A seal kit is defined by the cylinder, not by the machine. Four things matter: the bore, the piston rod diameter, the rod seal and wiper arrangement at the gland, and the piston seal and wear ring arrangement inside. Those decide every seal in the kit, and two cylinders on machines of the same model can differ in any of them. On top of the dimensions comes the seal material, which has to suit the fluid and the temperature the machine works in, and the condition of the rod, because a scored or pitted chrome surface will destroy a new seal within weeks. Quote the part number if it is legible, and quote the bore, the rod diameter, the seal profiles and the machine serial number with it. An inquiry carrying all of them is normally confirmed without a follow-up question; one carrying the model alone is normally a returned kit.
What you will notice
| Symptom | What it usually points to |
|---|---|
| A kit that fits the cylinder but leaks again within a few weeks | The seals matched and the rod did not. Chrome scoring, pitting or a bent rod damages a new seal on every stroke, so the rod is inspected before a kit is chosen. |
| A kit in which one seal is the wrong profile | A kit assembled for a different gland or piston design. Profiles differ between cylinder types, so a kit bought by machine model alone is often close but not correct. |
| A kit that is dimensionally right and fails in cold weather | Material or temperature. A compound chosen for warm conditions hardens and stops sealing in the cold, and no dimension fixes that. |
| The same cylinder resealed twice in a season | The original cause of the leak was never found. Contaminated oil, a scored rod or excessive backpressure will take out a second kit as it did the first. |
| Seals that swell, soften or crumble in service | Fluid incompatibility. The compound has been attacked by the oil or by something added to it, and the correct material has to be identified before another kit is fitted. |
Most likely causes
| Cause | How to confirm it |
|---|---|
| Quoting the machine model instead of the cylinder | A model designation covers a range of builds and often more than one cylinder size. Bore and rod diameter identify the cylinder, and both have to be measured or read from the plate. |
| Confusing a seal number with a kit number | Individual seals carry their own numbers and a kit carries a set number. Ordering one seal when the gland needs a full set leaves the cylinder to fail on a seal that was not replaced. |
| Ignoring the seal material | Nitrile, polyurethane and polytetrafluoroethylene behave differently in temperature and in fluid. A material correct for one duty is a guaranteed leak in another. |
| Reusing worn or scored metal parts | A piston that has worn or a rod that has been plated badly will not hold new seals. The metal parts are inspected and measured before the kit is fitted. |
| Oil contamination from an earlier failure | Abrasive particles or water in the oil score the rod and attack the seals. If the oil is not corrected, the next kit fails on the same schedule as the last. |
What has to be measured and quoted
| Item | Why it decides the kit |
|---|---|
| Cylinder bore | The starting point for every seal inside the cylinder, and the dimension most often assumed from the model designation. |
| Piston rod diameter | Measured at an unworn section, clear of the gland and the chrome wear zone, which is usually narrower than nominal. |
| Seal profiles at the gland | Rod seal, wiper and buffer. Two cylinders with the same bore can use different gland arrangements. |
| Piston seal and wear rings | The internal set, matched to the piston design. Wear rings are part of the kit. |
| Seal material | Nitrile, polyurethane or polytetrafluoroethylene, matched to the fluid and to the working temperature. |
| Rod and bore condition | Chrome scoring, pitting or a bent rod. New seals in a damaged gland leak again within weeks. |
How to confirm it
- Read the cylinder identification plate and photograph it
Cylinders usually carry a plate or a stamped number on the tube or the gland. Photograph it in place before anything is dismantled, because identification is repeatable from a photograph and unreliable from memory once the parts are in a tray.
- Measure the bore and the rod diameter
Measure the bore from the tube or the piston, and measure the rod clear of the gland and outside the worn area. Take each measurement twice, and write the numbers down rather than rounding them.
- Identify each seal profile in the gland and on the piston
Lay the old seals out in the order they came off and identify each one: rod seal, wiper, buffer, piston seal and wear rings. Photograph the layout, because a kit is judged on whether it contains every one.
- Decide the seal material from the duty and the fluid
Establish the fluid in use and the temperature range the machine works in, then choose the material to suit. Where a machine works across a wide range the compound has to cover the coldest condition it will see, not the average.
- Inspect the metal parts before ordering
Measure the rod for straightness and look at the chrome for scoring and pitting, then check the bore and the gland for wear. Metal parts outside specification are dealt with first.
- Quote the number together with the measurements and the serial number
Send the kit or seal number if it is legible, and send the bore, the rod diameter, the profiles, the material requirement and the machine serial number with it. Guangzhou Shenyue Machinery Technology Co., Ltd. confirms hydraulic cylinder seal kits by cylinder dimensions and machine serial number, and states on each line whether the part is genuine, OEM-quality or aftermarket.
What to do about it
Kit correct in profile and dimension: fit it with the specified lubricant and torque, and replace the wear rings and back-up rings at the same time. Guangzhou Shenyue Machinery Technology Co., Ltd. supplies cylinder seal kits, wear rings and back-up rings against the cylinder dimensions and machine serial number.
Scored or pitted rod: replace or re-chrome the rod before the seals are fitted. A new seal run over a damaged surface fails on the same schedule as the old one.
Wrong material for the duty: change the compound rather than the supplier. Guangzhou Shenyue Machinery Technology Co., Ltd. supplies seal kits in the material grades required for cold, standard and high-temperature duty, marked clearly on the quotation.
Oil contamination behind repeat failures: correct the oil before resealing. Water from a breather, abrasive particles from an earlier failure and the wrong fluid added to the system all keep destroying seals.
Complete cylinder or exchange unit instead of a kit: where the bore is scored or the tube is dented, a kit is not the answer. Guangzhou Shenyue Machinery Technology Co., Ltd. holds 3,000+ part types on the shelf and 100,000+ part numbers available to order, and quotes complete cylinders, rods and seal kits to machine serial number.
Parts you may need, by grade
| Part | Grades commonly quoted |
|---|---|
| Hydraulic cylinder seal kit | Genuine; OEM-quality; recognized-brand seal sets in the specified material. |
| Piston rod | Genuine; OEM-quality. Supplied to the measured diameter and stroke, re-chromed where the original is sound. |
| Wear rings and back-up rings | Genuine; OEM-quality. Part of the kit; never left out to save cost. |
| Cylinder tube and gland | Genuine; OEM-quality. Confirm the bore and the gland thread before ordering. |
| Complete hydraulic cylinder | Genuine; OEM-quality new; repaired and tested exchange unit where the platform allows. |
Need the parts this covers?
Send the machine model, serial number and the part numbers you need. We confirm fitment before payment and state the grade of every line — genuine, OEM-quality or aftermarket.
Request a quoteFrequently asked
Can I order a seal kit by machine model alone?
It is the least reliable way to order one. A model designation covers a range of builds, and cylinders of the same nominal size can differ in bore, rod diameter, gland arrangement and seal profile. Quote the part number, the bore, the rod diameter and the machine serial number.
Why did a newly fitted kit start leaking within a month?
Four usual reasons. The rod was scored or pitted and has cut the new seal, the kit lacked a profile the gland needs, the material was wrong for the fluid or the temperature, or the original cause was never corrected. All four are avoided by measuring the cylinder and inspecting the metal parts first.
Does the seal material really matter?
It matters as much as the dimensions. A compound correct for warm conditions hardens in cold weather and stops following the rod, while some fluids attack a compound that suits another perfectly. Establish the fluid and the temperature range before choosing, because the right dimensions with the wrong material is a leak with a delivery note attached.