What should not be done to valves connected to a water column while the boiler is in operation?

Removing valves connected to a water column while the boiler is in operation poses a significant risk and is generally prohibited due to safety concerns. The water column is an essential component that displays the water level in the boiler, and any disruption to this system can lead to inaccurate readings, which may result in unsafe operating conditions.

When a valve is removed, it can lead to a loss of pressure, which might cause a dangerous drop in the water level that is vital for maintaining safe boiler operations. This situation could result in boiler dry firing, overheating, and potential equipment failure or explosions.

In contrast, other actions such as opening or closing valves can be performed under controlled conditions as they can be part of operational procedures to manage water levels, although they should be done with caution. Adjusting valves, when done correctly, can also help in fine-tuning the operation of the boiler. However, the critical point remains that removing a valve during operation is highly unsafe, making it the most inappropriate action in this scenario.