Hydraulic, Pneumatic, Lubrication and Cooling Systems

Introduction

Machine tools do not operate through mechanical structures and drives alone. Auxiliary fluid systems provide the forces, controlled motion, friction reduction, heat removal, contamination management and workholding functions that determine whether a machine is accurate, reliable and safe. A hydraulic circuit may clamp a workpiece or actuate a heavy slide; a pneumatic circuit may operate a tool changer or provide air bearing support; lubrication controls wear at guides, bearings and gears; and coolant removes heat while transporting chips away from the cutting zone.

The design of these systems is closely related to machine-tool accuracy. Excessive hydraulic pressure can distort a workholding fixture, inadequate lubrication can produce stick–slip motion, contaminated coolant can damage a spindle bearing, and poorly controlled temperature can cause thermal growth larger than the machining tolerance. Consequently, auxiliary systems must be designed as integrated subsystems rather than as add-ons.

Learning Objectives

After studying this chapter, the reader should be able to:

1. Explain the operating principles and applications of hydraulic and pneumatic systems in machine tools.
2. Select basic pumps, valves, actuators, filters, reservoirs and air-treatment components.
3. Calculate actuator force, flow rate, hydraulic power and pneumatic requirements under stated assumptions.
4. Design lubrication and cooling arrangements for guides, bearings, gears, cutting zones and chip-removal systems.
5. Diagnose contamination, leakage, overheating, pressure loss and inadequate lubrication.
6. Evaluate maintainability, energy efficiency, safety and environmental effects in auxiliary-system design.

1. Functional Requirements in Machine Tools

An auxiliary system should be specified from the machine function rather than from the component catalog. Important requirements include:

• Actuation: movement of slides, pallets, steady rests, tailstocks, tool changers and guards.
• Clamping: secure holding of workpieces and tools without unacceptable deformation.
• Lubrication: separation of contacting surfaces and removal of frictional heat.
• Cooling: control of cutting temperature, thermal distortion and tool wear.
• Chip removal: transport of chips from the cutting zone to a collection point.
• Sealing and protection: exclusion of chips, coolant and abrasive particles.
• Control: repeatable pressure, flow, timing, position and temperature.
• Maintainability: access for inspection, filtration, draining and replacement.

The designer must distinguish between a system's rated capacity and its usable capacity. A pump rated at a specified flow may deliver less flow at operating pressure; an air compressor rating may be based on free-air delivery rather than pressure-line flow; and a coolant pump may lose performance as filters become blocked. Safety margins are therefore necessary, but excessive oversizing increases energy consumption, heat generation and cost.

2. Hydraulic Power Systems

2.1 Principle of operation

Hydraulic systems transmit power through an almost incompressible liquid, commonly mineral oil or a fire-resistant fluid. A pump converts mechanical input into fluid flow. Pressure develops when the flow encounters resistance in an actuator, valve, restriction or load. The basic relation between pressure and force is:

where F is actuator force in newtons (N), p is gauge pressure in pascals (Pa), and A is effective piston area in square metres (m²). This equation assumes that pressure acts uniformly over the effective area and neglects seal friction, leakage and dynamic effects. For a double-acting cylinder, the extension and retraction areas differ because the rod occupies part of the retraction side.

For a piston diameter D and rod diameter d:

where A_e and A_r are extension-side and retraction-side areas. The corresponding ideal forces are pA_e and pA_r. Actual force is lower because of seal friction, pressure losses and mechanical inefficiency.

Flow determines actuator speed. For a cylinder:

where v is piston velocity in m/s, Q is volumetric flow in m³/s, and A is the active area in m². The relationship applies to steady motion and assumes negligible leakage. Thus, force is primarily controlled by pressure and speed by flow.

