Pneumatic Troubleshooting - 70 Interview Q&A

Compressed air is the quiet utility of packaging, assembly and automation lines, and pneumatic faults are usually simple once you know where to look: a leak, a blocked silencer, wet air or a worn seal. Interviewers ask about slow cylinders, weak force, valves that do not shift, FRL units and air quality. The 70 questions below cover cylinders, valves, FRL units, tubing and fittings and compressed air supply. This page adds the interview structure, a revision list, three worked examples (a slow cylinder, cylinder force and an air consumption estimate) and the mistakes that show up in a pneumatic interview.

Original EngineerX flowchart: Pneumatic actuator: slow or no movement. Follow the numbered checks in order; a “No” sends you back to widen the search.

How pneumatic troubleshooting interviews usually run

Symbols and components — read a pneumatic circuit and name every part.
Fault scenario — slow, weak or jerky movement is described and you give the checks.
Calculations — force, speed and air consumption.
Air quality and savings — moisture, filtration, leaks and pressure setting.

Concepts and readings to revise first

Cylinders: single and double acting, cushioning and seal wear.
Valves: 3/2, 5/2 and 5/3 valves, solenoid and pilot faults.
FRL unit: filter, regulator and lubricator settings and drain.
Flow control: meter-in vs meter-out and speed adjustment.
Tubing and fittings: leakage, kinks and size selection.
Compressed air quality: water, oil and dust.
Leak finding: soap solution, ultrasonic detector and cost of leaks.
Safety: exhaust trapped air before work and guard moving parts.

Showing the first 70 questions free. The complete question bank is available as a PDF below.

Compressor & Air Supply

Q1The pneumatic machine suddenly becomes weak and several cylinders move slowly. What would you check first?

AnswerCheck the compressor outlet pressure, receiver pressure, and the pressure at the machine inlet while the machine is actually operating. If pressure falls sharply under load, inspect compressor capacity, leaks, clogged intake filters, and undersized piping before changing the actuator.

Q2The compressor reaches its cut-out pressure but the machine still cannot complete its stroke. How would you troubleshoot it?

AnswerMeasure pressure at the machine during the stroke rather than relying on the receiver gauge. A large pressure drop can indicate a blocked line, dirty FRL filter, undersized hose, or excessive flow demand; correct the restriction and verify the pressure at the actuator.

Q3The compressor runs almost continuously even when production is low. What should you investigate?

AnswerCheck for audible leaks around fittings, valves, hoses, and the receiver drain, then isolate machine branches to identify the leaking circuit. Also check whether the pressure switch setting is correct and whether the compressor is too small for the actual air demand.

Q4Air pressure is normal when the machine is idle but drops sharply whenever two cylinders operate together. Which fault is most likely, and how would you verify it?

AnswerThe available flow is probably insufficient for the combined demand. Check compressor FAD, main-line size, regulator capacity, hose diameter, and simultaneous actuator demand; increase supply capacity or sequence the motions if the system was designed with insufficient flow.

Q5The compressor trips on overload during repeated pneumatic operation. What checks would you make?

AnswerVerify motor current, compressor discharge pressure, cooling airflow, oil level where applicable, and the pressure-switch cut-in/cut-out settings. Excessive back pressure, poor cooling, mechanical resistance, or incorrect electrical settings can cause overload; correct the root cause before resetting the protection.

Q6The compressor takes much longer than usual to build receiver pressure. How would you locate the fault?

AnswerCompare the pressure build-up time with the normal cycle and listen for leakage. Inspect the intake filter, compressor valves, belts/coupling, unloading mechanism, and downstream isolation valve; a worn compressor or open leak can reduce effective capacity.

Q7The receiver pressure fluctuates rapidly even though demand seems steady. What would you examine?

AnswerCheck the pressure switch, compressor unloading operation, receiver gauge, and possible large intermittent leaks. If the gauge fluctuates but a second calibrated gauge is stable, the gauge itself may be faulty; otherwise investigate cycling caused by inadequate receiver volume or unstable demand.

Q8A compressor starts and stops very frequently. How can this be corrected?

AnswerCheck the differential between cut-in and cut-out pressures and confirm that the receiver volume is suitable for the load. A leaking system, incorrectly adjusted pressure switch, or very small receiver can cause short cycling; repair leaks and correct the control settings as specified by the compressor manufacturer.

Q9The compressor discharge line becomes unusually hot. What should you inspect?

