Hydraulics Interview Questions and Answers in 2025 (100+ Q&A)

Ques:- How to overhaul control valves.what are the proper procedures.

Right Answer:
1. **Preparation**: Isolate the valve from the system and depressurize it. Ensure safety protocols are followed.

2. **Disassembly**: Remove the valve from its piping connections. Take off any external accessories like actuators or positioners.

3. **Inspection**: Check all components for wear, damage, or corrosion. Pay special attention to the seat, plug, and seals.

4. **Cleaning**: Clean all parts using appropriate solvents and tools. Remove any debris or buildup.

5. **Replacement**: Replace worn or damaged parts with new ones, including seals, gaskets, and any other necessary components.

6. **Reassembly**: Reassemble the valve carefully, ensuring all components are correctly aligned and tightened to specifications.

7. **Testing**: Conduct functional tests to ensure the valve operates correctly. Check for leaks and proper movement.

8. **Reinstallation**: Reinstall the valve in the system and reconnect all piping and accessories.

9. **

Hydraulics Quality Engineer - Piping

Ques:- PLEASE TELL ME THE BASIC FOR INSTRUMENTATION WHICH IS APPLIED FOR CALIBRATION AND FOR ALL?

Asked In :- Shree Cement,

Right Answer:
The basic principles for instrumentation applied for calibration include:

1. **Accuracy**: Ensuring the instrument measures close to the true value.
2. **Precision**: Consistency of measurements under the same conditions.
3. **Linearity**: The instrument's output should be directly proportional to the input across its range.
4. **Sensitivity**: The ability of the instrument to detect small changes in the measured variable.
5. **Hysteresis**: The difference in readings when the input is increasing versus decreasing.
6. **Repeatability**: The instrument's ability to produce the same output under the same conditions over multiple trials.
7. **Drift**: Monitoring changes in instrument readings over time without any change in the input.

These principles ensure reliable and accurate measurements in calibration processes.

Hydraulics Quality Engineer - Piping

Ques:- What is viscosity of fluid and what is the viscosity ofgrease and lubricating oil

Asked In :- PVC,

Right Answer:
Viscosity is a measure of a fluid's resistance to flow. It indicates how thick or thin a fluid is.

- The viscosity of grease typically ranges from 100,000 to 1,000,000 cP (centipoise).
- The viscosity of lubricating oil generally ranges from 10 to 100 cP, depending on the specific type and temperature.

Hydraulics Quality Engineer - Piping

Ques:- What is the control valve?how many types of control valves are there

Asked In :- Princess Yachts, boskalis, jbm,

Right Answer:
A control valve is a device that regulates the flow of fluids by varying the size of the flow passage. There are several types of control valves, including:

1. Globe Valves
2. Ball Valves
3. Butterfly Valves
4. Gate Valves
5. Check Valves
6. Diaphragm Valves
7. Pinch Valves

Each type serves different applications and flow control needs.

Hydraulics Quality Engineer - Piping

Ques:- IF THE RANGE FOR FLOW IS -35 TO 125 WHAT WILL BE THE SPAN FOR ABSOLUTE AND FOR NORMAL?

Asked In :- vikram sarabhai space centre (vssc), burn manufacturing usa llc,

Right Answer:
For absolute pressure, the span is 125 - (-35) = 160. For normal pressure, the span is 125 - 0 = 125.

Hydraulics Quality Engineer - Piping

Ques:- Why we use 0.2 to 1.0 kg/cm2 output in control valve

Asked In :- burns & mcdonnell,

Right Answer:
We use 0.2 to 1.0 kg/cm² output in control valves to ensure precise control of fluid flow and pressure, allowing for effective regulation in various applications while maintaining system stability and responsiveness.

Hydraulics Quality Engineer - Piping

Ques:- Give five boiler mounting valves.

Asked In :-

Right Answer:
1. Safety Valve
2. Blow-off Valve
3. Feed Check Valve
4. Pressure Relief Valve
5. Water Level Gauge Valve

Hydraulics Quality Engineer - Piping

Ques:- HOW TO CALIBRATE TEMPERATURE TRANSMITTER?

Asked In :- Fischer Jordan, apm terminals,

Right Answer:
To calibrate a temperature transmitter, follow these steps:

1. **Prepare Equipment**: Gather a calibrated temperature source (like a dry block calibrator) and a multimeter or calibration device.

2. **Connect the Transmitter**: Connect the temperature transmitter to the calibration device and ensure it is powered on.

3. **Set Reference Temperature**: Set the temperature source to a known reference point (e.g., 0°C, 100°C).

4. **Record Output**: Allow the transmitter to stabilize and record the output signal (e.g., 4-20 mA) from the transmitter.

