Tanker: Tanker Loading

17 questions in the bank cover this topic. Everything below is drawn from the sources those questions cite.

Sources: 49 CFR 173.24, 49 CFR 173.33, 49 CFR 177.834, 49 CFR 177.837, 49 CFR 177.840, 49 CFR 392.9

What you need to know

177.834(e) requires the handbrake securely set plus any other reasonable precautions against the vehicle moving.

A tank that rolls during a transfer tears the hose.

No hazardous material shall be loaded into or on, or unloaded from, any motor vehicle unless the handbrake be securely set and all other reasonable precautions be taken to prevent motion of the motor vehicle during such loading or unloading process.

49 CFR 177.834

177.834(c) forbids smoking on or about the vehicle during loading or unloading of Class 1, 3, 4, 5 and Division 2.1 materials.

177.834(d) extends this to preventing others nearby from smoking or carrying any flame. The prohibition covers on or about the vehicle, and applies to Class 3 among others.

Smoking on or about any motor vehicle while loading or unloading any Class 1 (explosive), Class 3 (flammable liquid), Class 4 (flammable solid), Class 5 (oxidizing), or Division 2.1 (flammable gas) materials is forbidden.

49 CFR 177.834

177.834(d) makes the driver responsible for the area, not just their own behavior.

Preventing bystanders from introducing an ignition source is part of the duty. That covers lighting matches or carrying any flame in the vicinity.

Extreme care shall be taken in the loading or unloading of any Class 1 (explosive), Class 3 (flammable liquid), Class 4 (flammable solid), Class 5 (oxidizing), or Division 2.1 (flammable gas) materials into or from any motor vehicle to keep fire away and to prevent persons in the vicinity from smoking, lighting matches, or carrying any flame or lighted cigar, pipe, or cigarette.

49 CFR 177.834

392.9(a)(1) makes proper distribution and adequate securement under 393.100 to 393.136 a precondition for operating.

For a tank, distribution is governed by which compartments are filled. The securement rules apply in full to tank vehicles.

The commercial motor vehicle's cargo is properly distributed and adequately secured as specified in §§ 393.100 through 393.136 of this subchapter.

49 CFR 392.9

173.33(a)(2) turns on what the mixture would do, not on class labels.

Compartments do not remove the risk, because a bulkhead can fail or a transfer can go to the wrong compartment. Excessive pressure or heat counts equally.

Two or more materials may not be loaded or accepted for transportation in the same cargo tank motor vehicle if, as a result of any mixture of the materials, an unsafe condition would occur, such as an explosion, fire, excessive increase in pressure or heat, or the release of toxic vapors.

49 CFR 173.33

173.33(b)(1) requires compatibility between the lading and every tank surface it touches.

The wrong lining or an unsuitable shell material can be attacked by the cargo and fail in transit. The reaction the rule guards against is a dangerous one.

A hazardous material may not be loaded in a cargo tank if during transportation any part of the tank in contact with the hazardous material lading would have a dangerous reaction with the hazardous material.

49 CFR 173.33

173.33(b)(3) targets the vapour space.

Pushing air in can bring the mixture above the tank's liquid into the range where it will burn, turning the tank itself into the hazard. That mixture can fall inside the flammability range. That mixture can fall inside the flammability range in the vapour space.

Air pressure in excess of ambient atmospheric pressure may not be used to load or unload any lading which may create an air-enriched mixture within the flammability range of the lading in the vapor space of the tank.

49 CFR 173.33

173.33(b)(4) caps the rate at what the specification plate says, to prevent rupture.

Where no rate is marked, pressure must stay within 130 percent of the MAWP.

To prevent cargo tank rupture in a loading or unloading accident, the loading or unloading rate used must be less than or equal to that indicated on the cargo tank specification plate

49 CFR 173.33

173.24(h)(1) is about thermal expansion.

A tank filled to the brim in cool weather has nowhere to put the extra volume when the sun heats it, so it leaks or deforms.

When filling packagings and receptacles for liquids, sufficient ullage (outage) must be left to ensure that neither leakage nor permanent distortion of the packaging or receptacle will occur as a result of an expansion of the liquid caused by temperatures likely to be encountered during transportation.