AnswerCheck discharge pressure, cooling fan or ventilation, intake filter condition, and compressor lubrication where applicable. High compression ratio, restricted cooling, dirty intake filtration, or mechanical problems can raise discharge temperature; do not continue operation if the temperature exceeds the manufacturer's limit.

Q10The machine loses air pressure after the compressor stops. How would you troubleshoot this step by step?

AnswerClose the machine isolation valve and observe whether receiver pressure still falls. If pressure holds, the leak is downstream; reopen branches one at a time to locate it, then repair fittings, tubing, valves, or actuator seals and confirm the pressure remains stable.
2. FRL, Filtration & Air Quality

FRL, Filters & Air Quality

Q11Water repeatedly collects in the filter bowl and reaches the pneumatic valves. What should you do?

AnswerDrain the filter bowl safely and check the automatic drain, air dryer, and compressor aftercooling arrangement. Excess moisture can damage valves and cylinders, so repair the drain or dryer problem and verify that the air treatment capacity matches the compressor flow.

Q12A cylinder becomes sticky after the FRL filter is serviced. What would you check?

AnswerInspect the filter element, bowl, seals, and flow direction, and make sure the element has not been installed incorrectly. A damaged seal or incorrectly assembled filter can restrict flow or introduce contamination; clean the assembly and verify pressure drop across it.

Q13The regulator output pressure is lower than the setting when the actuator moves. How would you troubleshoot this?

AnswerThis is often a regulator capacity or upstream-flow problem. Check inlet pressure, regulator size, filter blockage, and the pressure at the outlet under load; if the pressure collapses only during flow, clean the filter or use a regulator with adequate flow capacity.

Q14The lubricator is not delivering oil even though the adjustment is open. What should you inspect?

AnswerConfirm that the lubricator is installed in the correct flow direction and that the oil level is adequate. Check the sight dome, metering adjustment, and internal passages for blockage; clean or replace the unit if contamination prevents proper oil mist generation.

Q15Pneumatic valves are failing repeatedly after a maintenance shutdown. What air-quality checks are important?

AnswerLook for water, compressor oil carryover, rust particles, and seal fragments in the filter bowl and valve ports. Check the filter element and dryer performance, flush contaminated lines where appropriate, and identify the contamination source instead of repeatedly replacing valves.

Q16The regulator pressure slowly rises above its set value while the downstream machine is idle. What could cause this?

AnswerA regulator with damaged internal sealing can allow upstream pressure to pass to the downstream side, a condition known as creep. Isolate the downstream circuit and confirm the rise with a calibrated gauge; replace or service the regulator if creep is confirmed.

Q17The filter differential pressure becomes high and cylinders slow down. What should be checked?

AnswerInspect the filter element for dirt, oil, and water contamination and compare upstream and downstream pressure. Replace the element according to the manufacturer's specification and investigate excessive contamination if the new element becomes blocked unusually quickly.

Q18The automatic drain keeps opening but water still remains in the filter bowl. How would you troubleshoot it?

AnswerCheck whether the drain float or drain mechanism is stuck and whether the drain outlet is blocked. Verify that the bowl is correctly fitted and the drain is suitable for the system pressure; clean or replace the drain and confirm complete water removal.

Q19A regulator works correctly at low flow but pressure becomes unstable at high flow. Which issue is most likely, and how would you confirm it?

AnswerThe regulator may be undersized or its internal seat may be contaminated. Measure inlet and outlet pressure at the actual peak flow and compare it with the regulator's flow rating; clean it or select a higher-capacity regulator if necessary.

Q20The pneumatic system works normally after morning start-up but becomes unreliable later in the shift. What air-treatment problem could explain this?

AnswerMoisture and contamination can accumulate as the compressor and air lines warm up or as the dryer reaches its operating load. Check filter bowls, drains, dryer performance, and pressure drop at the machine; correct the moisture source and drain the system properly.
3. Pneumatic Valves & Direction Control

Solenoid Valves & Cylinder Direction

Q21A double-acting cylinder moves out but will not retract. How would you troubleshoot the circuit?

AnswerCheck the valve exhaust and supply ports, then verify that the solenoid or pilot signal actually changes the valve spool. If the control signal is present but the spool does not shift, inspect the valve for contamination or mechanical sticking; also check the retract-side hose and flow-control restriction.

Q22A solenoid valve clicks but the cylinder does not move. What should you check?

