Tanker: Tanker Inspection
13 questions in the bank cover this topic. Everything below is drawn from the sources those questions cite.
Sources: 49 CFR 177.840, 49 CFR 180.407, 49 CFR 180.415
What you need to know
180.407(d)(4) requires thickness testing at least once every 2 years for these areas, with at least four symmetrically distributed readings to establish an average.
Hidden cavities are where corrosion goes unnoticed.
at least once every 2 years
49 CFR 180.407
180.407(g)(4) requires a hydrostatic test at least once every 5 years at no less than the maximum system design operating pressure, held for five minutes.
A heating system failure can put lading into the flues.
at least once every 5 years
49 CFR 180.407
180.407(g)(5)(ii) exempts these low-pressure lined tanks provided they get an annual external visual and lining inspection instead.
The exception trades one test for more frequent inspection, not for nothing. They must also receive an external visual inspection and a lining inspection at least once each year.
Pressure testing is not required for uninsulated lined cargo tanks, with a design pressure or MAWP of 15 psig or less, which receive an external visual inspection and a lining inspection at least once each year.
49 CFR 180.407
180.407(h)(1) requires at least 5 minutes.
A short test can miss a slow leak, which is exactly the kind that empties a tank over a long haul.
Test pressure must be maintained for at least 5 minutes.
49 CFR 180.407
180.407(h)(1) requires adjacent tanks empty and at atmospheric pressure, so a leak between compartments shows up instead of being masked by equal pressure on both sides of the bulkhead.
Each cargo tank of a multi-cargo tank motor vehicle must be tested with adjacent cargo tanks empty and at atmospheric pressure.
49 CFR 180.407
180.407(h)(1) sets no less than 80 percent of the marked MAWP, subject to listed exceptions.
Testing well below service pressure would not reproduce the conditions a leak appears under.
Leakage test pressure must be no less than 80% of MAWP marked on the specification plate
49 CFR 180.407
180.407(h)(1) includes all internal and external self-closing stop valves, and the test covers product piping with all valves and accessories in place and operative.
The valves are the usual leak path, not the shell.
All internal or external self-closing stop valves must be tested for leak tightness.
49 CFR 180.407
177.840(m) requires a visual and audio check of what is readily observable, made after discharge system pressure has reached at least equilibrium with the tank.
Operators need not use instruments or take extraordinary steps to reach what is not visible. You are looking for sound quality and secure connections on readily observable components.
Before unloading from a cargo tank motor vehicle containing a liquefied compressed gas, the qualified person performing the function must check those components of the discharge system, including delivery hose assemblies and piping, that are readily observed during the normal course of unloading to assure that they are of sound quality, without obvious defects detectable through visual observation and audio awareness, and that connections are secure.
49 CFR 177.840
180.407 treats a year out of service as a reason to pressure test regardless of where the normal interval stands.
Standing still is its own form of wear: seals dry, and corrosion continues without the lading moving.
Each cargo tank that has been out of hazardous materials transportation service for a period of one year or more must be pressure tested in accordance with § 180.407(g) prior to further use.
49 CFR 180.407
180.415 requires the date and the TYPE of test, both in English.
That is what lets you tell on a walk-around whether the test that is due is the one that was actually done. All three, durably and legibly, in English.
Each cargo tank must be durably and legibly marked, in English, with the date (month and year) and the type of test or inspection performed
49 CFR 180.415
Annually.
A failed lining lets the lading attack the shell itself, so the lining is inspected more often than the shell thickness it protects.
The integrity of the lining on all lined cargo tanks, when lining is required by this subchapter, must be verified at least once each year
49 CFR 180.407
Every 2 years, and annually once the measurement falls below the minimum thickness plus a fifth of the original corrosion allowance.
The interval tightens as the margin shrinks. None of the figures offered is the one the rule gives.
The shell and head thickness of all unlined cargo tanks used for the transportation of materials corrosive to the tank must be measured at least once every 2 years
49 CFR 180.407
The fifth wheel hides a patch of the tank from every walk-around you will ever do, so 180.407 requires removing it every two years to look underneath.
Hidden areas corrode precisely because nobody sees them. The fifth wheel hides a patch of tank from every walk-around.
For cargo tanks transporting lading corrosive to the tank, areas covered by the upper coupler (fifth wheel) assembly must be inspected at least once in each two year period
49 CFR 180.407
Check yourself
- Ring stiffeners and similar appurtenances that create air cavities preventing external visual inspection must be thickness tested how often?
- How often must the pressure bearing portions of your cargo tank heating system be hydrostatically pressure tested?
- Which cargo tanks are excepted from pressure testing, and on what condition?
- What is the required period for test pressure to be held during your cargo tank leakage test?
- What is the method by which each compartment of a multi-compartment tank leakage is tested?
- What is the minimum leakage test pressure for your cargo tank?
- Which valves must be tested for leak tightness during your cargo tank leakage test?
- What two things is the discharge system check looking for?
- A tank in your yard has sat unused for over a year. What is needed before you haul hazmat in it?
- You are inspecting your tank before a run. What must be marked on it?
- What is the inspection interval for your lining on a lined cargo tank?
- How often is shell and head thickness measured on an unlined tank carrying a corrosive lading?
- Why must your fifth wheel assembly be removed from a corrosive-service tank periodically?
Answers are in the practice test for this topic.