| Technical Info (GASKET) |
Why Gaskets Are Used
A gasket is a compressible material, or a combination of materials, which when clamped between two stationary members prevents the passage of the media across those members.
The gasket material selected must be capable of sealing mating surfaces, resistant to the medium being sealed, and able to withstand the application temperatures and pressures.
Gasket Selection
Gaskets can be classified into three categories: soft cut, semi-metallic and metallic types. The physical properties and performance of a gasket will vary extensively, depending on the type of gasket selected and the materials from which it is manufactured. Physical properties are important factors when considering gasket design and the primary selection of a gasket type is based on the following:
• Temperature of the media to be contained
• Pressure of the media to be contained
• Corrosive nature of the application
• Criticality of the application
Soft Cut Gasket
Sheet materials are used in low to medium pressure services. With careful selection these gaskets are not only suitable for general service but also for extreme chemical services and temperatures.
Types: Non-asbestos Fiber Sheets, PTFE, Insulating Gaskets, Flexible Graphite Gasket, Asbestos Gasket.
Semi-Metallic
These are composite gaskets consisting of both metallic and non-metallic materials. The metal provides the strength and the resilience of the gasket and the non-metallic component provides the conformable sealing material. These gaskets are suitable for low and high pressure and temperature applications. A wide range of materials is available.
Types: Spiral Wound Gaskets, Kammprofile Gaskets (covered serrated metal core), Metal Jacketed Gaskets, Metal Reinforced Gaskets.
Metallic
These gaskets can be fabricated in a variety of shapes and sizes recommended for use in high pressure/temperature applications. Except for weld ring gaskets, high loads are required to seat metallic gaskets, as they rely on the deformation or coining of the material into the flange surfaces.
Types: Ring Type Joints, Lens Rings, Weld Rings, Solid Metal Gaskets.
Standard Gasket Material
Carbon Steel
Commercial quality sheet steel with an upper temperature limit of approximately 1000º F., particularly if conditions are oxidizing. Not suitable for handling crude acids or aqueous solutions of salts in the neutral or acid range. A high rate of failure may be expected in hot water service if the material is highly stressed, Concentrated acids and most alkalies have little or no action on iron and steel gaskets which are used regularly for such services.
304 Stainless Steel
An 18-8 (Chromium 18-20%, Nickel 8-10%) Stainless with a maximum recommended working temperature of 1400º F. At least 80% of applications for non-corrosive services can use Type 304 Stainless in the temperature range of -320 F to 1000º F. Excellent corrosion resistance to a wide variety of chemical. Subject to stress corrosion crackling and to intergranular corrosion at temperatures between 800º F. to 1500º F. In presence of certain media for prolonged periods of time.
304L Stainless Steel
Carbon content maintained at a maximum of .03% Recommended maximum working temperature of 1400º F. Same excellent corrosion resistance as Type 304. This low carbon content tends to reduce the precipitation of carbides along grain boundaries. Less subject to intergranular corrosion than Type 304.
316 Stainless Steel
An 18-12 Chromium-Nickel steel with approximately 2% of Molybdenum added to the straight 18-8 alloy which increases its strength at elevated temperatures and results in somewhat improved corrosion resistance. Has the highest creep strength at elevated temperatures of any conventional stainless type. Not suitable for extended service within the carbide precipitation range of 800º F to 1650º F. when corrosive conditions are severe. Recommended maximum working temperature of 1400º F.
316-L Stainless Steel
Continuous maximum temperature range of 1400º F -1500º F. Carbon content held at a maximum of .03%. Subject to a lesser degree of stress corrosion cracking and also to intergranular corrosion then Type 304.
321 Stainless Steel
An 18-10 Chromium-Nickel steel with a Titanium addition. Type 321 stainless has the same characteristics as Type 347. The recommended working temperature is 1400º F to 1500º F. and in some instances 1600º F.
347 Stainless Steel
An 18-10 Chromium-Nickel steel with the addition of Columbium. Not as subject to intergranular corrosion as is Type 304. Is subject to stress corrosion. recommended working temperature of 1400º F -1500º F. and in some instances to 1700º F.
410 Stainless Steel
A 12% Chromium steel with a maximum temperature range of 1200º F. to 1300º F. Used for applications requiring good resistance to sealing at elevated temperatures. Is not recommended for use where severe corrosion in encountered but is still very useful for some chemical application. May be used where dampness, alone or coupled with chemical pollution, causes steel to fail quickly.
502/501(F5)
4-5% Chromium and 1/2 Molybdenum alloyed for mild corrosive resistance and elevated service. Maximum working temperature is 1200º F. If severe corrosion is anticipated, a better grade of stainless steel would probably be a better choice. Becomes extremely hard welded.
Admiralty
Arsenical Admiralty 443 has 71% Copper, 28% Zinc, 1% Tin and trace amounts of Arsenic. High corrosive resistance, holds up extremely well against salt and brackish waters, and water containing sulfides. recommended maximum working temperature of 500º F. Ideal for carrying corrosive cooling waters at relatively high temperatures.
Alloy 20
45% Iron, 24% Nickel, 20% chromium, and small amounts of Molybdenum and Copper. Maximum temperature range of 1400º F -1500º F. Developed specifically for applications requiring resistance to corrosion by sulfuric acid. Brinell hardness is about 160.
