What are the first two blinds turned on a tower being taken out of service?

• A. Outlet and inlet
• B. Inlet and outlet
• C. Top and bottom
• D. Front and back

Answer: (B)

Isolating process equipment by blocking the flow into and out of it is the first safety step when taking a tower out of service. A blind is a solid disk that plugs a flange to seal a line. The first two blinds you install go on the inlet and on the outlet, so no feed can enter and no product can leave while maintenance or disassembly occurs. This ensures the tower is fully isolated, preventing spills, pressure buildup, or exposure inside the tower as you depressurize, purge, or drain it.

The other orientations describe physical positions of parts rather than the actual flow paths. Top and bottom or front and back don’t guarantee stoppage of the process streams, so they don’t accomplish isolation like securing the inlet and outlet do.