Hydraulic rod seals, also known as piston rod seals, U-cup seals, gland seals or simply rod seals, provide the seal between the piston rod and the cylinder head. They form the pressure barrier that keeps the oil inside the cylinder while the rod moves. This is the most critical seal in the entire assembly, because leakage here is immediately visible, causes oil loss and, in machines operating outdoors, also creates an environmental risk.
Hydraulic rod seals therefore largely determine whether a cylinder operates reliably. Techniparts supplies every brand and every size, metric and inch, for low and high pressure. If we do not have a size in stock, we will provide a technically equivalent alternative.
A hydraulic rod seal is installed in the cylinder head around the piston rod. The sealing lip makes contact with the surface of the moving rod and forms the pressure barrier between the hydraulic fluid inside the cylinder and the external environment.
As the cylinder extends, the rod moves outward past the seal. Normally, a very thin lubricating film remains on the rod. When the rod retracts, this oil film must be able to return to the cylinder.
Leakage at a rod seal is immediately visible on the outside of the cylinder. A worn seal can therefore lead to oil loss, contamination of the machine and loss of hydraulic fluid.
When hydraulic pressure builds up inside the cylinder, the sealing lip is pressed against the piston rod. This increases the sealing effect as the pressure rises.
At the same time, the rod must be able to move smoothly through the seal. The profile must therefore provide a good balance between sealing pressure, friction, lubrication film and wear.
At high pressure, soft sealing material can be forced into the clearance gap between the rod and cylinder head. This is known as extrusion. Depending on the profile, backup rings or anti-extrusion rings can therefore be used to support the seal.
When selecting a hydraulic rod seal, it must be determined from which direction the pressure acts on the sealing profile.
Many traditional rod seals are single-acting and are designed to seal pressure from the cylinder side. Examples include various U-cups and lip seals.
When pressure can occur from multiple directions, the complete sealing arrangement must be designed accordingly. Therefore, do not use dimensions alone as the selection criterion, but also check the pressure direction and the operating principle of the profile.
Hydraulic rod seals are available in different profiles and sealing arrangements. The correct version is determined by factors including pressure, speed, temperature, medium and available installation space.
The U-cup or U-ring is a commonly used rod seal. The open side of the profile is installed facing the pressure side, allowing hydraulic pressure to press the sealing lips more firmly against the sealing surfaces.
A PTFE rod seal can consist of a PTFE sealing element that is preloaded by an elastomer O-ring. This type of design offers low friction and can be advantageous in applications where stick-slip must be limited.
In certain T-profiles, the central sealing element is combined with backup rings that support the profile against extrusion.
For heavy-duty industrial applications, chevron packings, V-packings or stacked seal sets can be used. In these designs, multiple sealing elements are installed one behind another.
To select a hydraulic rod seal, at least the operating pressure, rod speed, temperature and hydraulic fluid being used are required.
At high pressure, the risk of extrusion and damage to the sealing edge increases. The clearance gap, material hardness and any backup ring must therefore be assessed together.
At low speeds and with frequent start-stop movements, stick-slip can occur. A low-friction sealing profile, such as a suitable PTFE combination, can offer advantages in these applications.
With biodegradable oil, water-glycol or other special hydraulic fluids, the chemical resistance of the sealing material must be checked separately.
In heavily loaded hydraulic cylinders, a buffer seal can be installed ahead of the primary rod seal. This helps absorb pressure peaks before they reach the main seal.
A backup ring or anti-extrusion ring supports the softer sealing material on the side of the clearance gap and helps prevent the material from being forced into this gap under high pressure.
Also view the available backup rings and anti-extrusion rings for applications where protection against extrusion is required.
The rod seal works together with the hydraulic wiper. Both components have a different function and must be properly matched to one another.
During extension, the rod seal leaves a controlled thin lubricating film on the piston rod. This film helps reduce friction and must be able to return to the cylinder when the rod retracts.
If a wiper completely removes this oil film from the rod or prevents it from flowing back, oil can accumulate between the seals. This can ultimately lead to unwanted pressure build-up and visible leakage.
Proper guidance of the piston rod is important for the service life of the rod seal. Under lateral loading or misalignment, the seal can be subjected to significantly greater loads on one side.
This can result in uneven wear, damage and premature leakage. Therefore, when sealing problems repeatedly occur, do not only inspect the seal itself.
Also inspect the hydraulic guide rings and hydraulic guide strips when overhauling the cylinder.
Because a hydraulic rod seal seals the transition between the cylinder and the external environment, leakage is usually relatively easy to recognise.
