Pneumatic Components, Vacuum Systems and Circuits

Introduction

Pneumatics uses compressed air to transmit and control power. In machine technology, pneumatic systems are valued for their cleanliness, low mass, rapid response, simple overload behavior, and suitability for repetitive automation. Their limitations include compressibility, noise, energy inefficiency, leakage, and comparatively modest force capability. Effective pneumatic design therefore requires more than selecting a cylinder: the designer must match the actuator, valve, air preparation equipment, control logic, tubing, sensing method, and safety provisions to the complete machine task.

This chapter develops the principles needed to select pneumatic cylinders, rotary actuators, grippers, valves, and vacuum devices, and to design circuits for timing, logic, sequencing, speed control, and material handling. The emphasis is on engineering decisions rather than symbolic circuit drawing alone.

Learning Objectives

By the end of this chapter, the reader should be able to:

1. Explain the construction, operation, and selection criteria of common pneumatic actuators.
2. Select directional, flow-control, pressure-control, and logic valves for specified functions.
3. Calculate cylinder force, air consumption, and approximate cycle requirements.
4. Explain vacuum generation, gripping principles, and vacuum-system limitations.
5. Design pneumatic circuits using timing, signal logic, sequencing, and speed control.
6. Evaluate safety, efficiency, reliability, and maintainability in pneumatic installations.
7. Diagnose common faults in pneumatic material-handling systems.

1. Pneumatic System Architecture

A typical installation consists of six functional layers:

A design should begin with the required mechanical task: load, direction, stroke or angle, speed, cycle frequency, accuracy, environment, and fail-safe behavior. Component selection follows from these requirements.

Compressed air is normally specified by gauge pressure, while thermodynamic relationships use absolute pressure. The conversion is:

where p_abs is absolute pressure, p_g is gauge pressure, and p_atm is atmospheric pressure. At sea level, atmospheric pressure is approximately 101 kPa, although the actual value varies with altitude and weather.

2. Air Preparation and Distribution

2.1 Filters, regulators, and lubricators

A filter removes liquid water, rust, pipe scale, and solid particles. A regulator maintains a controlled downstream pressure despite moderate changes in upstream pressure and flow. A lubricator introduces oil mist where a component manufacturer permits it. Modern valves and cylinders are often factory-lubricated and designed for oil-free operation; unnecessary oil can damage seals, contaminate products, and impair sensors. Lubrication must therefore follow the manufacturer’s specification.

A filter-regulator-lubricator assembly is commonly called an FRL unit, although many installations use only a filter and regulator. The regulator should be located close enough to the actuator to limit pressure variation, and the filter should be sized for the required flow without excessive pressure drop.

2.2 Receivers, piping, and losses

An air receiver reduces compressor cycling, absorbs short demand peaks, and helps remove condensate. Distribution piping should be sized to limit pressure drop. Long, narrow tubes and restrictive fittings can cause a cylinder to move slowly even when the regulator gauge shows adequate pressure. Ring-main systems often provide more uniform pressure than long dead-end branches.

Water management is essential. Condensation promotes corrosion, freezes in cold conditions, and damages valves. Drains, dryers, correct pipe slope, and suitable filtration are part of pneumatic design, not optional accessories.

3. Pneumatic Cylinders

3.1 Construction and types

A cylinder converts pressure into linear force. Its principal parts are the barrel, piston, rod, seals, end covers, guide elements, and cushioning devices.

A single-acting cylinder uses compressed air for motion in one direction and a spring or external force for return. It is suitable for clamping, ejecting, marking, and short-stroke operations. A double-acting cylinder uses compressed air alternately on both sides of the piston, allowing controlled extension and retraction.

Other useful types include:

• Rodless cylinders, which provide long travel without a projecting rod.
• Guided cylinders, which resist side loads and prevent rod rotation.
• Tandem cylinders, which combine piston areas to increase force.
• Compact cylinders, used where installation space is limited.
• Multi-position cylinders, which provide selected intermediate positions.
• Telescopic cylinders, which achieve long strokes in a short retracted length.

A standard cylinder should not be used to absorb significant side load. Side loading causes rod bending, seal wear, and bearing failure. Use a guided actuator or an external linear guide when the load is not perfectly aligned.

3.2 Cylinder force

For an ideal extension stroke of a double-acting cylinder:

For retraction, the rod occupies part of the piston area:

where F_ext and F_ret are ideal extension and retraction forces in newtons, p is gauge pressure in pascals, A_p is piston area in square metres, and A_r is rod cross-sectional area in square metres. These equations assume static conditions and neglect friction, pressure losses, acceleration, and external resistance. Actual available force is lower.

