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Standard Interpretations - Table of Contents
• Standard Number: 1926.251; 1926.251(a)(4)

June 8, 2012

Mr. Trent Schon, CSP
Director of Safety/Renewable Energy Groups
Mortenson Construction
M.A, Mortenson Company
700 Meadow Lane North
Minneapolis, MN 55422

Dear Mr. Schon:

We are writing in response to your letter of August 11, 2011 concerning proof testing of lifting beams used to lift wind turbine components.

Question # 1:  Are lifting beams used to hoist wind turbine components, like nacelles, blades, hubs, rotors, etc., during construction of the tower considered lifting accessories of a special custom design for the application of § 1926.251(a)(4)?

Response: Yes.  Section 1926.251(a)(4) states:

Special custom design grabs, hooks, clamps, or other lifting accessories, for such units as modular panel, prefabricated structures and similar materials, shall be marked to indicate the safe working loads and shall be proof-tested prior to use to 125 percent of their rated load.

The process of mass-producing rigging equipment in accordance with industry-recognized manufacturing practices requires strict means of sampling and quality control, confirmed by proof-testing of batch samples, to ensure that the design specifications and construction of each piece of equipment produced are consistently sufficient to meet the equipment's intended load rating.

In contrast, although OSHA does not provide a definition of special custom design, the lifting beams that you describe are specifically designed for the sole purpose of hoisting components of a particular wind turbine with due consideration to its physical dimensions, weight, configuration, and the manner of rigging.  It is our understanding that the designs of your lifting beams can vary depending on the unique physical characteristics of the wind turbine component to be hoisted.  In addition, the physical properties of the materials of which your lifting beams are made and the conditions under which the beams are fabricated could also vary from job to job.  Each of these factors can affect the tolerance and performance of individual beams, making it necessary to proof test each one to verify that each one meets the required specifications for design safety.  In sum, because your lifting beams are not mass-produced designs, your lifting beams are considered special custom designs and each must be proof-tested.

Question # 2:  If over 400 of the lifting beams described above were fabricated at the same time, would each one still have to be proof tested?

Response: There is no exact number of lifting beams that must be fabricated at once for the beams to be considered mass-produced.  As explained in our response to Question # 1, the design specifications of your lifting beams are likely to vary, and the lifting beams are not mass-produced.  Therefore, each lifting beam must be proof tested.  However, it could be considered a de minimis violation of § 1926.251(a)(4) if industry-recognized acceptance sampling methods, such as those set forth in consensus standards like ISO 2859 series or ANSI/ASQC Z1.4-2008 and Z1.9-2008, are implemented and used to confirm the specifications and safety of your beams based on the size of the batches produced.  De minimis violations are violations of standards which have no direct or immediate relationship to safety or health.

Question # 3:  At what number of manufactured lifting beams does OSHA consider to be "regularly manufactured" so the requirement of proof-test can be substituted by professional engineered stamped calculations/drawings?

Response: See response to question # 2.

Question # 4:  As the wind turbine industry is a global industry, would proof testing documentation from outside of the U.S. be acceptable to provide verification of lifting beam proof test status if the beam is uniquely identifiable via serial number, referenced on this proof test documentation, and proof tested to 125% of the desired working load?

Response: Yes, provided the proof testing has been conducted in accordance with generally accepted international standards, such as EN 13155 Cranes - Safety - Non-fixed load lifting attachments.

Thank you for your interest in occupational safety and health.  We hope you find this information helpful.  OSHA requirements are set by statute, standards, and regulations.  Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations.  This letter constitutes OSHA's interpretation of the requirements discussed.  Note that our enforcement guidance may be affected by changes to OSHA rules.  Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at  If you have any further questions, please feel free to contact the Directorate of Construction at (202) 693-2020.


James G. Maddux, Director
Directorate of Construction

Standard Interpretations - Table of Contents

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