A clearly visible layer of hydraulic oil on the rod or oil running out along the cylinder head can indicate a worn or damaged rod seal.
In the event of leakage, also inspect the piston rod for scratches, corrosion, pitting and damage. A damaged rod surface can quickly cause a new seal to wear again.
Uneven wear can indicate clearance in the guiding system or an incorrectly aligned piston rod. Therefore, always inspect the complete cylinder assembly.
To select the correct hydraulic rod seal, the dimensions of the piston rod and seal groove are particularly important. The main installation dimensions are generally indicated as d × D × L: rod diameter, groove diameter and groove width.
The rod diameter d is the diameter of the piston rod over which the dynamic sealing lip moves. For a rod seal, this is the most important functional inside diameter.
The groove diameter D is the diameter of the installation groove in the cylinder head in which the rod seal is fitted. Together with the rod diameter, this dimension determines the available radial space for the seal.
The groove width L is measured in the axial direction and indicates the available installation space for the seal. In some sealing systems, a back-up ring, energizer or other sealing elements may also be installed in or around the same sealing arrangement.
When measuring the loose rod seal, the seal height H can also be recorded. This is the axial height of the seal itself. Please note that H is not always equal to the groove width L. With various profiles, the installation groove is deliberately slightly wider than the seal.
Tip: a used rod seal may be deformed or swollen due to pressure, temperature, wear and hydraulic fluid. If in doubt, preferably measure the piston rod and installation groove directly. Also provide the old brand, type number and, if possible, a photograph of the profile.
A hydraulic rod seal and piston seal are both located inside the hydraulic cylinder, but perform different functions.
The rod seal is located in the cylinder head and helps prevent hydraulic fluid from leaking out along the moving piston rod.
A hydraulic piston seal is located on the piston and helps prevent hydraulic fluid from flowing internally between the different pressure chambers.
Hydraulic rod seals are used in hydraulic cylinders across virtually all mobile and industrial sectors.
In excavators, cranes, aerial work platforms and earthmoving machinery, rod seals are used in cylinders that often operate under high pressure and demanding environmental conditions.
Hydraulic rod seals are also widely used in tractors, agricultural machinery and telescopic cylinders.
Other applications include hydraulic presses, lifting equipment, marine applications, material handling and industrial production machinery.
Techniparts supplies hydraulic rod seals from various well-known manufacturers. Depending on the application, different profiles and materials are available for operating pressure, sliding speed, temperature and hydraulic fluid compatibility. The overview below also includes historical brands and profile references to help identify existing seals.
Materials vary by profile and version. Availability, suitability and possible replacements are assessed using the type number, installation dimensions and operating conditions.
| Logo | Brand | Types / series and historical references | Materials / versions |
|---|---|---|---|
|
Freudenberg Sealing Technologies / Merkel | LF 300, NI 150, NI 250, NI 300, NI 400, N1, AUN 1, N100, AUN 100, T20, T22, T23, T24, T34, TM 20, TM 23, Syprim SM, OMS MR PR S, OMEGAT OMS-MRPR, OMS-S-PR, OMS-S, KI 310, KI 320, S 8, TFMI, ES, ESV packing sets, V1000, DIP, FOI, HDR-2C, H MF, H OF, L20, NRRI, NRRI-9442, NRS-0214, NRS-0216, NRS-0503, NRVI, NRVI-9492 | PU/AU, PTFE, NBR, FKM, HNBR and fabric-reinforced versions; compound references include 95AU V149, 95AU V925 and Disogrin |
|