The piston and rod areas are:

where D is piston diameter and d is rod diameter. A design commonly applies a utilization factor to account for friction and dynamic effects:

where η is an experimentally or manufacturer-established efficiency factor, normally less than 1, and A is the effective area for the stroke.

Worked Example 1: Cylinder selection

A cylinder must provide 900 N during extension at a regulated gauge pressure of 600 kPa. Assume an available-force factor of 0.85. The required piston area is:

The corresponding bore is:

Thus a nominal 50 mm bore is the minimum practical standard size. The designer should verify the manufacturer’s force table, rod strength, mounting arrangement, buckling risk, and required speed before final approval. A cylinder should not be selected solely from the ideal force equation.

3.3 Stroke, speed, and cushioning

Stroke is the required travel plus an allowance for adjustment where appropriate. Excessive stroke increases bending risk and air consumption. Cylinder speed depends on air flow, load, valve capacity, tube restrictions, and cushioning. End-of-stroke cushions restrict exhaust air near the end of travel, reducing impact. Adjustable cushions are useful when load and speed vary, but incorrect adjustment can cause sluggish motion or hard impact.

For a cylinder moving at average speed v, the approximate volumetric flow at cylinder conditions is:

where Q_c is flow in cubic metres per second and A is the relevant effective area. This is a cylinder-side volume flow, not necessarily the free-air flow reported by a compressor catalogue.

The approximate free-air volume for one stroke can be estimated, assuming isothermal behavior and negligible pressure losses, by:

where V_c is the swept cylinder volume at cylinder pressure, p_abs is absolute cylinder pressure, and p_atm is atmospheric pressure. For a double-acting cylinder, extension and retraction volumes must be calculated separately because their effective areas differ. Real consumption also depends on dead volume, valve cavities, leakage, temperature, and operating transients.

4. Rotary Actuators and Grippers

4.1 Rotary actuators

Pneumatic rotary actuators convert air pressure into angular motion. Vane actuators provide compact limited-angle rotation but may be sensitive to seal wear and pressure imbalance. Rack-and-pinion actuators provide positive torque transmission and are widely used for quarter-turn movements. Rotary actuators are specified by torque, angle, rotation speed, allowable inertia, shaft loading, and end-position adjustment.

For an actuator producing torque T against a resisting torque T_L, the design must satisfy:

where S_f is a selected safety factor. The appropriate value depends on load uncertainty, acceleration, friction, orientation, and manufacturer guidance. For rotational acceleration, the approximate dynamic relation is:

where T_net is net torque, J is mass moment of inertia, and α is angular acceleration. This relation is useful when rapid indexing is required; the actuator’s catalogue torque alone may be insufficient if the load has high inertia.

4.2 Pneumatic grippers

Grippers hold and release workpieces. Parallel grippers move jaws linearly and are generally easy to align. Angular grippers pivot around a pin and can provide useful clearance during opening. Three-finger grippers are suitable for approximately cylindrical parts. Magnetic and vacuum grippers are alternatives for ferromagnetic or smooth, nonporous materials.

Gripper selection considers:

• Part mass, shape, surface, and temperature.
• External or internal gripping method.
• Jaw stroke and required opening clearance.
• Gripping force and safety factor.
• Effects of acceleration and vibration.
• Jaw friction, contact geometry, and allowable part deformation.
• Confirmation sensors and behavior after air failure.

The holding force must exceed the force caused by gravity and machine acceleration. For friction gripping, a simplified condition is:

where μ is the coefficient of friction at each contact, F_g is gripping force at each jaw, m is part mass, g is gravitational acceleration, a is the relevant linear acceleration, and S_f is a safety factor. This model assumes two equal friction contacts and no mechanical interlock. Actual catalogued gripping force must be interpreted according to jaw position and pressure.

A spring-closing gripper can retain a part when air is lost, but spring force may be insufficient for all operating conditions. A pilot-operated check valve or dedicated safety gripper may be required where dropped loads create danger.

5. Valves and Pneumatic Logic

5.1 Directional control valves

A directional valve controls the path of air. Its designation gives the number of ports and positions; for example, a 5/2 valve has five ports and two spool positions. A 3/2 valve is common for single-acting cylinders and pilot signals. Valves may be manually, mechanically, pneumatically, or electrically actuated.

