Hydraulics Exam Questions for Small Vessel Engineer

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Questions and Answers

How can pressure changes that compress the air in small air bubbles affect the system?

Produce a large amount of heat

What can 'air bubbles' and 'frothing' in the oil reservoir potentially cause?

Damage to pumps or oil boiling out of the tank

What is the importance of proper hygiene in preventing dirt contamination in the system?

To prevent dirt from affecting the system

What are the consequences of water contamination in hydraulic systems?

Corrosion, rust, seizure, blocked filters Signup and view all the answers

What actions should be taken if water contamination is suspected in the system?

Check oil regularly, trace the root cause, treat the system if possible Signup and view all the answers

Why is it important to check the oil regularly onboard and via a laboratory in hydraulic systems?

To detect contamination Signup and view all the answers

How can the 'compressibility' of air lead to loss of control in the system?

Loss of control Signup and view all the answers

What measures can be taken to prevent air contamination in hydraulic systems?

Regularly check system pipework, check oil via a laboratory Signup and view all the answers

What are THREE possible contaminants in a hydraulic system?

Dirt, water, and air are three possible contaminants in a hydraulic system. Signup and view all the answers

What are the possible causes of dirt contamination in a hydraulic system?

Possible causes of dirt contamination include improper hygiene and flushing during commissioning, poor hygiene when filling the system, and through-life wear of system components. Signup and view all the answers

What are the possible causes of water contamination in a hydraulic system?

Possible causes of water contamination include condensation, leaking coolers, and contamination through system top-up. Signup and view all the answers

What are the possible causes of air contamination in a hydraulic system?

When a liquid contains undissolved air, system components can be affected. Signup and view all the answers

How are dirt contaminants prevented from affecting a hydraulic system?

Dirt contaminants are prevented from affecting the system through proper hygiene and flushing during commissioning, use of filtration when filling the system, and maintaining system cleanliness during maintenance. Signup and view all the answers

How are water contaminants prevented from affecting a hydraulic system?

Water contaminants are prevented from affecting the system by ensuring there are no sources of water leakage, such as from coolers, and by using proper filtration during system top-up. Signup and view all the answers

How are air contaminants prevented from affecting a hydraulic system?

Air contaminants are prevented from affecting the system by ensuring the liquid does not contain undissolved air. Signup and view all the answers

What are the effects of contaminants on a hydraulic system?

Contaminants such as dirt, water, and air can negatively affect the performance and reliability of a hydraulic system by causing wear, corrosion, and other issues with system components. Signup and view all the answers

What are the five properties that enable a hydraulic fluid to fulfil its purpose?

The five properties that enable a hydraulic fluid to fulfil its purpose are:1. Viscosity2. Lubricity3. Oxidation stability4. Thermal stability5. Corrosion inhibition Signup and view all the answers

Explain why each of the properties stated in the previous question are important.

<ol> <li>Viscosity - Correct viscosity is important to ensure proper lubrication and minimized energy losses.2. Lubricity - Good lubricity prevents wear and tear on components.3. Oxidation stability - Stable against oxidation to maintain fluid properties over time.4. Thermal stability - Stable at operating temperatures to prevent degradation.5. Corrosion inhibition - Prevents corrosion of system components.</li> </ol> Signup and view all the answers

Explain the effect of increasing the flow rate of the hydraulic oil on the operation of the windlass.

Increasing the flow rate of the hydraulic oil will allow the pump to meet an increasing load from the system and develop the required pressure to maintain operation. This will enable the windlass to lift heavier loads, as the increased flow rate can match the increased demand. Signup and view all the answers

Explain the effect of changing the displacement of the hydraulic motor on the operation of the windlass.

Changing the displacement of the hydraulic motor can alter the direction of the oil flow and therefore the direction of the windlass. It can also offer proportional speed control, as the amount the swash plate is moved from the neutral position will determine the speed of the windlass. Signup and view all the answers

Explain why a full system flush and laboratory test will be needed at some stage, even if the hydraulic fluid may be used to get the system to an acceptable level for continued use.

A full system flush and laboratory test is needed at some stage to ensure the hydraulic fluid maintains its properties and the overall system is functioning optimally, even if the fluid can be used to temporarily get the system to an acceptable level for continued use. Regular maintenance and testing is required to prevent long-term issues. Signup and view all the answers

Describe the purpose of a hydraulic fluid in a system.

The purpose of a hydraulic fluid in a system is to transmit power, provide lubrication, and protect against wear and corrosion of the system components. Signup and view all the answers

Explain how changing the displacement of the motor can affect the direction and speed control of the windlass.

Changing the displacement of the hydraulic motor can alter the direction of the oil flow, and therefore the direction of the windlass. It can also offer proportional speed control, as the amount the swash plate is moved from the neutral position will determine the speed of the windlass. Signup and view all the answers

Describe the effect of increasing the flow rate of the hydraulic oil on the load-carrying capacity of the windlass.

If the displacement of a hydraulic motor increases while the oil flow rate remains constant, what happens to the motor's speed and torque?

The speed will decrease, and the torque will increase. Signup and view all the answers

Describe the working principle of a variable delivery pump, such as the swash plate design, for controlling the speed of a hydraulic motor.

The angle of the swash plate alters the displacement of the pump, which in turn changes the flow rate of fluid through the system, thereby controlling the motor speed. Signup and view all the answers

How do flow control valves, such as variable orifices, control the speed of a hydraulic motor?

