We still get asked about tube equivalence, and there is no shortage of misinformation out there to be corrected. Sometimes the question is about a testing program with statistical parameters. At other times, it concerns listing as a supplier in ASTM D3241. Most often, the question concerns a non-existent "approval" that can somehow be had based on undefined terms and invisible, ever-moving, criteria. While the questions are tiresome, our answer is always and forever the same: equivalence is undeniable scientific fact.
While eternally argued in certain political subdivisions, tube equivalence is well-established fact in scientific circles. The proof of tube equivalence is actually simple and quite straightforward relying as it does upon official tube specifications. Just one letter and a single number within the specifications ensure and guarantee equivalence as an inherent tube quality. Those important letters are "T6."
T6 is the specific alloy tempering schedule demanded by specification. Once the tempering schedule is applied to the strictly defined material composition known as "aircraft aluminum," the alloy is permanently and irreversibly hardened. That hardening process "bakes in" every physical, chemical, mechanical, and material property of the alloy. It becomes unchanging and unchangeable. That's actually the very definition of equivalence. And, routine operation at mild JFTOT temperature cannot re-soften the material. Once tube composition and the tempering schedule are carefully set by specification, tube variance is impossible.
In fact, the alloy surface comprises impenetrable non-porous metal, so it simply isn't possible for heater tubes to impact of test results. The tube, itself, is inert. A catalytic effect is impossible when neither fuel components nor oxygen molecules can absorb into the metal; a requirement for reaction to occur.
Precisely to ensure equivalent quality, ASTM International presents strict tube specifications and requires tube users to employ only tubes meeting specification, which users determine are equivalent. The specifications define, in technical terms, the “fitness for service” of inert aluminum tubes; important tube qualities that are incorporated into a D3241 Table entitled “Critical Operating Characteristics of JFTOT Instruments.” There's also no reason to worry about equivalence when a Method Table 2 caveat clearly states that a reference to Alcor, Inc. “is not an endorsement or certification by ASTM International.”
Our inert tube with its finer, more consistent finish will always reveal the full, rich, colors of fuel-related deposits forming on the surface. The determination of deposit colors is still the critical aspect of a visual fuel determination or rating. The use of color has always resulted in an annoyingly subjective visually-based test, because the test itself is empirical or trial and error based. It's the test that is uncomfortably subjective; not the tube. No inert tube can fix the fact of test results being subjective or remarkably variable; a problem that ASTM's own ruggedness testing has confirmed.
The more technical deposit thickness approach to testing also favors our product. We offer the most consistent and finest tube surface. That produces the finest and most consistent determination of deposit thickness and volume. Other producers are limited by their comparatively coarse, inconsistent, abraded finish. They cannot match our tube finishing processes, which actually remove scratches, abrasions, random gouges and various random defects, and even the machine marks themselves, whose microscopic presence define inferior competing tubes.
Yes, we have also completed and submitted many equivalence studies to ASTM Subcommittee J on Aviation Fuel. Please click here to view one example of a comprehensive Equivalency Study. Data users are certainly free to consider this information, in addition to the tube specifications. Actually, our tube materials come from the exact same source, making a performance difference hard to even imagine. Once the mill supplies the specified alloy, there’s no way for suppliers to alter tube properties. That's why we say that tube equivalence is actually a built-in (guaranteed) tube feature. It cannot be otherwise.
By written policy, ASTM provides for product listing information to be incorporated into ASTM methods once new equipment has been "made available and shown to be equivalent." However, ASTM doesn't provide a meaningful, technical, or clear definition for equivalence in support of that policy (as they should and as we have asked). In the face of their confusion, we produced the required “showing of equivalence” in a simple, straightforward, scientific, and logical format. We think you'll agree it is plain common sense. Please click here to view the comprehensive “showing of equivalence.”
Suppliers of quality heater tubes for D3241 do employ a variety of technologies to fix the final finish onto their heater tubes. Our methods are patent-protected and published, compared to the unpatented, unpublished, unrecognized processes others employ. We also produced a Study of these various finishing methods and their effects; presenting results to ASTM during a recent meeting of Subcommittee J. It demonstrates that polishing has no effect on deposit-formation reactions. To view these results, please click here. As expected with an inert product, results proved equivalence among the various equipment suppliers irrespective of the tube finishing method. Plus, ours is the best!
Standard Heater Tubes are used in refinery and independent labs throughout the world; testing billions of gallons of jet fuel powering thousands of planes flying millions of miles around our planet. This fact is final evidence that users have great confidence in the established equivalence of our product.