Important characteristics include nominal port size, flow capacity, response time, operating pressure, leakage, electrical voltage, and return method. A monostable valve returns to its normal position by spring force or another bias. A bistable valve remains in its last commanded position until an opposite signal is applied.

Valve symbols describe function, not physical appearance. The designer must still check whether the selected valve can deliver the required flow at the available pressure.

5.2 Flow-control valves

A one-way flow-control valve combines an adjustable restrictor with a check valve. It permits free flow in one direction and restricted flow in the other. For most cylinder applications, meter-out control is preferred: exhaust air is restricted while inlet air is relatively free. This helps prevent a load from running away because the trapped exhaust air provides back pressure.

Meter-in control can be effective for resistive loads and some special applications, but it may produce unstable motion with overrunning loads. Needle valves should not be treated as precision speed controllers when pressure and load vary widely.

5.3 Pressure-control and logic valves

Pressure regulators set operating pressure. Pressure relief valves protect against excessive pressure, although the compressor system and machine circuit may use separate protection devices. Pressure sequence valves generate a pneumatic signal when a set pressure is reached, useful for clamping confirmation or force-dependent sequencing.

Shuttle valves implement an OR function: an output is available if either input is pressurized. Two-pressure valves implement an AND function: an output occurs only when both inputs are present. These pneumatic logic elements can reduce electrical control requirements, but they must be considered in relation to leakage, response time, and signal strength.

5.4 Timing valves and sensors

A time-delay valve produces a signal after a preset delay or removes it after a delay, depending on its configuration. Pneumatic timers are useful in simple environments but may be affected by pressure, temperature, and flow adjustment. Electronic timers and programmable controllers usually provide more repeatable timing.

Position sensors include mechanical roller switches, magnetic reed switches, solid-state sensors, and inductive or proximity sensors. A cylinder-end sensor confirms position; it does not necessarily confirm that the workpiece is correctly clamped. Process confirmation may require a pressure switch, vacuum switch, part-present sensor, or force measurement.

6. Vacuum Systems

6.1 Principles of vacuum gripping

A vacuum gripper uses atmospheric pressure acting on the outside of a suction cup to create a net holding force. The ideal force is:

where F_v is ideal holding force, Δp is the pressure difference between atmosphere and the cup, and A_eff is the effective sealed area. If vacuum is stated as a positive percentage of atmospheric pressure, the pressure difference must be converted to pascals before calculating force.

Worked Example 2: Vacuum cup estimate

A cup has an effective diameter of 40 mm and produces a pressure difference of 60 kPa. Its ideal force is:

If the cup lifts vertically and a safety factor of 2.5 is required, the permissible static load based on this estimate is approximately:

This corresponds to a mass of approximately 3.1 kg under static gravity alone, since m = F/g. In practice, porous surfaces, acceleration, cup deformation, leakage, contamination, and peel forces can reduce capacity substantially. Several cups may be needed, and their load distribution may not be equal.

6.2 Vacuum generators and components

Common vacuum sources include ejectors, vacuum pumps, and central vacuum systems. A Venturi ejector uses compressed air through a nozzle to entrain air from the suction port. It is compact and has no moving parts, but it can consume substantial compressed air. A pump is often more efficient for continuous high-volume vacuum service.

A vacuum system may include a filter, check valve, vacuum switch, blow-off valve, reservoir, and release valve. The filter protects the generator from dust and liquid. A check valve can retain vacuum if the supply is interrupted, but it cannot compensate for a large leak. Blow-off air accelerates release and prevents a part from remaining attached.

6.3 Porous and irregular materials

Vacuum gripping works best with smooth, nonporous surfaces. Cardboard, fabric, wood, and rough castings may leak continuously. In such cases, use a high-flow generator, a foam seal, a larger cup, multiple cups, mechanical fingers, or a different gripping technology. Vacuum switches should be set with enough margin to distinguish a secure grip from a partial seal.

7. Circuit Design for Timing, Logic, and Sequencing

7.1 Sequence notation

A sequence such as A+ A− describes extension and retraction of actuator A. A two-cylinder transfer mechanism might follow:

A+ → B+ → B− → A−

The sequence should be converted into discrete steps, each with an initiating condition and a completion signal. A robust sequence table is more reliable than connecting valves by intuition.

The notation A0 and A1 denotes retracted and extended confirmation, respectively. A programmable controller is usually preferred for complex sequences, while cascade or stepper methods can implement pneumatic-only control.

7.2 Cascade and stepper principles

In a cascade circuit, the sequence is divided into groups so that a cylinder does not receive contradictory signals from two stages. A group-change valve removes the previous group’s signals and enables the next group. This reduces signal conflict in pneumatic control.

