Frequently Asked Questions

Durlon® 8500, 9000, 9000N, 9002, 9200, 9600, Virgin PTFE (Skived) and Joint Sealant all conform to the requirements of 21 CFR 177.1550 for food and drug contact.

Electrically insulated gaskets are used as an insulator between dissimilar metal flanges or to electrically isolate sections of pipework in cathodic protection systems, preventing the flow of electrostatic charge along the pipelines. See iGuard™ Isolation & Sealing Kits.

Gasket stress is used to describe the unit load on its surface and one of the most important parameters of a bolted joint because it directly impacts the ability of the gasket to seal. A soft and conformable gasket may seal at a relatively low gasket stress while a hard metal gasket may require much higher stress.

The amount of compression expected on a particular gasket type depends on its compressibility data and the load applied. Sealing problems are often a result of lack of compression. Gasket torque values and the actual compression of your gasket will have an effect on the performance of your application. See Gasket Installation Training.

Hot bolting refers to tightening a flange while it is in service. It is used to stop small stable leaks or as a preventive measure in high temperature or cyclic services. It is potentially hazardous and the utmost caution needs to be exercised when planning and carrying it out. It is not recommended as best practice although it is widely carried out. However, any potential benefits arising from hot bolting should be carefully weighed against the risks encountered.

iGuard™ flange isolation and sealing systems consist of all the necessary components to seal, electrically isolate, and for cathodic protection (corrosion control) between flanges, from general to severe service applications such as water, wastewater, natural gas, hydrocarbons, caustics, acids, and other aggressive media to 232°C (450°F). Gaskets are available for full face (Type E), raised face (Type F), and ring type joint (RTJ) flanges (Type D), to meet all international piping sizes. iGuard™ gaskets meet AWWA, ANSI, API, DN, JIS, and all other dimensional standards.

Any of our NBR (Nitrile Butadiene Rubber) gaskets can withstand petroleum-based products due to its rubber binding. Durlon® 7900, 7925, 7950, 7910, 8300, 8400 and 8500 are all appropriate for jet fuel applications.

The gasket stress required to achieve the initial seal is considered the “y” constant. The “m” value ensures that the flange has adequate strength and available bolt load to hold the joint together, while withstanding the effects of hydrostatic end force or internal pressure (y-seating stress and m-gasket factor). In simple terms, a flange must be designed to create sufficient compressive load on the gasket contact area to create an initial seal and the gasket must conform to the flange surface and must be compressed enough to seal off any internal voids or spaces.

Yes, we manufacture several gaskets that have passed MIL-G-24696B Navy Adhesion Test (366°F/48 hrs.): Durlon® 7910, 8400, 8600, 8700 and 8900.

Modulus of elasticity relates to the elasticity or flexibility of a material.

Durlon® 7910 is a good quality commercial grade compressed sheet gasket material for moderate service conditions. It was specifically developed to meet the requirements of NSF/ANSI 61 for potable water application 23°C (73°F) to commercial hot to 82°C (180°F).

An oxidizer is a type of chemical, which a fuel requires to burn. Durlon® 9000 is for use in process piping and equipment in many industrial applications where resistance to highly aggressive chemicals is required. In addition, the shape of the fillers does not allow wicking, which can cause corrosion on flange surfaces. The 6 inch Class 300 Durlon® 9000 gasket passed the API Standard 6FA Fire Test. The test fixture was subjected to an external flame of 875°C (1607°F) average for 30 minutes. The measured leakage was 1.8 ml/min, where the max allowable limit is 1200ml/sec.

Modern gaseous and liquid oxygen services require extreme gasket performance flexibility in order to withstand the extremes that these services demand. Typically, PTFE is not recommended for cryogenic applications, however, we have developed Durlon® 9002 as an adaptation of our original glass-filled formula to better meet these extreme system demands. Durlon® 9002 has passed both gaseous, up to 260°C (500°F) and 52 bar (754 psi), and liquid oxygen tests performed by BAM Federal Institute for Materials Research and Testing as well as LOX Mechanical Impact Sensitivity Testing (ASTM G86 & ISO 21010), passing with zero reactions out of twenty tests (0/20) at a test reaction frequency of 0%.

