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Aboveground Storage Tanks - Leak-Before-Burst Capability
March 23, 2003

Victor Singer

As sent in a email to Senator David McBride on 3/23/03

Dear Dave:

At the DNREC Aboveground Storage Tank Technical Advisory Committee (ASTTAC) March 20 meeting, hard copies of Secretary Hughes' March 17 response to your e-mail of February 15 were distributed to all who cared to pick up a copy. Also, hard copies of my February 4 essay entitled "Thoughts on a Brittle Fracture Requirement for New Above-Ground Metal Storage Tanks" were distributed in like fashion. But neither your February 15 e-mail nor its antecedents were distributed. They are appended below.

In his letter, Secretary Hughes said that DNREC's Tank Management Branch is researching the "Leak-Before-Burst" (LBB) issue that I raised in my "Thoughts on a Brittle Fracture Requirement" essay. In particular, he said that preliminary contacts with the American Petroleum Institute (API) subcommittee responsible for API Standard 653 have disclosed that "the current standard specifically does not include the mathematical calculations suggested by Mr. Singer because . . . there are more sophisticated formulas in the more recently developed methods."

Upon my request at the March 20 ASTTAC meeting to see the records of DNREC's communications with API in this regard, I was given a copy of a February 20 letter from Jill Hall to Roland Goodman of API, which was NOT distributed to ASTTAC. It includes the following key text:

". . . A member of the general public has raised questions concerning brittle fracture failure of aboveground storage tanks. It is our understanding that the requirements of API 653 were formulated to ensure that the materials allowed by this standard in the construction of aboveground storage tanks are of adequate toughness to avoid brittle fracture failure. We would like to request a confirmation from API that this standard or others adequately address the issue of brittle fracture failure according to the research conducted by API. . ."

Note that the February 20 letter doesn't mention my name, and doesn't cite my "Thoughts on a Brittle Fracture Requirement" essay, in which I proposed requirements only for NEW tanks - - tanks that haven't yet been built. In support of my proposed LBB provision, I showed that the requirements of API Standard 650 - - a design standard for NEW tanks - - can lead to tank designs without LBB capability.

[As an example, at the API 650-prescribed minimum impact energy requirements, ASTM A-633D steel is permissible under API 650 for use at a 28 ksi allowable stress level in a tank with a wall thickness up to 1.5 inch at a service temperature as low as minus 10 degF. Under these conditions, API 650 doesn't even require that impact energy specimens be tested. Yet I showed in my "Thoughts on a Brittle Fracture Requirement" essay that below a 20 degF service temperature, ASTM A-633D steel tank wall thicknesses above 1.11 inch would not provide LBB capability at the 28 ksi allowable stress level and the minimum impact energy levels that API 650 would permit. Further, I showed that a more stringent US Department of Defense criterion in "Fracture Control Requirements for DoD Shuttle Payloads," which demands LBB capability all the way to the yield stress level, would prohibit use of ASTM 633D steel at 20 degF in thicknesses larger than 0.235 inch.]

By citing only API Standard 653 - - a standard for alteration and modification of existing tanks - - and by NOT providing API with a copy of my "Thoughts on a Brittle Fracture Requirement" essay, DNREC's February 20 letter suggested to API that I'm seeking to disqualify EXISTING tanks, which of course is absurd.

Somehow, Secretary Hughes neglected to tell you that DNREC assured an unfavorable response from API by changing the scope of my proposal.

And somehow Secretary Hughes chose to request that unfavorable response from API, which could hardly be expected to brand its own standard as inadequate, especially without a copy of such a showing. It shouldn't take a rocket scientist to seek out an unbiased expert, such as the U of D faculty member who teaches a graduate level course in Fracture Mechanics, and ask for her opinion. (No, I haven't ever met her, or spoken with her, or communicated with her.)

And somehow Secretary Hughes neglected to tell you that the "more sophisticated formulas" in API Standard 650 - - that I referred to - - have nothing to do with brittle fracture.

Secretary Hughes needs to be reminded that there are TWO public policy issues here, and several sub-issues, which I state according to my own views of what is appropriate:

  • In Delaware, all NEW tanks for hazardous liquids should be designed to have Leak-Before-Burst capability at the lowest service temperature and the highest allowable operating stress level.
    • Such a requirement should be explicitly stated in Delaware's regulation for Aboveground Storage Tanks containing hazardous liquids, unless explicit statements to that effect are shown in reference standards therein included.
    • For liquids more hazardous than petroleum, more stringent requirements should apply, as for instance UL Standard No.2285, "Protected Above Ground Tanks for Flammable and Combustible Liquids."
  • A computational methodology for assuring LBB capability should be explicitly stated in the regulation unless a methodology of like effect can be included by citation of a reference standard.
  • The computational methodology should be simplistic enough to assure error on the side of safety even when applied by practitioners without thorough understanding of the relevant technology.
  • More complex approaches should be permissible for those with the requisite facility with the subject matter.

