Question: Which blocking method is used on pressurized gases or liquids? Possible Answers: Bleeding Wedging Grounding Clamping

To safely block pressurized gases or liquids, it is essential to identify the pressure in the pipe or equipment being worked on. A secondary pressure gauge or valve should be used to confirm the system is depressurized, following established codes and standards. [1]

Key steps include:

• Lockout, block, disconnect, or use other positive means to disconnect the systems being worked on from the energy sources creating the hazard and prevent re-pressurization or exposure to energy sources.
• Always depressurize and drain the piping system completely before attempting to install, remove, adjust, or maintain any coupling or end cap connection.
• Verify the piping system has been completely depressurized and drained immediately prior to installation, removal, adjustment or maintenance of any coupling or end cap connection.

[1] Additionally, end caps installed for pressure testing should be equipped with ball valves to identify if pressure is present. Under no circumstance should coupling hardware or other system components be loosened to check if the system is pressurized or to depressurize the system. [1]

Ensure robust policies and procedures are in place for employees working with pressurized piping systems. Stored or residual energy (such as hydraulic systems, air, gas, steam, or water pressure) must be dissipated or restrained by methods such as blocking and/or bleeding down. [1]

In confined spaces, use two blocking valves with an open vent or bleed valve between them when isolating pipelines to prevent entry of materials and hazardous contaminants. [2]

Train employees in the identification of energy sources and the hazards associated with installing, testing, and maintaining pressurized systems. Emphasize that a pressure gauge alone is not an acceptable method of verifying system pressure. [1]