Figure 7-25.Typical thermal relief valve.
To adjust the opening pressure of a relief valve,
turn the adjusting screw clockwise to increase
opening pressure and counterclockwise to decrease
Do not attempt to adjust a relief valve while
it is installed on an aircraft. This action
will result in an incorrect pressure setting.
The valve must be removed and adjusted
on a test stand to ensure proper pressure
All hydraulic systems do not have shutoff valves
incorporated; however, in some systems a shutoff valve
is installed in the fluid supply line between the reservoir
and the engine-driven pumps, and other places where
shutting off the fluid is desirable. These valves, like
other valves, may be electrically or manually controlled,
depending upon the design of the valve.
The purpose of shutoff valves differ according to
their installation. All shutoff valves control the flow
of fluid; however, they may isolate troubles by
shutting off a complete system or subsystem, or they
may control the speed a component moves by
partially closing the valve (manual type).