What configuration ensures safety with two valves in a boiler system?

The Double Block and Bleed configuration is essential for ensuring safety in a boiler system because it involves the use of two isolation valves that create a physical barrier to prevent fluid flow in case one valve fails. In this configuration, two block valves are installed in series with a bleed (or drain) line in between them. This design allows for the isolation of the system and the ability to vent any trapped pressure or fluid, which enhances safety during maintenance or in case of a failure.

When both block valves are closed, the area between them can be vented to atmosphere, relieving any pressure that may have built up. This is particularly important in ensuring that no hazardous conditions can arise when work is conducted on the system, as it minimizes the risk of leaks or explosive release of steam or other fluids.

Other configurations, while they may provide certain operational benefits, do not offer the same level of protection as the Double Block and Bleed. For example, a Single Block Valve allows for isolation but does not provide a way to safely vent pressure, and Loop Configurations or Triple Valve Arrangements may not sufficiently isolate fluid and provide a means for bleeding off pressure effectively. Thus, the Double Block and Bleed configuration stands out as the safest choice for managing potential hazards in