Best Practices for Leak Prevention During Tank Car Loading and Unloading

Following these guidelines can help plant personnel eliminate non-accident releases while loading and unloading tank cars.

This guide is intended to assist shippers and receivers of hazardous materials in reducing NARs (non-accident releases) by outlining the recommended methods for the safe loading and unloading of non-pressure, general service, and pressure tanker tuck cars.

Due to improved equipment efforts of government regulators, shippers, and rail carriers, 99.997% of hazardous materials are loaded, shipped, transported, and unloaded safely. However, sometimes hazardous leaks still do occur during normal transportation.

While the amount of product released in an NAR may be small, the consequences of just one of these leaks can be significant:

  • Railroad and industry employees can be injured from exposure to an NAR of hazardous materials.
  • Shipments can be delayed while the car is secured.
  • Local communities may have to expend resources to respond.
  • Railyards may be shut down.
  • Shippers can be fined.
  • Product may become contaminated.
Non-accident releases (NARs) are hazardous leaks that occur during normal transportation.

Most NARs are small and the quantity released is generally limited.

The majority of these leaks can be prevented by educating employees about the effects of NARs, and by using proper loading/unloading and maintenance procedures. The safe transportation of hazardous materials involves the cooperation and collaboration of all involved. It takes proper preparation and correct handling to get a shipment from origin to destination safely and without incident.

This guide is comprised of three main sections:

  1. Recommended practices applicable to all types of tank cars.
  2. Proper securement practices for general service tank cars.
  3. Proper securement practices for pressure tank cars.

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Recommendations for Tank Car Loading.

To ensure safe operations prior to tank car loading or unloading:

  1. Put up a caution sign, commonly known as a blue flag. If the car can be approached from either direction, be sure to put a sign up at both ends.
  2. Prevent entry into the track by locking the switch and/or door locking derail.
  3. Check the hand brakes to make certain they have been applied. Do not assume that someone else has set them.
  4. Chock wheels in both directions.
  5. Verify that safety equipment such as safety showers and eyewash stations are present and operational before conducting loading/unloading activities.
  6. Ensure that proper tools are used for loading and unloading operations. They must be clean and in proper condition at all times.


Tank car tanks containing flammable or combustible gases or liquids should be electrically grounded and bonded during loading and unloading operations. A good safety practice is to check the continuity of the ground prior to loading or unloading.

truck grounding system as liquid being loaded

The loading/unloading area should have adequate lighting and be free of obstacles or unnecessary equipment. Before shipment, the condition of every tank car must be examined. A tank car cannot be offered for transportation if it contains a hazardous material, including a residue, unless it is determined that the tank car is in proper condition for safe transportation.

Prior to loading or unloading, conduct the following inspections of the car:

  • Examine the safety appliances, which include the steps, grab irons, ladders, and platforms, to ensure that none are broken, loose, or missing.
  • Look under the car to make sure that the break rigging is not broken.
  • Look at the end cap and be certain all three bolts are in place and secured with a tab to prevent movement.
  • Inspect the trucks and couplers to make certain there are no visible defects. Keep in mind that tank cars must be equipped with double shelf couplers.
  • Before loading/unloading, inspect the car for damage and the presence of a defect card. If either is found, contact the car owner for further instructions before loading.
  • Examine the tank shell and heads for defects such as dents, cracks, and evidence of leaks. The jacket on a tank car should not be torn or have significant damage.
  • Check all piping, valves, fittings, and gaskets, including those not used, for evidence of leaks or corrosion.
  • Look for missing or loose bolts.
  • Examine the pressure relief device, including any frangible disc, to ensure it is present and there is no sign of leakage.
  • Make certain there is no debris such as old seals in the safety valve.
  • If the safety device is a combination safety valve and ruptured disc, open the telltale to check that the rupture disk has not failed.

Qualification via Stenciling and Markings

Be sure to check all required markings and stenciling so they are legible and the qualification date marking is current. Verify that the tank car is a CTC, AAR, DOT, or TC specification tank, and is compatible with the product.

Also, check that the tank car linings, coatings, or material are compatible with the commodity being transported. Some types of hazardous materials require special protective features. For example, Flammable Gases (Division 2.1) must be shipped in tank cars that have heat shields and thermal protection. Some class A materials, such as acid,s must be shipped in tank cars that have a certain lining or coating. Know if your materials have any special requirements and are certain to check the stenciling to make certain your car meets these requirements.

In addition, all tank cars must be qualified periodically. The qualification stencil will show when inspections were done, what type of pressure relief device the car is equipped with, any lining or coating the car has, and when qualification is due. The date each was completed and the due date are stenciled on the tank car. Check the stencils prior to loading to make certain the tank car has not exceeded any of the stencil due dates.

