Direct answer: when a pneumatic rock-drill air leg will not extend, slips under drilling load, leaks continuously, moves in a jerky way, or cannot maintain feed force, do not replace the leg immediately. First separate the fault into three groups: air supply and hose problems, setup/alignment problems, or an internal air-leg problem such as leakage, control restriction, seal wear, or mechanical damage. The fastest diagnosis starts upstream, checks the leg unloaded and then under controlled load, and only then moves to internal service.
This guide is for underground mines, quarry crews, tunneling contractors, distributors, and maintenance teams using air-leg pneumatic rock drills. It focuses on the pusher leg itself rather than percussion-system troubleshooting.
1. What the Air Leg Actually Does
A pneumatic air leg is a pusher cylinder that supports the rock drill and applies controlled thrust toward the face. It does not create the drill’s percussion energy. That distinction matters because low penetration can come from the compressor, hose, rock drill, drill steel, bit, flushing, operating settings, or the air leg.
The current PerfoMax product page presents FT160A, FT160B, FT160C and FT170 as available configurations. FT160BC, FT160BD, FT160S or any other suffix found in historical or external documents requires document-based verification and is not currently presented as an available configuration. Confirm the exact model, manufacturer, pressure range, mounting interface, travel and approved rock-drill pairing in the controlled product documents and written quotation; no interchangeability is implied.
2. Symptom-to-Cause Troubleshooting Table
| Symptom | First checks | What it may indicate | When to stop and service |
|---|---|---|---|
| Will not extend | Air isolation, hose/coupling, working pressure, control movement | No supply, restriction, blocked control, stuck piston, severe internal leakage | Supply is confirmed but the leg still will not move, or movement is unsafe/abnormal |
| Extends very slowly | Pressure drop, hose restriction, couplings, contamination | Insufficient delivered air, restricted flow, internal bypass, sticking | Speed remains abnormal after supply and external restrictions are corrected |
| Extends unloaded but slips or collapses while drilling | Dynamic pressure at the tool, leaks, footing, angle, feed demand | Pressure loss, internal leakage, unstable setup, excessive demand | The leg cannot safely hold controlled thrust at verified supply conditions |
| Continuous air hiss | Hose, fittings, connections, control area, cylinder/rod area | External leak or internal seal/control leakage | Leak location points inside the leg or cannot be safely isolated externally |
| Jerky or sticky travel | Air quality, moisture, contamination, alignment, visible damage | Contamination, corrosion, damaged sliding surfaces, seal drag, misalignment | Rod/cylinder damage, binding, or unpredictable movement is present |
| Leg feels normal but drilling is slow | Percussion, drill steel, bit, flushing, compressor capacity | The air leg may not be the root cause | Diagnose the rock drill and drill string instead of repeatedly adjusting the leg |
3. Check the Air Supply Before Blaming the Air Leg
Pneumatic cylinder force and speed depend on the air actually delivered during operation. A compressor gauge can look acceptable while pressure at the drill falls because of long hoses, undersized passages, restrictive couplings, leakage, water, or simultaneous demand from other equipment.
Use this upstream-first sequence:
- Confirm the exact air-leg and rock-drill model. Record the leg suffix, drill model, hose arrangement, and any recent component changes.
- Inspect the hose route. Look for kinks, crushed sections, loose couplings, damaged fittings, and obvious external leakage.
- Check air quality. Excessive water and contamination can affect valves, seals, lubrication, and smooth actuator movement.
- Measure working pressure close to the tool under actual flow. Do not rely only on static pressure at the compressor receiver.
- Compare unloaded and loaded behavior. A leg that extends normally with no drilling load but loses thrust under load often points to delivered-air loss, leakage, or excessive demand rather than a fully seized cylinder.
For a PerfoMax FT160-series unit, compare the observed working condition with the exact product/model documentation. Do not apply one pressure number to a different pusher-leg design simply because the cylinder looks similar.
4. Won’t Extend: Diagnostic Sequence
If the leg does not extend at all, the main question is whether air reaches the leg and whether the control path can pass that air.
