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 https://www.osha.gov.

May 17, 2006

Mr. James Dean
7215 Mitchell Drive
Terrell, TX 75160

Re: Whether the motor on a portable concrete mixer has to be covered; §1926.300(b)(1)

Dear Mr. Dean:

This is in response to your letter dated July 29,2005, to the Occupational Safety and Health Administration in which you ask for guidance regarding the use of portable concrete mixers in construction applications. We apologize for the long delay in responding.

In accordance with your October 7, 2005, phone conversation with one of our staff members, we have paraphrased your question as follows:

Question: Some models of portable concrete mixers have motors and drive assemblies with exposed moving parts. However, I do not believe that there are any moving parts exposed when my mixer's motor cover is open. Based on the enclosed picture of my mixer's engine, is it required that the engine be covered when operating?

Figure 1 - Portable Concrete Mixer Engine, showing Engine Cover, Drive Mechanism Cover, and Drive Shaft.

Answer: Title 29 CFR 1926.300(b)(1), Guarding, states:

When power operated tools are designed to accommodate guards, they shall be equipped with such guards when in use.

It appears from the picture you submitted that your mixer has a cover for the drive mechanism and another, hinged cover, for the engine. We will discuss these separately.

Engine cover
It appears from the picture that the manufacturer of your mixer provided an engine cover. Assuming that to be the case, your mixer's engine was "designed to accommodate [a] guard[]. . ." Therefore, the engine cover is required to be used in accordance with §1926.300(b)(1).

If there were no unguarded moving parts with the engine cover removed or raised, the failure to use the engine cover would be considered only a de minimis violation.1 However, it appears from the picture that putting the engine cover in the raised position exposes a rotating component (drive shaft) of the drive mechanism.2 Therefore, based on the submitted information, the failure to use the engine cover in your case would not be considered de minimis, and the cover must be used.3

Drive mechanism cover
The mixer was also designed with a drive mechanism cover, which, under §1926.300(b)(1), is required to be used. The failure to use that cover would not be considered de minimis since it is apparent from the picture that the drive mechanism has moving parts that would be exposed in the absence of that cover.

If you need additional information, please contact us by fax at: U.S. Department of Labor, OSHA, Directorate of Construction, Office of Construction Standards and Guidance, fax # 202-693-1689. You can also contact us by mail at the above office, Room N3468, 200 Constitution Avenue, N.W., Washington, D.C. 20210, although there will be a delay in our receiving correspondence by mail.



Russell B. Swanson, Director
Directorate of Construction

1 Under OSHA's de minimis policy, de minimis violations are those that have no direct or immediate relationship to safety or health. Consequently, no citation is issued. [ back to text ]

2 While the drive shaft that is exposed with the cover open is positioned such that it would be difficult to contact a body part, it still could entangle items worn by a worker such as a fall protection lanyard or a loose article of clothing, drawing the worker in and causing injury. [ back to text ]

3 Note also that §1926.300(b)(2) states:

Belts, gears, shafts, pulleys, sprockets, spindles, drums, fly wheels, chains, or other reciprocating, rotating or moving parts of equipment shall be guarded if such parts are exposed to contact by employees or otherwise create a hazard. Guarding shall meet the requirements as set forth in American National Standards Institute, B15.1-1953 (R1958), Safety Code for Mechanical Power-Transmission Apparatus." [ back to text ]