Flow Control Valves Interview Questions & Answers
- What is the function of a flow control valve
Flow control valves are used to regulate the speed of hydraulic cylinders and motors by controlling the flow rate to these actuators.
- What are the three ways of applying flow control valves
Meter in, meter out and bleed off are ways of applying flow control valves.
- What is meant when a flow control valve is said to be pressure compensated
A pressure compensated flow control valve is one which provides the desired flow rate regardless of changes in system pressure.
- What is the meter in circuit and where it is used
In meter in circuit flow control is placed in in the pressure line. Pump delivery in excess of metered amount is diverted to tank through pressure relief valve. This is used where load characteristics are constant and positive
- What is the meter out circuit and where it is used
In meter out circuit flow control is placed in in return line. This is used in machine tools like drilling in which tools is dragged suddenly at the end of drilling.
- What are the advantage of meter in circuit
- Finer speed control is possible
- Suitable for high pressure applications
- Low level of friction – longer service life of components
- What are the disadvantage of meter in circuit
- Cannot be used for hydromotor
- Pressure drops across due to throttle and hence the pressure of the fluid fed into the actuator will be less than required
- Inefficient because excess flow goes to tank
- Cannot prevent the load from running away as in the case of drilling machine
- Heat generated due to throttling is fed to the actuator.
- What are the advantage of meter out circuit
- No loss of pressure of the oil at the head end of the cylinder
- The actuator movement is more stable
- Suitable for controlling the speed of both cylinder and motor
- Heat generated during throttling goes to the tank
- Provide positive speed control of cylinder
- Pump works against the maximum pressure
- Positive speed control and stable
- What are the disadvantage of meter out circuit
- Even at no load the cylinder is subjected to maximum pressure
- Piston rod side is subjected to counter pressure which increases as area ratio increases
- The friction is higher
- If the flow control is installed after the DCV, leakage in DCV will affect the accuracy
- What are the advantage of By pass or bleed off circuit
- Efficiency is better
- Heat generated due to throttling is fed into the tank
Also Read: Safety Relief Valves Questions & Answers
- What are the disadvantage of By pass or bleed off circuit
- Positive speed control is not possible
- Not suitable for accumulator circuit
- Fluctuation of flow rate in pump affects the speed of the actuator
- Pump works against the load
- Can be used for fixed displacement pump and motor
- The motor continues to rotate even when the pump delivery is cut off from the fluid motor
- Not efficient with variable displacement pump.
- What is a modular valve and what are its benefits
Modular valve is a stack of control valve one on the other to perform a complete valve pack. This arrangement forms a compact system, thereby reducing assembly cost and eliminates much of the complex interconnection of pipe work. Modular valve saves space and easy to troubleshoot.
- What is hydraulic fuse
A hydraulic fuse prevents hydraulic pressure from exceeding an allowable valve in order to protect circuit components from damage. It is analogous to an electric fuse.
- What is the need for temperature compensation in flow control valve?
As the viscosity of oil varies with temperature, the oil becomes less viscous when temperature increases. As the less viscous fluid flow more rapidly through an orifice, the increase in temperature causes increase in flow for a valve setting, so temperature compensation is needed to offset the effect of such temperature variations.
- What is the difference between hydraulic fuse and Pressure relief valve?
Pneumatic Valves Questions & Answers
- What is the function of a pneumatic valve?
Function of pneumatic valve is to control the pressure, flow rate and direction of air flow in pneumatic circuits.
2. How do you classify pneumatic valves?
We can classify the pneumatic valves as
- Direction control valves
- Non – return valves
- Flow control valves
- Pressure control valves
3. What is the function of a Direction control valve?
Directional control valves start, stop or change the direction of flow in compressed air applications.
4. Mention the application of a 2 way, 3 way and 4 way DCV
- 2 way valves are used for ON-OFF conditions.
- Three way DCV are used to control single acting cylinders.
- Four way DCV are used to control double acting cylinders
5. What are functions of a check valve
The check valves are used to allow free flow of compressed air in only one direction and it prevents the flow of compressed air in the opposite direction. Since check valves blocks the reverse flow, they are also known as Non-return valves
6. How do you classify the DCV based on construction?
Based on construction we can classify DCV as
1) Poppet direction control valves
2) Sliding spool valves
3) Rotary spool valves
- What are shuttle valves?
Shuttle valves, also known as double check valves, are used when control is required from more than one power source. It can be used as OR gate fluid logic control valve.
8. What is a quick exhaust valve?. Mention its applications
A quick exhaust valve is a typical shuttle valve. The function of quick exhaust valve is to exhaust the cylinder air to atmosphere quickly. It is used with spring return single acting cylinder to increase the piston speed of the cylinders.
- Mention two functions of pressure control valve
- Limit the maximum system pressure
- Regulate the force or torque an actuator generates
10. Mention five control elements used in valves
Five control elements used in valves are Poppet (ball or disc), Spool, Piston, Diaphragm and sliding plates.
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