Nine Thousand Gallons, a 2019 Test Date, and a Ninety-Six Degree Day
You are assigned a 9,000-gallon MC-306 tanker, single compartment, for gasoline (UN1203, Class 3, PG II). It is July 12, 2025, and the ambient temperature is 96°F.
At the rack:
- The loading ticket reads 8,900 gallons.
- The spec plate shows a pressure test and internal inspection dated 08/2019 and an external visual inspection dated 03/2024.
- The TM markings on the rear head read "Tested 08/2019."
- The delivery hose gasket is visibly cracked and the vapor recovery boot is torn.
The operator says the last three loads went out the same way and that "the tank's basically empty, there's plenty of room."
1. Do the outage numbers work? Show the math and state the rule.
Read the worked answer
No - the ticket overfills the tank.
Under 49 CFR 173.24b, a liquid may not be loaded so that the tank becomes liquid full at the 100°F reference temperature. In practice that means leaving vapor space and filling to no more than about 98 percent of capacity at the reference temperature.
The math:
- 9,000 gal × 0.98 = 8,820 gal maximum
- Ticket = 8,900 gal
- 80 gallons over the limit
And 96°F ambient is the worst case to be doing this in. Gasoline expands measurably across a 96°F day, and a tank loaded to 98.9 percent will not have room for that expansion. A tank that goes liquid full has nowhere to put the expansion except out the vents, the hatches, or through a fitting - that is a spill looking for an ignition source.
Action: tell the operator to cut the ticket to 8,820 gal or less and re-verify the outage against the product's actual temperature and specific gravity. "The tank's basically empty" is not a fill calculation; the tank has a fixed capacity regardless of what was in it last time.
2. Evaluate the tank's qualification status. Can you load it at all?
Read the worked answer
No. Two separate requalification failures.
1. Pressure test and internal inspection (both every 5 years on an MC-306):
- Tested 08/2019 → due 08/2024 → 11 months out of qualification
- The internal inspection is likewise due at 5 years and is on the same expired date.
2. External visual inspection (annual):
- Done 03/2024 → due 03/2025 → also expired as of today, July 12, 2025.
3. The TM marking: "Tested 08/2019" on the rear head confirms the expiration. The marking and the spec plate agree - this is not a paperwork dispute.
What happens if you load it anyway: you are operating an out-of-qualification cargo tank. That exposes the carrier to civil penalty per violation, exposes you personally, and, more importantly, the pressure test is the only thing that has ever confirmed the tank's shell and heads will hold. An untested 1990s-era MC-306 at 96°F with a full load of gasoline is a known failure mode.
Action: refuse the load, notify your carrier and the rack operator that the tank is out of qualification, and get the tank red-tagged for requalification. Do not "take it to the shop loaded" to save a trip.
3. Assuming a compliant tank and a corrected gallon figure, what pre-load checks still stand between you and a safe transfer?
Read the worked answer
The equipment defects you already spotted are independent grounds to stop.
- Cracked delivery hose gasket: a gasoline leak at the coupling during transfer is a pool of Class 3 liquid next to a running engine and a hot manifold. Do not connect. Get the gasket replaced.
- Torn vapor recovery boot: vapor recovery is a controlled-emissions and fire-safety system. A torn boot vents gasoline vapor uncontrolled at the connection point.
Transfer discipline for a Class 3 tank load:
- Bonding and grounding before the transfer starts, and maintain it until the transfer ends - static ignition is a real cause of gasoline fires at racks.
- Engine off, parking brake set, wheels chocked as the site requires.
- No smoking within 25 feet and away from any open flame.
- Attendance: loading must be attended by a qualified person with a clear view of the vehicle and close enough to shut down the transfer immediately. Do not walk away to the office.
- Markings and placards:"Gasoline" and UN1203 in the required orange panel configuration, plus the FLAMMABLE placard, properly displayed and legible.
- Emergency shutdown location known before you open the valve.
Bottom line: on this assignment you would be refusing the load twice over - once for requalification, once for the hose and boot. Both refusals are correct, and neither requires you to argue with the operator.