Hydraulic power delivered to the fluid is:

where P_h is hydraulic power in watts, p is pressure in pascals and Q is flow in m³/s. If pressure is expressed in MPa and flow in L/min, a convenient engineering form is:

The input motor power must be higher than P_h because pump, motor and valve losses are present. If overall efficiency is η, then:

2.2 Hydraulic circuit components

A typical machine-tool hydraulic circuit contains the following elements:

• Reservoir: stores fluid, allows air release and provides a place for settling contaminants. Baffles prevent turbulent return flow from entering the pump suction directly.
• Pump: gear, vane, piston or screw types may be used. Fixed-displacement pumps are simple; variable-displacement pumps can reduce throttling losses.
• Pressure-relief valve: limits maximum pressure and protects the circuit from overload.
• Directional-control valve: routes flow to extend, retract or stop an actuator.
• Flow-control valve: regulates actuator speed. Meter-in, meter-out and bleed-off arrangements have different stability and energy characteristics.
• Check valve: permits flow in one direction and prevents reverse flow.
• Pressure-reducing valve: supplies a lower controlled pressure to a branch such as a clamp circuit.
• Accumulator: stores pressurized fluid, absorbs pulsation and can provide emergency clamping or short peak-flow capacity.
• Filter: removes particles. Pressure-line filtration protects precision valves; return-line filtration protects the reservoir; suction strainers protect the pump but must not cause excessive inlet restriction.
• Cooler and heater: maintain viscosity within the selected operating range.

2.3 Hydraulic design example

A machine slide requires an extension force of 18 kN. The selected cylinder has a bore diameter of 63 mm and operates at 8 MPa. Theoretical extension force is calculated as follows:

If the estimated combined mechanical efficiency is 0.80, the usable force is:

The cylinder is therefore adequate for the required 18 kN under the stated assumptions. If a 0.12 m/s speed is required, the flow is:

Converting to litres per minute gives approximately 22.4 L/min. At 8 MPa, ideal hydraulic power is:

With an overall efficiency of 0.75, input power is approximately 3.99 kW. Motor selection must also consider acceleration, intermittent duty, pressure margin, ambient temperature and starting conditions.

2.4 Hydraulic clamping and precision

Hydraulic clamping provides high force in a compact package, but clamping pressure must be selected so that the workpiece is secure without distortion. A pressure-compensated circuit can maintain approximately constant force despite moderate supply variations. Sequence valves may ensure that a locating pin engages before the main clamp closes. Pressure switches or transducers can verify that clamping has occurred before machining begins.

For precision machines, hydraulic units should be isolated from the structure when pump vibration or fluid pulsation could affect accuracy. Flexible connections must not transmit excessive reaction forces, and cylinders should be mounted to avoid side loading. Side loads increase seal wear and can cause piston-rod bending.

3. Pneumatic Systems

3.1 Characteristics and applications

Pneumatic systems use compressed air. They are clean at the point of use, comparatively inexpensive and capable of rapid cycling. Typical applications include tool unclamping, door operation, chip blow-off, workpiece ejection, low-force clamping, air barriers and pneumatic tooling.

Air is compressible, so pneumatic actuators are less rigid and less positionally precise than hydraulic actuators. Stored compressed energy also creates safety hazards. Pneumatic systems are therefore well suited to rapid, moderate-force operations but are less suitable for high-force precision clamping unless special intensifiers or locking mechanisms are used.

The ideal gas relationship is useful for understanding storage and pressure changes:

where p is absolute pressure, V is volume, m is mass of air, R is the specific gas constant and T is absolute temperature in kelvin. The equation applies to an idealized gas and must use absolute pressure and temperature. Practical pneumatic sizing commonly relies on manufacturer data because valve geometry, leakage, pressure drop and non-isothermal effects are significant.

3.2 Air preparation and control

A machine-tool air system commonly includes a shut-off valve, filter, regulator and lubricator, often called an FRL assembly. Modern systems may omit a lubricator where oil-free valves and actuators are specified. The filter removes water and particles; the regulator controls downstream pressure; and a lubricator adds a controlled oil mist only when compatible components require it.

Compressed air quality is specified through particle, moisture and oil classes. Moisture causes corrosion, freezing and valve malfunction; oil or particles can contaminate optical scales, work surfaces and coolant. A dryer, automatic drain and coalescing filter may be necessary. The main distribution line should slope toward drain points, and branch connections should be taken from the upper side of the main pipe so that condensed liquid is not carried into the branch.

Pneumatic energy efficiency depends strongly on leakage. Leaks at fittings, hoses and quick couplers can operate continuously even when the machine is idle. Pressure should be no higher than required, and blow-off nozzles should be replaced by engineered low-noise air knives or pulse systems where possible.

3.3 Pneumatic actuator selection

Cylinder force is approximately:

where F_f represents friction and other losses. Because supply pressure may fluctuate and the cylinder must accelerate its load, a design factor is required. Pneumatic cylinders should not be selected solely from static force; cushioning, stroke time, exhaust restriction, load inertia and end-position shock must also be checked.