Tank cars with a safety vent ruptured disc will be stenciled with the burst pressure of the rupture disk and may be stenciled not for flammable liquids, or not for flammable or poisonous liquids. When the rupture disk is examined, make certain it is marked with a burst pressure rating that matches the safety vent burst pressure stencil on the tank car. The proper shipping name must be marked on two sides in lettering that is at least 3.9 in. high for all commodities listed in 49 CFR section 172.330 A12. This includes all flammable gases, poison gases, and certain other high hazard materials. Tank cars containing poison or toxic inhalation hazard material must be marked in inhalation hazard on both sides in lettering that is at least 3.9 in. high unless the words in inhalation hazard appear on the placards displayed on the tank car.

Examining Tank Car rupture disk
the placard must be readily visible from the direction it faces and be displayed on both sides and both ends of the railcar

On tank cars, the identification numbers must be displayed on an orange panel, on a white square-on-point display, or on a placard. A square-on-point configuration is a white card the same size as a placard with the ID number 3.5 inches high in the center. Most commonly, the identification number is displayed on a placard with the ID number 3.5 inches high in the center.


A hazardous material placard must be readily visible from the direction it faces and be displayed on both sides and both ends of the railcar. It must be securely attached or placed in a holder, be displayed so that the words or identification number read horizontally from left to right, be located clear of appurtenances, such as ladders. It must also be located so that dirt and water cannot be thrown upon it, and be in an area to be maintained so that its color, format, legibility, and visibility are not substantially reduced.

When Time to Load/Unload

When loading a tank car be certain to;

  1. Leave proper outage, recognizing how much outage is required for the material and the tank.
  2. Use the appropriate outage chart when loading compressed gases in a tank car.
  3. Do not overload by weight or volume.
  4. Monitor the car to make certain nothing is leaking.

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If you are needing to discontinue operation for a period of time, make sure all valves are closed, all connections are removed, and the car is prepared as if ready for transportation. However, operations can be discontinued on an attended or monitored car by closing valves on the car and at the facility without disconnecting hoses.

Prior to releasing the car, check that it is not overloaded, and ensure all fittings — including those not used — are properly closed. All caps and/or plugs must be in place and properly tightened by the proper tool and attached by a cable or chain to prevent misplacement. Verify that protective covers are closed and secure and the covers for openings are in the closed position. Also, check to ensure caps for interior heater coil inlet outlet pipes are on the pipes.

Enter an issue with a car that will require the shipper or car owner to get a one-time movement approval from the Federal Railroad Administration before the tank car can travel. Some examples would be a hole in a tank car jacket or a liquid valve that was repaired and needs a bubble leak test. Remember that any defects must be corrected prior to the shipment of the tank car. Notify the railroad of any defects found in safety appliances or running gear prior to the release of the tank car.

General Service Tank Cars

General service tank cars are used to transport liquids or flowable solids. The valves and fittings on most general service tank cars are visible on the top.

General service fittings may include the following:

  • Bottom outlets
  • Internal or external heater coil systems
  • Top valves and fittings
  • Top operated bottom outlets
  • Manways
  • Pressure relief devices, including safety valves and safety vents

Bottom outlets can be operated either from the bottom or the top of the tank car. Both types of bottom outlets must be checked to make sure they operate properly and are not leaking prior to loading. A recommended practice is to remove the bottom outlet cap or plug during loading. Make certain the outlet valve is closed and any auxiliary valves are open while loading.

Prior to removing the cap or plug, make sure car is positioned over railcar track pan or put a bucket or spill pad down to catch any spillage and check that there is no leakage through the valve. Check that the bottom outlet cap and door plug are attached to the car by a chain or cable to prevent misplacement of the cap or plug. Then, examine the condition of the gasket in the outlet cap and the threads on the outlet cap and plug. Make certain there are no leaks when finished loading or unloading. And be certain the operating handle is secured in the closed position.

spill containment Emergency Spill Response Plan

When a car is equipped with a top operated bottom outlet, be certain to loosen the packing nut prior to operating the valve. When finished, secure the packing nut to prevent any leakage. The operating handle must be attached to a chain or cable to prevent misplacement, again making certain the outlet is closed and the operating handle has been secured prior to shipping the tank car. If the tank car is equipped with interior heater coils, they must be checked for leakage during loading. A good way to test is to leave the outlet caps off the heater pipes and watch for leakage through the pipes.

After the car is loaded, secure the heater coil caps on the pipes to prevent a leak in case a heater coil fails in transit. Do not overheat the car and check for steam leaks from the coils. Examples of top valves and fittings include, liquid valves, vapor valves, vacuum relief valves, and safety valves. Check all top valves for operation, including valves and fittings you do not use. Examine valves for evidence of leaking through the plug where the valve attaches to the car and/or through the valve stem.