A stepper module advances from one stage to the next when the current movement is confirmed. Stepper methods are conceptually close to a state machine: the output command depends on the current state and the transition condition. This makes troubleshooting systematic.

7.3 Timing and dwell

A dwell may be required for clamping, adhesive setting, drilling, or stabilization. A timer should begin after the mechanical condition is confirmed, not merely after the command signal is sent. For example, the correct logic is “clamp extended and clamp pressure adequate, then wait 0.5 s,” rather than “start timer when clamp valve is energized.”

Timing should be tested under minimum and maximum pressure, temperature, load, and supply-flow conditions. If timing is safety-critical, use a monitored controller or redundant confirmation rather than relying on an unverified pneumatic timer.

7.4 Speed control and cushioning

Cylinder speed is adjusted using flow-control valves, normally with meter-out control. The circuit should be tested for stick-slip, load runaway, end impact, and sensitivity to supply pressure. Quick-exhaust valves can increase speed by exhausting near the actuator, but they may increase noise and impact. Silencers reduce noise but can become clogged and restrict exhaust flow.

8. Applied Case: Pneumatic Pick-and-Place Cell

Background

The following is an illustrative engineering case. A small packaging cell transfers plastic trays from a conveyor to a fixture. A horizontal cylinder A moves the gripper between pickup and placement positions. A vertical cylinder B lowers and raises the gripper. A parallel pneumatic gripper C holds the tray.

Problem

The cell must perform the sequence A−, B+, C close, B−, A+, B+, C open, B−, A−. The design must prevent motion unless the preceding position is confirmed, avoid dropping a tray during transfer, and limit shock at the end of travel.

Analysis

The sequence contains three actuators and several mutually exclusive conditions. A simple direct connection could permit a premature B+ command if A has not reached its pickup position. It could also open C if the vacuum or gripper confirmation is absent. The machine therefore requires position sensors at both ends of A and B, a gripper-closed sensor, and a part-present confirmation.

The gripper is selected from part mass and acceleration. If the tray mass is 1.2 kg, the horizontal acceleration is 1.5 m/s², and the friction coefficient is estimated as 0.35, the simplified required total gripping force is found from:

Using S_f = 2, g = 9.81 m/s², and a = 1.5 m/s²:

The catalogue force must exceed this requirement at the actual operating pressure and jaw position. Jaw geometry may provide mechanical interlock, in which case the friction-only model is conservative but not automatically invalidated.

Approach and solution

A regulated supply feeds separate branches for the cylinders and gripper. A 5/2 valve controls each double-acting cylinder. Meter-out flow controls are installed on the cylinder exhaust ports. End cushions are adjusted experimentally. A gripper valve is selected so that the normal state does not release the part unexpectedly; where risk assessment requires retention during air failure, a spring-closed or mechanically locking gripper is used.

The control sequence is implemented as states:

1. Home: A retracted, B raised, gripper open.
2. Move to pickup: A extends or retracts according to physical layout; transition occurs only when the pickup sensor is active.
3. Lower: B moves down and must confirm its lower position.
4. Grip: C closes; transition requires gripper-closed and part-present signals.
5. Raise and transfer: B rises, then A moves to the fixture.
6. Place: B lowers; the fixture confirms position.
7. Release: C opens; a part-absent signal confirms release.
8. Return: B rises and A returns home.

A timeout is assigned to each movement. If a sensor is not reached within the permitted time, the machine stops and vents or isolates motion according to the risk assessment. The timeout is a diagnostic and protective measure, not a substitute for guarding.

Outcome

The resulting design is more reliable than a purely time-based circuit because each transition depends on actual position or process confirmation. Meter-out control reduces impact, while pressure regulation prevents unnecessary gripping force and air consumption. The cell can be maintained using the sequence table, sensor diagnostics, and pressure measurements.

Learning points

The case demonstrates that pneumatic circuit design is a systems problem. Actuator selection, valve sizing, sensing, logic, mechanical guides, and safety behavior must be designed together. A circuit that works in an unloaded test may fail when friction, leakage, part variation, or acceleration is introduced.

9. Safety, Efficiency, and Troubleshooting

Stored compressed air can cause unexpected motion even after electrical power is removed. Machines require an accessible isolation valve, controlled exhaust, lockout/tagout provisions, and suitable guarding. A soft-start/dump valve can bring pressure up gradually and exhaust the circuit during shutdown. Designers must consider trapped air, gravity loads, pinch points, hose whip, and the behavior of actuators after a valve or sensor failure.