The pH of a solution is a measure of the molar concentration of hydrogen ions in the solution and as such is a measure of the acidity or basicity of the solution. If the pH level is less than 7, it is considered acidic and if it is above 7, then the solution is considered to be alkaline.

The lifetime of a gasket is dependent upon its quality and what it is exposed to and how it is installed. Additionally, inertia of the fluid may create a large spike in pressure resulting in pushing or forcing the gasket from the flange sealing surface and can cause leakage or even blow out.

Durlon® 8500, our “workhorse” material, contains our unique blend of high strength aramid and inorganic fibres, providing excellent results in new generation refrigerants and has passed the HVAC service fitness & compatibility test. And our top performer for original style HVAC OEM applications – Durlon® 8700 is proven to provide a tight seal in ammonia-based refrigerants, oils and fuels.

Durlon® 8300 maintains excellent scalability during thermal cycling in steam applications and is our premium grade, multi-service, high strength carbon fibre and NBR gasket sheet. It is designed to handle the extremes of pressure and temperature. As with all of our premium products, the versatility of this sheet enables the end user to standardize on one sheet for a multitude of applications and avoid the confusion of having to choose from several different sheets.
Superheated steam is an extremely high-temperature vapour generated by heating the saturated steam obtained by boiling water. Our premium grade compressed non-asbestos gasket material – Durlon® 8900 is a perfect solution for this application.

Torque wrench’s come in many shapes, sizes and styles ranging from the basic beam, clicker wrench or even electronic wrench. In 65-70% of gasket failures, the main cause of the failure is linked to under loaded gaskets. Applying the correct torque helps ensure that you are properly stretching the bolts, which in turn act like a spring pulling the flanges together, creating load on the gasket and achieving an effective seal. Torque wrenches can range in price and accuracy, however, despite the tool’s price tag, a torque wrench is only as good as its last calibration. So be sure to do this before putting it to use. Read more about Gasket Installation Training.

The inner retaining ring increases the axial rigidity and resilience of the gasket. Its purpose is to help avoid excessive compression due to high seating stress in high-pressure service and to reduce turbulence in the flange area. The advantages to using an inner ring include the following: Provides additional compression stop and blowout resistance, prevents build up of process fluid, minimizes erosion and turbulence, shields the gasket, prevents buckling and promotes tightness. To view our line of Spiral Wound Gaskets, click here.

An O-ring is a precisely molded shape with a specific profile to fit into a specific channel or groove and are known for their ability to seal extremely high pressures.
Gaskets are by far the most versatile seal, with different shapes, materials, coatings, methods, etc. Depending on the type of material chosen, they can seal at a wide range of temperatures and pressures. Click here to view our line of gasket products.

Never scrape off old gaskets with a razor blade or anything that can scratch the metal surfaces and create a leak path. Doing so may compromise the seal and the operation of the assembly. But failure to clean off old gasket or gasket materials may result in the mating surfaces coming together in an uneven alignment. Instead, use a plastic scraper or nylon brush. Click here to view our CNA enhanced anti-stick gaskets.

Sounds like a simple question, but in fact, requires more than a simple answer.
It is not always realistic to repair or adjust the misalignment of flanges. So, if flanges are corroded, uneven or not parallel, a thicker gasket may be recommended because of their compression capabilities.
So why do most gasket manufacturers recommend using thinner gaskets wherever possible?
Thinner gaskets offer many advantages:

  • Greater blow-out resistance and lower leakage rates due to the smaller cross-sectional area exposed to the internal medium pressure.
  • Environmental concerns
  • Better compressive strength and therefore higher gasket surface loads (pressure) can be safely applied to a thinner gasket.
  • Better fastener torque retention due to the lower creep relaxation characteristics of thinner gaskets.
  • Lower cost of the gasket itself.

Click here to view our line of gasket products.

