Methods for the Safe Loading and Unloading of Non-Pressure and Pressure Tank Cars

From Pamphlet 34 – January 18, 2013 []


This document presents general guidelines for the selection of tank cars and recommended procedures for loading and unloading of the cars. It is not a complete and comprehensive set of methods, instructions or procedures applicable for all situations and car types. Each user company is encouraged to develop specific procedures using this document as a general guide where it applies. A particular location may require the use of additional or different precautions for the loading or unloading operations to be performed safely. Appropriate individual company procedures and applicable government requirements, including U.S. Department of Transportation (DOT) Hazardous Materials or Transport Canada (TC) Transportation of Dangerous Goods regulations, must be followed.

All repairs must be performed by properly Certified or Registered Tank Car Facilities. Experienced, trained personnel who are knowledgeable of the safety requirements and loading/unloading operations must be used. For loading and unloading of Hazardous Materials/Dangerous Goods, these knowledgeable persons must be designated as and trained as “HazMat”/or qualified employees per government regulations. Loading/ unloading personnel must be responsible for compliance with all company procedures and regulatory requirements during the complete operation. See regulatory references at the end of this document.

CAUTION: Since the loading and unloading of tank cars involve the opening of valves, fittings, flanges, caps, plugs and other closures there is always a possibility of product spillage or leakage. While this should be minimized the loader/unloader must be prepared to capture, collect and dispose of any spilled or leaked product in an environmentally-acceptable manner.

Appropriate Personal Protective Equipment (PPE) should be worn throughout the loading or unloading procedure.

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Section 1: General Instructions for Loading and Unloading
1.1The car must have the hand brakes set and the wheel(s) blocked against
movement before any loading/unloading activities are started.
1.2When the car is positioned for loading or unloading, securely block access
to the track by use of derails, aligned and locked switches, bumper blocks or
other such apparatus.
1.3While a car is connected for loading/unloading, blue caution signs
(sometimes known as “blue flags”) must be placed on the track as required
by regulations and company procedures.
1.4Before loading/unloading, inspect the car for damage. If found, contact the
car owner for further instructions before loading.
1.5Safety equipment such as safety showers and eye wash stations should be
verified to be present and operational before conducting loading/unloading
1.6Proper tools should be used for loading/unloading operations. They must
be clean and in proper condition at all times.
1.7Tank car tanks containing flammable or combustible gases or liquids should
be electrically grounded and bonded during loading and unloading
operations. Grounding and bonding of cars carrying other commodities is
also encouraged.
1.8All loading/unloading inspections should be properly documented through a
check list or similar method.
1.9The loading/unloading area should have adequate lighting and be free of
obstacles or unnecessary equipment.
1.10During the loading/unloading process, cars must be attended by trained
personnel or monitored by an approved monitoring system. Do not allow
the loading/unloading operation to stand unattended or unmonitored while
connections are attached to the car. If necessary to discontinue operations
for a period of time, all valves must be closed, all connections removed and
the car must be prepared as if ready for transportation. However,
operations can be discontinued on an attended or monitored car by closing
valves on the car and closing valves at the facility without disconnecting
1.11When operating gauging devices, top operated bottom outlet valves, or any
other top fittings or closures, loaders/unloaders should not:


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1.11.1         Stand directly above or place any part of their body directly above the gauging device, valve, fitting, or closure.


NOTE: An excess flow valve is a device which closes automatically against the flow of the contents of the tank in case the external closure valve is broken off or removed in transit. Excess flow valves are neither designed, nor intended, to stop the flow of a tank car’s contents in the event of a failure of a loading/unloading system’s piping or hoses.


1.12             Prior to attempting to move the gage rod loosen the packing gland nut slightly. Do not use a wrench for additional leverage to raise and/or lower sticking gage rods. Remember to retighten the packing gland nut prior to offering for transportation.


1.13             During loading and unloading, the pressure in the tank must not exceed the lesser of:


75% of the pressure relief valve start-to-discharge pressure; or


75% of the tank test pressure; or


60% of the rupture disc burst pressure in a combination device.


NOTE: Limiting the pressure below the above values helps ensure that the pressure relief device will not function during product transfer operations. For example, for a DOT111A60W1 tank car with a 75 psig pressure relief device, the pressure within the tank must not exceed 45 psig. (75% of 60 psi). Maintaining the pressure below 75% of the pressure relief valve start-to-discharge pressure helps ensure that the pressure in the tank is below the vapor tight pressure of the device, and limiting the pressure below 60% of the rupture disc pressure in a combination device ensures the pressure is below the point which disc deformation may occur.