Noise from exhaust ports can damage hearing and should be controlled using correctly sized silencers and enclosure measures. Silencers must not be so restrictive that they cause unstable motion. Pneumatic systems should comply with applicable machinery safety, pressure-equipment, electrical, and workplace regulations in the relevant jurisdiction.

Common faults include:

Compressed air is an expensive energy carrier. Leaks, excessive pressure, inappropriate blow-off, and continuously operating ejectors increase cost. Good practice includes ultrasonic leak surveys, pressure optimization, automatic shutoff during idle periods, efficient vacuum generators, and demand-based blow-off. Pressure should be set only as high as required by the task.

10. Contemporary Developments

Modern pneumatic systems increasingly combine conventional actuators with electronic proportional valves, integrated sensors, IO-Link devices, and networked diagnostic modules. Smart valve terminals can report cycle counts, response times, pressure anomalies, and fault codes. Predictive maintenance can use trends such as increasing fill time, leakage rate, or compressor duty cycle to identify seal wear before failure.

These technologies improve observability but do not eliminate engineering fundamentals. A poorly sized cylinder remains poorly sized when connected to a network. Cybersecurity, access control, data integrity, and safe fallback behavior become relevant when pneumatic control is integrated with industrial networks. Artificial intelligence may assist anomaly detection using pressure and cycle data, but safety decisions should remain governed by validated control architectures and risk assessment.

Best-Practice Design Procedure

1. Define load, motion, stroke, speed, cycle rate, environment, and failure consequences.
2. Select the actuator type and calculate a preliminary force or torque requirement.
3. Apply realistic safety factors and verify the manufacturer’s performance data.
4. Select valves using required flow, pressure, response, porting, and return behavior.
5. Design air preparation, filtration, drainage, piping, and isolation provisions.
6. Select sensors that confirm the actual process condition, not merely a command.
7. Create a sequence table and identify every transition condition.
8. Use meter-out speed control and cushions where appropriate.
9. Test at minimum and maximum expected pressure, load, temperature, and part variation.
10. Validate guarding, emergency behavior, maintenance isolation, noise, leakage, and energy consumption.

Chapter Summary

Pneumatic machines combine compressed-air supply, air preparation, valves, actuators, sensors, and control logic. Cylinder force depends on pressure and effective area; retraction force is lower because the rod reduces piston area. Actuator selection must also consider stroke, speed, buckling, side load, cushioning, and air consumption. Rotary actuators are selected by torque, inertia, angle, and shaft loading, while grippers require analysis of mass, acceleration, friction, jaw geometry, and failure behavior.

Directional valves establish flow paths, flow controls regulate motion, pressure valves control force or sequence conditions, and shuttle and two-pressure valves provide OR and AND logic. Vacuum devices create holding force through atmospheric pressure difference, but surface porosity, leakage, contamination, and acceleration limit practical capacity. Reliable circuits use confirmed positions and process signals, structured sequence tables, suitable speed control, and controlled timing. Safety requires isolation, exhaust, guarding, consideration of stored energy, and compliance with applicable regulations. Efficient modern systems reduce leaks and excessive pressure and may use networked diagnostics without abandoning sound pneumatic design principles.

Key Terms

Compressed air: Air stored or supplied above atmospheric pressure for power transmission.

Gauge pressure: Pressure measured relative to atmospheric pressure.

Absolute pressure: Pressure measured relative to a perfect vacuum.

Double-acting cylinder: Cylinder powered by compressed air in both directions.

Single-acting cylinder: Cylinder powered by air in one direction and spring or external force in the other.

Meter-out control: Speed control achieved by restricting actuator exhaust flow.

Cushioning: Controlled deceleration near the end of actuator travel.

Rotary actuator: Pneumatic device that produces limited angular motion.

Gripper: End-effector used to hold and release a workpiece.

Vacuum cup: Flexible sealing device used to grip a surface by pressure difference.

Ejector: Venturi device that generates vacuum using compressed air.

Directional valve: Valve that routes air between supply, exhaust, and actuator ports.

Shuttle valve: Pneumatic OR element that passes either of two input signals.

Two-pressure valve: Pneumatic AND element requiring two input signals.

Sequence table: Structured listing of commands, transition conditions, and states.

Soft-start valve: Device that pressurizes a circuit gradually during startup.

Free-air consumption: Air consumption expressed relative to a reference atmospheric condition.

Pressure switch: Sensor that changes state at a specified pressure.