Secretary Hughes should be urged to READ and TRY TO UNDERSTAND what I proposed. If it would help, I would be happy to give a blackboard-and-chalk presentation - - or more properly in this day and age, a whiteboard-and-marker presentation - - on the relevant technical issues and background. I've often given such presentations to technically proficient and non-proficient groups over the past thirty years - - most recently, on March 13 this year, and before that in San Antonio last August. I can assure you that the underlying concepts are readily understood by folks without mental blocks, and that the underlying complex mathematics are avoidable.

The technology of fracture is a new science, developed over the 2nd half of the 20th century. Those who are sensitive about lesser proficiency in that technology than they might like, are reluctant to display that sensitivity. Formidable mathematical treatments are further discouragements. Yet except for the purists, it can be enough that certain mathematical expressions describe how structural materials fracture. After all, when Newton described how the apple falls from the tree, he didn't need to concern himself with why it falls.

Should Secretary Hughes take advantage of the presentation offer, and perhaps stage it at or after an ASTTAC meeting, it would overcome both the mental block and the reluctance. If YOU suggest it, it will have more weight than my suggestion.

Vic Singer

As read during the public comment time at the end of the ASTTAC meeting. A hard copy was provided with a request that it be included in the minutes.


But first, picture this: Some nut with a rifle shoots at a street light. The bullet goes thru the plastic globe and the bulb. The bulb shatters. The globe has two holes in it.

I want the Aboveground Storage Tank regulation now being written to assure that every new tank in Delaware for environmentally hazardous contents - - or worse - - built after a stipulated date, will be ductile like that globe, rather than brittle like the light bulb, in case the nut with the rifle shoots at a tank.

Opposition comes from one of the co-chairman of the Installation and Modification Subcommittee, which will draft that part of the regulation. The rest of the subcommittee has been silent on this issue. The co-chairman insists that Delaware shouldn't consider such a requirement until after the American Petroleum Institute (API) decides whether, when and how to think about it. His employer's Chief Engineer adds: ". . .The time frame to get something into an API document will likely take a few years at the minimum. I have seen much lesser discussions take many more than a few years. . ."

Yet draft language for the Delaware regulation already distributed by the subcommittee co-chairman requires compliance with UL Standard No.2285, "Protected Above Ground Tanks for Flammable and Combustible Liquids." UL 2285 requires - - GUESS WHAT ! ! - - shooting at the tank with a gun, and rejecting the tank if it leaks! All I want is assurance that it won't shatter, appropriately termed "Leak Before Burst Capability." I regard slow leaks as manageable.

I'm not suggesting that each new tank be shot at with a gun, as UL 2285 demands. Instead, achieve assurance analytically using data from tests on miniature samples that are already required by API Standards. All that's new is the interpretation of the data using three simple equations shown in draft text that I've sent to the subcommittee co-chairman, attached hereto also. To apply those equations, he needs only to learn how to use the square root button on his pocket calculator.

The equations come from a relatively new science - - Fracture Mechanics - - developed during the last half century, when premature pressure vessel bursts got engineers and rocket scientists into deep yogurt - - costly, time-consuming, and not conducive to longevity on the payroll. The equations define a threshold between brittle and ductile behavior of the material, and lead to a "keep it ductile" requirement. A requirement for ductile behavior has applied to structures in Department of Defense satellite systems for over 20 years.

The argument is about is whether it is or is not appropriate to require all new hazardous materials storage tanks in Delaware to survive without shattering, if attacked by that guy with a gun, which it turns out is equivalent to assuring that the tank will behave in a ductile fashion under all operating conditions.

Nothing thus far in API Standards guides tank designers towards controlling the fracture mode of their creations. Nevertheless, API respects Fracture Mechanics enough that its Standard 653, at Section 5.3.9, says: ". . . The owner/operator can also make a more rigorous analysis to determine the risk of failure due to brittle fracture by performing a fracture mechanics analysis based on established principles and practices. The procedures and acceptance criteria for conducting an alternative analysis are not included in this standard."

I seek formalizing an element of that "more rigorous analysis" for the sake of Delaware's environment. I don't object to helping the folks at API learn to use their square root buttons, and I would be glad to help them do it. But the co-chairman's suggestion, making progress in Delaware contingent on the folks at API learning something a quarter century old that's new to them, is an absurdity of high order. Insisting on refusing to learn unless API learns first is like insisting on not marrying a girl unless somebody else tries her out first. Patently ridiculous.

Your help is needed. Instruction to the subcommittee co-chairman. A policy edict from the full committee. Unless you prefer not giving a damn.

Victor Singer

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