What device is installed on main engine thrust bearings to indicate flow?

The device that is installed on main engine thrust bearings to indicate flow is the bullseye bubbler. This device is commonly used in marine engineering to monitor the flow of lubricating oil to thrust bearings. It operates by utilizing a sight glass that allows the operator to visually confirm the presence of oil flow through the use of bubbles in a liquid column. When the flow is adequate, the motion of the bubbles provides a clear indication of lubrication, which is crucial for the proper functioning of thrust bearings. Adequate oil flow is vital since it helps to prevent overheating and potential damage to the bearings due to insufficient lubrication.

Flow meters and pressure gauges would typically measure the flow rate or pressure of the oil but do not provide a direct visual representation of flow, which is the primary purpose of the bullseye bubbler. Temperature sensors, while important for monitoring the operating conditions of various engine components, do not provide any indication of flow and therefore are not suited for this application.