Kevlar Packing Coated with PTFE The Ultimate Sealing Material for High

Product Specification

Yellow Pure Kevlar Packing, Kevlar Braided Packing, Kevlar Packing Coated PTFE

Kevlar packing is a type of mechanical sealing material used to prevent leakage in pumps, valves, and other industrial equipment with rotating or reciprocating shafts. It is made from braided fibers of Kevlar® (an aramid fiber developed by DuPont), which is renowned for its exceptional strength, thermal stability, and resistance to abrasion.

Unlike traditional packings like flax or graphite, Kevlar packing is a high-performance synthetic material designed to handle more demanding conditions.

Key Advantages and Properties

Kevlar packing offers a unique set of properties that make it superior to many traditional materials:

1. Exceptional Strength and Toughness: Kevlar has a very high tensile strength (about 5 times stronger than steel on an equal-weight basis). This makes the packing highly resistant to extrusion, blowout, and wear, leading to a longer service life.

2. Excellent Thermal Stability: It can operate continuously at temperatures up to 550°F (288°C) and can handle short-term spikes up to 800°F (427°C). This makes it suitable for hot water, steam, and other high-temperature fluids.

3. High Chemical Resistance: It is resistant to a wide range of chemicals, including most solvents, oils, and acids (though it is not recommended for strong acids and strong alkalis).

4. Low Coefficient of Friction: Kevlar fibers are inherently lubricious. This reduces friction and wear on the equipment's shaft or sleeve, which lowers power consumption and prevents damage to expensive components.

5. Non-Abrasiveness: Unlike some reinforced materials, it is gentle on shafts and won't score or wear them down prematurely.

6. Non-Asbestos & Environmentally Friendly: Kevlar packing was developed as a direct, superior replacement for hazardous asbestos-based packing.

Common Applications

Kevlar packing is versatile and used across numerous industries for sealing:

• Centrifugal and Rotary Pumps: Handling hot water, chemicals, slurries, and hydrocarbons.

• Valves: Especially in steam valves, gate valves, and control valves.

• Mixers and Agitators: Where abrasion resistance and strength are critical.

• Expansion Joints: For its flexibility and thermal properties.

• Industrial Equipment: In paper mills, chemical processing plants, power generation facilities, and marine applications.

Common Media Sealed: Hot water, steam, chemicals, acids, alkalis, oils, fuels, solvents, air, dyes, and many other aggressive fluids.

Types and Construction

Kevlar packing is rarely made from 100% Kevlar fibers. It is typically braided and combined with other materials to enhance its properties:

• Pure Kevlar Braid: Braided from 100% Kevlar yarn, often impregnated with a lubricant like PTFE (Teflon) or a proprietary grease. Excellent for general high-temperature service.

• Kevlar/PTFE Blend: Combines the strength of Kevlar with the incredible chemical resistance and low friction of PTFE. This is an extremely popular combination for a wide range of chemical services.

• Kevlar/Graphite Blend: Incorporates graphite for superior lubricity and higher temperature performance, ideal for demanding steam applications.

• Kevlar/Carbon Blend: Offers enhanced thermal conductivity and additional lubricity.

The packing can be square braided, braided over a core (jacketed), or interbraided with other materials.

Installation and Break-in Procedure

Proper installation is crucial for performance and longevity:

1. Clean the Stuffing Box: Remove all old packing remnants and clean the shaft/sleeve.

2. Measure and Cut: Precisely measure the shaft diameter and stuffing box bore to cut new rings. Always cut rings at a 45-degree angle (skive cut) and stagger the joints around the shaft.

3. Install Rings: Carefully install each ring, using a tamping tool to seat each one firmly. Avoid twisting or distorting the rings.

4. Adjust the Gland: After installation, hand-tighten the gland nuts.

5. Break-in Period: This is critical. Start the equipment and gradually tighten the gland follower in small increments (e.g., 1/6 of a turn) every 10-20 minutes. The goal is to allow a few drops of leakage to cool and lubricate the packing. Never overtighten to stop all leakage immediately, as this will cause rapid, destructive overheating.

6. Final Adjustment: Once the packing has settled and run-in (which can take several hours), adjust the gland so there is a minimal, controlled weep of fluid.

Limitations and Considerations

• Not for Strong Acids/Bases: While chemically resistant, prolonged exposure to strong mineral acids (e.g., sulfuric, nitric) and strong caustics (e.g., sodium hydroxide) can degrade the fibers.

• UV Degradation: Kevlar can degrade under prolonged exposure to ultraviolet light, but this is rarely an issue in an enclosed stuffing box.

• Cost: It is more expensive than traditional materials like graphite or flax, but its longer life and reduced downtime often result in a lower total cost of ownership.

Comparison Table: Kevlar vs. Other Common Packings

Summary

Kevlar packing is a high-performance, durable sealing solution ideal for applications that combine high pressure, high temperature, and abrasive media. Its unique blend of strength, thermal stability, and chemical resistance makes it a go-to choice for upgrading from traditional packings and solving difficult sealing challenges in demanding industrial environments. Always consult the manufacturer's specifications for your specific fluid, temperature, and pressure conditions.