Buy flange insulation gasket kits direct from Ningbo Kaxite Sealing Materials Co., Ltd., a China-based manufacturer and exporter. Flange insulation kits are the most widely used form of controlling losses due to corrosion. The kit electrically isolates the two flange faces to break the metal-to-metal path, increasing the effectiveness of cathodic protection systems and confining or eliminating electrolytic corrosion.
Three gasket types are available — Type E full-face, Type F raised-face and Type D ring type joint (RTJ). Each kit is supplied with the insulation gasket, insulating sleeves, insulating washers and steel washers matched to the flange size, pressure class, service medium and required dielectric strength.
The correct type is determined by the flange face. Use the cards below to identify your type, then confirm with the full specification table.
For full-face (FF) flanges
Same outside diameter as the full-face flange, with precision-cut bolt holes. Provides full protection of both flange faces and facilitates proper alignment during installation. Minimizes ingress of conductive foreign matter between the flange portions outside the raised face and reduces the risk of bridging.
For raised-face (RF) flanges
Made to fit the raised-face portion of the flange only. No bolt holes. The outside diameter fits tightly into place, assuring a well-centered position without an outer ring.
For ring type joint (RTJ) flanges
Made to fit the ring grooves on ring type joint (RTJ) flanges. The Type D profile matches the standard RTJ groove so the gasket seats correctly in the groove.
This page is written for procurement engineers, pipeline maintenance teams, cathodic protection engineers and EPC contractors who need a reliable flange insulation gasket kit manufacturer. Whether you are comparing quotes, verifying kit components or scheduling a bulk delivery for an oil, gas, water or chemical plant project, the sections below cover the technical facts and commercial terms you need to place a firm order.
Flange insulation kits are the most widely used form of controlling losses due to corrosion. They can be used to control stray electric currents in piping at oil, gas, water, refinery and chemical plants, to increase the effectiveness of cathodic protection systems and confine or eliminate electrolytic corrosion.
Each kit consists of an insulating gasket, insulating sleeves, insulating washers and steel washers. The gasket provides electrical isolation between the flange faces. The insulating sleeves isolate the bolt from the flange. The insulating washers isolate the nut face from the flange face. The steel washers carry the bolt load. When all four components are correctly installed, no metal-to-metal path exists between the two flange faces.
The correct type is determined by the flange face. Use the comparison below as a starting point, then send the flange drawing for a firm recommendation.
| Property | Type E | Type F | Type D |
|---|---|---|---|
| Flange type | Full-face (FF) | Raised-face (RF) | Ring type joint (RTJ) |
| Bolt holes | Yes — precision cut | No | No |
| Outside diameter | Same as full-face flange OD | Matches raised-face portion | Fits the ring groove |
| Centering | Bolt holes align gasket | OD fits tightly into place | Groove profile seats gasket |
| Face protection | Both flange faces | Raised-face portion only | Ring groove contact only |
| Bridging risk | Lowest — outer foreign matter blocked | Moderate | Moderate |
| Typical service | Oil, gas, water, refinery, chemical plant piping | Raised-face flanges in the same services | RTJ flanges in high-pressure oil and gas service |
If your flange is a full-face design and you want maximum protection of both faces against conductive foreign matter, specify Type E. If your flange is a raised-face design, specify Type F. If your flange is a ring type joint (RTJ) design, specify Type D. Send the flange drawing for a firm recommendation.
Every component of the flange insulation gasket kit is selected to match the flange size, pressure class, service medium and required dielectric strength. The gasket core, sleeves and washers must all be rated for the same operating conditions.
NEMA G10 or G11 glass-reinforced epoxy laminate. Provides electrical insulation between the two flange faces. Machined to the Type E, Type F or Type D profile.
Mylar, Nomex, G10, G11 or Phenolic. Each sleeve electrically isolates the bolt from the flange. Dielectric strength and operating temperature selected to match the service.
Phenolic, Mica, G7, G10 or G11. Each washer isolates the nut face from the flange face. Mica is available for the highest water resistance and dielectric strength combination.
Zinc-plated carbon steel as standard. SS 304 or SS 316 available on request for corrosive environments.
| Component | Standard Material Options |
|---|---|
| Insulation gasket core | G10 or G11 glass-reinforced epoxy laminate |
| Insulating sleeves | Mylar, Nomex, G10, G11, Phenolic |
| Insulating washers | Phenolic, Mica, G7, G10, G11 |
| Steel washers | Zinc-plated carbon steel; SS 304 or SS 316 on request |
| Gasket types | Type E full-face, Type F raised-face, Type D ring joint, Seal Type O |
For a specific material certificate or dielectric test report, request it with your order. All values will be confirmed against the mill certificate before shipment.
Flange insulation gasket kits are used wherever two flange faces must be electrically isolated while still sealing the process medium. The three most common reasons are cathodic protection, galvanic isolation and stray current control.
Stray current control on distribution, transmission and process piping in oil, gas and water plants.
Flanged joints in refinery and chemical plant piping where electrolytic corrosion would otherwise occur.
Isolation of pipeline sections from cathodically protected structures to increase the effectiveness of the protection system.
Prevention of galvanic corrosion where two different metals are bolted together across a flange.
Control of stray electric currents from nearby rail, DC transit or welding systems that would otherwise reach the protected structure.
Type D ring joint insulation gaskets for RTJ flanges in high-pressure oil and gas service.
Correct installation is essential for the insulation kit to perform its function. The procedure below is the standard recommended sequence. Follow the flange manufacturer's torque values for the final torque stage.
Verify that the installation kit contains the material specified and the contents are not damaged.
Clean and inspect pipe flange faces and apply lubricant to all threads.
Install the gasket and align the flanges so the bolt holes will be centered.
Use alignment pins in two diametrically opposite bolt holes whenever possible to assure proper alignment of flanges and gasket.
Insert insulating sleeves into the bolt holes taking care not to use force which could damage the sleeve material.
Insert the bolt with both insulating washers against the flanges, followed by the steel washer and nut.
Tighten two diametrically opposite bolts to 30% of total torque.
Replace the two alignment pins with bolts and tighten the remaining bolts to 30% of the total torque value.
Tighten all bolts to 50%, then to 100% of final torque value.
Bolts should be of sufficient length to extend through the nut approximately 1/4 inch.
For critical services, verify continuity after installation with a megohmmeter. A correctly installed kit will show a high resistance reading across the flange joint.
To quote a flange insulation gasket kit correctly, we need the information below for your right application. Send these five items with your enquiry. If you already have a flange drawing, attach it and we will match it directly.
Nominal pipe size, pressure class (ANSI 150, 300, 600, 900, 1500, 2500 or PN), and the flange standard.
Type D, Type E or Type F. Specify Seal Type O if an O-ring sealing element is required.
G10 or G11 glass-reinforced epoxy laminate, selected to match the operating temperature and dielectric strength requirement.
Mylar, Nomex, G10, G11 or Phenolic for sleeves. Phenolic, Mica, G7, G10 or G11 for insulating washers. Zinc-plated carbon steel, SS 304 or SS 316 for steel washers.
Order quantity and destination port so we can quote FOB, CIF or freight-inclusive pricing. MOQ 10 sets.
Send your flange size, pressure rating, gasket type (Type D / E / F), sealing element material, sleeve and washer material, quantity and destination port. Our sales engineers reply with a firm unit price, lead time and available samples. For urgent cathodic protection, refinery or RTJ requirements, contact us by phone or WhatsApp.
Address
No 432 Zhenhai Middle Road, Luotuo Street, Zhenhai District, Ningbo City, Zhejiang China
