What device is installed to stop the high pressure air compressor automatically when the cooling water rises above a safe limit?

The correct answer is the automatic temperature shut down device, which is specifically designed to monitor the temperature of the cooling water used in conjunction with the high-pressure air compressor. This device ensures the safe operation of the compressor by automatically shutting it down if the cooling water temperature exceeds a predetermined safe limit. Operating a compressor with excessively high cooling water temperatures can lead to overheating and potential equipment failure, thus the automatic mechanism serves as a crucial safety feature.

In contrast, while a pressure relief valve is important for managing excess pressure in systems, it does not specifically monitor or respond to temperature changes. A manual switch requires human intervention for operation and is not automatic, making it less effective in critical situations where immediate response is necessary. Lastly, a liquid level sensor is more focused on detecting the presence or absence of liquid—such as monitoring water levels—but does not specifically shut down the system based on temperature fluctuations. The automatic temperature shut down device is directly aligned with ensuring equipment safety in relation to cooling water temperature.