4. Lubrication Systems

4.1 Purpose and lubrication regimes

Lubrication reduces friction, wear and temperature by introducing a material between contacting surfaces. It also provides corrosion protection, removes heat and flushes wear particles away from sensitive contacts. Common regimes are:

• Boundary lubrication: surfaces are partly supported by chemically active films; metal-to-metal interaction remains possible.
• Mixed lubrication: some load is carried by fluid film and some by asperity contact.
• Hydrodynamic lubrication: relative motion generates pressure in a converging fluid film that supports the load.
• Elastohydrodynamic lubrication: elastic deformation and pressure-dependent viscosity are important, especially in rolling contacts and gears.

A simplified viscosity–temperature relationship is often represented qualitatively by the fact that viscosity decreases as temperature rises. Exact selection should use the lubricant manufacturer's viscosity–temperature data rather than an assumed universal equation.

4.2 Lubricant selection

Important selection variables include viscosity, viscosity index, additive package, oxidation stability, compatibility with seals and paints, operating temperature, load, speed and contamination environment. Way oils require suitable tackiness and friction characteristics. Spindle oils generally have lower viscosity than heavily loaded gear oils. Grease is useful where leakage must be minimized or relubrication intervals are long, but excessive grease can cause churning and heat.

Lubricants should not be mixed casually. Incompatible base oils, thickeners or additives can cause separation, swelling, deposits or loss of performance. Identification labels, dedicated filling equipment and documented top-up procedures are essential.

4.3 Lubrication delivery methods

• Manual lubrication: simple but dependent on operator discipline and difficult to verify.
• Drip or wick feed: suitable for low-rate applications, but sensitive to viscosity and orientation.
• Splash lubrication: common in enclosed gearboxes; oil level and rotational speed must be controlled.
• Oil-bath or circulating systems: provide cooling and filtration for bearings and gears.
• Single-line automatic systems: meter lubricant to several points, often using progressive distributors.
• Minimum-quantity lubrication: supplies a very small oil quantity in an air stream, reducing fluid volume in suitable cutting operations.
• Grease metering systems: deliver measured quantities to bearings and guides.

For linear guides and ballscrews, over-lubrication can be as harmful as starvation. Excess lubricant raises drag, attracts chips and increases temperature. The correct interval depends on load, speed, stroke, environment and manufacturer guidance.

4.4 Seals and contamination exclusion

Seals must retain lubricant while excluding coolant, chips and abrasive dust. Common forms include lip seals, wipers, O-rings, mechanical seals and labyrinth seals. A wiper is particularly important on exposed guideways. Seal material must be compatible with the lubricant and coolant, and its temperature and speed limits must be respected.

Contamination control follows a hierarchy: prevent entry, separate contamination at the source, filter the fluid, monitor condition and remove accumulated waste. A clean reservoir cannot compensate for an unprotected guideway or a dirty filling funnel.

5. Cooling and Cutting-Fluid Systems

5.1 Functions of coolant

Cutting fluid may cool the tool and workpiece, lubricate the cutting interface, flush chips, prevent corrosion and improve surface finish. Flood coolant is common in conventional machining. High-pressure coolant improves chip control in deep holes and difficult materials. Through-tool coolant delivers fluid near the cutting edge, but requires suitable tooling, filtration and pump capacity. Minimum-quantity lubrication reduces fluid consumption and can be effective in selected cutting operations, particularly where chip evacuation can be achieved by air or gravity.

Coolant selection depends on workpiece material, tool material and coating, cutting speed, health requirements, machine materials and waste-disposal facilities. Water-miscible fluids require concentration control. Too little concentrate can reduce corrosion protection and biological stability; too much can increase skin irritation, residue and cost.

5.2 Heat balance and flow estimation

The heat carried by a coolant stream can be estimated by:

where Q̇_heat is heat-transfer rate in watts, ṁ is coolant mass-flow rate in kg/s, c_p is specific heat capacity in J/(kg·K), and ΔT is coolant temperature rise in kelvin. This estimate assumes a steady flow, negligible phase change and approximately constant specific heat.

