Every week, a factory manager calls me with the same question: "Cylinder's leaking, should I just order a new one?" Nine times out of ten, the answer is repair. Here's how I work it out on the phone, and why the maths almost always favours a rebuild.
Why cylinders fail (and what that tells us about the fix)
Pneumatic cylinders don't really "break". They wear out in predictable ways, and each failure mode has its own repair path.
- Seal degradation. The single most common issue. Piston and rod seals harden or tear over time. You get air leaking past the piston, slow strokes, weak force. A seal kit fixes this.
- Rod scoring or pitting. Usually contamination in the air supply cuts grooves into the chrome. If the pitting is shallow, we re-chrome; if the rod is bent or deeply damaged, we replace it.
- Bore scoring. High-cycle machines or bad lubrication chew up the barrel bore. Light scoring hones out; heavy scoring usually means the cylinder is done.
- End cap damage. Hydraulic lock or missing cushions can crack an end cap. Replaceable on most ISO 15552 cylinders.
- Corrosion. Common in humid Noida summers and food/chemical plants. If it's surface rust, we clean it. If it's pitted through, we replace.
What a "repair" actually looks like on the bench
If you dropped a faulty cylinder off at our Sector 9 workshop, here's what the repair technician would do:
- Disassemble: end caps off, piston out, parts laid out in order
- Inspect: rod for scoring, bore for scratches, seals for wear pattern
- Clean and degrease barrel and all components
- Re-chrome the rod if it's pitted (sent out to a chroming shop, adds a day)
- Hone the bore if it's lightly scored
- Fit a full new seal kit (piston seal, rod seal, wiper, cushion seals, O-rings)
- Reassemble to spec, torque the tie rods correctly
- Pressure test at rated working pressure, usually 7-10 bar
Simple reseal: half a shift. Rod re-chroming job: 2-3 days because the rod goes out to a chroming shop. Most of what we handle falls in the 24-72 hour window.
Repair vs replace: side by side
Lean towards REPAIR when…
- Seal wear is the main issue
- Rod and barrel are in decent shape
- Bore size is 40mm or bigger (more rebuild value)
- It's a tie-rod type (ISO 15552 / 6432)
- Stroke length or mounting is non-standard
- You need it back in days, not weeks
Lean towards REPLACE when…
- Barrel is badly scored or corroded through
- Cylinder body has cracks or impact damage
- Bore is under 20mm (labour ≈ new cost)
- Obsolete seal profile no supplier stocks
- It's already been rebuilt 3-4 times
- You're upgrading to a better spec anyway
The real numbers: repair vs new (Indian market, April 2026)
| Cylinder | New price | Repair cost | You save |
|---|---|---|---|
| ISO 15552, ⌀40 × 150 stroke | ₹3,000-4,500 | ₹900-1,500 | ~65% |
| ISO 15552, ⌀63 × 250 stroke | ₹6,000-8,500 | ₹1,800-2,800 | ~65% |
| ISO 15552, ⌀100 × 400 stroke | ₹14,000-22,000 | ₹3,500-6,000 | ~70% |
| ISO 15552, ⌀160 × 500 stroke | ₹28,000-45,000 | ₹6,000-10,000 | ~75% |
Notice the pattern: the savings go up with bore size. A small ⌀25 cylinder isn't worth resealing because the labour swallows the saving. Anything ⌀40 and above, the maths is obvious. That's why we get called in for the bigger cylinders more often.
Turnaround: repair usually wins here too
New cylinder from a dealer: 3-7 days if it's a standard model sitting in someone's warehouse in NCR. Two to four weeks if it's imported or an unusual bore/stroke. Custom builds can run longer.
Repair at our shop: 24 hours for a straight reseal, 48-72 hours if the rod needs re-chroming. Walk in Monday, most jobs are ready by Wednesday or Thursday. If your production is down, that difference alone pays for the repair.
When I honestly tell people to just replace
I'm not trying to sell you a repair you don't need. I'll tell you to replace if:
- The barrel is cracked or badly corroded all the way through
- The cylinder body is physically damaged (hit by a forklift, dropped, etc.)
- It's already been rebuilt three or four times. The tolerances won't hold again
- It's a micro cylinder (⌀20mm or smaller). The labour isn't worth it
- The seal profile is obsolete and no one stocks the kit
In those cases we'll source you a matching new cylinder. But honestly, most of what comes through our door is a seal job wearing a panic about replacement.
Send a WhatsApp photo of the faulty cylinder (brand, bore, stroke visible) to +91-9811104037. I'll tell you in one reply whether to repair or replace, and quote either way before you commit.