5. **Compare Values**: Compare the output signal with the expected value for the set temperature.

6. **Adjust if Necessary**: If there is a discrepancy, adjust the transmitter’s calibration settings according to the manufacturer’s instructions.

7. **Repeat**: Repeat the process for multiple temperature points to ensure accuracy across the range.

8. **Document Results**: Document all

Hydraulics Quality Engineer - Piping

Ques:- What type of pump

Asked In :-

Right Answer:
The type of pump used in hydraulics is typically a centrifugal pump or a positive displacement pump.

Hydraulics Quality Engineer - Piping

Ques:- Foe selecting control valve if i have the min,normal & maxdata of flow rate,inlet pressure& outlet pressure,inlettem.&density than how can i assure that these data arecorrect,pl. let me know if therew there is any method tocheck it.& also how we assure that the Cv we get from thisdata is suitable for valve for controlling require flow.

Asked In :- Mahle Filter Systems, TTI Techtronic Industries, textron aviation,

Right Answer:
To ensure the accuracy of your flow rate, inlet pressure, outlet pressure, inlet temperature, and density data, you can follow these steps:

1. **Validation**: Cross-check the data against manufacturer specifications, industry standards, and historical data from similar systems.
2. **Measurement**: Use calibrated instruments to measure flow rates, pressures, and temperatures directly in the system.
3. **Simulation**: Utilize hydraulic simulation software to model the system and verify that the input data produces expected results.

To confirm that the calculated Cv (flow coefficient) is suitable for the valve:

1. **Cv Calculation**: Use the formula ( Cv = Q / sqrt{(ΔP / SG)} ), where Q is the flow rate, ΔP is the pressure drop across the valve, and SG is the specific gravity of the fluid.
2. **Comparison**: Compare the calculated Cv with the Cv values provided by valve manufacturers for the selected valve size and type.
3. **Check Operating Range

Hydraulics Quality Engineer - Piping

Ques:- What is the function of neck ring in the centrifugalpump?

Asked In :-

Right Answer:
The neck ring in a centrifugal pump helps to minimize the recirculation of fluid within the pump casing, improving efficiency and maintaining a stable flow by directing the fluid towards the impeller.

Hydraulics Quality Engineer - Piping

Ques:- HOW TO CALIBRATE CAPILLARY TYPE LT?

Asked In :-

Right Answer:
To calibrate a capillary type level transmitter (LT), follow these steps:

1. **Prepare the Calibration Setup**: Ensure you have a reference level gauge or a calibrated liquid level source.

2. **Zero Calibration**: Fill the tank or calibration vessel to the zero level. Adjust the transmitter output to match the zero reference point.

3. **Span Calibration**: Fill the tank to the known span level (maximum level). Adjust the transmitter output to match the span reference point.

4. **Verify Linearity**: Check the output at several intermediate levels to ensure linearity. Adjust if necessary.

5. **Document Calibration**: Record all readings and adjustments made during the calibration process for quality assurance.

6. **Final Check**: After calibration, perform a final check by comparing the transmitter readings with the reference gauge at various levels to confirm accuracy.

Ensure to follow manufacturer guidelines and safety protocols throughout the process.

Hydraulics Quality Engineer - Piping

Ques:- How can we caliberate interface level troll

Asked In :-

Right Answer:
To calibrate an interface level troll, follow these steps:

1. **Prepare the Equipment**: Ensure the interface level troll is installed correctly and connected to the control system.

2. **Use Reference Standards**: Obtain a known reference liquid with a specific gravity that is different from the other liquid in the tank.

3. **Fill the Tank**: Fill the tank with the reference liquid to a known level.

4. **Adjust the Calibration**: Access the calibration settings on the interface level troll and adjust the output signal to match the known level of the reference liquid.

5. **Repeat for Accuracy**: Repeat the process with different levels of the reference liquid to ensure accuracy across the measuring range.

6. **Document the Calibration**: Record the calibration results and any adjustments made for future reference.

7. **Verify Functionality**: After calibration, verify the functionality by testing with actual interface levels in the tank.

Hydraulics Marine Engineer

Ques:- I saw one P&ID 6″ control valve has been connected with 8″ process line, and 2″ valve also connected in parallel with 6″ valve. why the 2″ valve connected in parallel, Is there any technical reason. please clarify. With Regards-Kittu

Asked In :-

Right Answer:
The 2" valve connected in parallel with the 6" control valve allows for better flow control and flexibility in the system. It can help manage lower flow rates more efficiently, provide redundancy, and ensure that the system can maintain operation even if one valve is closed or fails.

Hydraulics Quality Engineer - Piping

Ques:- Safety valve calculation?