- Isolate and depressurize the system before touching or disconnecting hoses.
- Verify that the correct hose is connected and that the supply path is open.
- Inspect couplings and hoses for obstruction, collapse, or damage.
- Restore air according to the site procedure and verify delivered working pressure.
- Operate the leg control through its normal range without forcing it.
- If supply is present but there is no movement, remove the leg from service for control, piston, cylinder, or seal inspection using the correct model procedure.
Do not bypass a control or improvise a pressure connection to “prove” the cylinder can move. Unexpected extension can create a crush hazard.
5. Extends Unloaded but Slips Under Drilling Load
This symptom is especially useful because it shows that the piston can move, but the system cannot maintain stable thrust. Work through these possibilities in order:
- Dynamic pressure loss: the leg has enough air to extend freely but not enough delivered pressure under combined drill demand.
- External leakage: a hose, fitting, or connection leaks more severely as demand rises.
- Internal leakage: worn or damaged sealing surfaces allow air to bypass the piston instead of maintaining force.
- Unstable footing: the leg foot moves, sinks, or skids and feels like pneumatic “slip.”
- Poor angle or alignment: side loading can make extension feel sticky and can reduce stable support.
- Excessive feed demand: using the air leg to compensate for poor percussion, a dull bit, or another drilling problem can overload the support system.
5A. Footing and Ground-Interface Check: Is the Leg Slipping or the Cylinder Bypassing?
Before authorizing seal or cylinder work, prove whether the air leg is actually losing extension or whether its foot is moving against the floor. These faults can feel identical at the drill: feed falls, the drill backs away from the face, and the operator adds more leg pressure. The evidence is different. An internal bypass changes the leg’s extension while the foot remains fixed; a ground-interface problem moves, pivots, or sinks the foot while the leg may retain its length.
Make this distinction only under the site’s approved isolation, ground-control and controlled-test procedure. Do not place hands or feet in the line of movement, stand behind a loaded leg, or improvise blocks, spikes, pads, wedges or restraints. If the ground or support method is not approved for the drilling position, stop the test and escalate it.
| Observed under the approved controlled-load test | Evidence to check | Most likely fault group | Next decision |
|---|---|---|---|
| Foot stays fixed, but exposed leg length decreases or the cylinder retracts | Mark or record the starting position without entering the movement zone; compare leg position with dynamic supply and leakage observations. | Internal bypass, control-path fault or insufficient delivered air under load. | Continue the pneumatic isolation sequence. Do not blame the ground interface merely because the drill moved. |
| Foot slides across the surface while the leg length remains substantially stable | Look for a clean movement track, polished or wet surface, loose fines, slurry, oil, ice, or a foot that cannot seat as designed. | Ground-interface or setup failure. | Stop, isolate and restore an approved working surface or relocate the setup. Do not compensate by increasing feed pressure. |
| Foot sinks progressively into loose, broken or soft material | Compare the initial and loaded foot position; inspect for disturbed material, voids or loss of bearing beneath the contact point. | Insufficient ground bearing or unsuitable support position. | Do not continue the loaded test until the supervisor has approved the location and any specified support method. |
| Leg rocks, twists or pivots instead of feeding along the hole axis | Check whether the foot seats evenly and whether the leg, drill and intended hole axis remain aligned through the planned travel. | Uneven surface, poor geometry or side loading. | Reposition under the approved setup method; inspect for bending or joint damage if side loading occurred. |
| Foot, spike, pad or attachment is loose, bent, cracked, missing or heavily worn | Inspect the complete foot assembly with energy isolated; record the part identity and damage rather than judging only by overall appearance. | Mechanical component defect. | Quarantine the leg or foot assembly and match the replacement to the exact air-leg suffix and parts information. |
| Movement appears only when feed is increased to overcome slow drilling | Check bit condition, percussion, rotation, flushing and hole alignment before increasing leg demand. | Excessive feed demand masking another drilling fault. | Correct the drill-string or drilling-performance problem; do not use more leg force as the first remedy. |
Controlled footing-versus-bypass sequence
- Isolate and inspect. Check the foot assembly, attachment, visible rod/cylinder condition, hose routing and the proposed contact area before applying energy.
