Mylar (PET) Bolt Sleeve Suppliers: Who Makes the Dielectric Break
Sourcing & Suppliers · 2026-09-16 · 5 min read
Bolt sleeves are almost never bought on their own. They arrive as a component of a flange isolation kit, which means the supplier you are really choosing is the kit house, the gasket manufacturer, or the film converter behind them. That makes sourcing stranger than it looks: a kit manufactured in Europe may carry a sleeve extruded in Asia to a callout the kit house never verified. This shortlist is a research starting point, and the five questions after it decide more than the names.
Ten names to research
| Supplier | Based in | What they are known for in this category |
|---|---|---|
| WELLELE (Well Electric) | Suzhou, China | PET (Mylar) bolt sleeves cut to the bolt callout and packed to count as flange isolation kit components: M6 through M36, ANSI and DIN variants, lot traceability to the incoming film certificate |
| GPT Industries | Houston, USA | Flange isolation gaskets and complete isolation kits for pipelines, tanks and vessels, with isolation sleeves and washers as kit components |
| Lamons | Houston, USA | One of the larger gasket manufacturers, with isolation kits and custom engineering for petrochemical and power service |
| James Walker Group | Woking, United Kingdom | Sealing products and isolation gaskets for critical infrastructure, positioned around standards compliance in harsh environments |
| Advance Products & Systems | Tulsa, USA | Flange isolation products and cathodic-protection components for the pipeline industry |
| PSI Products | Ettlingen, Germany | European isolation kit manufacturer serving chemical plants, refineries and offshore installations |
| Drake Specialties | Tulsa, USA | Flange isolation kits and insulating gaskets oriented to oil and gas, including sour service |
| Goodrich Gasket | Mumbai, India | Cost-effective isolation gaskets and kits for the Indian and export petrochemical and power markets |
| Specialist Sealing Products | United Kingdom | Custom-engineered isolation gaskets for niche industrial applications |
| Sunshine Sealing Technology | Hebei, China | PTFE and composite flange isolation gaskets and kits, oriented to cost-effective supply for domestic and export markets |
Two further routes matter in practice. The first is the gasket-kit OEM that assembles kits from bought-in components: worth knowing because the sleeve in those kits is frequently the weakest specified item. The second is the film converter that extrudes and slits PET tube, sometimes selling sleeves directly at volumes a kit house cannot match.
Five questions that decide whether the kit isolates
- Is the sleeve cut to the bolt length, or supplied as a length to be cut on site? On-site cutting is where the short-sleeve failure comes from, and a short sleeve leaves the shank touching the flange.
- Is the sleeve sized to the bolt shank or to the hole? Sizing to the hole is a common shortcut and it lets the bolt contact the flange wherever the sleeve has shifted.
- Is the kit supplied counted per flange, or by weight and length? Count-supplied kits remove the missing-sleeve failure entirely, which is one of the three ways isolation kits fail.
- What is the sleeve material rated to, and does the certificate name it? Ask specifically about continuous temperature and chemical exposure, because PET and PTFE are both common and they are not interchangeable.
- What does the kit house verify on the incoming sleeve? The answer tells you whether the isolation performance you are relying on is controlled or assumed.
The fit problem that beats material choice
Field failure reports on flange isolation rarely trace to a material defect. They trace to fit: sleeves that were cut to a nominal length rather than the actual bolt, flanges assembled with one sleeve missing, and kits where the sleeve inner diameter matched the hole and not the shank. All three are supply-discipline problems, which means they are solved by ordering behaviour rather than by a material upgrade.
How to run the shortlist
- Write the bolt schedule for the project: bolt callout, standard, coating, length, bolts per flange and the flange count.
- Fix the sleeve material from the service temperature and the fluid, then hold it across the whole schedule so the site is not mixing two materials.
- Ask three suppliers for the same schedule, and ask each one how they size the inner diameter and how they verify the length.
- Request a sample sleeve for the most common bolt on the schedule and check the fit on a real bolt, not a nominal one.
- Confirm the packing method. Counted and packed per flange is the answer you want.
- Keep a second source for the sizes that matter, because an isolation kit held up at the dock stops a flange at site.
Where it fits in the wider build: our Mylar (PET) bolt sleeve route gathers every part that goes into it.
Products for this job
These are the PET and mylar parts we cut to a bolt schedule or an insulation drawing. Sample and prototype quantities for Mylar (PET) Bolt Sleeve Suppliers are quoted before any tooling is committed.
Related reading
- Flange Isolation Bolt Sleeves: PET vs PTFE vs Nomex
- Mylar Bolt Sleeve Size Chart: M6 to M36
- Mylar (PET) Tubing for Transformer and Motor Insulation
- Heat Shrink vs Cold Shrink Tubing
Common questions
Who makes Mylar bolt sleeves for flange isolation kits?
Two groups. The flange isolation and gasket manufacturers such as GPT Industries, Lamons, James Walker, Advance Products & Systems, PSI Products and Drake Specialties supply complete kits with sleeves as a component. Drawing-based converters such as WELLELE make the PET sleeves themselves and supply them cut to the bolt callout and packed to count, either direct or into a kit house.
Is PET or PTFE the standard bolt sleeve material?
PET (Mylar) is the default for standard flange duty because it delivers the dielectric break at a fraction of the cost. PTFE is specified where the flange runs hot or sees chemicals that PET cannot take. Ask which one is in the kit you are buying, because the difference does not show in the kit part number.
How do I check the sleeve in a kit I am buying?
Take one apart. Measure the sleeve inner diameter against the bolt shank, its length against the bolt callout, and its wall at several points. If the inner diameter matches the hole rather than the shank, or the length is nominal rather than actual, the kit is relying on fit luck.
Why do isolation kits fail in the field?
Fit and count, most of the time. A sleeve cut short, a sleeve sized to the hole, or a flange assembled one sleeve short. The material is rarely the cause. Counted, cut-to-length supply removes all three.
Can I buy bolt sleeves without the rest of the kit?
Yes. If you already have approved gaskets and washers, sleeves can be bought separately in the sizes you need. That is the usual route where a kit house has the gasket right and the sleeve wrong.
What minimum order is realistic?
Sleeves are a low-cost part, so order size is driven by the size mix rather than the quantity. Mixed-size orders in modest volumes are normal. Ask for the sizes covering your bolt schedule in one shipment rather than ordering per size.
Does the country of origin matter?
It changes lead time, freight and the audit burden. The PET film itself comes from a small number of producers regardless of who cuts the sleeve. What differs is whether the supplier sizes to the bolt callout, holds the wall tolerance and packs to count.
What does WELLELE supply?
PET (Mylar) bolt sleeves for flange isolation kits, cut to the bolt length and packed to the bolt count, in M6 through M36 with ANSI and DIN variants, with wall from 0.05 mm to 0.25 mm, dielectric strength of 15 kV/mm or better and lot traceability to the incoming film certificate. Send the bolt schedule and the flange count.
Specifying this part?
Send the drawing for a manufacturability review.