In hydraulic and pneumatic systems flow control valves are necessary to vary the speed of actuator. Flow control valves are placed in between Actuator and Direction Control (DC) Valve

1. Aldel Education Trust’s
ST. JOHN COLLEGE OF ENGINEERING AND MANAGEMENT, PALGHAR
(ST. JOHN POLYTECHNIC)
DEPARTMENT OF MECHANICAL ENGINEERING
SUB: INDUSTRIAL HYDRAULICS AND PNEUMATICS
TOPIC: FLOW CONTROL VALVES
PREPARED BY:-
Prof. Pranit Mehata
Lecturer, SJCEM
7972064172

2. FLOW
CONTROL
VALVE
Flow rate Q and linear velocity is related by the formula,
V=Q/A
Rpm of motor is related by the formula
n=Q/V
The velocity and rpm are directly proportional to the flow rate.
Hence by changing flow rate (Q) we can vary the speed of actuator or
motor.
This function is performed by Flow Control Valves.
Flow is controlled either by throttling or diverting it

3. TYPES OF
FLOW
CONTROL
VALVES
FCV
Pressure
Compensated FCV
Pressure and
Temperature
Compensated FCV
Non Compensated
FCV
Check Valve (NRV)

4. SYMBOLS
OFFCV

5. PRESSURE
COMPENSAT
ED FCV
In any hydraulic circuit there are slight variations in pressure of
oil. When pressure changes the rate of flow changes but many
circuits require constant flow regardless of input or output
pressure variations in the circuit then the pressure compensated
FCV is used.
Symbol of Pressure
Compensated FCV
Fig. Pressure Compensated Flow Control
Valve

6. PRESSURE &
TEMPERATUR
E
COMPENSATE
D FCV
To control the rate of flow of oil, we use flow control valve
(FCV).
By opening the FCV valve, the area of flow is increased, and
thereby increasing the rate of flow and vice versa.
But the rate of flow also depends upon pressure and
temperature of oil. Hence any change in rate of flow of oil
needs to be compensated which happens due to change in
pressure and temperature in order to maintain constant required
rate of flow.
Fig. Pressure and Temperature Compensated FCV
Fig. Symbol of Pressure and
Temperature Compensated FCV

7. NON-
COMPENSAT
ED FCV
Non compensated flow control valve that controls the flow by
throttling or restricting.
Needle valve is non-compensated valve.
These are used system pressure is relatively constant and
motoring speeds are not too critical.
The operating principle behind these valves is that flow through
an orifice remains constant if the pressure drop across it
remains the same.
 Sometimes needle valves comes with
an integral check valve for controlling
the flow in only one direction. The
check valve permits easy flow in
opposite direction without any
restrictions.
Fig. Symbol of Non-Compensated
FCV

8. CHECK
VALVES
The valve which allows flow of oil in only one direction and do
not allow reverse flow of oil is called as check valve.
As there is no return of flow hence it is also called as Non-
Return Valve (NRV).
For example, foot valve of centrifugal pumps.
There are two types of check valve
1. Simple check valve
2. Pilot operated check valve

9. SIMPLE
CHECK
VALVES
When pressurized oil comes in through port A, it will lift the
cone by overcoming the spring force and flow will start from A
to B. When flow from A stops spring will expand and cone will
block the flow. There will be no flow from port B to port A.
Fig. Simple Check Valve
Fig. Symbol of NRV

10. PILOT
OPERATED
CHECK
VALVES
When pilot signal of pressurized oil is used to control
movement of poppet in the check valve, it is called as pilot
operated check valve.
 In normal position there is no flow from(A) to (B)
because the movable valve poppet has blocked the
flow.
 When pilot signal is given through port (C). Now the
flow from (A) to (B) will start. As and when we cut-off
the pilot signal the flow from (A) and (B) will continue.