Highway / Portable Tank Terms and Definitions

Term Definition Reference Picture
Adapter, Cam & Groove The male portion of a quick coupling device for pipe or hose ends. None adapter_cam_groove.jpg
Adapter, API A spring loaded shut-off valve mounted on the tank trailer designed to mate with the terminal loading device. API RP 1004 specifies dimensions for these adapters. None apiadapter.png,apiadapter002.jpeg,apiadapter003.jpeg,apiadapter004.jpeg
Adapter, Openable Bottom Loading A bottom loading adapter that is capable of being used to unload a product. None adapter_openable_bottom_loading_001.jpg
API Abbreviation for American Petroleum Institute. None api.jpeg
Appurtenance, Cargo Tank See 49 CFR 178.345-1 (c). None None
ASME Abbreviation for American Society of Mechanical Engineers. None asme.jpg
Baffle See 49 CFR 178.345-1 (c). None None
Baffle, Dished A baffle with a concave/convex surface. None None
Barrel, Tank Vessel weldment - shell and heads. None None
Blower A device to deliver a volume of air at a certain pressure for use in unloading pneumatic tanks. None None
Brake Interlock, Parking A system that applies the parking brakes upon actuation of an air interlock valve. This valve is typically actuated during the loading or unloading operation. None None
Bulkhead, Dished A bulkhead with a concave/convex surface. None None
Bulkhead, Double Two adjacent bulkheads forming a void space. Typically found when the bulkhead of one tank is next to the bulkhead of another tank. The area between the bulkheads typically forms a void. None None
Bulkhead, Flangeless Tank An internal bulkhead that is formed with neither a knuckle radius or straight flange. None None
Bulkhead, Tank See 49 CFR 178.345-1 (c) and 49 CFR 393.86. None None
Burner Gas or liquid fueled burner for heating product in the tank. None None
Cap, Dust Cover which mates with a male adapter. None dustcap001.jpg,dustcap002.jpg,dustcap003.jpg
Cap, Pipe A cap which mates with the male threads of a pipe and which forms a liquidtight seal. None None
Capacity, Commodity Total internal volume that does not include planned outage. None None
Capacity, Nominal That compartmental volume to which a vessel is designed that does not include the planned stage. None None
Capacity, Shell The absolute full capacity of a tank shell. None None
Certification, Design See 49 CFR 178.320 (a). None None
CFR Acronym for Code of Federal Regulations. None None
Christmas Tree See Vent. None None
Combination Vehicle An equipment configuration which includes separate power unit (tractor) and at least one trailer. None None
Cock, Shut-Off A device used to restrict or stop flow of air or liquid. None None
Compartment, Tank The product carrying space of a tank motor vehicle. A cargo tank motor vehicle may have one or more such spaces. (See Tank, Cargo) None None
Compartment, Void See Void Compartment. None None
Connection, Air Fitting used to apply air pressure from source to vessel. None None
Connection, Loading/Unloading See 49 CFR 178.345-1 (c). None None
Coupling, Pipe See 49 CFR 178.345-1 (c). None None
Coupler, Cam & Groove The female portion of a quick coupling device for pipe or hose ends. None None
Dam, Manhole See Manhole, Dam None None
Deflector A device placed inside a tank to change the flow direction during loading or unloading. None None
Degas To purge compartments, voids, piping and components of dangerous vapors rendering the cargo tank safe for both hot and cold work. None None
Dip Stick A separate measuring device used to determine the level of product in a tank. None None
Dip Tube (1) A piping arrangement installed in a tank which will be pressure unloaded out of the top. (2) May also be a tube installed in a pressurized containers to gage the level of liquid. None None
DOT Abbreviation for Department of Transportation. None None
DOT Specification See Specification, MC/DOT. None None
Doubler Plate A reinforcing pad, ring, collar or strap used to reinforce the shell or head. None None
Drain A hole, pipe of hose used to gravity discharge liquid from an enclosed area such as a void, void compartment or manhole dam. None None
Drain, Flashing See Flashing Drain. None None
Emergency Valve See Valve, Emergency. None None
Engineer, Design Certifying See 49 CFR 171.8. None None
Fill Cover, Spring Loaded A fill cover designed to meet the requirements for the pressure-actuated vent in MC 306 cargo tanks, 49 Code of Federal Regulations, 178.341-4 (d) (2) and DOT 406 cargo tanks, 49 Code of Federal Regulations, 178.346-10 (d). None None
