Bidirectional Piston Seal — Precision Sealing for Reversible Hydraulic Systems

Bidirectional Piston Seal — Reliable Sealing for Reversible Motion

Overview

Polypac's Bidirectional Piston Seal is engineered for reversible hydraulic cylinders where sealing must perform equally in both directions. Designed to minimize leakage and friction while maintaining stable contact under variable pressure, the Bidirectional Piston Seal is ideal for mobile hydraulics, industrial actuators, and heavy machinery that require consistent performance across stroke cycles.

Key Features

Key features of the Bidirectional Piston Seal include symmetrical lip geometry for equal sealing in both directions, optimized spring or energizer profiles for sustained contact, and low-friction PTFE or engineered elastomer faces. These design choices reduce wear, improve response, and extend service intervals—critical advantages for OEMs and maintenance teams focused on uptime and total cost of ownership.

Materials & Chemical Compatibility

Polypac manufactures Bidirectional Piston Seals in a wide range of materials, including bronze-filled PTFE, carbon-filled PTFE, MoS₂-filled PTFE, NBR, FKM, EPDM, silicone, and FFKM. Material selection is tailored to fluid type, temperature range, and abrasive or corrosive conditions to ensure reliable sealing and long-term compatibility with hydraulic oils, water-glycol, and specialty fluids.

Custom Solutions & Manufacturing Excellence

With a custom rubber ring and O-ring factory spanning over 10,000 m² and advanced production/testing equipment, Polypac offers bespoke Bidirectional Piston Seal designs for special working conditions. Our decades of collaboration with universities and research institutes enable rapid prototyping, materials development, and optimized seal geometry for unique cylinder designs.

Performance Validation & Quality Control

Each Bidirectional Piston Seal undergoes stringent testing for leakage, wear, extrusion resistance, and pressure cycling. Polypac's quality systems and laboratory testing ensure consistent dimensions, material integrity, and reliable performance under high-pressure, high-temperature, and contaminated-fluid scenarios.

Why Choose Polypac

As an award-winning hydraulic seal manufacturer since 2008, Polypac combines technical expertise, broad material capability, and scalable production to deliver Bidirectional Piston Seals that meet demanding industrial standards. Contact Polypac for material recommendations, CAD-ready designs, and rapid samples to optimize your reversible-cylinder applications.

Bidirectional Piston Seal Display

FAQ:

What is the difference between NBR and FKM materials?

NBR (Nitrile/Buna-N): A general-purpose, cost-effective material with excellent resistance to petroleum-based oils and fuels. It has a standard temperature range of -30°C to +100°C (-22°F to +212°F). FKM (Fluoroelastomer/Viton®): A premium material with excellent resistance to high temperatures (up to 200°C+), chemicals, and oils. It is used in more severe environments but is more expensive than NBR.

Why did my O-ring fail prematurely?

Common causes of O-ring failure include: Chemical Incompatibility: Swelling, softening, or cracking due to fluid exposure. Improper Sizing: Using an incorrect size leads to over-compression or inadequate sealing force. Abrasion: Wear and tear from rough surface finishes or contaminated fluid. Extrusion: The seal is forced into the gap between metal parts under high pressure. Installation Damage: Nicks, cuts, or twists during assembly.

When should I use a spring-energized seal instead of a standard elastomeric seal?

Consider a spring-energized seal (e.g., GSF, SPN types) for demanding applications involving: Extreme Temperatures (below -30°C or above +200°C) Aggressive Chemicals that elastomers can't handle Very Low Leakage or "Zero Leakage" requirements Poor Lubricity or dry running conditions The internal spring maintains constant sealing force, compensating for wear and system variables.

What is the difference between a static seal and a dynamic seal?

A Static Seal is used between two surfaces that do not move relative to each other (e.g., pipe flanges, end caps). O-rings and gaskets are common static seals. A Dynamic Seal is used between surfaces that do move (e.g., piston and cylinder, rotating shaft). Rod seals, piston seals, and rotary shaft seals are designed for this purpose.

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