This is a loaded question, to which the practical and factual answer is… an Application Engineer’s nightmare!
A gasket may last 5 years, or it could last 20 years. Here is some insight into factors that will give your gasket the best chance at a long and prosperous life between the flanges. Read more here.

As a trusted gasket manufacturer, our recommendation is that you never reuse a gasket.

For a gasket to seal under installed conditions, a minimum stress value is necessary. This value should include the relaxation that will occur during the gasket’s installed life. To prevent damage, it also has a maximum stress value that should not be exceeded, its crush strength. When a gasket’s crush strength is exceeded, the properties that provide the seal break down. An optimized solution targets a stress level that is as high as possible above its minimum value but a comfortably safe margin below its maximum value and a value that may cause a problem to the bolts or flanges. View our gasket installation video to learn more.

Here at Durlon®, our prime design objectives are to maximize the sealability of our gasket materials to meet fugitive emissions requirements. We offer two specific product categories that have been tested and proven to offer exceptional sealability in challenging conditions. Our filled-PTFE products – notably the most versatile product, Durlon® 9000 glass-filled PTFE, offers exceptionally tight sealing characteristics. Secondly, our specially engineered machined metal core gasket, Durlon® Durtec®, is ideally suited to fluctuating pressure and temperature conditions while being fire-safe and offering unparalleled sealability. When it comes to the hazardous and challenging conditions present in the oil & gas, chemical and mining industries, to name a few, these product specifications ensure safety, reliability and the assurance of a significant reduction in overall fugitive emissions.
The use of premium gasket materials with good seal ability numbers are the easiest ways to reduce emissions. Read more

Achieving the proper gasket compression via the torque placed on the bolts is a well-engineered, tested and verified process based on the specific type of gasket material.
Sometimes the torque values aren’t followed, or a material gets replaced, and flange surfaces change throughout the repetitive heat cycles. When this happens, you must trust the performance of your gasket material. In some cases, over-compression can happen, and that can lead to problems. View our gasket installation video to learn more.

No. This is highly NOT recommended because it will most often create a leak path. See FAQ: What thickness is best for a gasket?

We recommend that gaskets be installed with only the factory-applied anti-stick formulation. Additionally, grease or paste type materials may deteriorate or dissolve in service, leaving a possible leak path across the gasket. Our anti-stick technology is applied to the surface during the manufacturing process allowing for improved separation from flange surfaces during removal, saving time and energy, and all without compromising the performance of the gasket.

Ring type gaskets have no bolt holes. These gaskets are positioned inside the flange bolts and around the pipe bore and are typically used on raised face flanges. When used on a raised face flange, the ring gasket is positioned on top of the raised surface of the flange. An advantage of ring gaskets is that they can be installed without having to fully disassemble the joint.
A full-face gasket covers the entire face of the flange. Full-face gaskets are typically used on flat face flanges and are cut with bolt holes which allow the insertion of the flange bolts through the gasket. When installing full-face gaskets, the joint must be completely disassembled. View our full product line here.

Durlon® 9000, has passed the API 6FA, 3rd Edition Fire Test and Durlon® 8300, 8500, SWG DRI and SWG DRI ETG have all passed API 6FB. Additionally, our Durlon® 8900, Durtec®, SWG DRI ETG and HT1000 have passed ANSI/API 607 Fire Tests.

Flange surface finish is a critical aspect of gasket performance. Metallic, semi-metallic and nonmetallic gasket materials interact with flange surfaces differently. Each of these gasket types require specific ranges of surface finish for optimum gasket performance with lowest leakage. Metallic gaskets require a smoother flange finish than either semi-metallic or nonmetallic. Please consult with our technical department to determine the best combination of flange surface finish, gasket design and gasket material(s) for all your projects.

The compressed height of the gasket must be considered when installing gaskets in grooves or tongue and groove flanges. The fully compressed thickness, not the original thickness, must be greater than the groove depth or the space between the tongue and groove when flanges contact each other. Ideally, the tongue should be at least as tall as the groove depth.

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