For a liquid of density ρ and volumetric flow rate Q:

Suppose a system must remove 12 kW with a coolant temperature rise limited to 5 K. If ρ = 1,000 kg/m³ and c_p = 4,180 J/(kg·K), then:

The volumetric flow is 0.000574 m³/s, or approximately 34.4 L/min. This is the theoretical flow for the specified heat load. Pump selection must additionally account for nozzle pressure, pipe losses, filter fouling and bypass flow.

5.3 Coolant filtration and chip management

Filters, settling tanks, magnetic separators, centrifuges and hydrocyclones may be used according to chip type and particle size. Long stringy chips require an effective conveyor or breaker, while fine abrasive particles may require fine filtration. The filter must be accessible and equipped with differential-pressure indication where blockage could reduce flow.

Coolant reservoirs should provide adequate residence time for settling and air release. Return flow should not entrain excessive air, since foam reduces pump performance and can interfere with level sensing. Skimmers remove tramp oil, which otherwise reduces oxygen transfer, encourages microbial growth and degrades coolant performance.

6. Integrated System Design and Control

The hydraulic, pneumatic, lubrication and coolant subsystems interact. Coolant can contaminate guideway lubricant; compressed air can spread chips; hydraulic heat can warm the machine structure; and a leaking spindle seal can transfer lubricant into the coolant tank. The design process should therefore include a fluid-interaction map and identify all possible cross-contamination routes.

Sensors commonly include pressure transducers, flow switches, level switches, temperature sensors, filter differential-pressure switches and coolant-concentration refractometers. Interlocks should prevent machining when clamping pressure, spindle lubrication flow or coolant level is inadequate. A fault should produce a safe state rather than merely an alarm that can be ignored.

A practical control sequence for a hydraulic workholding system is:

1. Confirm part presence and locating-pin position.
2. Energize the clamp valve.
3. Verify pressure reaches the permitted range.
4. Permit spindle start only after confirmation.
5. Monitor pressure during cutting.
6. Stop the machine and depressurize safely before unclamping.

7. Illustrative Case: Thermal and Contamination Failure in a CNC Turning Cell

Background

A fictional medium-volume CNC turning cell uses hydraulic chuck clamping, pneumatic door actuation, centralized way lubrication and a water-miscible coolant system. Dimensional drift appears after several hours of production, and spindle-bearing alarms occur intermittently.

Problem

Investigation shows that the coolant temperature rises by 9 K during long cycles. Fine chips bypass a damaged return filter and enter the coolant tank. Tramp oil accumulates on the surface. The centralized lubrication pump continues to operate, but several guideway metering points receive insufficient oil because one distributor is partially blocked.

Analysis

The temperature rise causes thermal growth in the spindle housing and workholding structure. The contaminated coolant damages seals and carries abrasive particles toward exposed guideways. Blocked lubrication points increase friction and produce localized heating. Operators respond by increasing coolant flow, but this increases pump energy without correcting filtration or heat rejection.

Solution

The machine builder separates the coolant return path from the lubrication enclosure, replaces the damaged filter with a monitored unit, adds a magnetic separator for ferrous chips and installs a tramp-oil skimmer. A plate heat exchanger is added to control coolant temperature. The lubrication system receives transparent metering indicators, a reservoir-level alarm and a documented flushing procedure. The hydraulic power unit is fitted with a temperature switch and return filtration indicator. Pneumatic blow-off pressure is reduced and directed through guarded nozzles to prevent chip dispersion.

Outcome

After commissioning, coolant temperature remains within the specified operating band, guideway lubrication is visually verified and spindle alarms decline. The machine uses less coolant and experiences fewer unplanned stops. The principal improvement does not come from a larger pump; it comes from controlling heat, contamination and verification.

Learning points

1. Auxiliary systems must be diagnosed as interacting systems.
2. More flow is not a substitute for filtration and thermal control.
3. Monitoring must verify delivery at the point of use, not only pump operation.
4. Maintenance access and contamination exclusion are design requirements.

8. Efficiency, Safety and Environmental Responsibility

Hydraulic efficiency improves through correct pump sizing, variable-displacement control, reduced throttling, low-pressure standby operation and minimizing leakage. Pneumatic efficiency improves through leak surveys, lower operating pressure, efficient nozzles and automatic isolation during idle periods. Lubricant life can be extended through filtration and condition monitoring rather than excessive replacement.