Tube equivalence is scientifically undeniable, so equivalence is absolutely irrefutable and permanently true. The guarantee of Tube Equivalence relies only on scientific evidence and the fundamental principles of Chemistry. (The full name of the D3241 test itself actually tells us the test evaluates something about fuels; thermal considerations and fuel component oxidation, i.e. the Thermal Oxidative Stability of Jet Fuel. A moment's reflection will persuade even the most cynical observer that a test which is devised to indicate something about fuels simply cannot simultaneously reflect some variable about inert heater tubes. That idea defies logic and doesn't pass the smell test).
The well-established rule from General Chemistry mandates the rate of a chemical reaction will double for every ten degree increase in the reaction temperature. If you compare this established scientific principle to the ASTM notion that equivalence can be demonstrated by a statistical plus or minus 5 degree difference from one tube to another, you're left with the astounding conclusion that two tubes can be statistically defined as "equivalent" even if they vary by a 100% order of magnitude (namely, a ten degree temperature difference). So, the "equivalence problem" is actually mythical; the result of an entirely empirical trial and error ASTM test which isn't and cannot be accurate to plus or minus five degrees. (Check the D3241 scope statement for verification).
The notion that an empirical or trial and error test can ever disprove a cold hard fact constitutes a colossal fools errand. The only thing being proven by such attempts is that people who cling to and promote that fallacy are, themselves, charlatans who mislead others on a grand scale through incredible, even unbelievable, falsehoods. Statistics can do many things, but statistics cannot alter reality. As some say, you're entitled to your own opinion, but you're not entitled to your own facts.
So, tube equivalence is more than simply obvious on its face and beyond being demonstrably true. Equivalence is axiomatic fact; validated through scientific inquiry. Equivalence is guaranteed by inclusion and adoption of alloy tube specifications in ASTM D3241.
Still not persuaded? Then consider aluminum alloy 6061 as being a material whose chemical composition is tightly controlled in a way that distinguishes its behavior from any other alloy. Known as "aircraft aluminum," it is perfectly suited to aircraft applications. This uniquely specified material, once subsequently tempered to a regimented schedule called "T6" or "temper 6," fixes every chemical, mechanical, material, and physical property of the alloy permanently and irreversibly, creating a known, unalterable, set of features. The resulting material cannot be changed short of draconian measures (such as remelting the alloy at absurdly high temperatures). Contrast that reality with the fool's notion that "polishing differences" can produce important effects in a truly weak trial and error empirical fuel test. The presumed conclusion of non-equivalence becomes, well, unthinkable.
It's because of this number one mandated characteristic within tube specifications -- 6061-T6 -- that tube equivalence is actually guaranteed via specification. No serious investigator thinks otherwise.
Do you want to know why 6061-T6 alloy was selected for the JFTOT test? It's because that specific alloy, at conditions employed for the test, is already inert.
For the doubters, try googling "Aluminum as oxidation catalyst." That search will result in a dearth of applicable entries, and that doesn't even reflect the rather mild conditions for JFTOT-related fuel-related deterioration reactions. The concept that one inert 6061-T6 tube is somehow measurably more "inert" than an inert tube from another supplier is a concept that is simply beyond the pale. Nobody believes that. It's actually quite laughable.
You'll possibly hear some people talking about tube equivalence as if the real issue is that our product hasn't been "approved." That's simply disingenuous. For one thing, that approach attempts to move the discussion from something about technical features and technical capabilities to an entirely separate discussion about politics and ASTM politics. For another thing, the notion of tube "approval" is only relevant to an examination of what is required for listing as a supplier in the ASTM Method D3241. The criteria for listing is actually set forth in the official ASTM booklet, Facts for Members. Documents and criteria there contradict the very notion of "approval," as does a comparable Method footnote. The "Guidelines for Listing Suppliers of Alternative Equipment in ASTM Methods" set forth two concrete requirements, namely (1) that alternate equipment be made available, and (2) that it be shown to be equivalent. It just makes good sense that a scientific proof of equivalence is a sufficient showing for listing purposes. Otherwise, why bother?
This is to not even consider the fact that ASTM, by clear written policy, doesn't endorse or certify equipment suppliers. A statement of that reality is specifically included as part of ASTM D3241. And, as a voluntary consensus organization, ASTM already recognizes that it has no authority to mandate vendor "approvals." Anything else is conflicted and instantly discredited. All users of ASTM Methods, as well as every supplier of equipment for ASTM Standard Methods, enjoys a measure of autonomy regarding ASTM. If that were somehow not possible, the concept of "voluntary consensus" would be meaningless. So, in sum, the twin notions of "Alternate Equipment Guidelines" and "Listing Guidelines" have been somehow distorted and used as a smokescreen to disguise efforts to politically blackball a particular vendor of completely equivalent, inert aluminum heater tubes, for ASTM D3241. That's inescapably malevolent. So, there's that.
