Block, Bleed, and Spectacle Blind

Line blinding, which is often done in conjunction with the other methods, requires that a flat piece of metal be bolted to the flange at the end of the exposed line. The blind should be rated to take full line pressure plus the appropriate safety margins. In order to check that a blind is in place, it usually has a short handle which juts out from between the flange faces. 

Blinding must be done if any of the following conditions exist  

Whenever the system is open and personnel are not physically on scene and in control of the double blocks. System components might include pipelines, valves, strainers, meters, pumps, heat exchangers, and air eliminators. 

Double block and bleed valve arrangement is not permitted as an isolation device when working in permit-required confined spaces. 

Effectiveness in the selected location Verification of the blind s pressure rating Safe removal of the blind Safe accessibility for personnel and equipment Located at the flange closest to the equipment, tank, or vessel The blind must be stamped with its pressure rating and type Potential for exposure to toxic or corrosive material 

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