Hydraulic Cylinder Repairs Perth

A hydraulic cylinder that has stopped holding load is not automatically a write-off. Whether it can be saved comes down to the condition of a small number of components, and you can assess most of them yourself before you call anyone. This guide covers the six conditions we see most often on the bench, what causes each one, whether it can be repaired, and what has to happen next.

Fremantle Hydraulics repairs and overhauls cylinders for marine, mining, defence and transport operators across Perth and Western Australia. Our workshop dismantles cylinders from 2-inch bore up to 18-inch bore without applying heat, which removes the risk of distorting glands and barrels during strip-down.

Before you inspect anything, make the unit safe. Isolate the circuit, relieve stored pressure and support the load mechanically. A cylinder still holding pressure will move under its own energy, and it does not need much stroke to injure someone.

1. Scored or pitted rod chrome destroys your gland seals.

• What it looks like.
  You will see vertical score lines running along the rod, or rust-coloured pitting that catches your fingernail. Run a clean rag down the rod and it snags on damage you cannot see. Chrome damage nearly always shows up alongside a weeping gland seal, because the damaged surface is what destroys the seal.
• What causes it.
  Airborne grit gets past a worn wiper and is then dragged back and forth across the rod under load. On coastal and offshore work, chloride attack lifts the chrome from the base metal and it flakes away in patches.
• Is it repairable.
  In most cases yes. Light scoring is polished out. Deeper damage means the rod is ground undersize, re-chromed and ground back to the original diameter. Where pitting has gone through into the base metal, or where the rod is already at the limit of its remaining wall, a new rod is manufactured instead.
• What has to happen next.
  The rod is measured for straightness and diameter along its full length before any decision is made. Re-chroming a rod that is also bent puts the same seal failure straight back into service. 

2. Bore wear and ovality causes internal pressure bypass.

• What it looks like.
  The rod drifts under a held load with the valve in neutral, and cycle speed is uneven across the stroke. Fluid bypasses the piston internally, so you may see no external leak at all while the cylinder still fails to hold.
• What causes it.
  Side loading is the usual culprit. A misaligned mount, a worn pin bush or a cylinder working outside its designed line of action pushes the piston against one side of the barrel, so the barrel wears oval rather than evenly. Contaminated fluid accelerates it.
• Is it repairable.
  It depends on how much material is left. A barrel with light wear is honed and fitted with oversize piston seals. Where ovality exceeds what honing can correct without taking the wall below its pressure rating, the barrel is replaced and the rest of the cylinder reused. That is often more economical than a complete unit, particularly where mounts or ports are non-standard.
• What has to happen next.
  Bore diameter is measured at several points along the stroke and at right angles at each point. That is the only way to separate general wear from ovality, and the two lead to different outcomes. 

3. A bent rod will repeatedly destroy fresh seals.

• What it looks like.
  The rod binds at one point in the stroke and moves freely elsewhere. In service the giveaway is a gland seal that fails, is replaced, and fails again in the same number of hours.
• What causes it.
  Buckling under compressive load near full extension, shock loading, or an impact to the exposed rod. A cylinder specified with too small a rod diameter for its stroke will do this repeatedly no matter how often it is repaired.
• Is it repairable.
  Sometimes, but this is the condition where replacement is most often the right answer. A slight bend can be straightened and re-machined. A rod that has yielded significantly has work-hardened along the bend, and straightening introduces stress that shows up again in service. On any rod that has bent twice, fit a new rod in a larger diameter.
• What has to happen next.
  The rod is checked for run-out between centres. Anything beyond a small tolerance means the gland, bearing and seals have been running out of alignment, so those are replaced rather than reused. 

4. Gland and seal failures usually signal deeper mechanical issues.

• What it looks like.
  Oil weeps from the gland end and runs down the outside of the barrel, and there is a wet film on the rod when it retracts. On the machine you notice fluid loss, contamination around the cylinder and slower response.
• What causes it.
  Seals are consumables and they harden with heat and age, but most premature failures are a symptom of something else. Rod damage cuts them and misalignment loads them unevenly. A cylinder that eats seals is telling you to look at the rod and the mounts.
• Is it repairable.
  Almost always. A reseal is the most common cylinder repair we carry out. The unit is stripped, all soft parts are replaced, wear bands and bearings are checked, and the assembly is pressure tested before it goes back.
• What has to happen next.
  Every reseal includes an inspection of the rod and bore. New seals in a scored bore or on a damaged rod mean the same job again within months, so if the underlying cause is not identified at strip-down the repair is not finished. 

