Which Seal Material Is Best for High Temperature Hydraulic Cylinders?

by | Jul 10, 2026 | single acting cylinder

Hydraulic cylinder seal material selection is the specification decision with the greatest impact on seal service life — greater than oil cleanliness, greater than installation technique, and far greater than brand choice. The same hydraulic cylinder seal installed in a system 20°C outside its compound’s rated temperature window can fail within days. This guide covers every major seal compound for hydraulic cylinders, the exact temperature ranges each handles reliably, and how to match seal material to your application’s real operating conditions.

Tie rod hydraulic cylinder showing seal gland area temperature specification

The Four Main Hydraulic Cylinder Seal Compounds

NBR — Nitrile Butadiene Rubber

Temperature range: -20°C to +80°C. The traditional standard for hydraulic seals. Good mechanical strength and abrasion resistance. Compatible with mineral hydraulic oil. Low cost. Not suitable for outdoor machinery with cold-start below -20°C or sustained high-temperature duty.

PU — Polyurethane

Temperature range: -30°C to +90°C. Superior abrasion resistance versus NBR — typically 3–5× longer wear life in contaminated systems. Extends the cold end by 10°C versus NBR. The preferred default compound for agricultural, construction, and outdoor mobile machinery.

FKM — Fluoroelastomer (Viton)

Temperature range: -20°C to +200°C. Excellent chemical resistance and heat stability. The choice for high-temperature industrial applications, fire-resistant fluid systems, and chemical processing. 3–5× higher cost than NBR. Not suitable for cold climates — loses flexibility below -20°C.

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PTFE-Composite

Temperature range: -60°C to +200°C. Widest temperature range of all seal compounds. Lowest friction coefficient — important for precision position control. Excellent chemical resistance. Requires tighter rod surface finish (Ra 0.1–0.2 μm). No elastic recovery — groove geometry is critical.

Temperature Range Comparison: Which Compound Covers Your Application

Application Typical Temperature Range Recommended Compound
Indoor industrial press — climate controlled -5°C to +60°C NBR — cost-effective for this range
Agricultural machinery — UK/Europe outdoor -25°C to +75°C PU — covers cold start and summer peak
Agricultural machinery — tropical/subtropical +10°C to +85°C PU or NBR — confirm peak oil temperature
Construction machinery — cold climate -35°C to +70°C PU — NBR too hard below -20°C
Offshore marine — North Sea -15°C to +60°C (ambient) PU + stainless rod — salt corrosion priority
Steel mill hydraulics — furnace proximity +20°C to +120°C FKM — NBR and PU both fail above 90°C
Chemical processing — solvent exposure -10°C to +150°C FKM or PTFE-composite
Subsea — deep cold water -5°C to +60°C (oil temp) PTFE or low-temp FKM — pressure rating priority
Tie rod hydraulic cylinder 3000PSI seal compound selection temperature guide

Beyond Temperature: Chemical Compatibility

Temperature range is the primary selection criterion, but chemical compatibility must also be confirmed. The hydraulic fluid type affects seal compatibility independently of temperature.

Fluid Type NBR PU FKM PTFE
Mineral hydraulic oil (HLP, HM) ✅ Compatible ✅ Compatible ✅ Compatible ✅ Compatible
Biodegradable vegetable oil (HETG) ✅ Compatible ✅ Compatible ✅ Compatible ✅ Compatible
Biodegradable synthetic ester (HEES) ✅ Compatible ✅ Compatible ✅ Compatible ✅ Compatible
Polyglycol (HEPG) ⚠️ May swell ✅ Compatible ⚠️ Check grade ✅ Compatible
Water-glycol fire resistant (HFC) ⚠️ Limited ⚠️ Check grade ✅ Compatible ✅ Compatible
Phosphate ester fire resistant (HFD-R) ❌ Not compatible ❌ Not compatible ✅ Compatible ✅ Compatible

For applications with non-standard fluid chemistry, combined temperature-chemical exposure, or unusual operating conditions — such as repeated high-pressure washdown, fertiliser spray contact, or temperature cycling — submit the full application description to the Ever-Power engineering team for a compound recommendation before ordering. Specifying the wrong compound costs more in repeated seal replacement than the price difference between compounds.

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Frequently Asked Questions

1. Which seal material is best for high temperature hydraulic cylinders?+
FKM (Viton) is the best hydraulic cylinder seal material for sustained high-temperature operation above 100°C, with a reliable operating range of -20°C to +200°C. PTFE-composite seals also handle high temperatures (-60°C to +200°C) and provide excellent chemical resistance. For standard industrial and agricultural duty between -30°C and +90°C, polyurethane (PU) is the preferred choice combining abrasion resistance with a wide temperature range.
2. What temperature range does NBR hydraulic cylinder seal handle?+
NBR (nitrile butadiene rubber) hydraulic cylinder seals are reliable between -20°C and +80°C. Below -20°C, NBR hardens and loses its interference fit, causing cold-start leakage that disappears once the system warms. Above +80°C, NBR softens and extrudes past the gland. NBR is a cost-effective choice for indoor or climate-controlled applications within this temperature window, but is not recommended for outdoor machinery with wide temperature swings.
3. Can PTFE seals be used in hydraulic cylinders?+
Yes. PTFE-composite seals (PTFE filled with bronze, carbon, or glass fibre) are used in hydraulic cylinders for their wide temperature range (-60°C to +200°C), excellent chemical resistance, low friction, and long service life. They require a smoother rod surface finish than elastomeric seals — typically Ra 0.1–0.2 μm versus Ra 0.2–0.4 μm for PU and NBR. PTFE seals have no elastic memory, so the groove design must provide the correct mechanical pre-load.
4. What seal material should I use for biodegradable hydraulic fluid?+
Polyurethane (PU) and FKM seals are compatible with most biodegradable hydraulic fluids including HEES (synthetic ester), HETG (vegetable oil-based), and HEPG (polyglycol-based). NBR seals are compatible with HETG and HEES but may swell in HEPG. Always confirm compatibility with the fluid supplier before specifying seal compound for biodegradable fluid applications. Mineral oil compatibility alone is not sufficient for multi-fluid systems.
5. How do I know when hydraulic cylinder seals have failed due to temperature?+
Temperature-related seal failure produces characteristic symptoms: at low-temperature failure, cold-start leakage that stops after 10–20 minutes of running as the system warms (NBR hardening below -20°C); at high-temperature failure, a soft extruded lip visible at the gland face, progressive leakage that worsens as the system heats up, and seal material deposits on the rod surface. Both indicate a seal compound change is needed, not a seal size change.