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Section 2: Loading a Tank Car
2.1Before Loading a Tank Car
2.1.1Ensure that general procedures in Section A are followed.
2.1.2Shippers must ensure that the tank car selected is authorized for the
commodity being loaded. The tank car must comply with DOT or TC
regulations and/or AAR’s current Manual of Standards and Recommended
Practices, Section C-Part III, (Specifications for Tank Cars, Specification M-
2.1.3The tank car must be of sufficient capacity, both by weight and volume to
contain the quantity of the product being loaded. Applicable requirements
such as outage, filling density or weight restrictions must be met. Consult
the appropriate regulations/company policies for specific filling
2.1.4Inspect the car for overall integrity and any visible damage. All safety
appliances must be in proper condition. The car must show no sign of
leakage and have no visible defects.
NOTE: During the inspection of the car, look for any items that are not
typical of standard tank car designs as they may indicate a security breach
– follow company-specific procedures or guidelines if such items are found.
2.1.5Qualification stencils should be reviewed to confirm that the car is not
overdue for any tests, qualifications or inspections. Do not load a car with
overdue tests, qualifications or inspections.
2.1.6All fittings, valves, gaskets and fasteners must be in proper condition, i.e.
not corroded, torn, worn, stripped or otherwise damaged. Materials
contacting the lading must be compatible with the product being loaded into
the car.
2.1.7Unless the car is cleaned/purged, ensure that the residue in the car is
compatible with the product being loaded into the car. Do not load a car
that has an unidentified residue.
2.1.8If equipped with a safety vent, the rupture disc must thoroughly inspected. If
equipped with a pressure relief valve, the valve must be inspected to ensure
no debris is in its discharge area. If a combination pressure relief device is
present each detection device (including, for example, telltale indicator or
needle valve) should be checked to determine the integrity of the rupture
disk. These devices must be closed prior to transportation.
2.1.9If equipped with bottom outlet valve(s), the outlet cap(s) and/or plug(s) must
be removed to check the bottom outlet valve for leakage. If equipped with


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an auxiliary valve, open the auxiliary valve with its cap/plug removed to check the bottom outlet valve for leakage. Upon removal of the plug and/or cap or opening of the auxiliary valve, be prepared for the possible release of material from the outlet leg and from a leaking valve.

2.1.10         If equipped with a Top Operated Bottom Outlet Valve (BOV), if practicable, loosen the top packing nut and operate the valve to verify proper operation. Depending on findings, close the valve and tighten the top packing nut or stop the operation and repair the valve before loading the car.

CAUTION: This process may allow material to drain into the outlet leg of the car between its BOV and auxiliary valve.

2.1.11         If equipped with a Bottom Operated Bottom Outlet Valve, if practicable, operate the bottom outlet valve to verify its proper operation. Depending on findings, close the valve and lock the handle in the closed position or stop the operation and repair the valve before loading the car.

CAUTION: This process may allow material to drain into the outlet leg of the car between its BOV and auxiliary valve.

2.1.12         The bottom outlet plug and/or cap must remain off its fitting during entire loading process to ensure that the bottom outlet valve is not leaking. If equipped with an auxiliary bottom outlet valve, the auxiliary bottom outlet valve must be left open with the plug removed during the entire loading process to ensure that the primary bottom outlet valve is not leaking.

2.1.13         If equipped with a heating system, thoroughly inspect the exposed parts of the system. If the car is equipped with interior heater coils, remove the caps, be prepared for release of material and check for leaks prior to loading the car.


2.1.14         If so equipped, remove thermometer well cap and the magnetic gage rod cover cap slowly to determine if there is a leak. Inspect the o-ring on the thermometer well fitting and the magnetic gage rod body and replace as required. Verify that adequate ethylene glycol/anti-freeze mixture is present in the thermometer well to allow for taking an accurate product temperature reading.


2.1.15         Where applicable, connect the vapor valve to a recovery system. Open the vapor valve for displacement of the vapor before opening any product valve or manway.

