High Temperature Sealing
View this detailed comprehensive brochure of our product offerings for use in extreme temperature applications. Download here.
When exposing industrial bolted joints to extreme temperatures and pressure, you need to have the right gasket that not only provides effective sealing but lasts longer. Gasket temperature limits can be classified into (but are not limited to) the following temperature ranges: Phyllosilicate 1000ºC (1832ºF), Flexible Graphite 450ºC (850ºF), Compressed Fibre 400ºC (750ºF).
High-temperature applications such as gas turbines, heat exchangers, exhaust manifolds and others commonly found in the refinery, power generation, and chemical industries, Phyllosilicate is a good choice for the following reasons:
- high tensile strength
- low weight loss at extreme conditions
- laboratory tested for fire safety
- non-combustible
- sustainable solution
HT1000®
Phlogopite mica is a non-toxic naturally occurring hydrated silicate of potassium and magnesium with a lamellar and non-fibrous structure. It is flexible, has high tensile strength, can withstand substantial mechanical pressure perpendicular to the lamellar plane, is chemically resistant, fireproof, infusible, incombustible, nonflammable, and is a known alternative to asbestos.
Style S90
Phlogopite mica paper impregnated with an inorganic binder and no carrier.
Style L316
Phlogopite mica paper impregnated with an inorganic binder laminated with a 0.002” thick 316 stainless steel carrier.
Style T316
Phlogopite mica paper impregnated with an inorganic binder laminated with a 0.004” thick 316 stainless steel perforated carrier.
DRI-ETG SWG
(1,832°F). At extreme temperatures, flange assembly torque retention is the key component to maintaining a tight seal. Durlon® ETG combines a oxidation boundary material with the excellent stability and sealing characteristics of flexible graphite in order to preserve seal integrity and to retain the initial assembly torque.
Durlon® ETG adds an inner and outer protection boundary in the form of a mica-phyllosilicate based sealing material called Durlon® HT1000® which consists of phlogopite mica paper impregnated with an inorganic binder at less than half the binder amount found in a typical vermiculite-phyllosilicate filled product. This lower binder content allows for superior weight retention and results in ultimate extreme temperature sealing performance.
Style DRI
Sealing element (D) combined with a centering ring (R) and an inner ring (I) which improves radial strength and protects the sealing element from erosion and inward buckling.
K40-ETG Kammprofile
The serrated core is covered with soft sealing material and is dependent on the service conditions of the system. Flexible graphite and expanded PTFE sealing layers are most common, but other products like HT1000® or (Extreme Temperature Gaskets) ETG’s can be used as well. While providing the Durlon® Kammprofile gasket with excellent sealing properties, the soft sealing layers also fill in minor flange imperfections and protect the flange surfaces from damage.
Durlon® Kammprofile gaskets are the preferred choice for applications requiring improved performance at low seating stresses. The serrated peaks provide reduced contact area and when combined with the soft conformable sealing layers, the Durlon® Kammprofile gasket provides a virtual metal to metal connection. They feature excellent resistance to blowout and provide superior stability for ease of handling and installation.
Durlon® ETG’s engineered design principle is focused around providing oxidation protection zones around the central oxidation inhibited flexible graphite sealing component. Standard industrial-grade flexible graphite typically begins to rapidly oxidize at around 650°C (1,200°F). By adding oxidation inhibitors to the graphite, the rate and amount of oxidation can be significantly reduced, thus extending the seal life of the material. However, oxidation can still occur and at extreme temperatures, it can be fatal to the integrity of the joint.
Core materials are generally selected in an identical material to the piping system in order to reduce corrosion problems. The standard core material is 316 stainless steel with a nominal thickness of 0.125” (3mm). Other core materials: SS304, SS321, SS316Ti, Monel®, Titanium, Hastelloy® & Alloy 20 can be manufactured to your specifications on request.
Parallel Root Core
This core design is where the main sealing faces of the serrated metal core are parallel to each other. These are the standard design of Kammprofile gaskets.