- Record the start state. Capture the foot position, leg extension, setup angle, surface condition and exact drill/air-leg identity.
- Observe unloaded travel. Confirm smooth extension and retraction only by the method permitted in the manual and site procedure.
- Apply the minimum approved representative load. Keep personnel clear and observe the foot and leg body as separate reference points.
- Pair movement with air evidence. Record dynamic supply condition, visible or audible leakage, foot movement, leg-position change and whether the symptom follows increased drilling demand.
- Choose one disposition. Release only if the footing remains stable and the leg holds controlled feed; otherwise re-site the setup, quarantine a damaged foot, or route the leg to pneumatic service based on the observed evidence.
Copy-ready ground-interface diagnostic record
- Equipment: rock-drill model; air-leg make, complete suffix and asset ID; foot/spike/pad part identity if available.
- Location: heading or face; hole direction and collar height; surface description; water, fines, slurry, ice, loose rock or other contamination observed.
- Start state: foot position; leg extension reference; setup angle; visible foot, attachment, rod or cylinder defects.
- Controlled-load evidence: foot moved / sank / pivoted / remained fixed; leg shortened / held / moved unpredictably; dynamic supply and leakage observations.
- Disposition: approved re-site; surface-control action; foot assembly quarantined; pneumatic workshop inspection; other drilling fault investigated; released for service.
- Authorization: operator, supervisor or technician, date/shift, referenced procedure, corrective action and release signature.
When a replacement foot or complete leg is required, identify the exact configuration through the FT160-Series air-leg matching page and the active pneumatic rock-drill range. A family name or visual match is not enough for substitution.
6. Air Leak: External Connection or Internal Seal?
A continuous hiss does not automatically prove a failed piston seal. First localize the leak with the site’s approved leak-detection procedure and PPE. Check the hose, quick connection, threaded fitting, and control area before opening the cylinder.
If external connections are sound but the leg cannot hold thrust and leakage appears to be internal, seal wear becomes a stronger suspect. Pneumatic-cylinder manufacturers commonly treat piston seals as service components, and insufficient piston sealing is a recognized cause of internal leakage. The correct repair still depends on the exact air-leg model and parts specification.
Do not mix seals, pistons, rods, or control parts between FT160 suffixes without verified compatibility. Similar external dimensions do not prove interchangeability.
6A. Controlled-State Leak-and-Load Isolation Matrix
Use this matrix to identify the first operating state in which the air leg fails. Work under the site’s approved pneumatic-tool procedure and the exact air-leg service manual. Isolate and depressurize the system before touching a hose, fitting, control, mount, rod, foot, or internal component. Do not invent a universal pressure-decay time or leakage limit: record the model requirement and the test method used.
| Controlled state | Observe and record | Stronger indication | Next action or stop boundary |
|---|---|---|---|
| 1. Isolated, depressurized inspection | Hose damage, loose or mismatched fittings, cracked mount or foot, bent/scored rod, contamination and side loading | An external connection, structural or alignment fault exists before pneumatic testing | Correct the external fault or remove the assembly from service before pressurizing |
| 2. Gradual pressurization with the control in neutral | Where leakage first becomes audible or visible from a safe position | Leakage before commanded movement points first to the supply connection, fitting or control area—not automatically to the piston seal | Isolate and repair the proven external/control-zone fault; do not tighten a live joint |
| 3. Approved unloaded extension test | Start response, full travel, speed consistency, sticking and any change in leakage | No or jerky travel after verified supply suggests restriction, contamination, binding, control trouble or internal bypass | Stop if travel is unpredictable or any damaged structural part is visible |
| 4. Controlled hold under an approved load | Whether the leg holds position, creeps or collapses; delivered pressure at the tool; footing and setup angle; change in leakage | Good unloaded travel but loss under load separates a load-dependent supply/setup problem from likely internal bypass | Verify dynamic supply and geometry before authorizing seal or cylinder work |
| 5. Approved retraction test | Retraction response, hose routing, binding and whether the symptom differs from extension | Normal extension with poor retraction narrows the fault toward the retraction/control passage, contamination or mechanical binding | Do not force the rod or dismantle a pressurized unit |
| 6. Paired drill operating check | Leg stability versus percussion, rotation, bit/steel behavior and flushing | A stable leg with poor drilling performance shifts diagnosis to the rock drill, drill steel, bit, flushing or air delivery | Keep the air-leg Owner separate from the drilling-performance investigation |
Stop and tag out the assembly for uncontrolled movement, a cracked mount or foot, a bent or deeply scored rod, metal debris, escalating heat, or a fault that requires opening the pressurized system. The matrix localizes the fault zone; it does not replace the model-specific service procedure.
