Unit 8: Controlling the system knowledge check

When a valve is classified as normally open or normally closed, it is only in relation to the position of the internal elements when the system is ____.

Shut down

Controlling the flow rate of fluid entering an actuator controls the ____ of that actuator.

Speed

Restrictor-type, noncompensated flow control valves provide a consistent flow rate as long as the load on the system is constant and the ____ of the fluid does not change.

Temperature

____ directional control valves are designed for the actuation of rams and single-acting cylinders.

Three way

Bypass flow control valves are often referred to as ____ flow control valves because of their additional port.

Three-port

A pressure-reducing valve is normally open and must be externally drained. (T/F)

True

Flow control valves must be used to provide varying flow rates when using a fixed displacement pump. (T/F)

True

The ____ serves as the holder of all the working elements of the valve.

Valve Body

Only one-fourth turn of the handle is required to adjust the ____ directional control valve from fully closed to fully open.

ball

Three pressure operating terms that are key to the understanding of pressure control valve operation are ____.

cracking pressure, override pressure, and full-flow pressure

The pressure control valve placed in a hydraulic system to protect the system from damage if the relief valve should fail is the ____ valve.

safety

A heat-sensitive metal rod used in conjunction with a needle valve can be used as a ____.

temperature-compensating flow control device

Flow through an orifice is determined by ____.

-cross-sectional area of the orifice opening. -pressure drop between the inlet and outlet areas of the opening. -viscosity of the fluid.

Safety valves are typically set at a pressure ____% above the setting of the primary system relief valve.

25

___ valves may be adjusted from the fully open position to the fully closed position by turning the control handle only 90° (one-fourth turn).

Ball

The middle position in a three-position, four-way directional control valve is often called the ____ position.

Center

The pressure at which a pressure control valve just opens is called the ____ pressure.

Cracking

Heavy internal springs are used to establish the operating pressure of the ____-operated type of pressure control valve.

Direct

A normally closed valve shifts to a fully open position when the system is shut down. (T/F)

False

Control valves allow a hydraulic system to produce the type of ____ and level of force needed for machine operation.

Motion

The simplest of the adjustable, noncompensated flow control valves is a ____ valve

Needle

____ valves are used in hydraulic systems as both shutoff and metering devices.

Needle

The ____ method of directional control activation uses system pressure, which may be remotely sensed, to shift the valve.

Piloting

An unloading relief valve uses a(n) ____ mechanism to assist in the operation of the balancing piston in the pilot section of the valve.

Plunger

A(n) ____ flow divider valve allows pump output to be divided between system subsystems using a preselected ratio.

Proportional

The open-center, four-way directional control valve configuration connects the following ports:

Pump, reservoir, actuator A, and actuator B

Counterbalance and brake valves provide ____ control in hydraulic systems.

Retrained Movement