DURLON TECHNICAL INFO
Durlon Compressed Sheet
| Style | Composition | Description |
|---|---|---|
| 8300 | Carbon / NBR | A premium grade compressed sheet, Durlon 8300 is excellent in steam and hydrocarbon services in the refining, petrochemical and power generation industries. Other applications include oil, water, mild alkalis, mild acids and solvents. Durlon 8300 contains high strength carbon fibers bonded with nitrile (NBR) synthetic rubber. |
| 8400 | Phenolic / NBR | With an extremely wide pH application range, Durlon 8400 can be used in process piping and equipment in chemical, pulp and paper, and other general industrial applications. |
| 8500 | Aramid - Inorganic / NBR | Our workhorse material, Durlon 8500 is excellent in steam, natural gas, soybean processing and with new generation refrigerants. A high quality general service gasket material for use in a wide range of services in pulp and paper, food, beverage, pharmaceutical, chemical, refinery, gas pipeline and general industry. |
| 8600 | Aramid - Inorganic / SBR | A high quality gasket material containing high strength aramid and inorganic fibers bonded with SBR rubber. An excellent choice for steam or services where a white gasket material is required. |
| 8700 | Aramid - Inorganic / CR | A high performance compressed gasket material for use in processes that require a neoprene (CR) bonded sheet. Excellent for steam, oils and refrigeration services. |
| 7900 / 7950 | Aramid / NBR | An economy grade general service compressed sheet with NBR rubber binder for mild service in piping and equipment and OEM applications in steam, hydrocarbons and refrigerants. An economical alternative when service ranges and applications are not severe. |
| Anti-Stick Properties: Much effort has gone into improving the anti-stick release agents of all compressed Durlon products. All Durlon compressed gasket materials have passed the MIL-G-24696B Navy Adhesion Test (366°F / 48 hrs.) | ||
| Warning: These materials should never be recommended when both temperature and pressure are at the maximum listed. Properties and applications shown are typical. No application 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 of gasket selection could cause property damage and / or serious personal injury. Data reported on this web site 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 on this web site are subject to change without notice. | ||
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Durlon PTFE Sheet
| Style | Composition | Description |
|---|---|---|
| 9000 / 9000N | Pure PTFE resins with inorganic fillers | Durlon 9000 / 9000N is used extensively in chemical, pulp and paper, food and beverage and the railroad tankcar industries. It has been tested and approved for liquid chlorine, caustics, liquid oxygen, and high purity applications in the pharmaceutical industry (9000N, blood components manufacturing). The fillers in Durlon 9000 / 9000N are engineered shapes, homogeneously blended with pure PTFE resins that do not wick. |
| 9200W | Pure PTFE resins with barium sulfate fillers | Suitable for use in aggressive chemicals. Including caustics, hydrogen peroxide, sodium hypochlorite, nitric acid, liquors and digester in pulp and paper service. Applications in the chemical, pharmaceutical and plastics industries include butadiene, hydrofluoric acid, vinyl chloride, methyl methacrylates and styrene. Durlon 9200W is also used extensively in railroad tankcar applications. |
| 9400 | Pure PTFE resins with carbon fillers | Carbon filled PTFE is approved as a material of construction for anhydrous hydrogen fluoride (AHF). Durlon 9400 also demonstrates good electrical conducting properties. |
| 9600 | Expanded PTFE | Durlon 9600 is and expanded PTFE gasket material made with only pure PTFE resins. It is suitable for use in steel flanges and flanges with irregular surfaces. |
| Independent testing has shown the fillers in the Durlon method to be more homogeneously blended than calendared, or layered filled PTFE gasket materials, giving Durlon filled PTFE's more consistent physical and mechanical properties without voids, separation and chemical compatibility problems found in the layered construction method. | ||
| Warning: These materials should never be recommended when both temperature and pressure are at the maximum listed. Properties and applications shown are typical. No application 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 of gasket selection could cause property damage and / or serious personal injury. Data reported on this web site 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 on this web site are subject to change without notice. | ||
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Durlon Corrugated Flexible Graphite
| Style | Composition | Description |
|---|---|---|
| CFG | Flexible graphite / corrugated stainless 316 core | Designed for severe service conditions, the proprietary design of the corrugations gives CFG its superior sealing and recovery characteristics for tough conditions in the refining, chemical, petrochemical and pulp and paper industries. CFG is suitable for service in steam, oil, water, mild alkalis, hydrocarbons, mild acids and solvents. |
| Durlon CFG will maintain a tight seal in a wide range of initial seating stresses making it the universal replacement for spiral wound, double jacketed and traditional flexible graphite. | ||
Pressure - Temperature Considerations
| With gasketing, there is a relationship of pressure to temperature. Generally the higher the temperature, the lower the allowable gasket working pressure. This is called the PT factor of the gasket (pressure times temperature). For example, if the pressure is 700 psi and the temperature is 500ºF, we would need a material with a PT factor of 350,000. Some manufacturers feel this is the maximum level for safety. With compressed asbestos products there is a common base and structure in the material which makes comparing and using PT factors easy and predictable. Non-asbestos gasketing is not as predictable. Generally we find that all non-asbestos gasket material is temperature sensitive requiring the pressure to drop more quickly as temperature rises to insure the seal is maintained. We have reviewed performance by in-house tests, controlled operating performance, and in the field. There is no one PxT factor to use. Refer to the charts on the web page where the material is shown for the highest operating temperature given for the application. Find the highest pressure within the safety zone. Simple multiplication of the two will give you the PT factor. It is always assumed the flange is correct and in good condition, the fluid is not aggressive and that the ideal thickness is 1/16". These limits will be increased for 1/32", but will decrease 20% to 30% for 1/8". |
