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Flashcards in Directional Control Valves Deck (18)
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1

What is the major downside of rotary spool valves

High internal leakage, this limits there use to low pressure and flow applications

2

Spool housing are usually made of what

Aluminum
Fine grain cast iron

3

What must be replaced if a spool is damaged

The spool and housing must be replaced as a matched set

4

What is the function of the groves in the valve spool lands

Trap oil for better lube
Allow pressurized oil to act around the full circumference of the valve land centring it in the bore, reducing binding against wall

5

What are the 2 styles of feathering notch

C notch
V notch

6

Diverter valve

2 position, 3 way valve
Has P, A, B ports but no T ports

7

Tandem center

Open center, closed port

8

Motor spool / float center

Open center, open port

9

motor or float spool

Closed center, open port

10

Detents

Devices used to hold a directional control valve in position

11

Mechanical detent

Springs hold a balls into grooves in the spool
Represented on a schematic by v notches in spool on end

12

Electromagnetic detent

Holds a spool in a set position until a pre-determined height is reached (proximity switch on a loader)

13

What other control valves are commonly found inside of the directional control valve

Relief valves - system and circuit
Load check valves
Anti-cavitation check valves
Flow compensators

14

Load Check

Spring loaded check placed between the pump port and the DCV spool. Stops oil from flowing backward when the DCV spool is moved and the pressure in the work port is greater then the current pump pressure

15

Anti-cavitation Check

Prevent void from forming in a actuator when the load drives the actuator faster then the pump can supply it.
Allows oil to flow from tank line to work port when pressure in work port falls below pressure in tank line

16

DCV flow compensator

A compensator is placed ahead of the DCV to ensure that there is a constant pressure drop across the DCV spool, this results in the same speeds regardless of load

17

What are the 2 ways multiple control valves are usually constructed

Unibody
Valve stacks

18

What is the advantage of a mono-block design DCV

Is compact and has fewer point for external leakage