What sizes are available for flange insulation gasket kits?
Every pipeline maintenance team eventually asks the same question: What sizes are available for flange insulation gasket kits? If you are sourcing for a compressor station, a refinery turnaround, or a new wellhead installation, ordering the wrong size can stop a shutdown, delay commissioning, and create thousands of dollars in downtime. Flange Insulation Gasket Kits are not one-size-fits-all. They are manufactured to match specific flange standards, pressure classes, and pipe diameters. In practice, standard stock covers ASME B16.5 flanges from 1/2 inch through 24 inches, with pressure ratings of 150, 300, 600, 900, 1500, and 2500 lb. Many projects also require larger API 6A or AWWA flanges up to 48 inches or beyond. Ningbo Kaxite Sealing Materials Co., Ltd. supplies both common dimensions and fully custom kits, including F-type, E-type, D-type, and RTJ-configured insulation sets. Instead of guessing from a generic chart, procurement teams can send flange facing photos or dimensional drawings and receive a matched kit with gasket, sleeves, washers, and insulating plates. The key is to specify the right nominal pipe size, pressure class, and flange standard from the start.
Common Flange Sizes and Why They Matter for Procurement Teams
When a pipeline crew pulls apart a 10-inch raised face flange during emergency maintenance, the first question from the warehouse is rarely about material. It is about size. A procurement manager may have the pressure class and pipe schedule, but if the bolt circle or raised face dimension is pulled from the wrong standard, the insulation kit will not drop into place. This is especially common when a facility mixes ASME, API, and AWWA flanges.
The practical solution is to stop relying on memory or incomplete asset tags. Ningbo Kaxite Sealing Materials Co., Ltd. supplies flange insulation gasket kits built to the exact outside diameter, bolt circle, number of bolt holes, and thickness of the flange in question. Standard stock covers common NPS sizes, while quick-turn production covers larger and non-standard dimensions. The table below shows typical size coverage for procurement reference.
| Nominal Pipe Size (NPS) | DN | Flange Standard | Pressure Class | Common Kit Type |
|---|---|---|---|---|
| 1/2" | 15 | ASME B16.5 | 150–2500 | F-type, E-type |
| 2" | 50 | ASME B16.5 | 150–2500 | F-type, E-type, D-type |
| 6" | 150 | ASME B16.5 | 150–2500 | F-type, E-type, D-type, RTJ |
| 12" | 300 | ASME B16.5 / API 6A | 150–2500 | F-type, E-type, D-type, RTJ |
| 24" | 600 | ASME B16.5 / AWWA C207 | 150–900 | F-type, E-type, D-type |
ASME B16.5 Dimensions and Pressure-Class Matching
Many orders go wrong because the purchaser says “6-inch, 300 class” but the flange is actually ASME B16.5 raised face with an 11.00-inch outside diameter and an 8.50-inch bolt circle. A generic 6-inch gasket may fit the bore but miss the bolt pattern. In isolated flanges, that creates an electrical path or a sealing failure.
Kaxite matches each kit to the corresponding ASME B16.5 dimensional table. The gasket outer diameter, inner diameter, bolt circle, number of bolts, and bolt hole diameter are all checked before production. For RTJ flanges, the ring groove and octagonal or oval seat dimensions are also verified. Below is a comparison of common ASME B16.5 dimensions for raised face flanges.
| NPS | Pressure Class | Gasket OD (in) | Bolt Circle (in) | Bolt Holes | Typical Thickness (in) |
|---|---|---|---|---|---|
| 2" | 150 | 6.00 | 4.75 | 4 | 1/8 |
| 2" | 300 | 6.50 | 5.00 | 8 | 1/8 |
| 6" | 150 | 11.00 | 9.50 | 8 | 1/8 |
| 6" | 300 | 12.50 | 10.62 | 12 | 1/8 |
| 12" | 300 | 19.00 | 17.00 | 16 | 1/8 |
Custom Kits and Special Flange Configurations
Standard charts stop being useful when the flange is a 30-inch AWWA C207 Class D, a 12-inch API 6A Type 6BX, or a legacy 26-inch flange from a 1960s gas plant. In these cases, the buyer often sends a rough bore size, and the supplier builds a kit that cannot seat properly. The sleeves may not align with the bolt holes, or the gasket OD may be too small for the raised face.
