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Subchapter 7. General Industry Safety Orders
Group 13. Cranes and Other Hoisting Equipment
Article 93. Boom--Type Mobile Cranes

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§4922. Crane Boomstops.

(a) Cranes of such design that the boom could fall over backward shall be equipped with boomstops whenever the main boom is rope supported and the crane used for hook, clamshell, magnet, grapple, concrete bucket, or service presenting similar risk. The boomstop shall provide emergency protection against destructive damage and related hazard by opposing any unexpected upward and rearward boom movement beyond the working range. It shall not be used purposely as a substitute for normal procedures in stopping a boom being raised.

(b) In the case of new cranes over 10 tons in capacity purchased after January 1, 1971, the required boomstops shall satisfy the following standards and each involved employer shall have substantial assurance of this in the form of crane manufacturers' warranties, test reports, charts, engineering calculations, etc.

(1) The boomstops shall be strong enough to develop the ultimate strength of the boom in bending at the point of attachment or contact between boomstop and boom, which point should be located near the outer end of the basic inner section of the boom; however, the point must be at least 5 feet above the operator's normal seat level when the crane is level and the boom vertical.

(2) The ultimate bending strength of the boom referred to in (1) shall not be reduced by the nature of contact between the boomstop and boom; such points of contact to be so located and designed that forces developed by boomstop action on the boom will not cause prior local failure of any boom members.

(3) The boomstop shall prevent that portion of the boom below the point of boomstop contact from upward and rearward movement beyond 90 degrees, or some lesser angle, in reference to the horizontal machinery deck.

(4) The boomstop shall provide energy absorbing resistance to the upward and rearward movement of the boom throughout an angular range of the last 5 degrees of such movement as limited in (3).

(c) Jibs shall have positive stops to prevent their movement of more than 5 degrees beyond the straight line of the jib and boom on conventional-type crane booms.

(d) No boomstop shall remain in use unless it is in good operating condition and maintained in accordance with the certified agent's guidelines for maintenance and service.

NOTE: Authority cited: Sections 142.3 and 6704, Labor Code. Reference: Section 142.3, Labor Code.


1. New NOTE filed 8-29-86; effective thirtieth day thereafter (Register 86, No. 39).

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