Fill Opening An opening in top of a tank used for filling the tank. Usually incorporated in Manhole Cover. It may also be used for inspection. None None
Fire Tube See Heating Tube. None None
Fitting, Clean Out Fitting installed in the top of a tank to facilitate washing of the tank interior. None None
Fitting Guard A structure to protect pipe fittings from damage. None None
Fitting, Terminal The end fitting on a line. None None
Flange See 49 CFR 178.345-1 (c). None None
Flange, Companion See 49 CFR 178.345-1 (c). None None
Flange, Welded See 49 CFR 178.345-1 (c). None None
Flash Point Means the temperature at which the substance gives off flammable vapors which, in contact with a spark of flame, will ignite. None None
Flashing Liquidtight rail on top of a tank which contains water and spillage and directs it to suitable drains, and may be combined with the overturn protection. None None
Flashing Drain Metal or plastic tube which drains water and spillage from flashing to the ground. None None
Float Control A switching device which opens a circuit when product being loaded into a tank reaches a pre-determined level. None None
FMCSA Acronym that stands for Federal Motor Carrier Safety Administration None None
Gas Free See Degas. None None
Gauge, Liquid Level A device used to measure liquid commodity levels inside a cargo tank. None None
Gauge, Rotary A gauge for determining the liquid level in a pressurized tank. None None
Girth Seam (A Circumferential Joint) A welded joint around the entire circumference or partially around the circumference of the cargo tank joining two sections of the tank shell. None None
Head (1) See Bulkhead, Tank. (2) Also terminology for pressure of a liquid caused by its own weight. None None
Head, Hemispherical A head which is half a sphere in shape. Often used on MC 331 compressed gas cargo tanks and MC 338 cryogenic liquid cargo tanks. None None
Header A pipe, tube, etc., that connects two or more pipes or tubes permitting the transfer of vapors or liquids to a common outlet. (Also see Manifold). None None
Heat Panel A panel attached to the cargo tank's shell by welding, bonding or banding used to heat the contents. May also be called steam panel. None None
Heating Tube A tube installed inside a tank which is used to heat the contents. May also be called "fire tube" when the direct heat source is a flame. None None
Hood, Vapor Recovery A collecting device installed over tank vents or vapor valves for transfer of vapors during tank loading or unloading. None None
Hose, Air Jumper Hose connecting the truck tractor air supply to a trailer air line or hose. None None
Hose Carrier Hose tube, hose trough, hose tube ends and hooks, mandrel and bracket. None None
Hose, Discharge Hose used to unload the tank. None None
Hose Hooks Hooks which carry the hose. None None
Hose Trough An open type structure used on tank and bulk commodity trailers for the storage of cargo handling hoses. None None
Hose Tube A housing used on tank and bulk commodity trailers for the storage of cargo handling hoses. None None
Indicator, Liquid Level A device, usually a float or spew gauge, for determining the level of the product in a tank. None None
Indicators, Capacity Device installed on tank to indicate capacity at a specific level. (Sometimes called markers). None None
Inspector, Registered See 49 CFR 171.8. None None
Interlock, Parking See Brake Interlock, Parking None None
Jacket A metal cover which protects the tank insulation. None None
Lading, Hazardous See 49 CFR 178.345-1 (c). None None
Line, Blowdown A line through which tank air pressure is released by means of the blowdown valve. None None
Line Charging See 49 CFR 178.345-1 (c). None None
Line Crossover Installed in tank piping system to allow unloading from either side of tank. None None
Line, Pipe A product inlet or outlet line. None None
Line, Pump Off A pipeline which usually runs from the tank discharge openings to the front of the trailer. Most pumps are mounted on the tractor. None None
Line, Vapor Recovery A line which connects the vapor recovery hood to a convenient location for attachment to a vapor recovery hose. None None
Lining The material applied to the inside of a tank shell surface to protect the tank shell from its contents. None None
Manhole An opening usually equipped with removable cover and large enough to admit a man into a cargo tank or dry bulk trailer; may incorporate vents, fill opening and other devices. None None