5. Weld and mount cracking creates severe side-loading risks.

• What it looks like.
  Cracks usually start at the toe of a weld around a clevis, eye or trunnion mount. You may notice elongated pin holes, a bush worn oval or dropped out, or distortion where the mount meets the barrel.
• What causes it.
  Cyclic loading at the mount, where the load concentrates. Worn pins and bushes let the cylinder move out of line, which increases load on the weld and starts the crack. A loose mount also drives the side loading that causes bore ovality, so the two often arrive together.
• Is it repairable.
  Usually yes, and this is work that is difficult to buy off the shelf. Mounts are cut out, re-machined and re-welded, and bushes are replaced. Where the mount is integral to a cast end cap, the decision depends on whether the cap can be sourced or manufactured.
• What has to happen next.
  Weld repairs on load-bearing mounts need the correct procedure and consumables for the parent material, and some marine and defence applications need documented inspection afterwards. Tell us at enquiry if your application requires certification, because it changes how the job is planned. 

6. Cylinders overhauled too many times lose critical wall margin.

• What it looks like.
  The service history tells you before the cylinder does. The rod has been re-chromed more than once, the bore is on its second set of oversize seals, and the interval between repairs is getting shorter.
• What causes it.
  Each repair removes material. A rod can only be ground undersize and re-chromed so many times before its remaining wall no longer supports the load, and a barrel can only be honed so far before the wall falls below its pressure rating.
• Is it repairable.
  Technically often yes, commercially usually no. When intervals are shortening and the unit is on its second or third overhaul, a new cylinder built to the original specification, or to a revised one that fixes the root cause, costs less over its remaining service life.
• What has to happen next.
  Look at why the cylinder is wearing out rather than at the cylinder itself. A unit that keeps coming back is usually undersized, misaligned, or working outside the duty it was specified for. 

Deciding between repair and replacement comes down to wall thickness and damage severity.

Five key factors determine your hydraulic cylinder repair cost.

Two cylinders of the same size can differ by an order of magnitude depending on what is wrong with them. These are the factors that move the number:

• Bore and stroke.
  Larger and longer units take more time to strip, machine and reassemble, and carry more material cost.
• Chrome condition.
  A polish is a small job, grinding and re-chroming is a larger one, and manufacturing a new rod is larger again.
• Barrel honing requirements.
  Honing adds machining time and drives the need for oversize seals.
• Seal availability.
  Standard kits are sourced quickly. Non-standard sizes and older units may need seals manufactured, which affects cost and lead time.
• Certification requirements.
  Where an application requires documented testing or inspection, that work is planned in from the start. 

Providing exact cylinder specifications gets you an accurate repair quote.

Send these details to receive a definitive quote rather than an estimate range:

• The make and model of the cylinder.
• The serial number, if the plate is still legible.
• The bore diameter.
• The stroke length.
• The rod diameter.
• Photographs of the damage, including the full rod, both mounts and the data plate.
• A short description of what the cylinder does and what it is fitted to.

If the plate is missing, send the photographs anyway. Most cylinders can be identified from their dimensions and mount configuration.

Common questions clarify the hydraulic cylinder repair process.

How much does it cost to repack a hydraulic cylinder?

The cost of a repack depends on the bore and stroke of the unit, whether the seal kit is a standard size or has to be made, and what the strip-down finds on the rod and bore. A cylinder needing only soft parts is a small job. One that also needs honing or re-chroming is a different job, and the difference is only visible once the unit is apart. Send the make, model, bore, stroke and rod diameter and we will quote against the actual unit.

Can a leaking hydraulic cylinder be repaired?

Yes, in almost every case. External leaking at the gland is a seal failure and a reseal fixes it. Internal leaking past the piston, where the cylinder loses load without any visible oil, points to bore wear and needs honing or a replacement barrel. Find out what damaged the seals first, because a reseal on a scored rod will fail again.

What are the most common hydraulic cylinder problems?

The six most common are scored or pitted rod chrome, bore wear and ovality, a bent rod, gland and seal failure, weld and mount damage, and a unit overhauled to the end of its material. Most trace back to one of three causes: contamination, misalignment, or a cylinder working outside the duty it was specified for.

Are hydraulic cylinders expensive to fix?

Repairing a cylinder is usually less expensive than replacing it, particularly on custom units and on cylinders with non-standard mounts or ports where a replacement has to be manufactured. The exception is a unit already overhauled several times, where each repair has removed material and the intervals between failures are shortening. At that point a new cylinder built to the correct specification is the better decision.

Our Henderson workshop handles full cylinder overhauls across Western Australia.

Our workshop at the Australian Marine Complex in Henderson handles cylinder repair and overhaul for operators across Perth and regional Western Australia. Send the details above and we will tell you whether your unit is worth repairing.

Contact Fremantle Hydraulics with your cylinder details.