AnswerA click only proves that the solenoid mechanism is attempting to operate. Verify coil voltage, valve spool movement, supply pressure at the valve, port connections, and exhaust path; a stuck spool or blocked port can prevent movement even when the coil sounds normal.

Q23A cylinder moves in the wrong direction after a hose replacement. What troubleshooting approach would keep the test safe and effective?

AnswerStop the machine and compare the hose connections with the pneumatic schematic. Confirm the pressure and exhaust ports at the directional valve and reconnect the lines according to the drawing rather than changing the control logic blindly.

Q24The valve shifts correctly but the cylinder movement is jerky. What should you inspect?

AnswerCheck flow-control settings, contaminated valve ports, pressure stability, and whether the actuator load is changing during the stroke. Adjust meter-out flow controls gradually and clean contaminated components; also inspect cylinder alignment if the mechanical load is causing stick-slip motion.

Q25A normally closed pneumatic valve remains open after the electrical signal is removed. What could be wrong?

AnswerFirst confirm that the solenoid command has actually been removed and that no PLC output is still energized. If the electrical command is off, inspect the valve spool, return spring, and contamination; a mechanically stuck spool or damaged spring can keep the valve in the energized position.

Q26A solenoid valve becomes very hot during continuous operation. How would you investigate it?

AnswerMeasure coil voltage while energized and compare it with the rated voltage. Excess voltage, incorrect coil type, poor heat dissipation, or a coil designed only for intermittent duty can cause overheating; correct the electrical supply or replace the coil with the proper continuous-duty specification.

Q27The cylinder starts moving only after the valve is tapped lightly. What does this indicate?

AnswerThis strongly suggests a sticking spool, contamination, or mechanical binding in the valve. Isolate the air supply, inspect the valve according to the manufacturer's service procedure, clean or replace damaged components, and identify why contamination entered the circuit.

Q28A pneumatic valve exhausts continuously to atmosphere. What should you check?

AnswerListen at the exhaust ports and isolate the actuator to determine whether the leakage is through the valve or another component. Check spool seals, valve body damage, pilot pressure, and downstream cylinder seals; replace defective seals or the valve if internal leakage is confirmed.

Q29A 5/2 valve changes state too slowly and delays the machine cycle. What would you inspect?

AnswerCheck pilot pressure, exhaust restriction, solenoid condition, and contamination in the spool. A restricted exhaust or weak pilot signal can slow spool movement; restore correct pilot pressure and clean or replace the valve if necessary.

Q30Two cylinders start moving when only one valve should operate. How would you find the cause?

AnswerCheck whether valve outputs are electrically cross-connected and whether the pneumatic lines share an unintended pressure path. Review the schematic, isolate each branch, and test the solenoid outputs individually; correct wiring, manifold connections, or valve selection as required.
4. Cylinders & Actuators

Cylinder Positioning & Stroke Issues

Q31A cylinder reaches the end of its stroke but the machine does not detect the position. What should you check?

AnswerInspect the cylinder-mounted sensor, its alignment, wiring, and PLC input status. Manually move the sensor through its detection range and confirm the input changes; adjust or replace the sensor and verify the mechanical mounting if the cylinder is reaching the correct position.

Q32A cylinder slowly drifts from its extended position while the valve is centered. How would you troubleshoot it?

AnswerFirst determine whether the valve is leaking internally or the cylinder piston seals are bypassing. Block and isolate the cylinder safely, monitor pressure on both sides, and compare the result with the manufacturer's leakage limits; repair the valve or cylinder based on the isolation test.

Q33A cylinder has enough force but cannot complete the final few millimeters of travel. What should you investigate?

AnswerCheck for mechanical interference, end-of-stroke load increase, misalignment, and flow restriction. Verify pressure at the cylinder port during the final part of the stroke; if pressure is adequate, inspect the mechanism for binding rather than increasing pressure unnecessarily.

Q34A cylinder moves normally without load but stalls when the workpiece is present. How should you approach this fault?

AnswerMeasure cylinder pressure during the loaded stroke and compare the required force with the available pneumatic force. If pressure collapses, check supply and flow restrictions; if pressure remains adequate, inspect the machine for excessive friction, misalignment, or a jammed mechanism.

Q35A cylinder extends too fast and causes a hard impact at the end of the stroke. How can it be corrected?

AnswerAdjust the flow-control valve, preferably using controlled meter-out flow where appropriate, and check the cylinder cushioning adjustment. Reduce speed gradually and verify that the actuator still completes the cycle reliably without excessive impact.

Q36A cylinder retracts much slower than it extends. What would you inspect?