7. Jerky, Sticky, or Uneven Extension
Jerky movement usually requires a broader check than “add more oil.” Moisture and contamination in compressed-air systems can damage sealing surfaces, promote corrosion, disturb lubrication, restrict valves, and make actuator response unstable. Misalignment or visible damage can create a mechanical bind even when the air system is healthy.
Check:
- water and contamination in the air line;
- lubrication condition required by the drill/leg system;
- visible rod, cylinder, foot, or mounting damage;
- side loading caused by poor setup angle;
- whether the symptom changes unloaded versus under load;
- whether the problem began after a hose, control, seal, or drill-model change.
If travel is unpredictable, the leg binds, or structural damage is visible, remove it from service rather than forcing movement.
7A. Cylinder-Dent and Piston-Rod Inspection: Repair, Replace, or Quarantine?
A repeatable bind at the same point in the stroke is different from random hesitation caused by wet air or unstable supply. After the leg is isolated, depressurized, cleaned externally, and identified by exact model and suffix, use the stroke position and visible geometry to decide whether the assembly can proceed to controlled testing or must go to a workshop. This is an inspection and disposition method, not permission to straighten, hone, heat, or open an air leg in the field.
| Finding | What it suggests | Disposition |
|---|---|---|
| Travel catches at the same stroke position on repeated approved unloaded tests | Localized cylinder deformation, rod damage, bushing misalignment, or an internal obstruction is more likely than a changing supply fault | Stop repeated cycling. Mark the stroke position, isolate the leg, and hold it for model-specific workshop inspection. |
| Visible dent, flat spot, crease, crack, or deep impact mark on the cylinder tube | The working bore may be distorted even if the exterior damage looks small | Quarantine. A trained workshop may assess only small dents under the exact service manual with the specified mandrel or service tool; improvised hammering, heating, drilling, or straightening is not acceptable. |
| Piston rod is bent, deeply scored, pitted, flaking, or rubbing one side of the guide | Rod/seal contact and alignment are compromised; continued cycling can damage seals and the cylinder | Remove from service and replace or repair only to the model-controlled procedure. Do not polish away deep defects or force the rod through a bind. |
| Rod and tube look sound, but movement improves when side load is removed | Setup geometry, mounting wear, foot position, or end-bushing alignment may be creating side load | Correct the external setup first. If binding remains with approved alignment, hold for workshop inspection. |
| No visible damage and travel is smooth, but the leg still creeps or loses load | An internal seal, control, or bypass fault remains more likely than a geometry fault | Continue with the controlled leak-and-load matrix and the model-specific service test; do not condemn the cylinder on appearance alone. |
Workshop intake sequence
- Identify the assembly: record model, suffix, serial or fleet ID, paired drill, and the event that preceded the fault.
- Record the repeat point: note whether the bind occurs during extension, hold, or retraction and whether it repeats at the same stroke position.
- Inspect the full exterior: clean enough to see dents, flat spots, cracks, impact marks, corrosion, rod scoring, mount damage, foot damage, and uneven rubbing. Do not hide evidence by grinding or repainting before inspection.