Manhole, Dam Liquid tight box for the collection of spillage (also called spill box, flashing box or crows nest). None None
Manifold Used to join a number of pipelines to a common inlet or outlet. (Also see Header). None manifold001.jpg,manifold002.jpg,manifold003.jpg
MAWP See Pressure, Maximum Allowable Working. None None
Modification See 49 CFR 180.403. None None
Nameplate The NHTSA certification label containing the manufacturerxD5s name and vehicle identification number or for cargo tank vehicles manufactured prior to the NHTSA certification plate containing the manufacturer's name and cargo tank serial number. (See Plate, MC/DOT) None None
Nozzle, Tank See 49 CFR 178.345-1 (c). The pipe or tubular section of the nozzle is short and may be threaded instead of flanged. None None
Outage The space that remains unfilled in a cargo tank after being loaded with payload. None None
Outlet See 49 CFR 178.345-1 (c). None None
Outlet, Loading/Unloading See 49 CFR 178.345-1 (c). None None
Outlet, Vapor The terminus of the vapor recovery line. None None
Outrigger Structural load-carrying members attached to and extending outward from the main longitudinal frame members of a tank trailer, which cradle the tank shell or stiffeners. Sometimes called Cradle End. None None
Overturn Protection Protection for fittings on top of a tank in case of rollover. May be combined with flashing rail or manhole dam. Also known as Rollover Damage Protection. See 178.345-8 (c) for DOT 400 Series cargo tanks. None None
Pads A piece of material attached to the tank shall to which various attachments are made. None None
Pipe See Line, Pipe. None None
Plate, MC/DOT Tank Certification (As required by the Research and Special Programs Administration) Metal plate permanently affixed to a cargo tank and located near the front left side of the cargo tank stating that the cargo tank conforms with all applicable Federal Hazardous Materials Regulations in effect on the date of the original manufacture or modification. None None
Platform Area on top of the tank near the manhole designed for a person to stand upon. None None
Protection, Bottom Damage Device which protects outlets and piping located in the lower one-third of the cross section perimeter from damage during an accident. See 178.345-8 (b) for DOT 400 series cargo tanks. None None
Protection Device, Rear-End Tank See 49 CFR 178.345-1 (c). (Also see Bumper, Rear). None None
Protection Overturn See Overturn Protection. None None
PSIA Pressure expressed in pounds per square inch absolute. Add approximately 14.7 to gauge reading to give absolute reading. None None
PSIG Pressure expressed in pounds per square inch gauge. Gauge pressure is the difference between atmospheric pressure and pressure being measured. None None
PTO Abbreviation for Power Take Off. None None
Rebarrelling See 49 CFR 180.403. None None
Repair See 49 CFR 180.403 None None
Replacement Barrel To completely replace the vessel weldment of an existing cargo tank with a newly manufactured vessel weldment using only new materials. None None
Ring Stiffener Structure encircling the tank either inside or outside the tank shell to maintain the shape of the tank and its structural stiffness when under pressure/vacuum. None None
Rollover Protection See Overturn Protection None None
RP Abbreviation for Recommended Practice. None None
Rupture Disc (A frangible vent) A safety device which fails at a predetermined pressure and thus protects a pressure vessel from being over pressurized. (Also see Vent). None None
Sacrificial Device See 49 CFR 178.345-1 (c). (Also see Shear Section). None None
Seam, Girth See Girth Seam. None None
Sensor, High Level A liquid actuated sensor installed in a secondary shut-off system. Also, this sensor is sometimes used as a primary shut-off system. The signal from this sensor stops the loading pumps or closes the emergency valve upon overfill. (See Shutoff System, Secondary). None None
Sensor, Liquid Level See Indicator, Liquid Level. None None
Sensor, Retained A liquid actuated sensor installed in the bottom of a compartment to indicated the presence of liquid. None None
Shear Section, DOT 400 Series Cargo Tanks See 49 CFR 178.345-1 (c). (Also see Sacrificial Device). None None
Shear Section, MC 300 Series Cargo Tanks A machine groove located outboard of an emergency valve seat and within 4 inches of the vessel which should break under strain and leave the emergency valve seat and its attachment to the vessel and the valve head intact and capable of retaining product. None None
