What action should be taken if liquid refrigerant appears while draining oil?

The appropriate action to take when liquid refrigerant appears while draining oil is to follow the Standard Operating Procedures (SOP) established for the specific refrigeration system. SOPs are designed to ensure safety and efficiency while handling refrigerants and oils. They typically include procedures to manage unexpected occurrences, such as the presence of liquid refrigerant during oil drainage.

By adhering to the SOP, operators can mitigate risks, which may include safety hazards associated with refrigerant exposure or potential damage to equipment. SOPs often provide specific guidelines on how to handle such situations, ensuring compliance with regulations and safety standards.

While the other options may seem plausible actions, they do not provide the structured guidance that SOPs offer. For example, performing a vacuum purge could lead to additional complications without knowing the proper procedure. Shutting down the system immediately might not be necessary or appropriate depending on the circumstances outlined in the SOP. Continuing to drain oil without proper protocols could expose operators to safety hazards or mishandling of refrigerants. Therefore, following the SOP is the best course of action in this scenario.