Which option correctly identifies the control loop numbers?

• A. 100
• B. 101
• C. TE
• D. 100 and 101

Answer: (D)

Control loop numbers are numeric identifiers used to label each closed-loop in a process control system. They are written as numbers because each loop is a separate entity that the control system monitors and tunes.

Seeing two numeric loop numbers together reflects that there can be more than one control loop in the same system. In this case, both 100 and 101 are valid loop identifiers, indicating two distinct control loops. A non-numeric tag like TE isn’t a loop number, so it doesn’t serve as a loop identifier.

So listing both numeric identifiers correctly identifies the control loops present, rather than referring to a single loop or using a non-numeric tag.