Environmental design includes biodegradable or low-toxicity fluids where technically suitable, reduced coolant concentration, fluid recycling, spill containment and responsible disposal. Used oil, contaminated absorbents and coolant concentrate must be managed according to applicable environmental regulations. Safety requirements include guarding moving actuators, pressure-rated hoses, lockout and tagout, stored-energy release, safe chip handling and avoidance of skin or inhalation exposure to mist.

Risk assessment should consider hose rupture, unexpected cylinder motion, accumulator discharge, pneumatic ejection, hot surfaces, slippery floors and biological contamination. Hydraulic accumulators require particular attention because pressure may remain after the pump is stopped.

9. Commissioning and Maintenance

Commissioning should proceed systematically:

• Clean and inspect all tanks, pipes and fittings before filling.
• Confirm fluid type, viscosity and compatibility.
• Flush new hydraulic and lubrication circuits where required.
• Check rotation direction and prime pumps.
• Remove air from circuits using approved procedures.
• Set relief and regulating valves gradually with calibrated instruments.
• Verify flow, pressure, temperature and leakage at operating conditions.
• Test every interlock and emergency stop.
• Record baseline values for future condition monitoring.

Preventive maintenance includes filter replacement, leak inspection, fluid sampling, reservoir cleaning, lubricant-level checks, coolant concentration measurement, chip-conveyor inspection and air-leak testing. Predictive techniques include particle counting, oil analysis, vibration measurement, thermography and trend analysis of pump current, pressure and temperature.

Challenges and Limitations

No auxiliary system is ideal. Hydraulic systems provide force and stiffness but may leak, generate heat and require clean fluid. Pneumatics are fast and clean at the machine but inefficient when compressed-air leakage is uncontrolled. Lubrication improves life but can attract contamination or become incompatible with seals. Coolant improves machining but creates health, disposal and housekeeping obligations. Sensors also have limitations: a pressure switch may confirm pressure but not actual clamp force if a mechanical fault exists, and a flow switch may fail to detect poor distribution among parallel branches.

Design decisions must therefore balance performance, reliability, capital cost, operating cost, environmental impact and ease of maintenance. Manufacturer data, applicable standards and validated testing should be used for final component selection.

Chapter Summary

Hydraulic, pneumatic, lubrication and cooling systems are essential subsystems of modern machine tools. Hydraulics are suited to high-force actuation and clamping, while pneumatics provide rapid, relatively clean motion at moderate force. Hydraulic force depends on pressure and effective area, actuator speed depends on flow, and hydraulic power is the product of pressure and flow. Pneumatic design must account for compressibility, leakage, air quality and stored energy.

Lubrication must be matched to load, speed, temperature, materials, seals and contamination conditions. Correct delivery is as important as lubricant selection. Cooling systems control cutting temperature, thermal distortion and chip transport; their design requires attention to heat balance, filtration, concentration, biological stability and disposal. Integrated design, monitoring, interlocking, maintainability and contamination control are central to reliable operation.

Efficient and responsible systems minimize throttling, leaks, fluid waste and unnecessary energy consumption. Safe design requires pressure containment, stored-energy control, guarding, emergency isolation and appropriate handling of oils, coolants and chips.

Key Terms

Hydraulic system: A power system that transmits energy through pressurized liquid.

Pneumatic system: A power system that uses compressed gas, usually air.

Actuator: A device that converts fluid energy into mechanical motion.

Effective area: The piston area on which fluid pressure produces force.

Pressure-relief valve: A valve that limits maximum system pressure.

Accumulator: A vessel that stores pressurized hydraulic fluid.

Flow control: Regulation of fluid flow to control actuator speed.

FRL unit: Filter, regulator and lubricator assembly for compressed air.

Hydrodynamic lubrication: Lubrication in which motion-generated fluid pressure supports the load.

Boundary lubrication: A regime in which protective films carry load with significant asperity interaction.

Viscosity: A fluid's resistance to shear flow.

Way oil: Lubricant formulated for machine-tool slideways.

Minimum-quantity lubrication: Delivery of a very small quantity of lubricant, often in an air stream.

Coolant: Fluid used to remove heat, lubricate cutting and transport chips.

Tramp oil: Unwanted oil entering a water-miscible coolant system.

Differential pressure: Pressure difference across a filter or component.

Cavitation: Formation and collapse of vapour cavities caused by insufficient local pressure.

Interlock: A control condition that prevents unsafe or incorrect operation.

Contamination control: Prevention, removal and monitoring of unwanted particles, water, air or chemicals.

