SG series sight glasses are used to show:

1. The condition of the refrigerant in the plant liquid line.
2. The moisture content in the refrigerant.
3. The flows in the oil return line from the oil separator.

SG series sight glasses are fitted with an indicator which changes color to show the moisture content in the refrigerant.

The indicator shows dark blue while containing low water, and shows pink while containing much water. In case of showing pink, you have to look for what is cause from or change filter drier in system.