Dichtomatik | SDR 01, SDS 01, S01, SN 05, S05, SN 21, MA21, SN 25, MA25, SN 36, MA36, SNI 07, S07, SNI 24, MA24, SNI 39, MA30, MA39, SNI 43, MA43, SNI 73, 73, SPOR 30, S30, SPOR 31, S31, S72, SPOR06, SNI30, SNI35, N05, N21, N25, N36 | NBR, EPDM, TPU/PUR, PTFE and fabric-reinforced versions; compound references include NBR 90 30 06 (903006) and TPU 95 34 01 (953401) |
|
Angst & Pfister | RSA, RSB2, VSR100, SSR, DDR, LRC, DMR, RPS, UM. Historical references: Lubroseal, LDIMC, LS8C, LS25C, L9492C, LSMC, LT20C, LOMSC, LESC | NBR, PU/PUR/AU and PTFE, depending on the profile |
|
Bal Seal | Historical references: KI N 891, 897. Profile identification and replacement options on request | UHMW-PE, PTFE and filled PTFE compounds; specification on request |
| — | Claron | CP, P, GP, PRU, PFU, CPI, PEI, PV, PVM, PDS, EGS, CPU F, CPG, CPS, CPUI, CPGI, HBI, CS6, 741, 751, CS1, CS3, HBT, HBTY, DSI, PDI, PRF, PFD, PFI, PFC, top-hat seals, CPU.../OR, CPUI.../OR, CPGI.../OR, RRS | NBR 70 Shore A, NBR 90 Shore A, AU and polyurethane |
|
DLI Seals | MD/ID P, MDR, MD ID E, MGD/IGD P, MGD E, MU/IU E, MU IU RF FF, MUP/IUP, GPI, GPX, GPU, MUP I, MGM IGM, MV/IV, SAS, SAL. Rod seals, U-rings and chevron packing sets | NBR, TPU, polyester and fabric-reinforced versions |
|
ERIKS | 900, 2001, 0020, 0022, 9011, 0008, 0010, DVSS, DVVS, 0710, 0720, 0300, Omniseal, 0022AE, 0712, UTS-L, ERS, PSE | NBR, FKM/FPM, EPDM, PU/AU and PTFE; versions with metal components depending on the profile |
|
EVCO | 160, 170, GT, JAM, PSE, TB, TTI, TTS-L, TTX, JCI, TTH, TSE/G, TTI/AI, TTS/LAI, BETA RS | PTFE, PU/AU, NBR and composite sealing arrangements |
|
Guarnitec | TSE, TSE/AI, TSE AI, TGO, GT 5 7, GT5, GT7, PSE, PSE-K, TTS, TTS/L, TTS L AI, TTI, TTI/L, TTI L AI, TTH, TTX, TLI, SSI, GUA, GIR | AU, PU, NBR and rubber-metal versions |
|
Hallite | 13, 15, 16, 18, 511, 512, 513, 601, 605, 610, 616, 617, 620, 621, 622, 631, 652, 653, 658, 663, 673, 683, 716SPN, OL, R16, RCG, RDA, RDS | NBR, PU/PUR, polyester, PTFE and special Hallite compounds |
|
Hecker Werke GSM | UG1, UG2, UR1, UR2, UNX7, UNI 1, UNI 2, UNI 3 P, UNI1, UNI2, UNI3, UNX, UNX1, UNX2, ST1, ST2, ST3, ST4, UGA1, UGA2, UGA3, UGA4, UGA5, NK1, UK1, UD1, NOI1, NOA1, DS4, W, WB, WS, UES1, UES2, UES3, UES1 P, EUS2, PKK, PKK1 | NBR, PTFE, PU/AU, rubber and fabric-reinforced rubber |
|
Hunger | TDI, EVD, TDT, NDT, TDMI, GGDI, GGDI-SP, ZSDI, GODI, GDSI, GODI-SP, GODI-SPE, TRO-I, GD2000S. Historical Techniparts reference: TDD; identification required | NBR, PU, PTFE, POM, PA 6, PA-CF, UHMW-PE, PEEK, Hytrel, MVQ and FPM, depending on the sealing arrangement |
|
James Walker | Twinset, Lowfilm HD, Lionsele G, U-ring, Solosele G, Lionsele U1, Lionsele U2, Lofilm, self-aligning gland rings | NBR, PU and fabric-reinforced versions; material depends on the series |
|
JM Clipper | Historical brand references. Identification and replacement options based on the original type number, dimensions or drawing | NBR and FPM; original specification to be checked |
|
KACO | Hydraulic rod seals, lip seals and application-specific profiles; type identification on request | NBR, HNBR, FKM/FPM and AEM, depending on the version |
|
Kastas | K01, K04, K21, K22, K29, K31, K32, K33, K34, K35, K36, K37, K38, K39, K95, K96, K97, K98, K701, K704, K709, XT200, FR200 | PU, NBR and profile-specific material combinations; material specification on request |
|
Nordex | Historical mixed application references: ARUP, AWNS, ARAN, RU2, RU3, RUB, L-Cup. Hydraulic suitability and replacement options to be checked per profile | PU/AU; original material specification to be checked |
|
Parker Prädifa | B3, BS, BU, BA, BD, C1, C3, C5, C9, CR, GC, JA, M0, M2, M3, M5, OE, ON, Q2, Q3, R3, ZJ, W1, W2, W3, T Seal, OD, V6. Suitability depends on the specific profile and compound | NBR, PU, FKM/FPM, HNBR, PTFE and fabric-reinforced versions. Historical compound references include P5008, P5009, P6000, P5004, P5000, P5001, P5062, P5075, P5007, P5070, P5011, P5080, P5010, P5012, P4300, P5500, N3571, N3570, N3578, N3580, N3584, N3582, E3676, E8536, E8608, V3664, V3656, V3638, Z4017 |
