Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

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

April 11, 1989

Mr. Phillip M. Mapp
Safety Director
Kimmins Industrial Service Corporation
1704 Cannes Drive
La Place, Louisiana 70068

Dear Mr. Mapp:

This is in response to your correspondence to Mr. Paul Hansen, Director of OSHA's Baton Rouge Area Office and a followup phone conversation with Mr. Anthony Brown of my office requesting an interpretation of 29 CFR 1926.550(g)(i)(3)(C), "Crane and Derrick Operational Criteria".

The requirement for a "positive acting device" and the term "anti-two-blocking device" are interchangeable. The appropriate terminology would be "positive acting anti-two-block device." The purpose and intent of this requirement is to assure that a remote signaling device (flashing lights, bells, buzzers or horns) is not used to warn the operator if he is approaching a two-block situation. A positive acting anti-two-block device provides for an automatic cessation of the lifting action when the headache ball or block approached the end of the boom or jib.

In responding to your second request, the standard does apply to all cranes, including friction rigs and hydraulic cranes.

If this office can be of any further assistance, please let use know.


Gerald P. Reidy, Director
Office of Construction and
Maritime Compliance Assistance