The output volume of a positive fixed displacement pump can be changed only by （）.

An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.

A salinity indicator is used to determine the （）.

If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.

An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.

A salinity indicator is used to determine the （）.

On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.

The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.

A grease gun is generally used to lubricate a （）.

The general purpose of a heat exchanger is to （）.