- Check alignment evidence: compare the rod, guide/end-bushing area, mount, foot, and operating geometry for one-sided contact or side loading. Use the manual's gauges, limits, and fixtures where specified.
- Assign one disposition: correct external setup and retest; workshop inspect; replace the controlled component; or quarantine the complete leg when identity, limits, or damage severity cannot be verified.
- Release only after the existing gate: repeat the approved unloaded extension, controlled hold, retraction, leakage, and paired-drilling checks. A leg that merely moves on the bench is not automatically ready for production.
RFQ/service record: send the exact air-leg model and suffix, cylinder and rod photos, marked bind position, extension-versus-retraction behavior, delivered-air test result, observed leakage location, suspected impact event, and requested disposition. Suppliers should confirm the correct cylinder, rod, guide/bushing, seal set, and any model-specific inspection tool before parts are mixed or ordered. For current drill and air-leg configuration support, see pneumatic rock drills and air-leg options.
8. Air Leg or Rock Drill? Separate the Two Faults
A healthy air leg can hold the drill correctly while penetration is still poor. If the leg extends smoothly, holds controlled thrust, and shows no abnormal leakage, move the diagnosis to the drilling system:
| Observation | More likely next diagnostic area |
|---|---|
| Stable leg, weak percussion sound or hard starting | Rock drill, lubrication, compressor delivery |
| Stable leg, slow drilling with worn bit | Bit condition and rock match |
| Stable leg, poor cuttings removal | Flushing/water system |
| Stable leg, rod bends or collaring is unstable | Feed setting, alignment, rod condition, operating technique |
| Leg loses position or thrust while drill otherwise runs normally | Air leg, supply, footing, seals, controls |
For model-specific drill troubleshooting, see the related YT28 rock drill troubleshooting guide.
9. FT160 Suffix Matching Matters During Repair
PerfoMax's current product page lists FT160A, FT160B, FT160C and FT170 and treats exact model matching as a compatibility requirement. FT160BC, FT160BD, FT160S or any other suffix found in historical or external documents requires verification against the intended rock-drill model; the FT160 family name alone does not establish a pairing or interchangeability.
That affects troubleshooting because a “replacement FT160” that does not match the intended suffix can create a second problem after the first one is repaired. Before ordering a complete leg or internal parts, send the exact suffix and paired rock-drill model.
10. Eight-Step Field Troubleshooting Workflow
- Identify: record air-leg suffix, rock-drill model, hose configuration, and recent changes.
- Make safe: isolate and depressurize before inspection or disconnection.
- Inspect externally: hose, couplings, fittings, mounting, foot, rod/cylinder surface, and visible damage.
- Check air quality: drain/condition the system according to site procedure and investigate unusual water or contamination.
- Verify delivered air: check working pressure near the tool under operating flow.
- Test unloaded movement: confirm smooth extension and control response without forcing the leg.
- Test controlled loaded support: determine whether thrust is stable or collapses as drilling demand rises.
- Localize and service: if the supply/setup is correct but leakage, sticking, or force loss remains, remove the leg from service and inspect it with the correct model procedure and parts.
10A. Return-to-Service Gate After Air-Leg Repair
An air leg should not return to production merely because it extends smoothly without a drilling load. Release it only after the original symptom has been reproduced or clearly defined, the corrective action has been recorded, and the assembly has passed the same controlled operating states that exposed the fault. Keep the air branch, hose, coupling, lubrication arrangement, footing method, paired drill and drill steel consistent wherever practical so a changed test condition does not hide a remaining problem.
