Several clients design Double Block and Bleed (DB&B) isolation into their process, especially when they know they will regularly enter certain Permit-Required Confined Spaces (PRCS). When these DB&B arrangements are part of the design, the isolation valves and the bleed valve are near one another. This allows us to use a single lock with some cable/chain and lockout devices.
We CLOSE the two (2) isolation valves, OPEN the bleed valve, and run the cable/chain around (or if we are using lockout devices on these valves the cable passes through these devices), and we use a single lock to secure the cable in place.
Be sure to read my other 2021 article that argues against this practice: Does Double Block and Bleed require INDEPENDENT isolation points?