|
Polypac Sealing Systems | Balsele, Selemaster SM. Existing profile references: B, B/NEI, CH, CH1, CH2, CIM, DDI, DDIM, DH, DU, DUM, EU, EU/I, EU/NEI, EUS, EUS/C, EUS/I, EUS/NEI, IBF, I/GR A B, MU, NPSL, NPSL-P, RS, RS L LA, SM, TS L LA, VOR, VVR. Exact profile and application to be checked | NBR, HNBR, MVQ, FKM/FPM, EPDM, PTFE, PU/PUR/AU, fabric-reinforced versions and engineering plastics, depending on the sealing arrangement |
|
SKF / Economos / Seal Jet | S01-P/R, S02-P/PD/R/RD/S, S03-P/F/S/SX, STD-P, PTB-P/R, DZ-P, S04-P/PD, S05-P/R, S06-P/R, S07-P/F, S08-P/PE/R, S09-E/ES/D/DS/P, S1012-T/M, S1315-T, S16-A/B, S17-P/R, S18-P/R, S19-F/FX/B/X, S20-R, S21-P, S22-P/R, S24-P, S2527-F, S2931-F, S32-P, S35-P, ZBR-P. Historical references: SIL, TIL, TICLA, GS, SG, AG, SKY, UN, SI, TI, TILA, S, GL, CH 5, CH 7, STR, RI | ECOPUR and profile-specific SKF materials, including TPU, CPU, NBR and HNBR; exact compound depends on the application |
|
Trelleborg / Busak+Shamban | Turcon Stepseal 2K, Stepseal V, VL-seal, Glyd Ring, Glydring RG, Glydring-T, Glyd Ring Hz, AQ-Seal, Double-Delta, Variseal M2, Zurcon Rimseal, Rimseal IM, Buffer Seal LM, Wynseal M, L-cup, U-cup, RU0, RU2, RU3, RU6, RU9, Polypac Balsele, Selemaster SM. Application-specific profile selection | Turcon PTFE, Zurcon PU and UHMW-PE, NBR, FKM, HNBR, EPDM and FFKM components, depending on the profile and sealing arrangement |
| — | Sakagami | GNY, RNY, NHU, SMJ, STC | Profile-specific compounds; material specification on request |
| — | Ding Zing DZ | D-2, D-3, HD-2, HD-3. Combined piston/rod seal profiles: UN, D-4, D-6, D-7 | Polyurethane and elastomer versions; compatibility with the hydraulic fluid and operating conditions to be checked |
Is your existing brand or type number not included in this list? Send us the brand, type number, rod diameter, groove diameter, groove width and material. Please also specify the hydraulic fluid, operating pressure and temperature. A photograph or technical drawing will help us identify older or non-standard hydraulic rod seals.
When overhauling a cylinder, it is advisable to inspect the other sealing and guiding elements in addition to the rod seal.
View our hydraulic piston seals for separating the pressure chambers inside the cylinder.
For protection against dirt and moisture, hydraulic wipers can be used.
For supporting the piston and rod, hydraulic guide rings and hydraulic guide strips are also available.
A hydraulic rod seal is installed around the moving piston rod and helps prevent hydraulic fluid from leaking out of the cylinder.
Possible causes include a worn rod seal, damaged piston rod, incorrect material selection, high pressure peaks or worn guiding components.
The rod seal prevents leakage along the piston rod to the outside. A piston seal prevents internal leakage between the pressure chambers of the cylinder.
An anti-extrusion ring or backup ring helps prevent soft sealing material from being forced into the clearance gap under high hydraulic pressure.
Common materials include PU, NBR, FKM, HNBR, PTFE and EPDM. The correct choice is determined by pressure, temperature, speed and hydraulic fluid.
Important dimensions are the inside diameter (d), outside diameter (D) and groove width (L). If the seal is deformed, preferably measure the rod and groove directly.
In addition to the new seal, also inspect the piston rod, wiper, guiding components, alignment and pressure peaks. A problem elsewhere in the sealing arrangement can damage a new rod seal again.
Yes. For older cylinders, inch sizes and non-standard grooves, custom-made hydraulic rod seals or technically suitable alternatives can be supplied.
Receive personal advice or a tailored quotation from our product specialists. Fill in the form and discover which Z - Hydraulic Rod Seals - Nieuw best fit your needs.
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