Products
Hydraulic rod seals and wiper seals
A rod seal sits in the cylinder head and keeps fluid from leaking out along the rod as it strokes, so oil on the rod usually points to it. A wiper at the outer end of the head scrapes dirt, mud and water off the rod as it retracts, and cylinders on harder duty add a buffer seal inboard of the rod seal to take the pressure peaks. Conquest Seal supplies hydraulic rod seals and wipers in polyurethane, nitrile, FKM and PTFE, in inch and metric sizes, from the manufacturers we source from. Send the rod diameter and groove dimensions, the old seal's part number or the drawing, and a Conquest representative quotes it.
- Where it sits
- The cylinder head, sealing the moving rod
- What it does
- Keeps fluid in; a failure shows as oil on the rod
- Rod gland parts
- Rod seal, wiper, rod wear ring; a buffer seal on harder duty
- Common profiles
- U-cup, O-ring energized lip seal, cap seal, T-seal, V-packing
- Materials
- Polyurethane, nitrile, FKM, filled PTFE
- To quote
- Rod and groove sizes, pressure, fluid, temperature, or the drawing
Sources: Parker® Fluid Power Seal Design Guide, Catalog EPS 5370/USA, 2007, 2008, section 1, read 2026-09-25.
What a rod seal does
The rod seal holds system pressure where the rod leaves the cylinder, and it has to do that while the rod moves through it. Its job is to stop leakage to the outside, so a worn rod seal shows as oil on the rod or under the cylinder. The wiper outboard of it has the opposite job, keeping dirt, mud and water out, and the two work as a pair.
The rod gland as a system
A rod gland usually holds three or four parts: the rod seal, a wiper outboard of it, a rod wear ring, and on harder duty a buffer seal between the rod seal and the cylinder. As pressure, stroke speed and cycle rate rise, a buffer and rod seal pair takes over from a single rod seal, and a press-in wiper from a snap-in one, for better protection from dirt.
Rod seal profiles
Each profile below is a construction, not a brand; seal makers sell each one under their own series names. Which one a cylinder takes is set by its drawing or its existing groove, the pressure and the fluid.
| Profile | How it is built | Seals pressure from | Notes |
|---|---|---|---|
| U-cup | A U-shaped lip seal with its sealing lip on the rod; many add a second, molded lip behind the sealing lip | One side | Polyurethane is the usual material |
| O-ring energized lip seal | A lip seal energized by an O-ring | One side | Available with a back-up ring |
| Symmetrical U-cup | Both lips have the same shape, so one part fits a rod groove or a piston groove | One side | Also made to the old Army-Navy AN6226 standard |
| PTFE cap seal | A PTFE-based ring that rides on the rod, pressed inward by an O-ring or a rubber ring beneath it | Both sides | Low friction; also called a slipper seal; low-profile versions retrofit a standard O-ring groove |
| T-seal | A rubber seal with a T-shaped section, fitted with no, one or two back-up rings to suit the groove | Both sides | Back-up rings in PTFE, nylon or PEEK |
| V-packing set | V-shaped rings stacked and sold as a set, also called chevron packing; machined, molded or cut to size | One side | Fits rods and pistons; U-cups and O-ring energized lip seals have replaced it in many cylinders |
Where the old seal or the parts list prints a maker's series name or part number, send it exactly as printed and the quote works from it.
Sources: Parker Fluid Power Seal Design Guide, Catalog EPS 5370/USA, 2007, 2008, section 1, pages 1-2 to 1-5, read 2026-09-25; Parker PTFE Seals Design Guide, PDE 3354 GB, 02/2015, section 2.3, read 2026-09-25.
Rod seal materials
Polyurethane is the usual material for hydraulic rod U-cups and lip seals: it wears well, has high tensile strength and is compatible with mineral oil. Hot water and steam rule it out. In oil above its temperature range, nitrile and FKM rubber are the usual alternatives; for water or steam, the compound has to be one rated for that fluid.
PTFE has the lowest friction of any seal material and resists almost every fluid, but plain PTFE creeps under load, so cap seals are usually made from filled PTFE. Hydraulic rod and piston seals often use bronze-filled PTFE, glass fiber makes it harder wearing and stronger in compression, and the rubber energizer under the cap comes in nitrile, HNBR, EPDM or FKM.
Conquest Seal supplies rod seals in polyurethane, nitrile, FKM and filled PTFE, and quotes the compound the drawing calls out. Name the fluid and the temperature range with the request, because the fluid decides which compounds can be used.
Sources: Parker Fluid Power Seal Design Guide, Catalog EPS 5370/USA, 2007, 2008, sections 1 and 3, read 2026-09-25; Parker O-Ring Handbook ORD 5700, 2021 printing, section 2.2.12, read 2026-09-27; Parker PTFE Seals Design Guide, PDE 3354 GB, 02/2015, sections 1.1, 1.2 and 2.3, read 2026-09-25.
