BCIT: Millwright Level 3 (Hydraulics: Accessories 2)

What is the main hazard to always be aware of when you are working on hydraulic systems?

The main hazard to always be aware of when working on hydraulic systems is pressure.

What hazard can exist after a hydraulic system has been locked out?

After a hydraulic system has been locked out, there is still a hazard that it could be pressurized again.

What is the safety reason for taking time to completely understand a hydraulic system before you begin work on it?

Taking time to completely understand a hydraulic system ensures that you know how the system operates and can work safely.

Does a hydraulic system develop power?

A hydraulic system does not develop power; it transmits power.

List the five (5) main parts of a hydraulic system.

The five main parts of a hydraulic system are the pump, conductors, valves, tank, and actuators.

What is the first main valve after the pump in a hydraulic system?

The first main valve after the pump in a hydraulic system is the pressure relief valve (PRV).

What are the three (3) functions of a maximum pressure relief valve?

A maximum pressure relief valve functions to protect against overload, maintain the set pressure, and provide a bypass for excess fluid.

Is a pressure-reducing valve normally open or closed?

A pressure-reducing valve is normally open.

What is the purpose of a sequence valve?

The purpose of a sequence valve is to ensure that one actuator opens only after another actuator has opened.

What valve would you use to prevent the uncontrolled fall of a load due to gravity?

A counterbalance valve is used to prevent the uncontrolled fall of a load due to gravity.

Why is it important to attach an external drain to a sequence valve or to a pressure-reducing valve?

An external drain is important to prevent valve lock-up due to the load.

What is the purpose of a flow control?

The purpose of a flow control is to regulate the speed of an actuator.

Name three (3) types of flow controls.

The three types of flow controls are meter-in, meter-out, and bleed-off.

Which type of flow control is the most energy efficient?

Bleed-off flow control is the most energy efficient.

What is the purpose of cross port relief valves on a hydraulic motor?

Cross port relief valves protect the pump and motor from shock loads.

What term is used for the output component of a hydraulic system?

The output component of a hydraulic system is called an actuator.

What three (3) factors do the valves control in a hydraulic system?

Valves control the direction, speed, and force of hydraulic actuators.

What is an important reason for using electronic controls?

Electronic controls are used to achieve accurate control of hydraulic functions.

What are the five (5) main components in a hydraulic system?

The five main components in a hydraulic system are the reservoir, pump, actuator, valves, and conductors.

Name three (3) advantages of hydraulics.

Hydraulic systems provide power transmission, compact design, and accurate control of movement.

Name three (3) disadvantages of hydraulics.

Hydraulic systems can be expensive, heavy, and operate at high pressure.

Draw a schematic diagram using standard hydraulic graphics to show a circuit that can extend and retract a cylinder and control its speed.

(Refer to Notes)

Name three (3) types of conductors used in hydraulics.

Three types of conductors used in hydraulics are tube, hose, and pipe.

What safety function does a maximum safety relief valve perform?

A maximum safety relief valve ensures the system pressure does not exceed the set limit.

What valve controls the maximum force at which an actuator can operate?

The maximum pressure relief valve (PRV) controls the maximum actuator force.

What valve controls the speed of the actuator?

The speed of an actuator is controlled by a flow control valve (FCV).

What is a typical maximum pressure that you can expect in a hydraulic system?

A typical maximum pressure in a hydraulic system is 2900 psi (20,000 kPa).

What valve reduces the output force of a cylinder below the force it would have at the maximum pressure relief valve setting?

A pressure-reducing valve (PRV) reduces the output force of a cylinder.

Draw a two-cylinder circuit to have one cylinder operating with reduced force and the other cylinder to have speed control.

(Refer to Notes)

In what direction should the V-shaped seat point when it is used in a reverse flow bypass for a pressure-reducing valve?

The V-shaped seat should point in the same direction as the flow.

Should the inlet of a sequence valve be connected to the first cylinder that is to operate or to the second cylinder in the sequence?

The inlet of a sequence valve should be connected to the first cylinder that is to operate.

What would happen if you did not connect the drain line to a pressure-reducing valve?

If the drain line is not connected, the pressure-reducing valve can get stuck open.

Draw a sequence circuit.

(Refer to Notes)

Draw a circuit to control the speed of extension on a cylinder, using meter-out control.

(Refer to Notes)

Name three (3) types of schematic circuits used in hydraulic system design.

Schematic circuits include a cylinder extension/retraction circuit, a sequence circuit, and a speed-control circuit with meter-out control.