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Hydraulic Cylinder Stepseals and Glyd Rings
Both Stepseals and Glyd Rings are common combination seals in hydraulic systems, but their structures, functions, and application scenarios differ significantly. Here are three key points to keep in mind:
1.Direction of Action
• Stepseal = One-way seal, blocking pressure from only one side;
• Glyd Ring = Two-way seal, blocking pressure from both sides simultaneously.
2. Typical Structure and Installation Location
• Step Seal: Has a stepped cross-section and is typically installed on the piston rod (shaft), with the sealing lip facing inward.
• Glyd Ring: Has a rectangular cross-section and is typically installed on the piston (bore), with the sealing lip facing outward.
3. Application Scenarios
• Requires unidirectional pressure retention (e.g., when the piston rod is extended, it only experiences oil pressure in one direction) → Choose a Step Seal.
• Requires bidirectional pressure retention (e.g., when pressure is applied alternately on both sides of the piston) → Choose a single Glyd Ring; no need to install two back-to-back.
Both types share the commonality that they consist of a rubber O-ring (providing preload) and a polytetrafluoroethylene (PTFE) slip ring (providing primary sealing and friction reduction). They offer similar pressure, temperature, and wear resistance, with operating pressures of 0–40 MPa, a maximum speed of approximately 4–5 m/s, and a temperature range of −25°C to +200°C (depending on the O-ring material).
In short:
A “Step Seal” only blocks oil in one direction and is mounted on the rod; a “Glyd Ring” blocks oil in both directions and is mounted on the piston.
How to Understand Material
Stephen seals and Glyder rings are both composite materials—a low-friction slide ring and an O-ring that provides preload. Durability is determined by the filler formula of the slide ring and the type of rubber used in the O-ring.
1. Slide Ring Body: Polytetrafluoroethylene (PTFE) is used in 90% of applications.
• For greater wear resistance → Add bronze powder, carbon fiber, MoS₂, or graphene.
• For greater cold flow resistance → Add glass fiber or PPS.
• For greater corrosion resistance → Use pure PTFE or modified ETFE or PEEK.
2. Elastomers:
• For standard mineral oil: NBR (nitrile butadiene rubber) is sufficient.
• For temperatures above 150°C or oils containing additives: FKM (fluororubber).
• For low temperatures below -40°C or water-based fluids: HNBR, EPDM, or FVMQ (fluorosilicone rubber).
There’s no definitive answer to the question of the “most durable” Stepseal/Glay Ring material. It depends on the operating conditions you face: pressure, temperature, medium, movement speed, and cost budget. Below is a quick reference table for “Working Conditions – Recommended Materials” so you can select directly based on the scenario.
*Lifespan refers to the industry average statistical value under normal installation and pollution-free conditions. The actual lifespan will fluctuate with usage conditions.
Both Stepseals and Glyder Rings are “hydraulic reciprocating seals,” so they appear in all hydraulic (or pneumatic) devices that require linear reciprocating motion while maintaining internal pressure. A table listing common applications by “equipment – installation location – typical model” will help you understand their specific applications at a glance.
Quick Tips:
“Step seals for rods, Glyd rings for bores” –
• Rods (piston rods, plungers) typically only bear pressure from one side: a Step seal is used;
• Bores (piston outer diameters) typically bear pressure from both sides alternately: a Glyd ring is used.
Whenever you see a hydraulic cylinder with a reciprocating rod or piston, 95% of the time you’ll find a Step seal or Glyd ring in these locations.