2.1.16         If equipped with a hinged and bolted manway thoroughly inspect the manway nozzle and cover assembly assuring that:      The manway cover is functional, properly aligned and centered on the manway nozzle, hinge pin operates freely, is in place and not bent, cut or

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damaged and the eyebolt slots and ears are not bent, worn, damaged or
deformed. The cover must be free of commodity or other build up that would
prevent proper operation of the eyebolts. The area adjacent to the gasket
sealing surface must be free of commodity or other build up that would
interfere with adjacent surfaces and adjacent areas must be free of
corrosion or damage that would allow passage of commodity with the cover
in the closed and bolted position. manway nozzle sealing surface is free of gouges, nicks, corrosion,
displaced metal, residual commodity and remnants of old gaskets. manway gasket is in place, intact, has not taken a permanent
compression set that interferes with sealing, is the style and design
compatible with the manway nozzle assembly and is of a material
compatible with the commodity. eyebolts, nuts and washers are not bent, damaged, corroded, and the
assemblies are free of excess paint or commodity. Nuts and washers must
be of size to fully bridge the eyebolt slots and washers must not be
deformed. The manway nozzle is equipped with safety eyebolts at the
proper locations opposite the hinge side of the nozzle. eyebolt pins and hinges are not bent, damaged, deformed or worn to
the extent to prevent free movement of the eyebolts and proper
engagement in the manway cover eyebolt slots.
2.2During Loading a Tank Car
2.2.1During loading continually monitor the car for any signs of leakage.
2.2.2Ensure adequate outage space remains in the car when loading is
completed to prevent overloading by volume or by weight and to allow
expansion in transit. Refer to applicable regulations for correct outage,
filling density and other weight restrictions for the commodity loaded.
2.3After Loading a Tank Car
2.3.1When loading is complete re-check the car for any signs of leakage. If there
are any signs of leakage and if the leak cannot be stopped, the car must not
be offered for transportation.
2.3.2Document, per company procedures, the outage level, seal numbers and
product identification information.
2.3.3Close all valves after car is loaded. Verify there is no detectable leakage
from valves, flanges, threaded connections and packing glands. Secure all
plugs and outlet caps with a suitable tool. Use non-sparking tools if required
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by company procedures. (PTFE, Teflon®, paste or not more than three wraps of PTFE tape have been found to be acceptable materials for use in sealing plugs and caps.) {Note: In most cases exterior coils should not have caps}. Do not offer the car for transportation if any leaks are found!

NOTE: Association of American Railroads Interchange Rules require that any leaky tank, regardless of the commodity carried, shall be stenciled, “LEAKY TANK, DO NOT LOAD UNTIL REPAIRED”, in 3-inch letters, on each side adjacent to the car number, and the location of the leak must be identified by an “X”. In addition, the car must be stenciled or decaled


2.3.4            When securing a manway cover tighten the bolts using the appropriate star pattern and internal procedures. Lubricate manway eyebolts as required to maintain serviceability of the bolts and to ensure that proper torque values are achieved. Verify that the manway cover ears have not deformed or bent out of plane due to the torque applied to the eyebolts.

2.3.5            After loading, apply and hand-tighten magnetic gauge cover and thermometer well cap.

2.3.6            After the tank car has passed the appropriate leak test, top unloading valve handles that are not enclosed in a protective housing, must be removed before the car is offered for transportation.

NOTE: All valves, fittings, closures, plugs, caps, and fasteners are to be checked for tool tightness even if the item was not utilized during the unloading process (thermometer and magnetic gauging device covers with o-rings are to be hand tight, not tool tight.)

2.3.7            Product spillage on the tank exterior must be removed.

2.3.8            The car must be properly placarded and marked before it is offered for transportation.

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Section 3: Unloading a Tank Car
3.1Before Unloading a Tank Car:
3.1.1General procedures in Section A should be followed.
3.1.2All fittings seals should be examined before removing them for evidence of
3.1.3Verify that valves and fittings are closed before removing plugs, caps and
3.1.4Any dirt or debris should be removed from the fittings before opening them.
3.1.5Before unloading, verify the contents of the tank car and of the receiving
vessel for compatibility.
3.1.6If the tank car is a general service car, relieve tank pressure by one or more
of the following methods: opening the vent valve. open the fill hole cover or hinged manway cover. If using the
manway cover for pressure relief, use caution when loosening bolts. The
bolt(s) by the handle are the safety bolt(s). Loosen the safety bolt(s) by one
or two turns at a time, and then loosen the remaining bolts. necessary, vent to a scrubber or vapor collection system.
NOTE: CAUTION should be exercised because any tank car may be under
NOTE: The vacuum relief valve should not be used to vent pressure.
NOTE: Atmospheric venting may create a safety and/or environmental
3.1.7Venting is not necessary if the tank car is to be pressure-unloaded.
However, a means to prevent over-pressure must be provided.
3.2If Heater Coils Are Needed For Unloading
3.2.1If equipped with interior heater coils, remove heater coil caps and check for
leakage before connecting steam hoses.
3.2.2Connect steam hoses to inlet connections of the heating system. Use a
shut-off valve to control the steam flow. The tank should be vented before
and during steaming to prevent excess pressure build-up.