Use the exact air-leg manual, site procedure and authorized service criteria. There is no universal acceptable creep distance, hold time, leakage rate or pressure-drop limit for every FT160-family or other pneumatic support leg. If the model limit is unavailable, do not invent one: place the assembly on hold and request the correct service information.
| Disposition | Evidence required | Action |
|---|---|---|
| READY | Correct model and suffix confirmed; no structural damage; controlled extension, hold and retraction are repeatable; no abnormal leakage or uncontrolled movement; paired drilling check is stable within the approved model/site limits | Return the identified leg to service with the completed release record and normal monitoring |
| CORRECT EXTERNAL AND RETEST | The fault follows footing, hose route, fitting, coupling, delivered air or setup geometry rather than the air leg after a controlled comparison | Correct the proven external condition, then repeat the complete release sequence; do not release from a partial retest |
| HOLD FOR WORKSHOP | The leg moves unloaded but creeps, collapses, binds, retracts poorly or leaks after supply and setup have been verified; the symptom follows the leg when permitted comparison conditions are held constant | Isolate, tag and send the exact leg for model-controlled seal, control, rod, cylinder or internal inspection |
| REMOVE / REPLACE | Cracked mount or foot, bent or deeply scored rod, uncontrolled movement, metal debris, unverified mixed parts, missing identity, or a repair that cannot be accepted against an authorized procedure | Do not pressurize for further field trials; replace with a verified compatible assembly or obtain an authorized repair disposition |
Controlled release sequence
- Lock the identity. Record the air-leg model and suffix, paired rock-drill model, asset number and any replacement-part identifiers. Similar overall dimensions do not prove compatibility.
- Preserve the as-found symptom. State whether the problem appeared in neutral, during unloaded extension, during a controlled hold, during retraction or only while drilling. Record whether the leg slipped, crept, collapsed, stuck or leaked.
- Verify the external system. Inspect the hose, couplings, fittings, mount, foot, rod surface, alignment and footing. Record working pressure near the tool while the fault condition is reproduced using the approved method.
- Repeat unloaded travel. Check extension and retraction through the permitted stroke without forcing the rod. Stop for unpredictable motion, binding, structural damage or increasing leakage.
- Repeat the approved hold test. Use the same safe load method, stroke position, footing and setup angle used during diagnosis. Record the model/site acceptance limit and the actual observation rather than writing only “passed.”
- Separate the leg from the drilling system. Where the procedure permits, compare the suspect leg with a verified compatible leg or compare the paired drill under the same controlled setup. Change one variable at a time and record where the symptom follows.
- Conduct a guarded operating check. Confirm stable support while percussion, rotation and flushing operate under an approved test condition. Stop if the leg loses position, extends unpredictably or requires the operator to compensate for the fault.
- Assign one disposition. READY, CORRECT EXTERNAL AND RETEST, HOLD FOR WORKSHOP or REMOVE / REPLACE. A repaired assembly remains on hold until the complete sequence is repeated.
Copy-ready air-leg service release record
| Record field | What to enter |
|---|---|
| Asset identity | Air-leg model/suffix, serial or asset number, paired drill model and service date |
| Original trigger | Won’t extend, slips/creeps under load, leaks, binds, retracts poorly or another precisely described symptom |
| External baseline | Hose/coupling arrangement, footing and angle, leak zone, working-pressure measurement point/method and result |
| Controlled-state results | Neutral, unloaded extension, approved hold, retraction and guarded paired-drill observations |
| Work completed | Adjustment, cleaning, external fitting repair, authorized parts replaced or workshop action; include part identifiers |
| Acceptance basis | Manual/site procedure reference, model-specific limits used and person responsible for approval |
| Final disposition | READY, CORRECT EXTERNAL AND RETEST, HOLD FOR WORKSHOP or REMOVE / REPLACE |
This release gate complements the earlier isolation matrix: the matrix identifies where the failure is strongest, while the release record proves whether the corrected assembly can safely return to its assigned drill and working setup.
11. Common Troubleshooting Mistakes
- Replacing the air leg before checking pressure at the tool under flow.
- Using compressor receiver pressure as proof that the leg receives adequate air.
- Increasing feed aggressively to compensate for a dull bit or weak percussion.
- Calling every leg “FT160” and ignoring the suffix.
- Treating a slipping foot or poor drilling angle as an internal seal failure.
- Continuing to operate with contaminated or water-laden compressed air.