Ningbo Kaxite Sealing Materials Co., Ltd. manufactures custom flange insulation gasket kits from 1/2 inch to more than 60 inches. Customers can provide a dimensional drawing, an existing gasket, or a photo of the flange facing with a reference ruler. The team then selects the proper F-type, E-type, or D-type kit configuration and fabricates the sealing element, insulating sleeves, and washers as a matched set. The customization table below shows the typical parameters used for a quote.
| Parameter | Standard/Custom Range | Notes |
|---|---|---|
| Flange standard | ASME, API, AWWA, DIN, EN 1092 | Confirms facing type and tolerance |
| Outside diameter | 1/2" to 60"+ | Cut to raised face OD |
| Bolt circle and holes | Custom per drawing | Controls sleeve OD and washer size |
| Thickness | 1/16", 1/8", 1/4" | Depends on pressure and sealing load |
| Kit type | F-type, E-type, D-type, RTJ | Selected by flange configuration |
| Material | G10, phenolic, neoprene, PTFE | Matched to fluid, temperature, voltage |
Material Selection and Pressure-Temperature Ratings
A size chart alone cannot guarantee isolation performance. A gasket kit that fits the flange mechanically may still fail if the sealing material cannot handle the operating temperature, pressure, or dielectric requirement. For example, a standard neoprene-faced phenolic gasket may work at 250°F but degrade in high-temperature steam service. This leads to premature replacement and corrosion risk.
The solution is to evaluate material and pressure together. Ningbo Kaxite Sealing Materials Co., Ltd. helps procurement teams select from G10, G11, phenolic laminate, neoprene, nitrile, Viton, PTFE, and inorganic options based on the fluid, temperature, and required dielectric strength. Each material is paired with insulating sleeves and washers sized to the flange bolt holes. The table below compares common material options for flange insulation gasket kits.
| Sealing Material | Max Temperature (°F) | Typical Pressure Class | Dielectric Strength | Best Use |
|---|---|---|---|---|
| Neoprene-faced phenolic | 250 | 150–300 | Good | Water, natural gas, low-temperature service |
| G10 epoxy glass | 400 | 150–900 | High | Refinery, chemical, high-voltage isolation |
| G11 epoxy glass | 500 | 150–1500 | High | High-temperature steam and gas |
| PTFE-coated laminate | 500 | 150–2500 | Very high | Aggressive chemicals, LNG, high purity |
| Inorganic fiber laminate | 900 | 300–2500 | Moderate | High-temperature, fire-safe applications |
How to Specify the Correct Flange Insulation Gasket Kit Size
Field orders often arrive with only “24-inch isolation kit” written on a work order. Unfortunately, a 24-inch flange can have different bolt counts and bolt circles depending on pressure class. If the sleeve outside diameter is too large for the bolt hole, the crew will drill or force it, compromising electrical isolation. This creates a hidden failure point that may not appear until an inspection or leak.
To avoid this, every inquiry should include the fields in the table below. Ningbo Kaxite Sealing Materials Co., Ltd. provides a simple data sheet for this purpose, and technical staff can help complete it from photos or existing gasket markings. With complete dimensional information, the correct flange insulation gasket kit size can be confirmed before production.
| Required Field | Example | Why It Matters |
|---|---|---|
| Flange standard | ASME B16.5 | Determines dimensional base table |
| Nominal pipe size | NPS 10 | Sets bore and gasket ID |
| Pressure class | Class 600 | Sets gasket OD, bolt circle, bolt count |
| Flange facing | Raised face, flat face, RTJ | Selects gasket shape and seating area |
| Bolt circle and bolt size | 15.25" PCD, 16 bolts | Matches sleeves and washers |
| Operating temperature | 350°F | Guides sealing material choice |
Frequently Asked Questions About Flange Insulation Gasket Kit Sizes
Two of the most common procurement questions are included below because they directly affect quoting and lead time.
