What precaution is used for safety from leakage in a liquid level sight glass?

The use of ball checks in a liquid level sight glass acts as a critical safety feature to prevent leakage and maintain system integrity. Ball checks function by using a movable ball that seals the opening of the sight glass when there is no flow or when the pressure differential changes due to system fluctuations. This design ensures that if there is a failure or breach in the sight glass, the ball will block the passage, thereby minimizing the potential for liquid to leak out into the environment.

This design is particularly important in refrigeration systems, where pressurization and temperature variations can cause liquid to expand or contract, raising the risk of leaks. The ball check provides a reliable closure that prevents unintended discharge while still allowing for visibility of the liquid level under normal operating conditions.

In contrast, other options, such as pressure relief valves, are primarily used to prevent overpressure situations, vacuum seals are designed to maintain vacuum conditions without leakage, and flow restrictors are used to control the flow rate in a system. While all components serve essential functions in a refrigeration system, it is the ball checks that specifically address the safety concerns related to liquid leakage in sight glass applications.