directional control valves

A. DIRECTIONAL CONTROL VALVES

DIRECTIONAL CONTROL VALVES

1. What are Directional Control Valves ?

• As the name suggests, the function of a directional control valve (DCV) is to control the direction of flow in a hydraulic circuit.

• In other words, directional control valves (DCVs) regulate the direction in which the fluid flows in a hydraulic circuit.

• In addition to controlling direction of actuator motion, the directional valves are also used (i) to select alternate control circuits, and (ii) to perform logic control functions. 

• These valves are not intended to change the rate of flow of fluid; but they are either completely open or completely closed. They can be actuated to switch the fluid flow direction by various actuating means such as electrical, mechanical or fluid pressure signals. This results in corresponding connection or disruption of flow between various port openings.

2. Classification of Directional Control Valves

The directional control valves can be classified in many different ways.

I. The directional control valves are basically classified, according to the construction, into three groups, as :

1. Poppet (or seat) valves,

2. Sliding spool valves, and

3. Rotary spool valves.

II. Based on the number of ports' present, the directional control valves may be

classified as :

(i) Two way valves,

(ii) Three way valves, and

(iii) Four way valves.

III. Based on the mode of actuation, the directional control valves can be classified as : (i) Manually operated directional valves,

(ii) Mechanically operated directional valves,

(iii) Solenoid operated directional valves, and

(iv) Pilot operated directional valves.

IV. However, for our study we can classify the directional control valves into three:

1. Check valves,

2. Position valves, and

3. Shuttle valves.

Now, we shall discuss the construction and operation of some of the important directional control valves, in the following sections.