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Subchapter 14. Petroleum Safety Orders--Drilling and Production
Article 10. Opening and Blinding Pipe Lines and Equipment

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§6536. Blinding or Isolating Pipe Lines and Equipment.

(a) Employees whose duties require them to perform work within a tank, vessel or still/heater shall be protected from the hazards of liquid, vapor or gas that may be discharged through connected pipe lines. Isolation of equipment shall be accomplished by blinding or disconnecting and disaligning.

(1) Where blinding or disconnecting and disaligning is not possible, a double block and bleeder system (DBBS) shall be utilized to isolate pipe lines or equipment. When th DBBS will be used, written operating procedures containing at least the following, must be approved by the Location Management and available:

(A) Block valves used in DBBS shall be monitored for leakage while in use.

(B) Double block valves shall be tagged and locked in the closed position. The bleeder shall be tagged and locked in the open position.

(C) The bleeder valve shall be checked to ensure that it is not plugged and is functioning properly.

(D) The bleeder valve shall be sized to handle the flow and pressure if the block valve fails.

(E) Discharge of leakage through the bleeder valve shall be directed so as not to create a hazard if the block valve fails.

(F) Block valve bonnets must be vented to ensure that no gases or liquids are trapped in the valve.

(G) Before the double block valve(s) is opened, a qualified person shall determine that it is safe.

(b) Blinds shall be designed and installed to preclude failure when subjected to the conditions of service.

(c) When isolated as a unit, vessels, tanks or stills/heaters with compartments or trays shall have the top and bottom manhole covers removed and it shall be determined that ventilation is established through these manholes.

(d) When welding or flame cutting on oil or gas pipe lines, the lines shall be isolated and gas free unless hot-work method in accordance with American National Standards Institute/American Welding Society F4. 1-1988-Recommended Safe Practices for the Preparation for Welding and Cutting of Containers That Have Held Hazardous Substances, pages 1-4, which is hereby incorporated by reference, recommendations or equivalent are used.

(e) Blinds installed in a line shall clearly indicate whether the line is open or closed.

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


1. Amendment filed 7-20-59; effective thirtieth day thereafter (Register 59, No. 12).

2. Amendment of section heading, section and Note filed 5-8-95; operative 6-7-95 (Register 95, No. 19).

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