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Quick Answer: A hydraulic wiper seal is mounted in the cylinder head to scrape dirt, dust, moisture and metal particles from the piston rod before the rod seal contacts the rod. CORASEALS supplies hydraulic wiper seals in standard and custom profiles with materials such as polyurethane, NBR, FKM, HNBR and PTFE. Send the rod diameter, bore diameter, groove dimensions, pressure, speed, hydraulic fluid and seal profile for a quotation.
Hydraulic cylinders operate in dirty environments. The piston rod retracts into the cylinder after every stroke. Dirt, sand, ice, dust, water and metal chips stick to the rod surface. The wiper seal scrapes these contaminants off the rod. That scraping action protects the rod seal from scoring. The wiper seal also protects the hydraulic oil from solid contamination. A wiper seal is not a rod seal. A rod seal keeps hydraulic oil inside the cylinder. A wiper seal keeps external material outside.
Hydraulic wiper seals are available in several profiles. The profile controls how the seal fits in the cylinder head and how the lip contacts the rod.
Catalog codes such as W, AN, WS and similar codes may differ between suppliers. Do not assume full interchangeability from a code alone. Compare the section drawing, rod diameter, bore diameter, width and material before ordering. CORASEALS can review the existing seal drawing or photo.
Material selection depends on hydraulic fluid, rod speed, temperature and external contamination. Polyurethane is a common wiper seal material because polyurethane resists abrasion and extrusion. NBR suits many standard mineral oil systems. FKM handles elevated temperatures and aggressive fluids. HNBR offers improved wear and temperature resistance compared with NBR. PTFE based wiper seals work in high sliding speed and low friction applications. Verify the compound with the supplier before changing materials.
| Material | Common Advantage | Main Limitation |
|---|---|---|
| Polyurethane (TPU) | High abrasion resistance, good extrusion resistance | May degrade in hot water or certain esters |
| NBR | Good oil resistance, lower cost | Limited ozone and weather resistance |
| FKM | High temperature and chemical resistance | Not always suitable for low temperature |
| HNBR | Better wear and temperature range than NBR | Higher cost than NBR |
| PTFE | Low friction, broad chemical resistance | Less elastic, may require housing design changes |
To measure a hydraulic wiper seal, record the rod diameter. Measure the bore diameter in the cylinder head where the wiper seal seats. Measure the groove width and groove depth. If the old seal is available, measure the outside diameter and the lip opening. Record the seal profile and installation direction. A drawing or photo helps avoid profile confusion.
Many catalogs describe hydraulic wiper seals by rod diameter × bore diameter × width. Check the catalog drawing because dimension order may change. Groove dimensions are just as important as seal dimensions. A correct seal can fail if the groove is too wide, too narrow or too shallow.
A new wiper seal cannot fix deep scratches or pitting on the rod. Repair or replace the rod surface first. The rod surface finish and runout must meet the seal supplier recommendation.
Send the following data to CORASEALS for a hydraulic wiper seal quotation.
Send the rod diameter, bore diameter, groove dimensions, pressure, speed, hydraulic fluid and seal profile to CORASEALS. If the cylinder needs rod seals, piston seals, buffer seals or wear rings, include that request with the wiper seal inquiry.
Q: What is the difference between a rod seal and a wiper seal?
A: A rod seal keeps hydraulic oil inside the cylinder. A wiper seal removes external contamination from the piston rod before the rod seal contacts the rod. The two seals work in series but perform different jobs.
Q: Can a hydraulic wiper seal work with all hydraulic fluids?
A: No. The seal material must be compatible with the hydraulic fluid. NBR works with many mineral oils. FKM suits aggressive fluids and higher temperatures. Polyurethane may degrade in hot water or certain phosphate ester fluids. Always confirm compatibility.
Q: Do I need a snap-in wiper seal or a metal-cased wiper seal?
A: A snap-in wiper seal fits a machined groove in the cylinder head. A metal-cased wiper seal presses into the housing and gives stronger retention. The choice depends on the housing design. Compare the existing groove layout and contamination level.
Q: How do I measure a hydraulic wiper seal without a drawing?
A: Measure the rod diameter, the housing bore diameter, the groove width and the groove depth. If the old seal is available, measure the lip opening and the outside diameter. Send the measurements and a photo to CORASEALS.
Q: Can I replace a hydraulic wiper seal with the same code from another supplier?
A: Not always. Catalog codes may look similar but profile details can differ. Check the section drawing, dimensions and material. Send the old sample or drawing to confirm the correct replacement.