- Installing unverified seals or internal parts because they appear dimensionally similar.
- Disconnecting or opening a pressurized leg.
12. Pre-Shift Air-Leg Checklist
- Confirm hose and coupling condition.
- Check for obvious external leakage.
- Inspect the leg foot, mounting, rod/cylinder surface, and visible damage.
- Confirm smooth control and extension response.
- Check that the paired rock drill and air-leg suffix are correct.
- Confirm the compressed-air system is drained/conditioned and lubricated according to the equipment procedure.
- Stop if the leg binds, collapses unexpectedly, or shows unsafe structural damage.
13. What to Send in a Service or Replacement RFQ
To shorten diagnosis and avoid an incorrect replacement, send:
Minimum diagnostic record
| Record field | Required evidence |
|---|---|
| Asset identity | Air-leg model and suffix, paired rock-drill model, readable nameplate and full assembly photo |
| Symptom by state | Neutral, unloaded extension, controlled loaded hold, retraction and paired-drill result |
| Supply evidence | Measurement point, approved instrument/method and working-pressure result while the symptom occurs |
| Leak location | First proven leak zone: hose/coupling, fitting, control area, cylinder/rod area or not located |
| Setup evidence | Footing, mounting, angle, hose route and any side loading or visible damage |
| Recent change | Last repair, seal/control/hose change, contamination or moisture event and when the symptom began |
| Disposition | External repair, controlled workshop inspection, model/suffix verification or complete replacement review |
- rock-drill make and model;
- exact air-leg model and suffix;
- clear nameplate and full-leg photos;
- whether the problem occurs unloaded, under drilling load, or both;
- working pressure measured near the tool during operation;
- hose length, internal diameter if known, and coupling arrangement;
- observed leak location or sound;
- air quality/moisture history and recent maintenance;
- photos of damaged seals, rod, piston, control parts, or fittings after safe disassembly;
- quantity and whether you need a complete leg or verified spare parts.
For current supply options, review the PerfoMax FT160-Series Pneumatic Air Legs, browse Rock Drills, or send an RFQ for model and suffix review.
FAQ
Why will my pneumatic air leg not extend?
Start with the supply path: isolation, hose, coupling, working pressure, and control movement. If delivered air is confirmed but the leg still does not move, investigate control restriction, piston sticking, internal leakage, or mechanical damage using the correct service procedure.
Why does the air leg extend normally but slip while drilling?
This often points to a problem that appears only under load: dynamic pressure loss, external or internal leakage, unstable footing, poor alignment, or excessive feed demand. Measure conditions under drilling flow rather than diagnosing from an unloaded test alone.
Does a constant air leak always mean the piston seal is bad?
No. A hose, fitting, coupling, control component, or another external joint may be leaking. Localize the leak first. Internal seal leakage becomes more likely when external joints are sound and the leg cannot maintain thrust.
Can FT160A, FT160B, FT160C, FT160BC, and FT160BD be interchanged?
Do not assume interchangeability. The current PerfoMax product page presents FT160A, FT160B, FT160C and FT170 as available configurations; FT160BC, FT160BD and FT160S are not currently presented as available. Confirm the exact nameplate, manufacturer, suffix, dimensions, mounting interface, travel and approved rock-drill pairing from controlled documents before ordering a replacement or internal parts.
How can I tell whether poor drilling is caused by the air leg or the rock drill?
If the leg extends smoothly, maintains controlled thrust, and has no abnormal leakage, investigate percussion, drill steel, bit condition, flushing, lubrication, and compressor delivery. If the leg itself loses position, collapses, leaks, or binds, troubleshoot the pusher system first.
Technical Sources
- UK Health and Safety Executive — Compressed Air Safety
- U.S. OSHA — Power-Operated Hand Tools (Pneumatic Tools)
These sources establish compressed-air and pneumatic-tool safety boundaries. Exact operating limits, test sequences, seal specifications and acceptable leakage remain controlled by the air-leg manufacturer’s model-specific documentation and the site procedure.