Phenolic Sleeve
Product Description
Product Detail
Phenolic Insulating Sleeve for Flange Bolt Isolation — OEM Bulk Supply
Phenolic sleeves and tubes slide over the flange bolt shank to break the electrical path between the bolt and the two flange plates. Together with an insulating gasket at the face and insulating washers under the nuts, they complete the three-component isolation system used on every mixed-metal or cathodically protected flanged joint.
Manufactured from laminated phenolic — a composite of woven fabric and phenolic resin — the sleeve offers a low-cost general electrical insulation solution for joints where the operating environment is neutral or acidic and the bolt torque is moderate. For alkaline environments, high-torque joints, or installations where installation damage is a concern, Mylar sleeve is the recommended alternative.
When to Specify Phenolic Sleeve — and When to Choose Mylar
Phenolic sleeve is a low-cost general-purpose bolt-hole dielectric used widely in the pipeline industry for many years. It is not a universal substitute for Mylar, and the correct choice depends on the joint's operating conditions, the torque level, and the installation environment.
Cost-sensitive, moderate-duty joints
- General electrical isolation applications
- Joint operates in a neutral or acidic environment
- Moderate bolt torque — no risk of sleeve crushing
- Dry, indoor or sheltered installation
- Matching phenolic washer and gasket from same supplier preferred
- Standard metric and imperial sizes required from stock
High torque or alkaline environments
- Joint operates in an alkaline environment — phenolic is not recommended here
- Heavy bolt torque — phenolic can crack or break under load
- Installation requires bending or misalignment handling
- Wet, humid or buried service where brittleness increases risk
- Long service life is critical and installation damage must be avoided
- See the Mylar insulating sleeve page
Technical Specifications
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- Material
- Laminated phenolic / non-asbestos
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- Product Code
- PHENSLV
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- Function
- Bolt-hole dielectric — prevents bolt shank contacting flange plates
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- Position in Kit
- Second dielectric component — sleeve through bolt hole
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- Available Sizes
- Standard metric and imperial bolt sizes
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- Custom Sizes
- Non-standard ID / OD / length on request
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- Supply Format
- Full length or cut to bolt length
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- Compatible Washers
- Phenolic, G-10 / G-11 glass epoxy
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- Chemical Resistance
- Unaffected by most organic solvents
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- Chemical Limitation
- Not recommended in alkaline environments
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- Mechanical Note
- Brittle under heavy torque; handle with care during installation
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- Standard Lead Time
- 5–10 days for stock, 10–20 days for custom
Phenolic vs Mylar Sleeve — Selection Matrix
Both materials are used for the same role — bolt-hole dielectric in a flange insulation kit. The two are not equivalent in performance, and the industry has shifted toward Mylar as the primary sleeve material in most applications. The matrix below shows where each is the right choice.
| Property | Phenolic Sleeve | Mylar Sleeve | G-10 / G-11 Sleeve |
|---|---|---|---|
| Material | Laminated phenolic / non-asbestos | Polyester (PET) film | Woven glass fabric + epoxy |
| Cost | Lowest | Low-moderate | Highest |
| Installation durability | Brittle — can crack under torque | Flexes — survives bending and misalignment | High mechanical strength |
| Alkaline environments | Not recommended | Suitable | Suitable |
| Dielectric strength | Good | Excellent | Good |
| Water absorption | Low | Very low | Very low |
| Best used for | Cost-sensitive, moderate-duty, dry joints | Standard pipeline joints — industry default | Higher temperature, structural demands |
Where the Sleeve Sits in the Isolation System
A fully insulated flanged joint requires three dielectric components working together. Removing any one of the three causes the isolation to fail.
Typical B2B Applications
Ordering Phenolic Sleeves
Sleeves are supplied in full lengths or cut to your specified bolt length. Send the following five details and Kaxite will return a quotation — typically within one working day for standard sizes.
Phenolic Sleeve — FAQ
What is a phenolic sleeve made from?
It is manufactured from laminated phenolic — a composite of woven fabric and phenolic resin, cured into a rigid tube and machined to the required ID, OD and length. A non-asbestos laminate variant is also available on request.
Why is Mylar now often used instead of phenolic?
Phenolic is effective but brittle — it can crack or break under heavy bolt torque or if it is not handled carefully during installation. Mylar (polyester film) flexes rather than cracks, which makes it the more robust sleeve material for pipeline joints. The industry has largely shifted to Mylar as the standard sleeve for this reason. See the Mylar insulating sleeve page for the recommended alternative.
Can phenolic sleeves be used in alkaline environments?
No. Phenolic sleeve is not recommended for use in alkaline environments. If the joint will be exposed to alkaline media, specify a Mylar or glass epoxy sleeve instead.
How does the phenolic sleeve fit into a flange insulation kit?
A fully insulated joint has three dielectric components: the gasket at the flange face, the sleeve through the bolt hole, and the washer under the nut (and typically under the bolt head). The phenolic sleeve is the second of these — it slides over the bolt shank so the shank cannot contact either flange plate. Removing any one of the three components will cause the isolation to fail.
Is phenolic sleeve affected by organic solvents?
No. Phenolic laminate is unaffected by most organic solvents, which is one of its advantages in chemical service. The main limitation is alkaline environments, which are not compatible with phenolic.
Do you supply both metric and imperial sleeve sizes?
Yes. Sleeves are supplied in all standard metric and imperial bolt sizes. Custom non-standard inside and outside diameters are produced to order — send the dimensioned drawing and we will confirm feasibility and lead time.
Can phenolic sleeves be supplied together with matching washers and gaskets?
Yes. Sleeves are supplied as individual components or as part of a complete flange insulation kit with matched gaskets and washers. See the phenolic insulating washers page for matching washers, or contact us with the flange standard and size for a complete kit quotation.
What quantity is required for OEM / wholesale pricing on phenolic sleeves?
OEM and wholesale pricing applies from the first order for standard metric and imperial sizes, and from 500 pieces per size for custom-cut sleeves. Send the annual or project quantity and we will quote the volume tier.
Request a Phenolic Sleeve Quotation
Send the bolt diameter, sleeve outside diameter, length and quantity — or the flange standard and size for a complete kit quotation. Kaxite supplies phenolic sleeves for cost-sensitive general pipeline applications, maintenance replacement, and standalone bolt-hole isolation. For high-torque or alkaline service we will recommend the Mylar sleeve instead.