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3.2.3            Caution must be taken when applying steam to the system. Apply steam slowly until steam is observed at the heater coil outlet. Rapid expansion of the coils could cause breakage of the steam system. If steam is bubbling in the product, the interior steam coil is broken. Shut off the steam. If there is a dual system on the car, use the other bank. Report defects per company procedures to the shipper of the product and/or to the car owner.

3.2.4            Steaming operations should be carefully monitored to ensure the product or container does not become over-heated.

3.2.5     If the bottom outlet valve is steam jacketed, steam should be applied to the outlet steam jacket. DO NOT apply steam directly into the outlet chamber!

3.2.6            When unloading general service tank cars with protective linings it is important to remember that steaming of a partially filled tank car may damage the coating due to localized overheating. Once unloading is in the process, steam pressure should be reduced or shut off to the car to avoid damaging the protective lining.

3.3               Unloading

3.3.1            When unloading through the bottom outlet, with the manway open, take care to prevent contamination of the product or, in the case of flammable materials, sparks or other sources of ignition.

3.3.2            Verify that the bottom valve is closed before loosening bottom outlet plug or cap.

3.3.3            Be prepared to collect any materials trapped in the bottom outlet leg upon loosening of the cap/plug assembly. Slowly loosen the outlet cap. If more than 2 – 3 quarts are collected in the containment system, there is a probability of bottom outlet valve leakage. Do not remove the cap completely. If the valve continues to leak tighten the cap/plug assembly. Inform the tank car owner of the leaking condition and request what action to take.

3.3.4            Before opening the unloading valves, securely attach the transfer system and perform a leakage test, if possible.

3.3.5            If a non-pressure tank car is being unloaded by pumping through the bottom outlet valve or top-mounted liquid valve, a means of preventing vacuum (which may cause a collapse of the tank) must be provided. Relieve all pressure used to unload the car, except for those products that may have a nitrogen padding applied. A warning should be applied in the manway area to indicate when nitrogen or other non-life supporting gas is present as a pad.

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3.4After Unloading a Tank Car
3.4.1If the steam supply is still active, shut it off and remove connections. Check
the heating coils for water removal and check for leaks per company
procedures. If leaks are found, notify the car owner and/or the shipper.
3.4.2Verify that all valves are closed.
3.4.3Verify that all unloading connections are removed.
3.4.4Secure all fittings, valves and openings in the appropriate manner. (All
plugs and outlet caps must be secured with a suitable tool. Use non-
sparking tools per company procedures when required.) Exceptions:
Thermometer and magnetic gauging device covers with o-rings are to be
hand tight, not tool tight.
NOTE: All valves, fittings, closures, plugs, caps, and fasteners are to be
checkedfor tool tightness) even if they were not utilized during the
unloading process again with the exceptions of the thermometer and magnetic
gaging device covers with o-rings that are to be hand tight, not tool tight.)
3.4.5If the manway was opened during the operation, be sure to inspect the manway gasket for damage, deterioration and proper alignment. Tighten the manway bolts using the appropriate star pattern and torque values per company procedures.
3.4.6If equipped with a safety vent, the rupture disc must be examined for
integrity, proper burst-pressure rating and condition. If the tank car is to be
reloaded at the same facility one inspection of the rupture disk may be
adequate. The key requirement is that the rupture disk be thoroughly
inspected per federal requirements prior to offering for transport with the
following exceptions: of some class 8 and 9 materials by Special Permit in the USA and residue cars in Canada except class 2.
3.4.7Relieve all pressure used to unload the car, except for those products that
may have a nitrogen padding applied. A warning should be applied in the
manway area to indicate when nitrogen or other non-life supporting gas is
present as a pad.
3.4.8All cars (except class 9 material under certain circumstances) must be
properly placarded and marked before being offered for transportation.
3.4.9Ensure proper documentation for transportation is available.
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3.4.10         Visually inspect the car to verify that no obvious defects are present.

NOTE: A car containing the residue of a dangerous good or hazardous material must be offered for transportation in the same condition as a car loaded with that material. It must be leak free, load placarded, marked, closed with seal present if required and properly documented.

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Section 4: Reprint of Parts of M-1002 Appendix D

The information provided within this section includes a reprint of sections 6.0 through 6.6 and tables D7 through D-13 of Appendix D of AAR Manual of Standards and Recommended Practices Section C Part III “Specification for Tank Cars” (M-1002). NOTE: This material will continue to be maintained under Appendix D of AAR MSRP Section C Part III (M-1002).