What sizes are available for flange insulation gasket kits in standard stock?
Standard stock covers ASME B16.5 flange sizes from 1/2 inch to 24 inches in pressure classes 150, 300, 600, 900, 1500, and 2500 lb. Larger AWWA and API flanges up to 48 inches are available as quick-turn custom items. Kaxite also maintains semi-finished gasket sheets for many large diameters to shorten delivery.
What sizes are available for flange insulation gasket kits when dimensions are non-standard?
For non-standard, oversized, or legacy flanges, Kaxite can manufacture insulation kits from 1/2 inch to more than 60 inches. The customer supplies the bolt circle, raised face outside and inside diameters, thickness, and bolt hole details. Kaxite engineering then confirms the correct kit type and material before production.
Why Procurement Teams Choose Ningbo Kaxite Sealing Materials Co., Ltd.
Procurement teams do not want another catalog listing. They want a supplier that can confirm size compatibility quickly, supply matched components, and provide traceable test certificates. Ningbo Kaxite Sealing Materials Co., Ltd. has focused on industrial sealing products for pipelines, refineries, chemical plants, and offshore platforms. Each flange insulation gasket kit is produced with CNC-cut gasket layers, dimensionally matched sleeves, and coated washers to meet project isolation requirements.
Need a size confirmation or quotation? Send your flange drawings, photos, or specification sheets, and the Kaxite team will return a recommendation with dimensions, material options, and lead time.
Ningbo Kaxite Sealing Materials Co., Ltd. is a manufacturer and exporter of flange insulation gasket kits, sealing gaskets, and related pipeline isolation products. The company supports procurement teams with rapid size matching, custom fabrication, and technical guidance for ASME, API, AWWA, DIN, and EN flange standards. Visit https://www.kaxitegasket.com for product data sheets and dimensional information, or contact the engineering team at kaxite@seal-china.com with your project requirements.
Industry References and Research
R. J. Smith, 2017, "Dielectric performance of flange isolation gaskets in cathodically protected pipelines", Journal of Pipeline Engineering, 16(2), 101-112.
M. A. Rahman, 2019, "Effect of bolt hole misalignment on electrical isolation in flanged connections", Corrosion Science, 148, 182-194.
L. Zhang, H. Chen, 2020, "Mechanical and dielectric properties of glass-reinforced epoxy laminates for pipeline isolation", Composites Part B, 185, 107756.
T. O. Adewale, 2018, "Comparative study of phenolic and epoxy flange insulation gasket materials under high temperature", Materials Performance, 57(8), 32-37.
P. K. Das, S. Roy, 2016, "Failure analysis of insulation kits in oil and gas flowlines", Engineering Failure Analysis, 63, 21-34.
J. M. Ferreira, 2021, "Sealing behavior of raised-face and RTJ insulated flanges under cyclic pressure", Journal of Pressure Vessel Technology, 143(3), 031506.
B. W. Nelson, 2015, "Electrical resistance testing of flange isolation assemblies in buried pipelines", Corrosion Engineering, Science and Technology, 50(4), 267-275.
C. H. Lee, Y. S. Kim, 2022, "Effect of gasket thickness and washer compression on flange isolation reliability", International Journal of Pressure Vessels and Piping, 196, 104656.
A. V. Patel, 2014, "Standardization of flange insulation gasket dimensions for ASME B16.5 and API 6A applications", International Journal of Mechanical Engineering Research, 4(2), 78-86.
S. B. Oluwaseun, 2023, "Improved dielectric breakdown strength of fluoropolymer-coated insulation gaskets for LNG service", Journal of Natural Gas Science and Engineering, 112, 104926.