Integral Centering Ring
The centering ring is used to position the gasket between flat face and raised face type flanges.
Durtec® ETG
The Durtec® gasket is designed to withstand high temperatures and pressures, to be blowout resistant, to be fire safe, and to resist toxic and or corrosive chemicals for such applications as pipeline flanges, valves, small & large pressure vessels, heat exchangers, towers, and tanks.
Core Materials
Standard core material is 316 stainless steel with a nominal thickness of 0.125” (3mm). Other core materials: SS304, SS321, SS316Ti, Monel®, Titanium, Hastelloy® & Alloy 20 can be manufactured to your specifications on request.
HT1000® Paste
CONTAINER SIZES: 170 g and 90 g.
Fire Safety Tests and High-Temperature Gasket Performance Testing
In high-temperature applications, accurately assessing and comparing the performance of gasket materials presents a significant challenge due to the lack of standardized testing procedures. This gap underscores the crucial role of rigorous, application-specific gasket fire safety tests like API 6FB. These tests not only evaluate fire safety of the gaskets but also serve as a benchmark for measuring gasket performance under extreme conditions.
Understanding the API 6FB Fire Test
Type 1 (Onshore Test) vs. Type 2 (Offshore Test)
The American Petroleum Institute (API) has developed the API 6FB standard, a rigorous testing protocol that assesses the fire safety of flange gaskets used in upstream, midstream, and downstream applications. This standard is divided into two types of applications: Type 1 – Onshore, and Type 2 – Offshore.
In both tests, the gasket is installed in a bolted flange assembly. The flange is then pressurized to 550-570 psig and exposed to intense external flames for a total of 60 minutes. After cooling down and depressurizing, the gasket is repressurized to 550-570 psig. To pass the test, the allowable leak rate for both the burn/cooldown and depressurization/repressurization phases is 24.0 ml/min for 6” Class 300# gaskets. The primary distinction between them lies in the testing conditions and the intensity of fire exposure. Almost all fire safety tests are performed with 6-inch ANSI Class 300 gaskets.
As shown in Table 1: Temperature Differences in API 6FB test types, API 6FB Type 1 (Onshore) tests involve multiple burners with flame temperatures ranging from 1400 to 1800°F and a calorimeter block temperature of 1200°F. The test setup and the flame intensity are shown in Figure 1A and Figure 1B.
API 6FB Type 2 (Offshore), recognized as the more stringent test, involves a single, more intense burner with flame temperatures between 2000 to 2500°F and a calorimeter block temperature reaching up to 1800°F. This test setup, and the flame intensity are shown in Figure 2A, Figure 2B, and Figure 2C (below).
The elevated requirements of the Type 2 (Offshore) test are designed to simulate the harsher, more unpredictable conditions typical of offshore environments, such as drilling rigs and platforms. This makes it a critical standard for equipment expected to withstand extreme scenarios.
Table 1: Temperature Differences in API 6FB test types
| Type 1 (Onshore) | Type 2 (Offshore) | |
|---|---|---|
| Number of Burners | Multiple or widespread | 1 |
| Flame Temperature | 760-982°C (1400-1800°F) | 1093-1371°C (2000-2500°F) |
| Calorimeter Block Temperature | 648°C (1200°F) | 982°C (1800°F) |
Distinguished Performance in API 6FB Testing – Type 2 (Offshore)
Durlon® SWG DRI-ETG sets a new industry precedent with its performance in fire safety tests. The API 6FB Type 2 (Offshore) test, recognized as the most stringent standard, challenges the gasket to perform under the harshest conditions, akin to those found in offshore oil drilling operations. Durlon® SWG DRI-ETG not only passed this rigorous test but did so with zero leakage, an unmatched achievement among high-temperature gasket products on the market. In fact, its performance in the API 6FB Type 2 (Offshore) test demonstrated zero leakage during both the Burn and Cool Down and the Depressurization – Repressurization Tests, a feat unprecedented in any competitor’s Type 1 (Onshore) or Type 2 (Offshore) test report.