Shell, Tank See 49 CFR 178.345-1 (c). None None
Shutoff System, Secondary A system that provides overflow protection during bottom loading. None None
Splash Guard A device which deflects road spray. None None
Stack The exhaust pipe for tanks with burners. None None
Steam Panel See Heat Panel. None None
Stick, Dip See Dip Stick. None None
Stiffener, Ring See Ring Stiffener. None None
Stretching See 49 CFR 180.403. None None
Structure, Connecting See 49 CFR 178.345-1 (c). None None
Subframe The frame to which the undercarriage is attached. None None
Sump See 49 CFR 178.345.1 (c). None None
Sump, Cleanout The low point of a tank which may be opened for cleaning. None None
Swivel Joint A movable metallic product transfer conductor usually used on discharge lines to eliminate the bending or twisting of hoses. None None
Tank Design Type See 49 CFR 178.320 (a). None None
Tank, DOT 406 Tank built after October 1, 1990, meeting US DOT specifications DOT 406 as defined in 49 Code of Federal Regulations 178.346. This tank is typically used to carry gasoline, fuel oil, alcohol, or other liquid flammables. This tank is typically constructed of aluminum and designed with an elliptical cross section. None None
Tank, DOT 407 Tank built after October 1, 1990, meeting US DOT specifications DOT 407 as defined in 49 Code of Federal Regulations 178.347. This tank is typically used to carry solvents, plasticizers, casinghead, gas, etc. This tank is typically constructed of stainless steel or aluminum and designed for pressure of at least 25 psig. None None
Tank, DOT 412 Tank built after October 1, 1990, meeting US DOT specifications DOT 412 as defined in 49 Code of Federal Regulations 178.348. This tank is typically used to carry corrosives. This tank is typically constructed of stainless steel or carbon steel and designed for a pressure of 35 psig. None None
Tank, MC 304 Tank built prior to December 1, 1967 to old US DOT Specifications MC 304 for the transportation of flammable liquids or poisonous liquids. This tank was constructed of steel and aluminum with a design pressure of at least 25 psig. This tank is a predecessor of the MC 307 tank. None None
Tank, MC 305 Tank built prior to December 1, 1967 to old US DOT Specification MC 305 for the transportation of flammable liquids or poisonous liquids. This tank was constructed of aluminum and designed for atmospheric pressure. This tank is a predecessor of the MC 306 tank. None None
Tank, MC 306 Tank built after December 1, 1967 and prior to April 21, 1994, meeting US DOT Specification MC 306 as defined in 49 Code of Federal Regulations 178.341. This tank is typically used to carry gasoline, fuel oil, alcohol, or other liquid flammables. This tank is typically constructed of aluminum and designed for atmospheric pressure. This tank is a predecessor of the DOT 406 cargo tank. None None
Tank, MC 307 Tank built after December 1, 1967 and prior to April 21, 1994, meeting US DOT Specification MC 307 as defined in Code of Federal Regulations 178.342. This tank is typically used to carry solvents, plasticizers, casinghead gas, etc. This tank is typically constructed of stainless steel and designed for a pressure of at least 25 psig. This tank is a predecessor of the DOT 407 cargo tank. None None
Tank, MC 311 Tank built prior to December 1, 1967 to old US DOT Specification MC 311 for the transportation of corrosives. This tank was constructed of steel or aluminum. This tank is a predecessor of the MC 312 tank. None None
Tank, MC 312 Tank built after December 1, 1967 and prior to April 21, 1994, meeting US DOT Specification MC 312 as defined in 49 Code of Federal Regulations 178.343. This tank is typically used to carry corrosives. This tank is typically constructed of stainless steel of carbon steel and designed for a pressure of 35 psig. This tank is a predecessor of the DOT 412 cargo tank. None None
Tank, MC 330 Tank built prior to December 1, 1967 to old US DOT Specification MC 330 for the transportation of compressed gases. This tank was typically constructed of quenched and tempered or carbon steel for a pressure of 250 to 265 psig. This tank is a predecessor of the MC 331 tank. None None
Tank, MC 331 Tank meeting US DOT Specification MC 331 as defined in 49 Code of Federal Regulations 178.337. This tank typically used to carry anhydrous ammonia, propane, or other liquefied or pressurized gases. This tank is typically constructed of quenched and tempered or carbon steel and designed for a pressure of 265 psig. None None
