Identify a hydraulic cylinder by measuring it, not by naming the machine. Record five things before ordering: bore diameter measured in an unworn area of the barrel, rod diameter measured outside the seal track, stroke measured pin to pin fully retracted and fully extended, mounting style with pin bore diameters and eye width, and gland or head style, because the seal kit depends on it. Then record the port thread and position, the rod end thread, and whether the barrel is welded or tie-rod construction. Casting or stamping numbers on the gland and barrel are useful confirmation but are not part numbers, and they will not identify a cylinder that has been reconditioned with parts from another unit.
What you will notice
| Symptom | What it usually points to |
|---|---|
| New seal kit leaks immediately after fitting | Wrong kit for the gland style. Several kits share a bore size and differ only in the head design. |
| Replacement cylinder has the wrong stroke | Measured from a catalog rather than from the machine. Stroke must be measured pin to pin, both ends. |
| Rod end does not match the original | Different rod thread or eye configuration for the same nominal bore. Common across build breaks. |
| Mounting pins will not enter the new eyes | Pin bore diameter or eye width differs. Both must be measured, not assumed from the model. |
| Port fittings do not seal | Different port thread standard. BSPP, JIC and metric ports appear on the same machine family. |
Most likely causes
| Cause | How to confirm it |
|---|---|
| Identifying by machine model alone | One model can carry different cylinders by build number, attachment and market. The model narrows the search; the measurements confirm it. |
| Confusing nominal with actual bore | A cylinder described as 120 mm may measure differently once wear and plating thickness are accounted for. Measure in an unworn band near the base, never where the piston has traveled. |
| Ignoring gland and head style | Welded gland, threaded gland, bolted gland and tie-rod designs all take different seal arrangements and different tools to open. The style decides the kit. |
| Overlooking rod surface specification | Chrome thickness, hardness and finish vary. A rod refinished to a different specification will destroy the wiper seal and then the gland. |
| Assuming a casting number is a part number | Casting numbers identify the casting, which may be shared across several assemblies. They help confirm what you have but will not order it. |
What to record before ordering a cylinder
| Dimension or feature | How to take it |
|---|---|
| Bore | Caliper or internal gauge in an unworn band near the base, three positions. |
| Rod diameter | Micrometer outside the seal track and away from any scoring. |
| Stroke | Pin center to pin center, fully retracted and fully extended. |
| Mounting | Pin bore diameter, eye width, and boss or clevis style at both ends. |
| Gland style | Welded, threaded, bolted or tie-rod, with the spanner or pin holes noted. |
How to confirm it
- Measure the bore where the piston does not travel
Take three readings at right angles near the base of the barrel and average them. Measuring in the worn band overstates the bore and produces a piston that fits the wear rather than the design, and a replacement cylinder built to that figure will be wrong.
- Micrometer the rod outside the seal track
Measure the chrome in an area the wiper does not reach, and check the same rod in the seal track for scoring and taper. If the rod is worn or pitted in the track, a seal kit alone will not hold and the rod has to be replaced or reconditioned.
- Measure stroke pin to pin, both ends
Fully retract and fully extend the cylinder and measure center to center. Note whether the machine has stops that limit travel, because a cylinder specified longer than the linkage allows will bottom internally and bend the rod.
- Record mounting geometry
Pin bore diameters, eye widths, the offset of the eye from the barrel axis and the angle of any clevis. These dimensions decide fitment more often than bore and stroke, and they are the ones most often left off an inquiry.
- Note the gland style and port details
Photograph the gland, note whether it is welded, threaded or bolted, and measure the port thread and its position relative to the barrel. Port standard is a sealing issue, and an adapter is not always acceptable on a high-pressure circuit.
- Cross-check stampings against the documentation
Record any numbers stamped on the barrel, gland or rod end and compare them with the parts catalog for the serial number range. Treat a match as confirmation and a mismatch as a reason to measure again rather than to guess.
What to do about it
Order against measurements plus the part number, never one without the other. A part number from a catalog for the right model is the fastest route when the cylinder is original, and the measurements are what catch the case where it is not. Guangzhou Shenyue Machinery Technology Co., Ltd. confirms fitment from bore, rod, stroke, mounting and gland details supplied with the inquiry, and supplies complete cylinders, barrels, chrome rods, glands, pistons and seal kits from Guangzhou with 3,000+ part types on the shelf and 100,000+ part numbers available to order.
Match the seal kit to the gland, not to the bore. Kits are frequently returned because the bore was right and the head design was not. Send a photograph of the gland and the kit reference together, and the ambiguity disappears.
Specify the rod finish when a rod is replaced. Chrome thickness and surface finish are part of the seal's working environment, and a rod finished to a general plating shop standard will leak again regardless of the kit used. State the application and the oil type when ordering.
Keep the removed cylinder until the replacement is proven. A cylinder that has been scrapped before the new one is fitted leaves nothing to measure when the mounting does not line up, and identical-looking units from different build ranges are exactly where that happens.
Parts you may need, by grade
| Part | Grades commonly quoted |
|---|---|
| Complete cylinder assembly | Genuine; OEM-quality. Confirm mounting geometry, not only bore and stroke. |
| Barrel | Genuine; OEM-quality. Honed bore and correct port configuration are both required. |
| Chrome rod | Genuine; OEM-quality. Chrome thickness and finish must match the application. |
| Gland and head assembly | Genuine; OEM-quality. Style decides which seal kit fits. |
| Seal kit | Genuine; OEM-quality; aftermarket. Matched to gland style and oil type. |
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 cylinder using only the machine model and serial number?
Often, yes, when the cylinder is the original one. The risk is the machine that has had a cylinder replaced before, or that was built with an attachment package the catalog does not assume. Measuring takes twenty minutes and removes that risk entirely.
Is a casting number the same as a part number?
No. A casting number identifies the casting and may be shared by several assemblies with different bores, strokes or port arrangements. It is useful evidence, but the order has to be placed against a part number confirmed by measurement.
Why does the same bore size need different seal kits?
Because the gland design differs. Welded, threaded and bolted heads use different seal arrangements and different retaining methods, and the piston seal can differ too. Bore alone does not describe the sealing system.