AnswerCompare the flow path and flow-control settings for both directions. A restricted exhaust, incorrect one-way flow-control orientation, undersized tubing, or a clogged muffler can affect one direction more than the other; correct the restriction and retest the cycle.

Q37A cylinder rod shows side wear and the movement is becoming rough. Which root cause should you investigate first?

AnswerSide wear commonly indicates misalignment or excessive side loading rather than an air-supply problem. Check guide rails, mounting faces, rod-end alignment, and the load path; correct the mechanical alignment and replace damaged rod seals if required.

Q38A compact cylinder becomes hot during rapid cycling. What should be checked?

AnswerCheck the cycle rate, supply pressure, flow restrictions, and whether the cylinder is being operated beyond its rated speed. Rapid cycling can generate heat through compression and friction; reduce unnecessary speed and verify lubrication and component ratings.

Q39A cylinder makes a hissing sound near the rod end. How would you confirm the leak?

AnswerUse an approved leak-detection method such as listening closely or applying leak-detection solution around external connections, while keeping hands clear of moving parts. If leakage is from the rod seal, inspect rod condition and alignment and replace the seal or cylinder as specified.

Q40The cylinder stops at different positions from cycle to cycle even though the command timing is unchanged. What could cause this?

AnswerLook for inconsistent supply pressure, varying load, unstable flow-control settings, or cushioning changes. Check the cylinder speed and pressure during several cycles and inspect sensors if the position is controlled electronically; correct the unstable component rather than simply changing timer values.
5. Flow Control & Speed Problems

Speed Control & Flow Regulation

Q41A cylinder speed suddenly becomes very slow after a hose change. What should you check?

AnswerCompare the new hose diameter and fittings with the original specification and inspect the flow-control valve orientation. A smaller hose, restrictive push-in fitting, or incorrectly oriented one-way flow control can create a large pressure drop; restore the correct flow path.

Q42The actuator speed is unstable even though regulator pressure is steady. How would you troubleshoot it?

AnswerCheck the flow-control valve, load variation, valve spool condition, and exhaust restrictions. If the pressure remains stable but speed changes, the restriction or mechanical load is likely changing; test the actuator with a controlled load and inspect the flow-control components.

Q43A speed controller works in one direction but has almost no effect in the other direction. What should you inspect?

AnswerCheck the one-way check valve inside the flow-control unit and confirm the valve orientation. A wrongly installed or damaged check element can make both directions behave incorrectly; reinstall or replace the flow control and verify meter-in or meter-out operation.

Q44A pneumatic cylinder oscillates near the end of its stroke. What could cause this?

AnswerExcessive speed, poor cushioning adjustment, unstable flow control, or a changing mechanical load can cause end-position oscillation. Reduce speed, adjust cushioning gradually, and inspect the mounting and load for looseness before changing the control sequence.

Q45A muffler on the exhaust port becomes clogged and the machine slows down. What should be done?

AnswerInspect the muffler for oil, dust, or carbon-like contamination and compare exhaust back pressure with the normal condition. Clean or replace the muffler using the manufacturer's recommendation; if it clogs repeatedly, investigate contamination upstream.

Q46The machine becomes slow only when several exhaust ports discharge at the same time. What does this suggest?

AnswerThe common exhaust path may be too restrictive. Check manifold exhaust capacity, mufflers, valve sizing, and common silencers; increasing exhaust capacity can restore speed without increasing supply pressure.

Q47A cylinder speed increases when the regulator pressure is raised, but the force requirement has not changed. Should pressure simply be increased further?

AnswerNot automatically. Higher pressure may increase speed but can also increase impact, seal stress, and energy consumption; first correct flow restrictions and set pressure only high enough to provide the required force and reliable motion.

Q48A flow-control valve is fully open but the cylinder remains slow. Where else should you look?

AnswerCheck the upstream filter and regulator pressure under load, tubing size, valve port size, exhaust muffler, and actuator seals. Opening the flow control cannot overcome a restriction elsewhere, so measure pressure at the cylinder ports during motion to identify the bottleneck.

Q49A cylinder moves smoothly at low speed but becomes unstable when speed is increased. How would you correct it?

AnswerCheck cushioning, flow-control settings, load guidance, and the actuator mounting. Increase speed gradually while observing the end-of-stroke behavior; if instability is mechanical, improve guidance rather than trying to control it only with air flow.

Q50The machine cycle time increases after adding another pneumatic branch. What should be checked?