Fluid Resistance - pH Range
| The pH of an aqueous solution is merely an expression related to the hydrogen ion (H+) concentration of the solution. Pure water has a pH of 7. This really means that the concentration of hydrogen ions in moles / liter is .0000001. This can be expressed as 10-7, which is an exponential equivalent of the number with all the zeros. PH is defined as the negative of the exponent of the hydrogen ion concentration. In the above case, pH = -(-7) = 7. An acidic solution has a pH of less than seven. A caustic solution has a pH of more than seven. Our main concern in discussion of pH is the pulp and paper industry. The industry has both acidic and caustic streams and several of these streams go from acidic to caustic and cycle from one to the other due to treatment systems. Some of these streams are: |
| White water - Kraft - pH 9 - 10 White water - Bleached stock - pH 5.5 - 7 Liquor - black weak - pH 10 - 13 | Effluents - Bleach plant - pH 1.5 - 3 Effluents - Chemical prep area - pH 1.5 - 7 Liquor - black strong - pH 11 |
| The pH application ranges for Durlon gasket materials are: |
| Material | pH Range |
|---|---|
| Durlon 8300 Durlon 8400 Durlon 8500, 8600 & 8700 Durlon 9000/9000N, 9200W, 9400 & 9600 Durlon CFG | 3 - 11 2 - 13 3 - 11 0 - 14 0 - 14 |
| The pH range of serviceability is a guide and must always be used in conjunction with the chemical resistance chart. For example, Durlon 9000 is serviceable from pH 0 to 14 (the entire range) yet we do not recommend it for hydrofluoric acid. |
GASKET FACTORS, TORQUE LOSS
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Proposed ASME Gasket Factors: Gb, a and Gs
| New gasket factors to replace the ASME Code m and y are currently being developed by the Pressure Vessel Research Council (PVRC) and ASME. The current m and y are difficult to replicate for non-asbestos gaskets and do not consider joint leakage. The new approach to bolted joint design makes the tightness of the joint a design parameter. In a manner similar to the traditional ASME Code method, the design bolt load for a joint is calculated for operating and seating requirements from the new constants Gb, a and Gs and the required tightness class associated with the minimum tightness. Gb and a, gives the gasket seating load and are similar to y in the present Code. Gs is associated with the operating stress and is similar to the m value in the Code. The proposed ASME constants Gb, a, and Gs give a design bolt load obtained by interpretation of leakage test data as plots of gasket stress Sg, vs. a tightness parameter, Tp. Tp is the pressure (in atmospheres) normalized to the atmospheric pressure required to cause a helium leak rate of 1 mg/sec for a 150 mm OD gasket in a joint. Since this is about the same as the OD of an NPS 4" joint, the pressure to cause a leak of 1 mg/sec of helium for that joint is its tightness. A standard test procedure, the PVRC Room Temperature Tightness Test (ROTT) has been designed to produce the constants Gb, a and Gs. Low values for Gb, a and Gs are desirable while a higher value of Tp means a tighter joint. |
Torque Loss
| Torque loss is inherent in any bolted joint. The combined effects of bolt relaxation, (approximately 10% during the first 24 hours after installation), gasket creep, vibration in the system, thermal expansion and elastic interaction during bolt tightening contribute to torque loss. When torque loss reaches an extreme, the internal pressure exceeds the compressive force holding the gasket in place and a leak or blow-out occurs. A key to reducing these effects is the proper gasket installation. By bringing the flanges together slowly and parallel when installing a gasket and taking a minimum of four bolt tightening passes, following the correct bolt tightening sequence, there is a payoff in reduced maintenance costs and increased safety. Proper gasket thickness is also important. The thicker the gasket, the higher the gasket creep which in turn can result in torque loss. On standard ANSI raised face flanges a 1/16" thick gasket is normally recommended. Thinner gasket materials can take a higher gasket load and therefore higher internal pressures. Even when the installation is ideal, where the bolt stress is uniformly applied to each bolt, and the gasket is properly compressed, problems can still arise. Inherently with time, loosening will occur due to the factors already mentioned. If other factors such as cycling, thermal upsets, water hammer or just a piping system with inadequate pipe supports are present, periodic retorquing might be necessary. For problem areas, high temperature applications or where there is temperature cycling, or where a flange cannot be retorqued, conical spring washers have been found to be very helpful as an aid to torque retention. They act as a spring and help lessen the effects of torque loss. Other factors affecting torque loss include:
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Gasket Installation
| The importance of proper gasket installation cannot be stressed enough. The following is a basic explanation of how to properly bring the flanges together parallel and in stages, once the gasket is in place and to properly compress the gasket. As a minimum, four passes are required. Using the right torque value for the lubricant being used to get the proper gasket compression is important as well. In the torque tables that follow for Durlon gasket materials, it is assumed the flanges are in good condition, anti-seize has not been used on any gasket contact surfaces and a proper installation technique such as what is outlined below is used. Never use any gasket material as insulating washers in flange insulation kits. |
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Torque Values - ASME B16.5 Raised Face Flanges
ANSI B16.21 - Ring Gaskets
1/16" & 1/8" Durlon Gasket Material
Torque: ft-lbs.
| CLASS 150 Internal Pressure = 225 psi | CLASS 300 Internal Pressure = 740 psi | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Note: It is assumed that new ASTM A193 Gr.B7 studs with 2H heavy hex nuts and hardened steel washers are used and studs, nuts and nut facings are lubricated with a never-seize paste using the installation and bolt tightening practices outlined above. Torque is based on the higher of 40% of bolt yield, T3 or 4800 psi gasket stress up to either the maximum allowable material stress or a maximum bolt yield of 60%. The above was calculated using the proposed ASME Gasket Constants (ROTT Testing, Ecole Polytechnique) for each material. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||