49 CFR 173.24

173.33(c)(5) requires 25 psig or greater for the more dangerous poisonous liquids.

A stronger tank is less likely to release its contents in a crash.

Any material that meets the definition of a Division 6.1, Packing Group I or II (poisonous liquid) material must be loaded in a cargo tank motor vehicle having a MAWP of 25 psig or greater.

49 CFR 173.33

177.837(a) stops the engine unless it is driving the transfer pump.

There is a narrow extra allowance for a diesel engine at or below minus 12 degrees Celsius, which is 10 Fahrenheit.

Unless the engine of a cargo tank motor vehicle is to be used for the operation of a pump, Class 3 material may not be loaded into, or on, or unloaded from any cargo tank motor vehicle while the engine is running.

49 CFR 177.837

177.837(b) specifies the order and says 'not in any other order'.

The final connection is the one that could spark, so it is made at the supply container, well away from the opening where vapour is escaping. Bonding order matters: fill side first.

Such bonding shall be made by first connecting an electric conductor to the container to be filled and subsequently connecting the conductor to the container from which the liquid is to come, and not in any other order.

49 CFR 177.837

177.837(b) places the last connection, the one that can spark, away from the vapour.

Bonding exists to equalise static charge, but making the connection is itself the moment a spark is most likely. That is where vapour collects, and a spark there would find it.

To provide against ignition of vapors by discharge of static electricity, the latter connection shall be made at a point well removed from the opening from which the Class 3 (flammable liquid) material is to be discharged.

49 CFR 177.837

177.837(c)(1) brackets the whole operation.

Charge builds while liquid moves and persists afterwards, so removing the bond early is as dangerous as never fitting it. It stays in place until after the last filling hole is closed.

This connection must be made before any filling hole is opened, and must remain in place until after the last filling hole has been closed.

49 CFR 177.837

177.837(c)(2) exempts vapour-tight transfers, because with no vapour escaping there is nothing for a spark to ignite.

The connection must be made before flow starts and not broken until flow is complete. And none released anywhere a spark could occur.

When a cargo tank is loaded or unloaded through a vapor-tight (not open hole) top or bottom connection, so that there is no release of vapor at a point where a spark could occur, bonding or grounding is not required.

49 CFR 177.837

177.840(d) mirrors the Class 3 rule in 177.837(a).

It adds that unless the delivery hose has a shut-off valve at its discharge end, the engine must be stopped at the finish while connections are broken.

No Division 2.1 (flammable gas) material shall be loaded into or on or unloaded from any cargo tank motor vehicles with the engine running unless the engine is used for the operation of the transfer pump of the vehicle.

49 CFR 177.840

177.840(g) requires them closed in transit.

An open discharge valve turns any impact that breaks a line into an immediate release of the whole load. The engine fuel line valve is excepted.

Each liquid discharge valve on a cargo tank motor vehicle, other than an engine fuel line valve, must be closed during transportation except during loading and unloading.

49 CFR 177.840

Check yourself

• How do you prepare the vehicle before a cargo tank transfer begins?

• Is smoking permitted near a tank being loaded with a flammable liquid?

• Beyond your own conduct, what does the rule require during a flammable transfer?

• What is required of cargo distribution and securement?

• When may two materials not share your cargo tank motor vehicle?

• What must be true of the tank itself before loading a hazardous material?

• Why is above-atmospheric air pressure prohibited for loading certain ladings?

• What limits the rate at which your cargo tank may be loaded or unloaded?

• Why must outage, or ullage, be left when filling a liquid tank?

• What minimum MAWP must your cargo tank have for a Division 6.1 Packing Group I or II poisonous liquid?

• May the engine run while transferring a Class 3 flammable liquid?

• In what order must bonding connections be made between containers?

• Where must the final bonding connection be made, and why?

• When must the bond wire be connected and disconnected for open-hole filling?

• When is bonding or grounding NOT required for your cargo tank transfer?

• What engine rule applies to flammable gas transfers?

• While in transit, liquid discharge valves must be ______.

Answers are in the practice test for this topic.