Aside from the irrefutable, permanent, scientifically demonstrated and guaranteed (by specification) proof of heater tube equivalence, and with no further regard for the separate issue that ASTM seemingly denies that it is already required by it's own policy and guidelines to provide an alternate supplier listing, there is a final and absurd testing hurdle. That hurdle is called the Equivalence Testing Protocol. It has an official name as well: ASTM RR:D02-1550.
RR:D02-1550 is, in actuality, an official ASTM Research Report. Strangely, this "Research Report" reports no research. It also offers no data. However, even that shortcoming isn't the real issue with the Equivalence Testing Protocol. The two primary issues with it are (1) it is so obsolete as to be devoid of meaning, and (2) there is a grossly erroneous, absurd, approach taken within the Protocol; that heater tube equivalence, although undefined, can be statistically measured.
Recall that earlier we discussed the curious ASTM notion of how a plus or minus 5 degree testing difference may indicate equivalence. Science teaches ten degrees of difference would also reflect a doubling in observed reaction rate. That's definitely a testing problem. A larger, more intimidating testing problem, is that equivalence is already guaranteed by the Specifications. Equivalence is a known fact, and known facts aren't subject to statistical evaluation. In other words, you can't use statistics to disprove something that is already axiomatically true.
RR:D02-1550 was adopted by ASTM in 2004. At that time, testing of jet fuels involved, exclusively, a visually-determined test result. That visual result no longer defines jet fuel stability, but is still a requirement of the Equivalence Test Protocol. In a word, RR:D02-1550 is obsolete. As a consequence, nobody in their right mind is going to deploy resources to complete a test program whose result isn't relevant or meaningful. Additionally, of course, ASTM "approval" isn't likely to be forthcoming based on results of an obsolete test program. ASTM needs an ungraded Protocol; one which doesn't employ statistics in a misguided effort to disprove equivalence, and one which provides a definition of tube equivalence that can actually be measured in some meaningful manner other than color. Until/Unless that is done, RR:D02-1550 exists as an obsolete, meaningless, relic. Maybe soon, ASTM will join the 20th Century (No, Wait!).
In this section, I have shown how it is undeniable and beyond reasonable doubt that tubes of viable suppliers are inherently equivalent. The basis for this fact is that the material composition and the alloy tempering schedule are both firmly established by tube specification, which permanently, irreversibly, and unalterably fixes every chemical, physical, mechanical, and material feature of these inert aluminum tubes. Consequently there is no technical basis for a belief that tubes could somehow be made "non-equivalent" through action -- accidental or even deliberate -- of an equipment manufacturer.
Additionally, I demonstrated how statistics are inapplicable as a means to "prove" tube equivalence. This is so because the JFTOT test is empirical or trial and error based. The test is empirical, so it actually lacks any scientific or technical basis, so there is no reason to think that statistics could ever result in a valid technical result. Nor has any sensible theory been proposed, ever, by which non-equivalence can even reasonably exist. It is a mere false presumption. Factually, multiple studies have recently emerged and have been presented to ASTM (including a "Ruggedness Study" of ASTM's own creation and completion). These, without exception, indicate that the range of variable results when testing fuels is closer to twenty degrees than to plus or minus five degrees. This result was obtained while employing only "ASTM-approved" tubes (an oxymoron, itself). Accordingly, Study results showing a wide variance have to be attributed only to already "approved" tubes. The ASTM Study actually does show that "ASTM-approved" tubes aren't equivalent by that test. To ASTM, however, that's a mere inconvenient factlet.
A third conclusion about inert heater tubes (separate from any technical elements of factual tube equivalence or the inapplicability of statistics as a basis to "prove" tube equivalence) is that ASTM's written "Committee Guidelines for Listing or Replacement of Test Equipment Suppliers in Standard Test Methods" actually require that Equipment Suppliers be Listed in Standard Test Methods once such equipment has (1) been made available and (2) shown to be equivalent.
Notwithstanding these technical conclusions, there is a single political conclusion: There is no benefit to be had in contesting the unfairness or injustice being perpetuated against our company by a political ASTM subdivision. The existence of this political conclusion creates a natural tension to the three clear technical elements of (1) Equivalence, (2) Use of Statistics, and (3) requirements under ASTM Listing Guidelines and ASTM Antitrust Policy. That tension between politically-based forces and technical reality is one that only Subcommittee J, Committee D02, or ASTM International itself can resolve. Someday soon, it will.
The only course for us is to maintain a steady focus on our rational customers and rational potential customers, while we and others wait for ASTM to display something approaching rational behavior. That is what we continue to do.