Vacuum switch: Sensor that confirms a specified vacuum level.

Fail-safe behavior: Designed response intended to reduce hazard after a fault or loss of energy.

Review Questions

Short Answer Questions

1. Why is retraction force lower than extension force in a double-acting cylinder?
2. What is the purpose of meter-out flow control?
3. State two differences between a pneumatic ejector and a vacuum pump.
4. What functions do a shuttle valve and a two-pressure valve perform?
5. Why should a sequence transition be based on position confirmation rather than command timing alone?

Long Answer Questions

1. Explain the complete procedure for selecting a double-acting cylinder for a material-handling task, including force, stroke, speed, mounting, cushioning, and air consumption.
2. Compare parallel, angular, and three-finger pneumatic grippers, and discuss the factors governing safe gripping-force selection.
3. Describe the construction and operation of a vacuum gripping system and explain why theoretical vacuum force differs from practical lifting capacity.
4. Explain cascade or stepper sequence control and compare pneumatic-only control with programmable electronic control.
5. Discuss the safety, efficiency, maintenance, and regulatory issues that must be addressed in a modern pneumatic machine.

Analytical / Application Questions

1. A double-acting cylinder operates at 500 kPa gauge pressure. Its bore is 63 mm and its rod diameter is 20 mm. Calculate the ideal extension and retraction forces. State the assumptions and explain why actual forces will be lower.
2. Design a sequence table for two cylinders that must perform A+ → B+ → A− → B−. Identify the position signal required to initiate each transition and explain how signal conflict can be prevented.
3. A vacuum cup grips a smooth metal sheet, but the sheet is porous after painting and becomes unreliable at high acceleration. Analyze at least four possible causes and propose a revised gripping and sensing strategy.

Multiple Choice Questions with Answers

Question 1

Which expression gives the ideal extension force of a pneumatic cylinder?

A. F = pA_p

B. F = p(A_p + A_r)

C. F = A_p/p

D. F = p/A_p

Correct Answer: A. F = pA_p

Question 2

Why is meter-out control commonly preferred for an overrunning pneumatic load?

A. It increases supply pressure automatically

B. It restricts exhaust flow and helps maintain back pressure

C. It eliminates the need for a directional valve

D. It converts a double-acting cylinder into a single-acting cylinder

Correct Answer: B. It restricts exhaust flow and helps maintain back pressure

Question 3

A 5/2 directional valve has:

A. Five positions and two ports

B. Five ports and two positions

C. Two ports and five springs

D. Two positions and five cylinders

Correct Answer: B. Five ports and two positions

Question 4

Which pneumatic component performs an OR logic function?

A. Two-pressure valve

B. Pressure regulator

C. Shuttle valve

D. Quick-exhaust valve

Correct Answer: C. Shuttle valve

Question 5

The ideal holding force of a vacuum cup is determined primarily by:

A. Pressure difference multiplied by effective sealed area

B. Atmospheric pressure divided by cup diameter

C. Tube length multiplied by vacuum percentage

D. Compressor power divided by part mass

Correct Answer: A. Pressure difference multiplied by effective sealed area

Question 6

A cylinder has a piston area of 0.002 m² and operates at 400 kPa gauge pressure. Neglecting losses, its extension force is:

A. 200 N

B. 400 N

C. 800 N

D. 2,000 N

Correct Answer: C. 800 N

Question 7

Which sensor most directly confirms that a gripper has successfully retained a workpiece?

A. Supply-pressure gauge only

B. Gripper command output only

C. Part-present or gripping confirmation sensor

D. Compressor temperature sensor

Correct Answer: C. Part-present or gripping confirmation sensor

Question 8

What is a principal disadvantage of a Venturi vacuum ejector?

A. It cannot generate vacuum

B. It commonly consumes compressed air continuously

C. It requires a mechanical crank

D. It can operate only below atmospheric pressure

Correct Answer: B. It commonly consumes compressed air continuously

Question 9

In a pneumatic sequence, a timeout is primarily used to:

A. Increase cylinder bore

B. Replace all position sensors

C. Detect a movement that has not completed within an expected period

D. Lubricate the actuator

Correct Answer: C. Detect a movement that has not completed within an expected period

Question 10

Which action is generally appropriate for improving pneumatic energy efficiency?

A. Increase regulator pressure regardless of load

B. Allow leaks because compressors compensate for them

C. Use continuous blow-off at maximum pressure

D. Repair leaks and set pressure only as high as required

Correct Answer: D. Repair leaks and set pressure only as high as required