【Daily Question 20090222 Supplement】 When installing a pressure gauge, how should one choose the gasket?

Select based on the media and pressure at the site

Selection is based on the corrosivity of the medium, temperature, and pressure. Last edited by qiuqiuwenzi on 2009-2-23 13:19.]

For any type of gasket, to ensure effective sealing over an extended period in harsh operating conditions, it must possess the following eight important characteristics: The airtightness of the gasket – the gasket must not leak under the medium involved in the sealing system, at the recommended temperatures and pressures, over a certain period of time. Compressibility of the gasket: The contact surface between the gasket and the flange should fit well together after the connection bolts are tightened, in order to ensure sealing. Creep resistance of gaskets: Under the influence of pressure loads and operating temperatures, gaskets should have good creep resistance; otherwise, it can lead to a loss of bolt torque, resulting in reduced surface stress on the gaskets and thus leakage in the hydraulic system. Chemical corrosion resistance of gaskets: The gaskets selected should be resistant to corrosion by chemical agents, and they must not contaminate the medium. The resilience of the gasket: Even when the system is stable, the two flanges connected together will inevitably experience slight displacements due to temperature and pressure effects; the elastic properties of the gasket should be sufficient to compensate for these displacements in order to maintain the system’s sealing integrity. Adhesion resistance of gaskets: Gaskets should be able to be removed from the flanges easily after use, without sticking. Corrosion resistance of gaskets: Gaskets must not cause corrosion to the surfaces of the flanges they are connected to. Temperature tolerance of gaskets: The gaskets selected must ensure proper operation at both the lowest and highest temperatures of the system.

Generally, graphite wound gaskets, PTFE gaskets, and copper gaskets can be chosen.

Answer: 1. When the temperature of the medium being tested is below 80°C and the pressure is below 2 MPa, rubber gaskets or seals can be used； When the temperature is below 450°C and the pressure is below 5 MPa, asbestos or lead gaskets can be used ； At higher temperatures and pressures, annealed copper or aluminum gaskets can be used. 2. When measuring oxygen pressure, oil-immersed gaskets or organic compound gaskets must not be used ； Copper gaskets must not be used when measuring acetylene pressure. Because they all pose a risk of exploding.

For any type of gasket, to ensure effective sealing over an extended period in harsh operating conditions, it must possess the following eight important characteristics: The airtightness of the gasket – the gasket must not leak under the medium involved in the sealing system, at the recommended temperatures and pressures, over a certain period of time. Compressibility of the gasket: The contact surface between the gasket and the flange should fit well together after the connection bolts are tightened, in order to ensure sealing. Creep resistance of gaskets: Under the influence of pressure loads and operating temperatures, gaskets should have good creep resistance; otherwise, it can lead to a loss of bolt torque, resulting in reduced surface stress on the gaskets and thus leakage in the hydraulic system. Chemical corrosion resistance of gaskets: The gaskets selected should be resistant to corrosion by chemical agents, and they must not contaminate the medium. The resilience of the gasket: Even when the system is stable, the two flanges connected together will inevitably experience slight displacements due to temperature and pressure effects; the elastic properties of the gasket should be sufficient to compensate for these displacements in order to maintain the system’s sealing integrity. Adhesion resistance of gaskets: Gaskets should be able to be removed from the flanges easily after use, without sticking. Corrosion resistance of gaskets: Gaskets must not cause corrosion to the surfaces of the flanges they are connected to. Temperature tolerance of gaskets: The gaskets selected must ensure proper operation at both the lowest and highest temperatures of the system.

1. When the medium under test is at temperatures below 100°C and pressures below 1 MPa, PTFE gaskets can be used； At temperatures below 450°C and pressures of 5 MPa, asbestos, lead, or soft iron gaskets can be used ； For higher temperatures and pressures, annealed copper gaskets can be used ； When oxygen is used as the medium, oil must be avoided, and organic compound gaskets cannot be used ； Copper gaskets must not be used when measuring acetylene as the medium.

Commonly used materials include asbestos rubber; aluminum gaskets can be used for pressure ratings of PN10.0 and above. Refer to the ‘Instrument Installation Manual’’

Determined by temperature, pressure, and medium； If the medium is corrosive, TELFON washers should be used ； At a temperature and pressure of 10 KGF/CM2 and below 200 degrees, using paper washers is no problem ； High pressure and temperature require the use of metal gasket washers ；

Depending on the medium and pressure at the site, graphite wound gaskets, PTFE gaskets, and copper gaskets can generally be chosen.

①When the medium under test is at temperatures below 80°C and pressures below 2 MPa, rubber or elastic gaskets can be used； When the temperature is below 450°C and the pressure is below 5 MPa, asbestos or lead gaskets can be used ； At higher temperatures and pressures, annealed copper or aluminum gaskets can be used; for even higher conditions, steel gaskets are preferred. ————Personally, I recommend using aluminum gaskets for the most part, as it makes it easier to have spare parts on hand. ②When measuring oxygen pressure, oil-impregnated gaskets or organic compound gaskets must not be used ； Copper gaskets must not be used when measuring acetylene pressure. Because they all pose a risk of exploding.

