE LADDER
One of two ladders, generally located near the center of each side of a tank car, for the purpose of providing access from the ground to the top operating platform.

SIDE PLATE
Longitudinal structural members on house and covered hopper cars that connects the roof to the sides.

SIDE POSTS
Any one of a series of vertical structural stiffening members located along the length of a covered hopper car side sheet, and attached thereto.

SIDE SAFETY RAIL
A railing running the length of each side of a tank car at ground level.

SIDE SHEET
The steel (or aluminum) panels that close in the sides of a covered hopper car.

SIDE SILL
The outside longitudinal structural member extending the length of the car at the bottom of the sides of hopper cars and house type cars.

SILL
See "Center Sill."

SILL PAD
The bottom reinforcing pad to which the center or stub sill is attached and which, in turn, is attached to the tank.

SILL STEP
The steel step located at each bottom corner of a railcar.

SILVER DOLLAR
The large flange used on pressure cars for the manway cover.

SINGLE LEVEL PLATFORM
See "Full Grating Platform."

SIPHON PIPE
A pipe that extends from the top of a tank to the bottom, often extending into a bottom sump, thereby enabling the tank contents to be unloaded from the top.

SIPHON PIPE GUIDE
Generally a fabrication mounted to the tank bottom whose purpose is to stabilize the siphon pipe.

SKID
The cast or fabricated structure mounted to the bottom exterior of a tank to provide shear-off protection for bottom discontinuities such as, bottom valves, sumps, or washouts.

SLACK ADJUSTER
A device installed in the foundation brake rigging of a railway car, usually near the brake cylinder line lever, used to automatically compensate for variations in the brake riggings caused by brake shoe and wheel wear or replacement. The slack adjuster function to take up rigging slack as wear occurs, or to let out slack when new shoes or wheels are applied. Brake cylinder piston travel is thereby automatically maintained at its optimum length without the need for manual brake rigging adjustments.

SLID FLAT WHEELS
Railcar wheels with flat spots resulting from sliding on the rail; generally, due to overbraking or failure to release the car handbrake. Flat spots larger than the AAR maximum allowed are a cause for wheel replacement.

SLOPE SHEET
The sheets that slope from the sides and ends to form the hoppers in the bottom of a hopper car.

SMAW
Acronym for Shielded Metal Arc Welding.

SONIC TESTING
Means by which thickness of a tank car is measured.

SPARK TEST
An inspection procedure used to detect minute gaps and pin holes in rubber tank linings.

SPECIFIC GRAVITY
The ratio of the density of a substance (tank car commodity) to the density of water.

SPRING GROUP
The specific combination of standard coil springs mounted in each truck side frame that support the weight of the car body and the lading.

SPUR TRACK
A track extending out from or alongside, and connecting only at one end with another track.

STAINLESS STEEL
An alloy steel containing relatively large amounts of chromium and nickel which greatly enhance corrosion resistance.

STAINLESS STEEL TRIM
Refers to a valve with stainless steel internal working parts (e.g., ball, stem, plug, etc.) but, whose body is carbon steel.

STAMPED
Marked by means of a steel stamp.

STANCHION
On current Union Tank Car tank cars, the vertical structural support located at the "B" end of the car upon which the handbrake is mounted.

STAND PIPE
See "Siphon Pipe."

STAR SYMBOL
A star stenciled to the left of the load limit stencil, indicating a reduced load limit below what would normally be expected for the size of bearings, axles, and wheels under the car.

START TO DISCHARGE PRESSURE
The pressure, measured at the valve inlet, at which there is a measurable lift of the closure device on a safety relief valve, or at which discharge becomes continuous.

START TO LEAK PRESSURE
The pressure measured at a safety valve inlet, at which fluid is first detected at the valve outlet.

STEAM JACKETED
An enclosure around a pipe, valve, or nozzle to enable steam to be injected and circulated around the equipment to facilitate flow of the product within the system.

STENCIL
Marked by means of paint or decal.

STICK WELDING
See "Shielded Metal ARC Welding."

STORAGE TRACK
A track on which cars are placed when not in service, or when awaiting assignment.

STRAIGHT FLANGE
The 2 1/2" to 3 1/2" long portion of a tank head which terminates at the circular edge that is butted against and then welded to a tank ring section.

STRAIGHT SHELL
A term used to describe a straight tank, i.e., one without a sloping bottom.

STRESS RELIEF
Commonly used as a synonym for post weld heat treatment.

STRIKER
The heavy cast forged, or fabricated bar fastened to the end of the center sill at the top, and designed to be the first point of contact in the event the car coupler is driven back far enough to strike the car body. Its function is to absorb the resulting impact and prevent damage to the center sill and surrounding area.

STRIPPING
Encompasses chemical, thermal, and mechanical techniques of removal of existing linings or coatings.

STUB SILL

Longitudinal structural member attached to the tank toward each end of a "stub sill tank car".  The tank acts as the structural member between the stub sills.  The couplers are mounted into the stub sills.  "Underframe tank cars" have center sills rather than stub sills.

STUD
A headless bolt either welded or otherwise secured to some component, and used for attaching an adjoining component by means of a threaded nut.

STUFFING BOX
An enclosure containing packing to prevent leakage around a machine part.

SUBMERGED ARC WELDING
An automatic arc welding process capable of depositing relatively large amounts of weld metal in a single pass, and the process used by Union Tank Car to assemble tank car tanks.

SUMP
A small depression in the bottom of the tank located directly under the siphon pipe(s), used to facilitate complete tank unloading.

SURFACE AREA
Normally refers to the surface area of a tank expressed in square feet.

SUSPENSION
The resilient system through which a car body is supported on its wheels. Suspension systems involve the use of hydraulic devices, friction elements and coil, elliptic, rubber, or pneumatic springs.

SWITCHING
The moving of cars from one place to another in a limited switching area.