All valves must be closed when the car is shipped and the closures should be tightened, including fittings you don’t use at your location. Listen to vacuum relief valves for evidence they are not closing properly, as they may be allowing vapors to escape.

Never use a vacuum relief device to relieve pressure in a tank car. When the top valves are not under a protective cover, handles for the valves must be removed. All protective covers must be pinned in a closed position during transportation. Be certain the pin is not damaged and will stay in place.

Manway Gaskets

Failure of manway gaskets is a significant source of leaks in transportation.

Manway gaskets must be inspected for condition, positioning, and compatibility with the material in the tank car. They should stay in place when manways are opened. If a manway gasket does not stay open, it could be the wrong size and may slip out of position when the manway is closed.

Inspect manway gasket surfaces and bolts for damaged or bent bolts, bad threads, or bad washers that would prevent the proper closure of the manway. If there is extensive dirt or rust on the bolt, use an appropriate lubricant. Manway bolts must be tightened in a star pattern to ensure that the manway is evenly tightened and the gasket has a good seal.

All bolts must be tool tight when finished. When tightening manway bolts, use a torque wrench to achieve uniform tightness. Contact the car owner for proper manway torquing values for the type of gasket being used.

During unloading, the tank car must be vented either by use of a closed system or to the atmosphere. Do not rely on the vacuum relief valve. When a tank car is equipped with a safety vent, check both sides of the rupture disc for damage. Prior to shipment of the tank car, verify that closures are secure and not leaking by either doing a pressure test or by holding the car for 24 hours, then reinspecting the car.

Pressure Tank Cars

Pressure tank cars are used for compressed gases and certain high hazard materials. They differ visually from most of the general service cars, as the valves and fittings are mounted on the top of the tank car in a protective housing and are not visible.

Pressure car fittings may include:

  • Liquid and vapor valves
  • Gauging devices
  • Sample lines
  • Thermometer wells
  • Safety valves and regulating valves

Safety Features of the DOT Specification 117 Tank Car

  • Full-height 1/2 inch thick head shield
  • Tank shell thickness increased to 9/16 in. minimum TC-128 Grade B, normalized steel
  • Thermal protection
  • Minimum 11-gauge jacket
  • Top fittings protection
  • Enhanced bottom outlet handle design to prevent unintended actuation during a train accident

Examine the base of the valves, the closure plugs, and valve stem seals of each valve on pressure cars for leakage. Plugs other than quarter-inch plugs in sample lines and gauging devices must be attached to a cable or chain to prevent misplacement. On magnetic gauging devices, examine the rod for a commodity name. If one is present, ask if it is appropriate for the material the cars are carrying. Thermometer wells and magnetic gauging devices have an o-ring that must be inspected. If there is a problem with either of these, the o-ring is a failsafe that prevents material from escaping.

The cover on thermometer wells and magnetic gauging devices are intended to be hand tightened. Do not overtighten these covers with a tool, as it will damage the o-ring. Check sample lines to ensure that they are closed and the plug is tight. Check for leaks at the base of the sample lines. The protective covers must be secured in a closed position. The access ports in the housings must have covers that are closed. Prior to shipment of the tank car, verify that closures are secure and not leaking by either doing a pressure test or by holding the car for 24 hours then reinspecting the car.


Examine the condition of the tank car and fittings, making certain that all fittings, including those not used, are secure and not leaking. Properly close and secure all fittings and protective covers including the ones you did not use. Check the condition of the stenciling and pay close attention to due dates and commodity stencils. Do not overload by weight or volume. Make sure the placards and markings are correct and in good condition. And remember to always use a checklist to ensure that all components are checked and in good order.

According to DOT regulations, if a tank car leaks in transit during normal rail operations, it is assumed the car was not properly prepared and inspected prior to being released for transportation. Not only may the shipper be liable for all costs associated with the response and cleanup, but they can also be subject to penalties for failure to comply with the requirements.


For further information, please refer to the US Department of Transportation requirements found in 49 CFR, sections 173.31 and 174.67 of the hazardous material regulations. In Canada, these requirements are found in Canadian General Standards Board 43.147 Part IV – Sections 30.14 through 30.17, as referenced in the Canadian Transport Dangerous Goods Regulations. The Association of American Railroads Manual of standards and recommended practices M – 1002 contains information on authorized valves and fittings and maintenance requirements.

For further information on loading and unloading of tank cars, review the Bureau of Explosives pamphlet 34 contained in the BOE tariff or available at the NAR website at You can also contact the loading and unloading specialists at for more information on how to improve processes and safely load and unload your materials before and after transportation.