Wiper seals
A wiper, also called a scraper or dirt excluder, sits at the outer end of the head and keeps dirt, mud and water off the rod as it retracts, while the rod seal inboard of it keeps the fluid in. Wipers come in snap-in, press-in and double-lip forms: a snap-in wiper sits in an open groove, and a press-in wiper, pressed into the housing bore, keeps out more dirt. Conquest Seal supplies snap-in and press-in wipers with polyurethane or rubber lips, from the manufacturers we source from.
A double-lip wiper adds a second lip against the rod for heavier duty, and like any wiper it is chosen for the conditions the cylinder works in. For a double-lip wiper, send the part number or drawing and we quote it.
Sources: Parker Fluid Power Seal Design Guide, Catalog EPS 5370/USA, 2007, 2008, section 1, page 1-2; section 4, page 4-3, read 2026-09-25.
Buffer seals
A buffer seal sits in the head between the cylinder and the rod seal and takes the pressure peaks, so the rod seal behind it works at a steadier pressure. A buffer seal of this kind lets oil caught between it and the rod seal return to the cylinder, and pressure cannot build up between the two seals. Buffer seals come as polyurethane lip seals or as rubber-energized PTFE seals, and they are found on heavy-duty cylinders and wherever pressure or cycle rate is high. For a buffer seal, send the part number or drawing and we quote it.
Sources: Parker Fluid Power Seal Design Guide, Catalog EPS 5370/USA, 2007, 2008, section 1, page 1-4; section 4, page 4-3; section 5, page 5-45, read 2026-09-25.
Rod wear rings
A rod wear ring sits in the head inboard of the rod seal, in the oil, and carries the rod's side load so the rod never rubs the head and the seal is not crushed. Side load is best kept out of a cylinder, because it bends the rod and speeds wear, and the wear ring carries what remains. Wear rings come in filled PTFE, polyacetal, composite resin and glass-reinforced nylon; nylon swells in water, so it is kept out of wet service.
Sources: Parker Fluid Power Seal Design Guide, Catalog EPS 5370/USA, 2007, 2008, section 4, page 4-3, and section 9, read 2026-09-25.
What to send for a rod seal quote
Measure the hardware, not the worn seal. The drawing, or the part number on the old seal or the seal kit, replaces most of this list; without one, send:
- Rod diameter, and the groove diameter and groove width for each seal in the head
- Radial clearance between the rod and the head
- The parts needed: rod seal and wiper (snap-in or press-in)
- Pressure: normal working pressure and any peaks or shock loads
- The fluid by name, and the temperature at the seal: lowest, normal and highest
- Stroke length, speed and cycle rate, and any side load on the rod
- What the old seal is, if known: the profile, the material and any markings, with a photo of its cross section
- The quantity
Send the list with any drawing through the request-a-quote form and a Conquest representative replies with the quote. If the drawing calls out a gland standard, such as SAE AS4716, name it, because the standard sets the groove.
Sources: Parker Fluid Power Seal Design Guide, Catalog EPS 5370/USA, 2007, 2008, Appendix A, read 2026-09-25; SAE AS4716: Gland Design, O-Ring and Other Seals, AS4716D, read 2026-09-24.
Certificate of conformance with every order
Every order ships with a certificate of conformance naming the part number, the specification, the manufacturer, the lot and the quantity. Orders are handled under Conquest Seal's AS9100D quality management system, whose certificate scope includes distribution. The compliance documents page lists the rest of the onboarding paperwork.
Parker is a trademark of Parker Hannifin Corporation. No affiliation or endorsement is implied.
Reviewed by Grant Midstokke, Conquest Seal Corporation. Last updated . Statements on this page are drawn from the sources listed above; the seal maker's datasheet and your application conditions govern the final choice.
Industries that buy rod seals
Frequently asked
What does a rod seal do?
It keeps pressurized fluid from leaking out of the cylinder along the moving rod. It sits in the cylinder head, inboard of the wiper, and a failure shows as oil on the rod or under the cylinder.
What is the difference between a rod seal and a wiper seal?
The rod seal keeps fluid in; the wiper keeps dirt, mud and water out. The wiper sits outboard of the rod seal at the outer end of the head, and the two work as a pair.
What is a buffer seal?
A buffer seal sits between the cylinder and the rod seal and takes the pressure peaks, so the rod seal behind it sees a steadier pressure. It lets oil caught between the two seals return to the cylinder, so pressure cannot build up between them. For a buffer seal, send the part number or drawing and we quote it.
Why does a cylinder leak oil at the rod?
Usually because the rod seal is worn or damaged, or the rod is scored or pitted. Dirt that gets past a worn wiper scores the rod and the seal, so the wiper is normally replaced along with the rod seal.
Can a U-cup be used as a rod seal?
Yes. A rod U-cup has its sealing lip on the rod, and a symmetrical U-cup, with both lips alike, fits a rod or a piston groove. A U-cup seals from one side only, so its open side faces the pressure.
Do rod seals ship with a certificate of conformance?
Yes. Every order ships with a certificate of conformance naming the part number, the specification, the manufacturer, the lot and the quantity.
Related pages
Send the rod, the groove or the drawing
The rod and groove dimensions or the old seal's part number, the pressure, the fluid and the quantity. A Conquest representative replies with the quote.
Request a quote