Flow control valves, or variable orifices, control the rate of flow through to the motor, thereby regulating its speed. Signup and view all the answers

Explain the working principle of an air flow control valve for controlling the speed of a hydraulic motor.

An air flow control valve uses control air to pneumatically operate a flow valve, which in turn regulates the flow rate to the hydraulic motor, thereby controlling its speed. Signup and view all the answers

How can the use of a frequency drive for the electrical motor driving the pump help in controlling the speed of a hydraulic motor?

Using a frequency drive for the electrical motor driving the pump allows for very fine control over the pump's speed, which in turn affects the flow rate and speed of the hydraulic motor. Signup and view all the answers

What is the typical mark distribution for a 10-mark question involving sketches and descriptions?

For a 10-mark question, it is typical to allocate 4 marks for the diagram and 6 marks for the description. Signup and view all the answers

In the context of the given text, what does the term "orifice" refer to?

The term "orifice" refers to a variable opening or restriction in a flow control valve that regulates the flow rate of hydraulic fluid. Signup and view all the answers

What is the purpose of the hydraulic cylinder shown in Figure Q4?

The hydraulic cylinder shown in Figure Q4 operates a safety barrier. Signup and view all the answers

What is the purpose of check valve 'D' in the hydraulic system described?

Check valve 'D' allows the supply to fill the right side of the cylinder. Signup and view all the answers

In the cross-over position (6), how does the fluid flow through valves 'A', 'B', and 'C'?

The supply enters from the right port of valve 'A', leaves through the left port, enters the bottom of valve 'B', and opens check valve 'D' via the pilot line. Signup and view all the answers

What is the relationship between the force exerted on the piston 'E' and the pressure and area of the cylinder?

The force exerted on the piston is equal to the pressure multiplied by the area: $Force = Pressure \times Area$. Signup and view all the answers

Why does the piston 'E' move to the right in the cross-over position?

The piston 'E' moves to the right because the force on the left side (greater area) is higher than the force on the right side. Signup and view all the answers

What is the purpose of the ports in the valves in controlling the speed of the piston 'E'?

The size of the ports in the valves roughly controls the speed of the piston 'E' by regulating the flow of fluid. Signup and view all the answers

How does the fluid flow through the system when the piston 'E' moves to the left?

When the piston 'E' moves to the left, the supply fills the right side of the cylinder via check valve 'D', and the left side of the cylinder is drained back to the tank through the left port. Signup and view all the answers

What is the purpose of valve 'B' in the hydraulic system?

Valve 'B' is a 3-position valve that, when moved to the right in the cross-over position, allows the supply to be fed to the bottom of valve 'C' and opens check valve 'D' through the pilot line. Signup and view all the answers

How does the controlled movement of the piston 'E' relate to the difference in forces on the left and right sides?

The controlled movement of the piston 'E' is due to the difference in forces on the left and right sides, where the force on the left (greater area) is higher than the force on the right. Signup and view all the answers

Study Notes

Hydraulic Motor Speed Control

If the hydraulic oil flow rate remains constant and the displacement of the motor increases, the speed will decrease, and the torque will increase.
Conversely, if the displacement of the motor decreases, the speed will increase, and the torque will decrease.

Methods for Controlling Hydraulic Motor Speed

Variable delivery pump: adjusting the swash plate angle alters the direction and speed of the motor due to changes in fluid flow.
Flow control valves: variable orifices control the flow rate to the motor, affecting speed.
Air flow control valves: pneumatically operated valves control flow rate, similar to flow control valves.
Frequency drive for electrical motor driving the pump: allows for fine control of speed.

Hydraulic System Contamination

Contaminants: dirt, water, and air.
Dirt: caused by improper hygiene, poor flushing, and wear from pipework and system components.
Water: present from condensation, leaking coolers, and contamination during system top-up.
Air: undissolved air in the liquid can affect system components.

Preventing Contamination

Dirt: maintain proper hygiene, use filtration during filling, and regular system checks.
Water: check oil regularly, take immediate action to trace the source, and treat or flush the system as needed.
Air: regular system checks, including pipework and oil analysis, to prevent air bubbles and frothing.

Hydraulic System Properties

Five properties that enable a hydraulic fluid to fulfill its purpose:
- Viscosity
- Compressibility
- Lubricity
- Corrosion protection
- Thermal stability
Each property is important for the fluid to function correctly and maintain system performance.

Effect of Changing Flow Rate and Displacement on a Hydraulic System

Increasing the flow rate of the pump: meets increasing load demands, maintains pressure, and changes speed.
Increasing the displacement of the motor: alters the direction of oil flow, offers proportional speed control, and changes speed.

Hydraulic System Components and Operation

Hydraulic cylinder: can operate a safety barrier, affected by pressure changes and air bubbles.
Windlass: hydraulically operated by a variable displacement motor, affected by changes in flow rate and displacement.
Valves: 3-position valves, check valves, and pilot lines control fluid flow and pressure in the system.

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Description

Test your knowledge on hydraulic systems in small vessel engineering with past questions about contaminants, causes, and prevention methods. This quiz includes questions similar to those found in the May 2018 exam paper.

Small Vessel Engineering - Hydraulics & Pneumatics Past Questions