Notably, most gasket manufacturers focus almost exclusively on Type 1 tests, often avoiding the more demanding Type 2 tests due to their stringent requirements.
Superior Material Quality – HT1000® Phlogopite Mica and APX2® Graphite
Poor thermal stability and excessive weight loss are common issues with gasket materials at elevated temperatures, which can compromise their structural integrity and sealing capabilities. A crucial factor in the success of Durlon® SWG DRI-ETG is its use of HT1000®, a high-performance phlogopite mica. This material has shown superior weight loss resistance at high temperatures compared to other fillers, such as those based on vermiculite and talc. The exceptional thermal stability of HT1000®, contrasted with vermiculite-based and talc-based fillers, is illustrated in Figure 3 (below). This characteristic ensures that the gasket maintains its integrity and sealing performance over time in high-temperature applications.
Figure. 3: Weight lost test results under various high temperature test conditions.
The combination of HT1000’s thermal stability and superior insulation characteristics with the sealing performance of high-end APX2® flexible graphite enables successful and durable high-temperature sealing.
Comprehensive Certification and Industry Recognition
Durlon® DRI-ETG SWG is the only high-temperature gasket to pass the API 6FB Type 2, API 607, and API 6FB Type 1 (Onshore) tests, demonstrating its superior fire safety and adaptability to various operational challenges.
Custom High Temperature Testing
In this test, the nitrogen sealability of Durlon® DRI-ETG was evaluated under the most challenging conditions imaginable, where an entire pressurized gasketed flange was placed inside an oven and exposed to extremely high temperatures. This method, unprecedented among gasket manufacturers, was designed to push the DRI-ETG gasket to its limits by subjecting the entire gasketed flange to severe heat and assessing its performance. Additionally, the test aimed to evaluate the ETG configuration and measure how well graphite improves sealability at elevated temperatures when thermally shielded by HT1000®.
Two types of 4-inch Class 600 Durlon® spiral wound gaskets were prepared for this testing procedure: one with the ETG configuration and one using only mica filler. The gaskets were tested at 14,500 psi and 25,000 psi gasket stresses according to the following procedure:
- The test assembly was calibrated for pressure drops versus volumetric leak rate.
- The assembly was pressurized with nitrogen to 150 psig, and leakage was measured.
- The entire assembly was heated in the oven to 1382°F and held for 24 hours.
- After stabilization, the leakage was recorded using the pressure decay method.
- The assembly was then cooled to ambient temperature and pressurized with nitrogen to 150 psig to measure the leakage one final time.
As shown in the chart below, the ETG configuration, consisting of high-temperature flexible graphite thermally protected by the high-performance HT1000® material, improved leakage performance by 14 to 17 times—a staggering enhancement.
Leading Innovation in High-Temperature Sealing
Durlon’s commitment to using high-quality materials such as APX2® high temperature flexible graphite and HT1000® phlogopite mica, combined with precise manufacturing processes, establishes Durlon® DRI-ETG SWG as a leader in sealing technology for high-temperature applications. Its unmatched performance in rigorous fire tests assures industry stakeholders of its reliability, making it the preferred choice for any high-temperature application. With the ever-growing requirements for safety and low fugitive emissions across the industry, Durlon® remains dedicated to providing innovative solutions that redefine safety and sustainability standards.
Warning: Durlon® gasket materials should never be recommended when both temperature and pressure are at the maximum listed. Properties and applications stated are typical. No applications should be undertaken by anyone without independent study and evaluation for suitability. Never use more than one gasket in one flange joint and never reuse a gasket. Improper use or gasket selection could cause property damage and/or serious injury. Data reported is a compilation of field testing, field service reports and/or in-house testing. While the utmost care has gone into publishing the information contained herein, we assume no responsibility for errors. Specifications and information contained within are subject to change without notice. This edition cancels and renders all previous editions obsolete.