Pneumatic Cylinder Troubleshooting: Causes & Fixes

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Problems on this page:

Slow, weak or erratic motion Air leaks Will not extend or return Hard impact at the end of the stroke Rod seal leak or damaged rod Cylinder will not hold position End position sensor not switching Water or oil in the air supply

Slow, weak or erratic motion

Hits OEE: Performance

Symptoms: Cylinder moves slowly, lacks force, or stutters.

Low air pressure / supply restriction

Check regulator setting and supply; clear restrictions/filters.

Worn seals (internal leak)

Rebuild or replace the cylinder; check rod for scoring.

Flow controls misadjusted

Reset meter-out flow controls; remove kinks.

Sticking valve

Clean or replace the directional valve; check pilot air.

Prevention: Clean dry air (FRL), seal/valve maintenance, flow-control setup.

Air leaks

Hits OEE: Performance

Symptoms: Audible leaks, high compressed-air demand, pressure drop.

Worn rod/piston seals

Rebuild the cylinder; replace seals.

Loose fittings or damaged tubing

Tighten/replace push-fit fittings and tubing.

Failed valve seals

Service or replace the valve.

Prevention: Leak surveys, fitting/tubing checks, scheduled seal renewal.

Will not extend or return

Hits OEE: Availability

Symptoms: Cylinder stuck in one direction or fully stalled.

Valve not shifting / no pilot air

Check the directional valve and pilot supply; manual-override test.

Blocked exhaust / muffler

Clear or replace the blocked muffler/exhaust.

Jammed load or failed seal

Clear the mechanical jam; rebuild if seals bypass.

Prevention: Clean dry air, valve/muffler checks, mechanical guarding.

Hard impact at the end of the stroke

Hits OEE: Availability

Symptoms: The cylinder bangs at the end of travel, loosening brackets and damaging the load.

Cushion screws open too far or cushion seals worn

Adjust the cushion screws and replace worn cushion seals.

Speed too high for the moving mass

Reduce speed with flow controls or fit external shock absorbers.

Load heavier than the cylinder was sized for

Check the moving mass against the cylinder's cushioning capacity.

Flow controls removed or bypassed

Refit and set the flow controls.

Prevention: Cushion and flow settings recorded and checked after changes.

Rod seal leak or damaged rod

Hits OEE: Quality

Symptoms: Air hissing at the rod end, a scored rod, a torn wiper.

Dirt or weld spatter on the rod

Fit a scraper or gaiter where the rod is exposed.

Side load on the rod

Use external guides or a guided cylinder for side loads, and a floating joint at the rod end.

Scored or bent rod

Replace the rod or cylinder; new seals will not hold on a damaged rod.

Seals at the end of their life

Replace the rod seal and wiper.

Prevention: Rods inspected on the route and guarded from spatter and dirt.

Cylinder will not hold position

Hits OEE: Quality

Symptoms: The cylinder creeps when the valve is in its middle position or when air is off.

Valve centre position exhausts the cylinder

Use a closed-centre valve or pilot check valves where a hold is required.

Internal piston seal leak

Test and replace the piston seal.

Leaks between the valve and the cylinder

Find and fix the leaks in that run.

Compressed air relied on to hold a load

Use a rod lock or mechanical stop where the position must hold safely.

Prevention: Holding requirements written into the design and checked at commissioning.

End position sensor not switching

Hits OEE: Availability

Symptoms: The machine waits for a cylinder that has already moved and the sensor light stays off.

Sensor slid along the tube

Re-set the sensor position and lock it.

Sensor does not suit the cylinder (no magnet or wrong slot)

Use the sensor the cylinder maker specifies.

Damaged sensor cable

Replace the cable and route it away from moving parts.

Strong magnetic fields from nearby welding

Use sensors rated for weld fields.

Prevention: Sensor positions marked on the cylinder.

Water or oil in the air supply

Hits OEE: Performance

Symptoms: Sluggish valves, water spraying from the exhausts, swollen seals.

Air dryer not working

Check the dryer and its drains.

Filter drains blocked

Clear or replace the automatic drains.

Too much or the wrong lubricator oil

Set the lubricator to the lowest rate needed, or remove it if the components are lubricated for life.

No filter at the point of use

Fit a filter regulator before the valve.

Prevention: Air treatment checked on the route.

Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.

Stop the same fault coming back

Recurring pneumatic cylinder stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: it tracks OEE and downtime live from PLCs, IoT sensors or AI cameras; where cameras are fitted, the video of a stop sits next to its machine data so the cause can be reviewed; and a technician opens the work order from the stop in the same system. Data is hosted in the AWS EU region, and Fabrico and the company behind it hold ISO/IEC 27001, ISO/IEC 20000-1 and ISO 9001.

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Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover