I love these types of threads. They start small and grow from the seed that was planted.

First point that should be clarified is who typically writes a code, a standard, and specification?

Anyone can write a specification. A specification can be written to describe and define purchasing requirements of an item such as a pencil. It can describe the particulars of a welding process, i.e., a welding procedure specification. It can be written by an individual, a company, or a professional organization. An example of a specification would be a filler metal specification developed by a committee under the auspices of the American Welding Society or a base metal specification developed by ASTM.  A specification may only have standing within the organization that writes it or it can have national or international standing when it is developed by an organization that has national or international recognition.

A code is a special category of standards that is developed by an organization with the intention of being incorporated as a legal requirement once it is adopted by a government body. They are consensus documents where the committee membership votes on the proposed requirements or any proposed changes. Codes are organized for easy reference and can be adopted by government bodies and incorporated into legal statues, at which point they become law. Think of the building codes that reference the electrical codes, plumbing codes, welding codes, codes of standard practice, etc. Technically, the code is a standard that has legal standing. The codes also include various specifications by reference, in which case, they too become legal requirements. AWS D1.1 is an example often given as an example of a code that has legal standing once it is adopted by a governmental body such as the federal government, state government, or a municipality. Another example is the ASME Boiler and Pressure Vessel Code. Until the consensus code is adopted by a government body, it is no different in a practical sense than any other standard, that is, it has no legal standing.

A standard is an umbrella term that includes any document, i.e., codes, specifications, recommended practices, etc., that has national recognition.  The committee tasked with developing the standard has to have a diverse membership and there are formal rules for the voting process.  A standard has industry recognition, but may or may not become a legal requirement. AWS D1.1 is an example of a standard that is also a code. The “Statement of Use of AWS Standards” contained in AWS D1.1 describes the process and is well worth reading.

A National Standard has specific rules of how the document is developed and approved for publication. ANSI has been adopted as the organization that defines how nationally recognized documents are developed by organizations such as AWS or ASME. The committees charged with developing codes have a membership that represents fabricators, owners, suppliers, and interested parties. Even the general public has an opportunity to input and comment on the contents of the code. Examples of standards that are not codes, i.e., they are not intended to be incorporated in to legal statues include welding standards for machinery such as the D14.X welding standards, AWS B2.1 Specification for Welding Procedure and Performance Qualification, AWS B4.0 Standard Methods for Mechanical Testing or Welds, and of course AWS A3.0 Standard Welding Terms and Definitions.

Guides can be included under the banner of a standard. Two examples I like are AWS B1.10 Guide for the Nondestructive Examination of Welds and AWS B1.11 Guide for the Visual Examination of Welds. All the AWS documents cited are examples of American National Standards that comply with the requirements of ANSI.

I hope this helps answer your inquiry.

Best regards - Al

I just looked at the listing of D14.X specifications. It appears D14.6 is the correct specification for rotating elements.

Since the question appears to be initiated by a manufacturer who seems to have the latitude to select an appropriate welding standard, I assume there is no contractual obligation imposed by a customer.

The adoption of one welding standard over another should be based on the nature of the weldments and how it will be used. D1.1 is primarily intended for steel structures. The D14.X specifications may be similar to D1.1 at first look, but many of the requirements have been modified to include materials not typically used in buildings and reflect the design stresses used. For instance, machinery that is subject to static loads, but must be very rigid with very little deflection utilize allowable stresses on the order of 3 ksi to 5 ksi rather than 21 ksi to 27 ksi allowed for steel structures. The permitted deflection for a building are much greater than that permitted for a machine required to hold precise tolerances. The lower allowable design stress means deeper undercut, more porosity, etc. can be tolerated without paying a penalty. Likewise, the size of the welds can be smaller for a given thickness because the stresses on the welds are usually rather low. Low cost fillet welds can be used rather than higher cost groove welds. On the other hand, rotating elements subject to fatigue loads may have to meet acceptance criteria more stringent than that provided by D1.1 due to the nature of the loads.

The manufacturer has to be careful to select the welding standard that is applicable to the nature of the work because it is expensive to meet stringent acceptance criteria when there is no need to do so. The competitive advantage can be lost when the weld quality is needlessly too high.

Best regards - Al

Milles,

Along with the added info that Al and myself added about your application, I would like to give you a little more based upon personal past experience.  I have worked on large heavy equipment on log yards throughout the Pacific Northwest.  Equipment most definitely being stressed in ways that a structural building being constructed to D1.1 never begins to see.  Those kinds of forces are not even present in an earthquake and need to be dealt with completely different than what is required within D1.1. 

For example, the way welds can be ended at the edge of a stiffener plate being welded into the inside of a wide flange beam.  If I ended a weld that way on a log stacker it would start to break the first day and within a week things would literally be coming apart.

How you transfer stresses, how you grind/sand to get minimal stress risers going in the proper direction, how much you restrict movement, the size and location of weld discontinuities, and many other factors that hopefully engineers and more educated and experienced people than I have examined thouroughly as they developed these various codes/standards and/or specifications.

So be very careful about applying the correct set of standards and using it in it's complete context to get the best possible end product and make sure your customers won't need to repair certain items before they even start using your product.

Have a Great Day,  Brent