Tank, MC 338 Tank built after October 1, 1984, meeting US DOT Specification MC 338 as defined in 49 Code of Federal Regulations 178.338. This tank is insulated and designed to carry cryogenic liquids. None None
Tank, Self Supporting A tank trailer whose shell is the structural support member for the vehicle. None None
Tank, Vacuum Tank equipped with a pump to reduce the pressure in the tank to much less than atmospheric pressure. This reduced pressure of vacuum is used for loading the tank. (See Tank, Waste). Also see 49 CFR 178.345-1 (c). None None
Tank, Washout A tank holding solvent for cleaning pump and discharge hose. None None
Tube, Dip See Dip Tube. None None
Valve, Blow Down A manually operated valve whose function is to quickly reduce tank pressure to atmospheric. None None
Valve Box See Fitting Guard. None None
Valve Check A valve built to provide free fluid flow in one direction only. None None
Valve, Crossover A valve which allows the discharge to be directed to either side of the tank via the crossover line. None None
Valve, Emergency A remote controllable valve installed in a tank outlet sump or its companion flange which is capable of self-closing in the event of an emergency. Also known as Valve, Internal Self-Closing Stop. None None
Valve, Emergency, Operator A device used to open and close emergency valves. None None
Valve, Emergency, Remote Control A secondary closing means, remote from tank discharge openings, for operation in event of fire or other accident. None None
Valve, Excess Flow A valve which automatically closes at its rated flow of gas or liquid. None None
Valve, Internal See Valve, Emergency. None None
Valve, Internal Self-Closing Stop See 49 CFR 178.345-1 (c). Also known as Valve, Emergency. None None
Valve, Loading/Unloading Stop See 49 CFR 178.345-1 (c). None None
Valve, Outlet The valve which is farthest downstream in a tank piping system to which the discharge hose is attached. None None
Valve, Outlet Stop See 49 CFR 178.345-1 (c). None None
Valve, Pressure Relief Valve with predetermined start to discharge pressure to protect the tank from being over-pressurized. (Also see Vent, Pressure Actuated). None None
Valve, Product Valve for holding or releasing product into or out of the tank. None None
Valve, Pump Off Valve on pump-off line which when open allows the product to be pumped out of the tank. None None
Valve, Self-Closing Stop See 49 CFR 178.345-1 (c). None None
Valve, Self Contained Shut Off An emergency valve that closes upon receiving a signal from the high level sensor. None None
Valve, Splitter A valve installed to divide pipeline manifold. None None
Valve, Stop See 49 CFR 178.345-1 (c). None None
Valve, Vapor Recovery (See Vent, Vapor Recovery) A valve typically found in a vapor recovery system to control the flow of vapors. Also a vent that opens and closes with the actuation of the emergency valve permitting the transfer of vapors when in the open position. (Typically opens inward into the tank compartment). None None
Valve, Y A valve which can be used for both bottom loading and off-loading. Incorporates American Petroleum Institute standard adapter. None yvalve001.jpg,yvalve002.PNG
Vapor Free See Degas. None None
Vehicle, Cargo Tank Motor See 49 CFR 171.8 and 49 CFR 178.320 (a). None None
Vehicle Assembly, Cargo Tank Motor See 49 CFR 107.502. None None
Vehicle, Multi-Specification Cargo Tank Motor See 49 CFR 178.345-1 (c). None None
Vent Devices which control or limit tank pressure. Some type are: 1. Outbreathing (pressure relief) 2. Inbreathing (vacuum relief) 3. Fusible (opens at elevated temperature) 4. Christmas tree (slang for a combination vent) 5. Rupture disc ( See Rupture Disc) None None
Vent, Overflow Vent on hot products tanks for overflow of product due to surge and/or expansion. None None
Vent, Pressure Actuated A normally-closed, spring-loaded vent for pressure protection. Required on MC 306 cargo tanks, 49 Code of Federal Regulations, 178.341-4-(d); MC 307 cargo tanks, 178.342.4 (c); MC 312 cargo tanks, 178.343-4 (a); DOT 406 cargo tanks, 178.346-10 (d); DOT 407 cargo tanks, 178.347-10 (d); and DOT 412 cargo tanks, 178.348-10 (d). None None
Vent, Vacuum Breaker A spring-loaded normally closed vent for vacuum protection. None girard_vacuum_vent.jpg
Vent, Vapor Recovery A vent that opens and closes with the actuation of the emergency valve permitting the transfer of vapors when in the open position. (Typically opens outward from the tank compartment). None None
