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Subchapter 7. General Industry Safety Orders
Group 8. Points of Operation and Other Hazardous Parts of Machinery
Article 67. Laundry and Dry Cleaning Equipment

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§4493. Boilers and Pressure Vessels.

(a) Boilers and pressure vessels shall comply with the Boiler and Fired Pressure Vessel Safety Orders and the Unfired Pressure Vessel Safety Orders.

(b) Where pressure-reducing valves are used, a safety relief valve shall be provided on the low-pressure side of the reducing valve to prevent pressure build-up in excess of the maximum allowable working pressure. The safety relief valve shall be located as close as possible to the reducing valve, and it shall be vented to the atmosphere in a manner to avoid injury or damage caused by escaping fluid. The relief valve and vent system discharge capacity shall be sized so that the pressure rating of the low-pressure piping and equipment are not exceeded if the reducing valve sticks or fails to close.

NOTE: The relief valve may be omitted if the pressure before the reducing valve does not exceed the maximum working pressure of the equipment.

NOTE: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. New Sections 4493 and 4494 filed 9-19-75; effective thirtieth day thereafter (Register 75, No. 38).

2. Amendment filed 11-2-86; effective thirtieth day thereafter (Register 86, No. 47).

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