How can the closing feature and rotary disc assembly of the 413AF-5A high level shut off valve be tested?

The closing feature and rotary disc assembly of the 413AF-5A high-level shut-off valve can be tested effectively using a manual tester on the high-level shutoff float assembly. This method directly engages the float assembly, which is designed to work closely with the valve's operation. By utilizing a manual tester, you can simulate the circumstances under which the float assembly indicates a high level, thereby allowing you to observe whether the valve closes as expected.

This testing method is significant because it directly assesses the functionality of the float assembly alongside the closing mechanism of the valve, ensuring that it will respond appropriately in actual operational scenarios. The manual tester provides a controlled environment to verify the operational integrity of the system and confirm that the shutting-off process occurs, thereby preventing overfills and potential hazards associated with high liquid levels.

The other options do not specifically engage the float assembly directly. For instance, using a manual tester on the high-level valve itself would not account for the complete system's feedback mechanism, while pushing buttons on different panels may not reflect the conditions that initiate the high-level shut-off function. Therefore, utilizing a manual tester on the high-level shutoff float assembly stands out as the most effective method for ensuring the shielded safety feature of the system.