Asked In :- Sharda Motor industries, CR Asia Group, hitachi rail europe,

Right Answer:
To calculate the size of a safety valve, use the formula:

[
A = frac{Q}{C_d cdot sqrt{2 cdot Delta P / rho}}
]

Where:
- ( A ) = required valve area (in square inches or square centimeters)
- ( Q ) = flow rate (in GPM or L/min)
- ( C_d ) = discharge coefficient (typically between 0.6 and 0.9)
- ( Delta P ) = pressure drop across the valve (in psi or bar)
- ( rho ) = density of the fluid (in lb/ft³ or kg/m³)

Ensure to convert units appropriately and consider the specific application and fluid properties for accurate results.

Hydraulics

Ques:- Construction of hydro electric power project as per drawing and specification.

Asked In :- Trane Technologies,

Right Answer:
The construction of a hydroelectric power project involves the following key steps:

1. **Site Selection**: Choose a suitable location with adequate water flow and elevation.
2. **Design and Planning**: Create detailed designs and specifications for the dam, turbine, and other infrastructure.
3. **Environmental Assessment**: Conduct studies to evaluate the environmental impact and obtain necessary permits.
4. **Civil Works**: Construct the dam, spillway, intake structure, and power house according to the specifications.
5. **Installation of Equipment**: Install turbines, generators, and electrical systems.
6. **Water Management**: Ensure proper water flow management for optimal energy production.
7. **Testing and Commissioning**: Test all systems and ensure they meet safety and performance standards before going operational.
8. **Maintenance Plan**: Establish a plan for ongoing maintenance and monitoring of the facility.

Hydraulics

Ques:- What is fluid mechanics

Asked In :- GSPC Group, E-T-A,

Right Answer:
Fluid mechanics is the branch of physics that studies the behavior of fluids (liquids and gases) at rest and in motion, including the forces acting on them and the effects of those forces.

Hydraulics Quality Engineer - Piping

Ques:- HOW TO CALIBRATE LEVEL TROLL AND HOW TO CONNECT?

Asked In :- fme, etihad rail, kiewit corporation, apa engineering pvt ltd,

Right Answer:
To calibrate a level troll, follow these steps:

1. **Preparation**: Ensure the level troll is installed correctly in the piping system and is powered on.

2. **Zero Calibration**: Fill the tank or vessel to the lowest level (zero point). Adjust the zero setting on the level troll to match the actual level reading.

3. **Span Calibration**: Fill the tank to the highest level (span point). Adjust the span setting on the level troll to match the actual level reading.

4. **Verification**: Check the readings at various levels between zero and span to ensure accuracy. Make further adjustments if necessary.

5. **Connection**: Connect the level troll to the control system using the appropriate wiring (usually 4-20 mA or digital signals) as per the manufacturer's instructions.

6. **Testing**: After calibration, test the system to confirm that the level troll is providing accurate readings.

Ensure to follow safety protocols during the calibration process.

Hydraulics

Ques:- What are the differences between pneumatics and hydraulics?

Asked In :-

Right Answer:
Pneumatics uses compressed air or gas to transmit power, while hydraulics uses liquid, typically oil, to transmit power. Pneumatics is generally faster and cleaner, but hydraulics can provide more force and is better for heavy loads.

Hydraulics Marine Engineer

Ques:- What is mass flow meter principal?

Asked In :- columbia shipmanagement, daikin ac,

Right Answer:
A mass flow meter measures the mass of a fluid flowing through it, typically using principles such as the Coriolis effect or thermal dispersion. It calculates mass flow rate by detecting changes in the fluid's properties as it moves through the meter.

Hydraulics is an applied science and technology concerned with the mechanical properties and use of liquids in motion or under pressure. The fundamental principle governing all hydraulic systems is Pascal’s Law, which states that a pressure change at any point in a confined incompressible fluid is transmitted equally throughout the fluid. This principle allows a small force applied over a small area to be converted into a much larger force over a larger area, a concept known as force multiplication.

A typical hydraulic system consists of several key components working in concert: a reservoir to hold the hydraulic fluid, a pump to pressurize the fluid and convert mechanical energy into fluid power, control valves to direct the flow of the fluid, and an actuator (such as a cylinder or a motor) that converts the fluid power back into mechanical force or motion to do the work.

Hydraulics is a cornerstone of modern engineering and has a vast array of applications across numerous industries. In construction, hydraulic systems power heavy machinery like excavators, cranes, and bulldozers, enabling them to lift and move massive loads with precision. The automotive industry utilizes hydraulics for braking systems, power steering, and car lifts. In manufacturing, hydraulic presses are used to shape and form metal, while in aviation, hydraulics are essential for operating landing gear, flaps, and other flight control surfaces. The power and reliability of hydraulic systems make them indispensable for any application requiring high force, high precision, and controlled movement.

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