This was sent to me via a traction engine list I belong to. I strongly disagree with the board, as good guality boiler steel, with very strict chemical specifications, has been a hallmark of US boiler practice since the 1880's, and I would put the steel in most any pressure vessel against anything out of the mill today.

I also understand that the FRA is considering National Board Recomendations in any amendments to CFR 49 Steam Locomotive Rules.



Bruce E. Babcock
Registered Join Date: Oct 2005
Location: Amanda, Ohio USA
Posts: 25

The National Board & Old Boiler Steel

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After receiving many negative comments regarding their allegation that steels manufactured during the era of riveted boiler construction were of much poorer quality than the pressure vessel steel that is currently available for boiler fabrication, the National Board rewrote their allegations. This rewriting was done with no additional input from the task group on historical boilers and possibly little or no additional input from the locomotive task group.

It is my understanding that the new wording has been, or will be, inserted into both Appendix C, Historical Boilers and Appendix 3, Locomotives.

The meeting of the task group on historical boilers that had been tenatively scheduled for Corpus Christi was cancelled. It appears that the changes were made at the Board's meeting in Corpus Christi.

The new wording is:


NB04-1402

3-1300(a) and C-10150

Caution shall be used in performing weld repairs to steels that were manufactured during the era of riveted boiler construction, as the steels utilized may have been of much poorer quality than the materials that are currently available for boiler fabrication. Older steels are frequently rimmed steels which have very poor toughness properties, contain elevated phosphorus and/or sulfur content, or the material may be of unknown chemical composition. Weld repairs in such materials can make the boiler susceptible to sudden unexpected fracture which may have serious consequences; a simple arc strike can be a critical flaw size. Competent technical advice should be obtained to evaluate the weldability characteristics of the steel. The concern for the determination of chemical composition of a steel is to assure proper selection of filler metal and preheat requirements to assure a sound weld repair.

If the boiler was designed and fabricated in accordance with the ASME Boiler and Pressure Vessel Code, and stamped accordingly, then weld repairs are permitted. If the chemical composition of the material to be repaired is unknown, the repair organization must determine, as a minimum, the carbon and manganese levels of the steel that will undergo the repair. The carbon cannot be greater than 0.35% and the manganese should be within the range of 0.60 to 1.20%. Also, it would be preferred if the steel was melted to fine-grain practice. Any arc strikes must be removed prior to hydrostatic test. It is recommended that only low hydrogen electrodes (or a low hydrogen welding process) and a minimum of 200 °F (93 °C) preheat be used during welding.

Note: The concern for the chemical composition of the steel and the recommendation that low hydrogen electrodes or a low hydrogen welding process be used is to assure a sound weldment. Steels with carbon content above 0.35% may transform to a hard microstructure that is susceptible to hydrogen induced cracking. The presence of hydrogen exacerbates the problem, therefore the recommendation for a minimum of 200 °F (93°C) preheat is to assure that no moisture is present during welding. The desire for a killed steel (aluminum treated) is to assure that the material has acceptable toughness and is not susceptible to brittle fracture. The presence of a small flaw such as an arc strike has been shown to be a critical flaw size in rimmed steels not treated.



I received this via email last week along with a questionnaire asking if:

I felt the new language adequately responded to my comments,
I did not fully accept the committee's response, or
I felt that the committee's response did not resolve my concerns.
I responded with (3). Their response did not resolve my concerns.

Sincerely,

Bruce E. Babcock

Jim:

With all due respect, I would have to disagree.

The National Board's assessment goes to the heart of what we code welders have known for a while: pre-WWI boiler steel is a challenging and difficult weldment. We don't call it "Titanic" steel for nothing. I've watched cracks form, as I was welding in this kind of steel, right along side or behind the weldment. We've chased all kinds of fractures and cracking through rivet patterns, trying to rehab what was essentially a weak course.

We're bullish about riveted boilers, riveted repairs and all the classic, old-time practices. But steel samples go out to be tested and we're not afraid to tell a customer that this or that part of their boiler is essentially shot because it just doesn't have the strength or the durability to pass the calculations.

Furthermore, for weldability and boiler durability, and given the correct specs, I'd take modern boiler steel from any mill in the world over pre-WWI steel. (Modern hot-rolled steel in other applications such as ambient oxidation, weather resistance, etc., is a whole other problem that's beyond the scope of the topic.)

I also understands as a working man where it hurts: Many traction boiler owners are on a six-pack budget and pride themselves in their own maintenance and skills. Boiler repairs can be prohibitively expensive. There's not an easy answer for this and I'm sorry for the overall development.

I agree with what S. Weaver has said. For example;

I recently did a ut survey on a boiler and had to put away my digital thickness tester due to the level of inclustions in all of the plates on that boiler. It was only with my A scan machine that I could determine the thickness of the steel.

Continous cast steel is pristene conpared to the old steel rolled from an ingot. Ingots were prone to have 'piping' in their core which when rolled into plate form ends up in the center of the plate. This is what the digital testers get confused over.

Robert Yuill

I would be curious as to how many "old" boilers have had tensile and charpy v-notch testing performed on them after 100 years of service? I think to draw conclusions on this without such data would not make sense.

As part of the qualification of a flush type repair we performed our locomotive 630 (ALCo 1904), we performed such physical testing (in addition to the chemical testing) and we found there to be no loss in any of these properties. The % elongation was still within acceptable limits as well. I should add that the mechanical records for this locomotive (we have the original files) show no records of the 1st course ever being replaced.

When we did the qualification of our detailed weld procedure for the flush patch installation, ALL the coupons broke in the NEW A516, Grade 60 plate and one of the breaks in the new plate even revealed a lamination.