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Jul 22 2026
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A mobile crane is a lifting machine, so hydraulic cylinder condition is treated differently from the same components on an earthmoving machine. A cylinder that drifts slightly on a loader is an inconvenience; on a crane it affects load positioning and, in the case of an outrigger, the stability of the whole machine. Sealing maintenance on lifting equipment therefore tends to follow inspection schedules rather than hour meters.
This page is general application information for mobile crane hydraulic sealing. Hydraulic sealing applications for selected mobile crane and lifting equipment models from major brands. Confirm the crane model, component and part details with JR Seal before ordering.
Mobile cranes use hydraulic cylinders for outrigger extension and levelling, boom luffing and boom telescoping, and some designs also use hydraulic cylinders for counterweight or jib functions. Outrigger cylinders work close to the ground in mud, dust and standing water, which makes contamination a significant factor even though these cylinders move only twice per lift. Boom cylinders, by contrast, work under continuous load and are sensitive to any loss of holding performance.
Because lifting equipment is inspected regularly, seal wear is often identified earlier than on other machines. Typical findings are a light oil film on a rod, a slow change in boom position under load, or an outrigger that settles after levelling.
The components most often re-sealed are the outrigger cylinders, the boom luffing cylinder and the telescopic cylinders, together with the hydraulic pump and the control valve sections on higher-hour machines. The seal groups are the same family as those used on construction equipment cylinders: rod seals, wipers or dust seals, buffer seals, piston seals, wear rings and static O-rings with backup rings.
Confirm the crane model, component and part details with JR Seal. General component information is provided for maintenance planning, not as a statement of coverage for a specific machine.
To check a match, provide the crane make and model, the hydraulic component involved, and the seal dimensions or the original part number. For telescopic cylinders in particular, a cross-section drawing or measurement of the removed seal is valuable, because the seal stack includes several stages and the parts must not be interchanged between stages.
Quantity, packing preference and destination port should also be confirmed. Matching is normally done from the component rather than from the crane model alone.
You can also browse the full hydraulic seal products catalogue.
On lifting equipment, hydraulic sealing maintenance is normally driven by the inspection schedule rather than by the hour meter. Outrigger cylinders are checked for settling, boom cylinders for drift under load, and telescopic cylinders for any change in extension behaviour. Catching a seal problem during an inspection is considerably cheaper than finding it during a lift.
Outrigger cylinders deserve particular attention because they work close to the ground and are exposed to mud, water and grit. Even though they move only a few times per lift, contamination that enters past the wiper will remain in the assembly and damage the pressure seals over time. Cleaning the rod before and after use, where the site allows it, is a simple measure that makes a measurable difference.
Telescopic cylinder seals must be matched stage by stage. The stages of a boom are different sizes and their seal profiles are not interchangeable, so mixing parts between stages is a common cause of a repair that does not hold. Identifying each stage and treating it separately is the reliable approach.
Confirm the crane model, component and part details with JR Seal before ordering.
Internal leakage past the piston seal is the usual cause, sometimes combined with a pilot-operated check valve that is not seating correctly. Re-sealing the cylinder restores holding performance when the bore and rod are in good condition.
No. Each stage has its own seal sizes and profiles, so the stages must be identified and matched individually.
Send the crane model, the hydraulic component and either the seal dimensions or the original part number. JR Seal will review the application and reply with a suitable option or a request for further details. Please contact JR Seal to start a matching enquiry.