Vents, Normal A pressure-vacuum vent specified in 49 Code of Federal Regulations, 178.341-4 (b) and (c) and required in each MC 306 compartment and may be installed in each DOT 406 cargo tank. None betts_normal_vent.jpeg
Void An enclosed space in a vessel which does not contain product and has no manhole. Also see 49 CFR 178.345-1 (c). None None
Void Compartment A void equipped with access manhole. None None
Walkway That portion top of a tank designed for personnel to walk on. None None
Wall, Cargo Tank See 49 CFR 178.320 (a). None None
Weight per Gallon, Allowable The maximum density, as pounds per gallon, of products which be loaded into a given tank without exceeding the load limits of the tank container or tank trailer. None None
Weldment, Vessel The entire tank vessel and welded appurtenances such as nozzles, manholes, flanged and threaded fittings, etc. Bolted-on appurtenances are not included. None None
Fusible Plug A fusible plug device is a nonreclosing pressure relief device designed to function by the yielding or melting of a plug. These are typically 1/8", made of brass, and used in air or hydraulic systems as a thermal protection device. It can be installed in emergency valves, air actuators, or tied in with any air or hydraulic system. If the fusible plug is subjected to temperatures in the range of 200 to 250 Fahrenheit, the solder will melt and relieve line pressure to facilitate closing of emergency valves and vapour recovery valves. None fusible_plug.jpg
Frangible Device None None fusible-frangible.jpg
Appurtenance (CSA B620) Any tank part or accessory that has no product containment function and provides no structural support to the tank. None None
Assembler In CSA B620, an assembler is a legal entity registered by Transport Canada for the assembly of highway or portable tanks. CSA B620:20 None
Assembly In CSA B620, assembly is a portion of the fabrication process of a highway or portable tank that does not involve welding on the tank wall, on integral structural components of the tank such as the rollover dam, tank sill or baffles, and on any components such as piping that contain lading. Assembly includes any of the following functions that are necessary to meet the specification requirements prior to the certification of a highway or portable tank: a) the fabrication and installation of component parts of a highway or portable tank; and b) the mounting of one or more tanks onto a vehicle chassis or onto a vehicle suspension component. CSA B620:20 None
Attachment In CSA B620, attachment is any part or device attached to the tank or mounting pad, including structural supports to the tank. CSA B620:20 None
Baffle In CSA B620, a baffle is a non-liquidtight transverse partition device that deflects, checks, or regulates fluid motion in a tank, and that can also provide circumferential reinforcement. The transverse partition has at least one opening that allows, at minimum, the equivalent maximum loading or unloading flowrate to pass from one side to another. CSA B620:20 None
Brazer In CSA B620, a brazer is a person who performs manual and semiautomatic brazing and is qualified in accordance with Clause 4.4. CSA B620:20 None
Brazing Operator In CSA B620, a brazing operator is a person who operates machine or automatic brazing equipment and is qualified in accordance with Clause 4.4. CSA B620:20 None
Bulkhead (CSA B620) In CSA B620, a bulkhead is a liquidtight transverse closure at the ends of or between tanks. CSA B620:20 None
Companion Flange In CSA B620, a companion flange is one of two mating flanges where the flange faces are in contact or separated only by a thin leak-sealing gasket and are secured to one another by bolts or clamps. CSA B620:20 None
Coating In CSA B620, a coating is a material applied and used on the interior wall of a tank, partially or completely, to protect the tank material from being corroded or abraded and that after application is substantially immune to attack by the lading. Note: A coating does not affect the ability of the tank to contain lading and can be removed or changed, at the discretion of the owner. CSA B620:20 None
Connecting Structure In CSA B620, a connecting structure is the structure joining two tanks in a multi-tank vehicle. CSA B620:20 None
Vacuum Stiffener Ring Rings made of flat bar or plate, or structural shapes welded around the circumference of the vessel. These rings are installed on vessels operating under external pressure to prevent collapse of the vessel. Also used as insulation support rings. CSA B620:20 None