AnswerMeasure pressure and flow before and after the new branch during simultaneous operation. The added branch may be consuming the available compressor capacity or causing a main-line pressure drop; resize the supply or change the sequence if necessary.
6. Air Leakage & Tubing

Air Leaks & Tubing Faults

Q51The compressor's duty cycle increases after a new pneumatic station is installed. How would you check for leaks?

AnswerDivide the system into branches using isolation valves and monitor pressure decay with the compressor off. Once the leaking branch is identified, inspect fittings, tubing ends, valve manifolds, and actuator seals using a suitable leak-detection method.

Q52A push-in fitting leaks intermittently when the machine vibrates. What should you inspect?

AnswerCheck that the tube is cut square, fully inserted, and free from scratches or deformation at the sealing area. Inspect the fitting collet and seal and replace damaged parts; also provide proper tube support so vibration does not load the connection.

Q53A pneumatic tube keeps popping out of a fitting. What could be wrong?

AnswerVerify the tube size and fitting specification and inspect the tube end for damage. Incorrect tubing, incomplete insertion, damaged collets, or excessive side loading can cause pull-out; replace the fitting or tube and secure the line correctly.

Q54You hear a continuous hiss near a valve manifold, but the exact leak point is unclear. How would you isolate it?

AnswerShut down the supply safely and isolate individual branches or valve sections where possible. After repressurizing the smallest section, use an approved leak-detection solution or acoustic method around fittings and valve ports to identify the exact source.

Q55A pneumatic hose rubs against a moving machine part and develops a small hole. What corrective action is best?

AnswerReplace the damaged hose rather than relying on a temporary patch. Then reroute the hose with adequate bend radius, clamps, and protective sleeving so it cannot contact sharp edges or moving parts during the full machine stroke.

Q56Pressure falls overnight even though the machine is not operating. What should you check?

AnswerClose the machine isolation valve and observe whether the receiver or upstream pressure still decays. If the receiver holds, inspect the machine branch for leaks; if it does not, check the main distribution line, compressor non-return valve, and receiver connections.

Q57A leak is found at a threaded pneumatic fitting after maintenance. How should it be repaired?

AnswerDepressurize the line before working on the fitting, then inspect the threads and sealing method. Reassemble using the correct approved sealant or sealing method and avoid excessive tightening, which can crack fittings or damage ports.

Q58A small leak is difficult to hear because the factory is noisy. What method can help?

AnswerUse a compatible leak-detection solution or an ultrasonic leak detector if available. Test systematically from the main line toward branches rather than checking random points, and repair leaks that contribute to pressure loss or unnecessary compressor loading.

Q59A hose becomes soft and swollen near the compressor outlet. What should you investigate?

AnswerCheck the hose's temperature and pressure rating and verify whether it is compatible with the actual compressed-air conditions. Excessive temperature, chemical exposure, or an incorrect hose material can degrade it; replace it with a properly rated hose and correct the source condition.

Q60A machine loses pressure only during vibration-heavy cycles. What leak-related cause is likely?

AnswerConnections may be moving enough to open a marginal seal or fitting. Inspect flexible hoses, fittings, manifold mounts, and tube supports while the machine cycles, then secure or replace the affected connection rather than tightening everything indiscriminately.
7. Pneumatic Sensors & Feedback

Cylinder Position Sensors

Q61A cylinder reaches the end position but the PLC does not receive the sensor signal. What should you check?

AnswerCheck sensor alignment, supply voltage, wiring, connector condition, and the PLC input LED. If the sensor output changes at the sensor but not at the PLC, trace the wiring or input circuit; if it never changes, adjust or replace the sensor.

Q62A magnetic cylinder sensor works sometimes and fails after the cylinder is replaced. What should you inspect?

AnswerConfirm that the replacement cylinder has the correct magnetic piston and that the sensor type matches the cylinder profile. Check sensor position and sensitivity, then verify the input signal over several cycles; incorrect mounting or incompatible hardware can cause intermittent detection.

Q63A proximity sensor indicates the cylinder is home even when it is not fully retracted. How would you troubleshoot it?

AnswerCheck sensor mounting position and sensing distance, then inspect the target and bracket for movement. Verify whether the PLC input is changing too early; reposition the sensor or target so the signal represents the required mechanical position, not just partial movement.

Q64A sensor signal flickers rapidly while the cylinder is stationary. What could cause this?