The material selection for gaskets mainly depends on the following three factors: temperature, pressure, and medium. I. Materials for metal gaskets 1. Carbon steel: It is recommended that the maximum operating temperature not exceed 538°C, especially when the medium is oxidizing. High-quality low-carbon steel plates are not suitable for use in equipment designed to handle inorganic acids or neutral or acidic salt solutions; if such carbon steel is subjected to stress, the accident rate in equipment operating under hot water conditions is very high. Carbon steel gaskets are commonly used in high-concentration acids and many alkaline solutions. Brinell hardness is about 120. 2. 304 stainless steel 18-8 (18-20% chromium, 8-10% nickel); the recommended maximum operating temperature is no more than 760°C. Within the temperature range of -196 to 538°C, stress corrosion and intergranular corrosion are likely to occur. Brinell hardness 160. 3. 304L stainless steel has a carbon content of no more than 0%. 03%. It is recommended that the maximum operating temperature not exceed 760°C. Its corrosion resistance is similar to that of 304 stainless steel. The low carbon content reduces the precipitation of carbon from the lattice, resulting in better resistance to intergranular corrosion compared to 304 stainless steel. Brinell hardness is about 140. 4. 316 stainless steel: 18-12 (18% chromium, 12% nickel); it contains about 2% more molybdenum than 304 stainless steel, and its strength and corrosion resistance increase as the temperature rises. It exhibits higher creep resistance than other ordinary stainless steels when the temperature increases. It is recommended that the maximum operating temperature not exceed 760°C. Brinell hardness is about 160. 5. For 316L stainless steel, it is recommended that the maximum continuous operating temperature not exceed 760°C to 815°C. The carbon content is kept low, resulting in superior resistance to stress and intergranular corrosion compared to 316 stainless steel. Brinell hardness is about 140. 6. 20 alloy: 45% iron, 24% nickel, 20% chromium, and small amounts of molybdenum and copper. It is recommended that the maximum operating temperature not exceed 760°C to 815°C. It is particularly suitable for manufacturing equipment resistant to sulfuric acid corrosion, with a Brinell hardness of about 160. 7. Aluminum: Aluminum (with a content of not less than 99%). Aluminum has excellent corrosion resistance and machinability, making it suitable for manufacturing double gasket inserts. Brinell hardness is about 35. It is recommended that the maximum continuous operating temperature not exceed 426°C. 8. Red copper: The composition of red copper is similar to that of pure copper; it contains trace amounts of silver to increase its operating temperature under continuous use. It is recommended that the maximum continuous operating temperature not exceed 260°C. Brinell hardness is about 80. 9. Brass (66% copper, 34% zinc) exhibits good corrosion resistance under most operating conditions, but is not suitable for acetic acid, ammonia, salts, and acetylene. It is recommended that the maximum continuous operating temperature not exceed 260°C. Brinell hardness is about 58. 10. Hastelloy B-2 (26-30% molybdenum, 62% nickel, and 4-6% iron). It is recommended that the maximum operating temperature not exceed 1093°C. It exhibits excellent resistance to corrosion by concentrated hydrochloric acid. It also exhibits excellent resistance to corrosion by humid hydrogen chloride gas, as well as by sulfuric acid, phosphoric acid, and reducing salt solutions. It possesses high strength under high-temperature conditions. Brinell hardness is about 230. 11. Hastelloy C-276: 16–18% molybdenum, 13–17.5% chromium, 3.7–5.3% tungsten, 4.5–7% iron; the remainder is nickel. It is recommended that the maximum operating temperature not exceed 1093°C. It has excellent corrosion resistance. It exhibits excellent corrosion resistance to various attempts using cold nitric acid or boiling nitric acid at a concentration of 70%, as well as good resistance to hydrochloric and sulfuric acid corrosion, along with outstanding resistance to stress corrosion. Brinell hardness is about 210. 12. Inconel 600 nickel-based alloy (77% nickel, 15% chromium, and 7% iron). It is recommended that the maximum operating temperature not exceed 1093°C. It possesses high strength at high temperatures and is typically used in equipment where stress corrosion issues need to be addressed. It exhibits excellent workability at low temperatures. Brinell hardness is about 150. 13. Monel 400 (30% copper, nickel); the recommended maximum continuous operating temperature is not exceeding 815°C. It exhibits excellent corrosion resistance to most acids and bases, except for strongly oxidizing acids. Stress corrosion cracks tend to form in hydrofluoric acid, mercuric chloride, and mercury-based media; therefore, it is not suitable for use in these media. Equipment widely used in the production of hydrofluoric acid. Brinell hardness is about 120. 14. Titanium: The recommended maximum operating temperature is not exceeding 1093°C. It exhibits excellent corrosion resistance under high-temperature conditions. As is well known, it resists chloride erosion, and exhibits excellent resistance to nitric acid corrosion over a wide range of temperatures and concentrations. Titanium is rarely used in most alkaline solutions and is suitable for oxidation conditions. Brinell hardness is about 216. II. Non-metallic gasket materials 1. Natural rubber NR exhibits good corrosion resistance to weak acids and bases, as well as to salt and chloride solutions; however, its resistance to oils and solvents is poor, and it is not recommended for use in ozone-containing environments. Recommended operating temperature: -57°C to 93°C. 2. Neoprene CR: Neoprene is a synthetic rubber that is suitable for withstanding corrosion from acids, bases, and salt solutions with moderate corrosivity. It provides excellent corrosion resistance for commercial oils and fuels. However, its corrosion resistance is poor in strongly oxidizing acids, aromatic hydrocarbons, and chlorinated hydrocarbons. Recommended operating temperature: -51°C to 121°C. 3. Nitrile rubber NBR: Nitrile rubber is a synthetic rubber that exhibits good resistance to corrosion by oils, solvents, aromatic hydrocarbons, basic hydrocarbons, as well as petroleum and natural gas, over a wide temperature range. It exhibits good corrosion resistance to hydroxides, salts, and nearly neutral acids. However, its corrosion resistance is poor in strongly oxidizing media, chlorinated hydrocarbons, alcohols, and lipids; the recommended operating temperature is 51°C to 121°C. 4. Fluororubber exhibits excellent corrosion resistance to oils, fuels, chloride solutions, aromatic hydrocarbons, aliphatic hydrocarbons, and strong acids; however, it is not suitable for use with amines, fats, oils, and steam. The recommended operating temperature range is -40°C to 232°C. 5. Chlorosulfonylated polyethylene synthetic rubber exhibits good corrosion resistance to acid, alkali, and salt solutions, and is unaffected by climate, light, ozone, or commercial fuels such as diesel and kerosene. But it is not suitable for aromatic hydrocarbons, chlorinated hydrocarbons, chromic acid, and nitric acid. Recommended operating temperature: -45°C to 135°C. 6. Silicone rubber has good corrosion resistance to hot air. Silicone rubber is not affected by sunlight and ozone. But it is not suitable for steam, similar compounds, aromatic hydrocarbons, and lipid hydrocarbons. 7. EPDM exhibits good corrosion resistance to strong acids, strong bases, salts, and chloride solutions. But it is not suitable for oils, solvents, aromatic hydrocarbons, and hydrocarbons. Recommended operating temperature: -57°C to 176°C. 8. Graphite: This is a purely graphite material that contains no resins or inorganic substances; it can be divided into graphite materials with metal additives or those without such additives. This material can be bonded to manufacture pipe gaskets with a diameter of over 600 MM. It exhibits extremely excellent corrosion resistance against many acids, bases, salts, organic compounds, heat transfer fluids, and even high-temperature solutions. It cannot melt, but it will sublimate at temperatures above 3316°C. Use of this material in strongly oxidizing media at high temperatures should be approached with caution. In addition to being used for gaskets, this material can also be used to manufacture packing and the non-metallic winding strips in spiral wound gaskets. 9. Ceramic fibers, particularly those shaped into strips, are excellent gasket materials suitable for high-temperature and low-pressure conditions as well as in applications with lightweight flanges. The recommended operating temperature is 1093°C, and they can be used to manufacture the non-metallic winding strips in spiral-wound gaskets. 10. PTFE combines the advantages of most plastic gasket materials, including a temperature resistance range of -95°C to 232°C. It exhibits excellent corrosion resistance to chemicals, solvents, hydroxides, and acids, in addition to free fluoride and alkali metals. PTFE material can be filled into glass in order to reduce its cold flow and creep properties.