Thermal distortion: Dimensional or positional change caused by temperature variation.

Review Questions

Short Answer Questions

1. Distinguish between the roles of pressure and flow in a hydraulic cylinder.
2. Why is compressed-air leakage an important energy problem?
3. Name four common hydraulic circuit components and state the function of each.
4. What is the purpose of a coolant filter and a tramp-oil skimmer?
5. Explain the difference between boundary and hydrodynamic lubrication.

Long Answer Questions

1. Describe the design and operation of a hydraulic clamping circuit for a machine tool, including safety and verification features.
2. Explain pneumatic air preparation and discuss the effects of moisture, particles and oil contamination.
3. Discuss lubricant selection for machine-tool guides, bearings and gears.
4. Explain how coolant flow, filtration and temperature control influence machining accuracy.
5. Develop a maintenance and commissioning plan for an integrated machine-tool fluid system.

Analytical / Application Questions

1. A hydraulic cylinder has a 50 mm bore and operates at 6 MPa. Calculate its ideal extension force. State the assumptions and explain how seal friction and pressure losses would alter the result.
2. A coolant system must remove 8 kW with a temperature rise not exceeding 4 K. Using ρ = 1,000 kg/m³ and c_p = 4,180 J/(kg·K), calculate the minimum theoretical flow in L/min and identify practical factors requiring additional capacity.
3. A CNC machine shows dimensional drift, rising coolant temperature and intermittent lubrication alarms. Propose a diagnostic sequence that separates thermal, contamination, delivery and control faults.

Multiple Choice Questions with Answers

Question 1

Which variable primarily determines the ideal force produced by a hydraulic cylinder?

A. Fluid pressure and effective piston area

B. Reservoir volume only

C. Return-line temperature only

D. Filter element length only

Correct Answer: A. Fluid pressure and effective piston area

Question 2

A hydraulic actuator requires 10 MPa and 30 L/min. What is its ideal hydraulic power?

A. 0.5 kW

B. 3 kW

C. 5 kW

D. 300 kW

Correct Answer: B. 3 kW

Question 3

What is the main reason for using a pressure-relief valve?

A. To increase reservoir capacity

B. To limit maximum system pressure

C. To remove tramp oil

D. To measure coolant concentration

Correct Answer: B. To limit maximum system pressure

Question 4

Which characteristic most clearly distinguishes pneumatic systems from hydraulic systems?

A. Pneumatic systems use incompressible oil

B. Pneumatic systems use compressible air

C. Pneumatic systems cannot use valves

D. Pneumatic systems require no maintenance

Correct Answer: B. Pneumatic systems use compressible air

Question 5

What is the principal function of a machine-tool way lubricant?

A. To increase chip length

B. To reduce friction and wear at sliding surfaces

C. To raise coolant concentration

D. To pressurize pneumatic lines

Correct Answer: B. To reduce friction and wear at sliding surfaces

Question 6

In the heat-removal relation Q̇_heat = ṁ c_p ΔT, what does c_p represent?

A. Coolant pressure

B. Specific heat capacity

C. Pump displacement

D. Filter differential pressure

Correct Answer: B. Specific heat capacity

Question 7

Which condition is most likely to cause hydraulic pump cavitation?

A. Excessive suction restriction or inadequate inlet supply

B. A clean and fully flooded suction line

C. Correct fluid viscosity and low inlet loss

D. A properly sized reservoir breather

Correct Answer: A. Excessive suction restriction or inadequate inlet supply

Question 8

Why is a coolant system commonly fitted with a tramp-oil skimmer?

A. To remove unwanted oil from water-miscible coolant

B. To increase hydraulic actuator force

C. To dry compressed air

D. To increase spindle speed

Correct Answer: A. To remove unwanted oil from water-miscible coolant

Question 9

Which maintenance action best verifies that lubricant is reaching distributed lubrication points?

A. Checking only that the pump motor runs

B. Inspecting metering indicators or point-of-use flow

C. Increasing coolant pressure

D. Removing the reservoir baffle

Correct Answer: B. Inspecting metering indicators or point-of-use flow

Question 10

A cylinder has an effective area of 0.002 m² and pressure of 5 MPa. What is its ideal force?

A. 1 kN

B. 2.5 kN

C. 10 kN

D. 25 kN

Correct Answer: C. 10 kN