AnswerLook for loose wiring, vibration, marginal supply voltage, sensor sensitivity issues, or a target positioned at the edge of the sensing range. Monitor the signal at the sensor and PLC while gently checking the connector and mounting; correct the mechanical or electrical instability.

Q65The cylinder reaches the correct position but the machine faults with a timeout. What should you verify?

AnswerCheck whether the sensor signal reaches the PLC before the programmed timeout and whether the sensor is correctly mapped to the input. Also check slow actuator motion, pressure drop, and flow restrictions; increase the timeout only if the process genuinely requires more time, not to hide a pneumatic fault.

Q66Two cylinder sensors appear active at the same time when they should not be. What should you investigate?

AnswerCheck sensor mounting positions, wiring cross-connections, PLC input mapping, and whether one sensor is sensing an unintended metal target. Test each sensor individually and trace its wire to the correct input before changing PLC logic.

Q67A reed switch sensor becomes unreliable at high cycle rates. What would you inspect?

AnswerCheck the sensor's switching frequency rating, mounting position, cable condition, and electrical load. A sensor operating beyond its rated frequency or with excessive electrical noise may miss transitions; use a suitable sensor and verify the signal at the PLC input.

Q68A sensor LED is ON, but the PLC input remains OFF. How would you trace the troubleshooting path?

AnswerMeasure the sensor output and confirm common/return wiring first. If the sensor output is correct but the PLC input does not respond, inspect the input module, terminal, fuse, and wiring; avoid replacing the sensor without proving where the signal is lost.

Q69A sensor fails only after water enters the pneumatic cabinet. What should be checked?

AnswerInspect the sensor connector, cable insulation, terminal blocks, and enclosure sealing for moisture. Drying alone may not restore a damaged sensor; correct the source of water ingress and replace components whose insulation or contacts have been compromised.

Q70A cylinder position is detected correctly but sometimes the machine still starts the next sequence too early. How would you investigate?

AnswerCheck sensor repeatability, mounting rigidity, PLC input filtering, and the sequence logic. Verify the actual mechanical position when the input turns ON; if the sensor activates before the required end position, reposition it and confirm the control sequence uses the correct confirmation signal.
8. Pressure Control & Regulators

Three worked fault examples

Example 1: “A double acting cylinder moves slowly. What do you check?”

Check the supply pressure at the valve, not only at the main gauge. A pressure drop in the line or a clogged filter reduces it.
Check the flow control valves. A flow control set too closed slows the stroke.
Check the exhaust: a blocked silencer can slow the movement.
Check for internal leakage across the piston seal, which shows as air hissing from the exhaust when the piston is at the end.
Check the mechanical side too: a binding guide or an overload will also slow the cylinder.

Example 2: “A 50 mm bore cylinder is supplied at 6 bar. What is the theoretical push force?”

Area = π/4 × (5 cm)² = 19.6 cm² = 19.6 × 10⁻⁴ m².
6 bar = 6 × 10⁵ Pa.
Force = 6 × 10⁵ × 19.6 × 10⁻⁴ = about 1,180 N.

With seal friction, an efficiency of around 90% is common, so allow roughly 1,060 N in practice. The pull force is lower because of the rod area.

Example 3: “Estimate the free air used by a 50 mm bore, 100 mm stroke double acting cylinder at 6 bar gauge, 20 cycles per minute.”

Volume per cycle (ignoring the rod) = 2 × 19.6 cm² × 10 cm = 392 cm³ = 0.392 L.
Compression ratio = (6 + 1.013) / 1.013 = 6.9.
Free air per cycle = 0.392 × 6.9 = 2.7 L. At 20 cycles/min: about 54 L/min.

A single 3 mm leak at 6 bar can waste more air than several machines use, which is why leak finding pays back quickly.

Common mistakes that cost candidates the job

Looking only at the main pressure gauge and ignoring the pressure at the machine.
Not draining the FRL filter and the receiver, so water reaches the valves.
Adjusting flow controls the wrong way (meter-in vs meter-out confusion).
Working on a circuit without exhausting the trapped air.
Replacing a valve without checking the silencer or the pilot supply.

Frequently asked questions

Is lubrication always needed in pneumatic circuits?

Not always. Many modern components are pre-lubricated and can be damaged by oil of the wrong type.

Why do pneumatic cylinders jerk at low speed?

Stick-slip friction and compressibility of air, often improved with meter-out control and better lubrication.

What does a leak cost?

A lot. Compressed air is among the most expensive utilities per unit of energy.

Keep preparing

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