Generally, the choice is made based on basic characteristics such as the properties, pressure, and temperature of the material being processed!

Selection is based on the corrosiveness of the medium, as well as temperature and pressure. 1. When the temperature of the medium being measured is below 100°C and the pressure is below 1 MPa, PTFE gaskets can be used； 2. At temperatures below 450°C and pressures of 5 MPa, asbestos, lead, or soft iron gaskets can be used ； 3. For higher temperatures and pressures, annealed copper gaskets can be used ； When oxygen is used as the medium, oil must be avoided, and organic compound gaskets cannot be used ； 4. When measuring acetylene as the medium, copper gaskets must not be used

1. When the medium under test is below 100°C and 1 MPa, 2. a PTFE gasket can be used； 3. At temperatures below 450°C and pressures of 5 MPa, asbestos, lead, or soft iron gaskets can be used ； 4. For higher temperatures and pressures, annealed copper gaskets can be used ； 5. When the measuring medium is oxygen, oil must be avoided, and organic compound gaskets cannot be used ； 6. When measuring acetylene as the medium, copper gaskets must not be used.

1. When the temperature of the medium under test is below 80°C and the pressure is below 2 MPa, rubber or elastic gaskets can be used； When the temperature is below 450°C and the pressure is below 5 MPa, asbestos or lead gaskets can be used ； At higher temperatures and pressures, annealed copper or aluminum gaskets can be used. 2. When measuring oxygen pressure, oil-immersed gaskets or organic compound gaskets must not be used ； Copper gaskets must not be used when measuring acetylene pressure. Because they all pose a risk of exploding.