Aluminum
Alloy 110 is commercially pure (99% minimum). Its excellent resistance and workability makes it ideal for double jacketed gaskets. For solid gaskets, stronger alloys like 5052 and 3003 are used. Maximum continuous service temperature of 800º F.
Brass
Yellow brass 268 has 66% Copper and 34% Zinc. Offers excellent to good corrosion resistance in moist environments, but is not suitable for such materials as acetic acid, acetylene, ammonia, and salt. Maximum recommended temperature limit of 500 F.
Cooper
Nearly pure copper with trace amounts of silver added to increase its working temperature. Recommended maximum continuous working temperature of 500º F.
Cupro Nickel
Contains 69% Copper, 30% Nickel and small amounts of Manganese and Iron. designed to handle high stresses, it finds its greatest application in areas where high temperatures and pressures combined with high velocity and destructive turbulence would rapidly deteriorate many less resistant alloys. Maximum recommended temperature limit 500º F.
Hastelloy B
26-30% Molybdenum, 62% Nickel and 4-6% Iron. Maximum temperature range of 2000º F. resistant to hot, concentrated hydrochloric acid. Also resists the corrosive effects of wet hydrogen chlorine gas, sulfuric and phosphoric acids and reducing salt solutions. Useful for high temperature strength.
Hastelloy C-276
16-18% Molybdenum, 13-17.5% Chromium, 3.7-5.3% Tungsten, 4.5-7% Iron and the balance is Nickel. Maximum temperature range of 2000º F. Very good in handling corrosives. High resistance to cold nitric acid of varying concentrations as well as boiling nitric acid up to 70% concentration. Good resistance to hydrochloric acid and sulfuric acid. Excellent resistance to stress corrosion cracking.
Inconel 600
Recommended working temperatures of 2000º F. and is some instances 2150º F. Is a nickel base alloy containing 77% Nickel, 15% Chromium and 7% Iron, Excellent high temperature strength. Frequently used to overcome the problem of stress corrosion. Has excellent mechanical properties at the cryogenic temperature range.
Incoloy 800
32.5% Nickel, 46% Iron, 21% Chromium, resistant to elevated temperatures, oxidation and carburization. recommended maximum temperature of 1600º F.
Monel
Maximum temperature range of 1500º F. Contains 67% Nickel and 30% Copper. Excellent resistance to most acids and alkalies, except strong oxidizing acids. Subject to stress corrosion, cracking when exposed to fluorosilic acid, mercuric chloride and mercury, and should not be used with these media. With PTFE (Polytetrafluoroethylene), it is widely used for hydrofluoric acid service.
Nickel 200
Recommended maximum working temperature is 1400º F. and even higher under controlled conditions. Corrosion resistance makes it useful in caustic alkalies and where resistance in structural applications to corrosion is a prime consideration. Does not have the all around excellent resistance of Monel.
Phosphor Bronze
90-95% Copper, 5-10% Tin and trace amounts of phosphorus. Maximum temperature range of 500º F. Excellent cold working capacity. Limited to low temperature steam applications. Excellent corrosion resistance, but not suitable for acetylene, ammonia, chromic acid, mercury and potassium cyanide.
Titanium
Maximum temperature range of 2000ºF. Excellent corrosion resistance even at high temperatures. Known as the “Best solution” to chloride ion attack. Resistant to nitric acid in a wide range of temperatures and concentrations. Most alkaline solutions have little if any effect upon it. Outstanding in oxidizing environments.
Note: Maximum temperature ratings are based upon hot air constant temperatures. The presence of contaminating fluids and cyclic conditions may drastically affect the maximum temperature range
Installation – Troubleshooting Leaking Joints
One of the best available tools to aid in determining the cause of leakage is a careful examination of the gasket in use when leakage occurred.
| Gasket Badly Corroded
Gasket Badly Corroded |
Select replacement material with improved corrosion resistance. |
| Gasket Extruded Excessively | Select replacement material with better cold flow properties, select replacement material with better load carrying capacity – i.e., more dense. |
| Gasket Grossly Crushed | Select replacement material with better load carrying capacity, provide means to prevent crushing the gasket by use of a stop ring or re-design of flanges. |
| Gasket mechanically damaged due to overhang of raised face or flange bore | Review gasket dimensions to insure gaskets are proper size. Make certain gaskets are properly centered in joint. |
| No apparent gasket compression achieved | Select softer gasket material. Select thicker gasket material. Reduce gasket area to allow higher unit seating load. |
| Gasket Substantially thinner O.D. than I.D. | Indicative of excessive “flange rotation” or bending. Alter gasket dimensions to move gasket reaction closer to bolts to minimize bending movement. Provide stiffness to flange by means of back-up rings. Select soft gasket material to lower required seating stresses. Reduce gasket area to lower seating stresses. |
| Gasket unevenly compressed around circumference | Improper bolting up procedures followed. Make certain proper sequential bolt up procedures are followed. |
| Gasket thickness varies periodically around circumference |
Since all properties, specifications and application parameters shown throughout this product information are approximate and may be mutually influenced, your specific application should not be undertaken without independent study and evaluation for suitability. All technical data and advice given is based on experiences SpiraSeal Gaskets Private Limited has made so far. Failure to select proper sealing products can result in damage and/or personal injury. Properties, specifications and application parameters are subject to change without notice. SpiraSeal Gaskets Private Limited does not undertake any liability of any kind whatsoever.
