ARMY MIL-HDBK-212-1958 GASKET MATERIALS (NONMETALLIC)《垫圈原料(非金属)》.pdf
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1、. MILITARY HANDBOOK i ! GASKET MATERIALS (NONMETALLIC) Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-_- - . “. .I . .- - i . .- . .1 . .- . -. _. . -e.-.- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS
2、-,-,-. . _“ . . MIL-HDBK-212 53 W 7777770 000bBb7 T W MIL-HDBK-2 12 26 SEPTEMBER 1958 SUPERSEDING ORDP 20-307 DECEMBER 1956 DEPARTMENT OF DEFENSE OFFICE OF THE ASSISTANT SECRETARY OF DEFENSE (SUPPLY AND LOGISTICS) STANDARDIZATION DIVISION Washington 25, D. C. Gasket Materials (Nonmetallic) 26 Septem
3、ber 1958 MIL-HDBK-212 1. This handbook on Gasket Materials (Nonmetallic) has been de- veloped by the Ordnance Corps, under the direction of the Standardization Division, OASD (S this loss is instantaneous at 1300 deg. F. When the water of crystallization is driven from asbestos, slight rubbing will
4、reduce the material to a powder. In actual application, however, asbestos is rarely used alone or in its pure form. Therefore, the heat resistance of asbestos materials also depends upon the heat resistance of the constituents in the composition. Asbestos and asbestos-composition gas- kets have exce
5、llent resistance to the pres- sure of heavy loads and the cutting action of narrow, sharp-edged flanges, Asbestos materials are, for the most part, unaffected by changes in humidity. As a re- sult, they maintain their original size and 3 I 000b872 3 m MIL-HDBK-212 26 SEPTEMBER 1958 shape regardless
6、of variations in the amount of moisture present in the atmosphere. Pure asbestos products are porous and weak, and therefore, are almost always com- bined with other substances. Asbestos fibers may be combined with cellulose or metallic fibers for added strength ; they may be joined with binders and
7、 saturants for greater im- perviousness ; or they may be added as a filler to rubber and plastic compounds. 7, Principal Compositions. The two types of asbestos fibers from which asbestos gasket materials are made are chrysotile and cro- cidolite. Crocidolite is more commonly known as blue asbestos
8、and is a sodium-iron-silicate complex. It is used chiefly for the manufac- ture of acid resistant gaskets. Chrysotile is common white asbestos, a mineral consisting primarily of magnesium silicate combined with approximately 14 percent water of crystallization. It is resistant to weak acids and most
9、 alkali solutions, but is susceptible to the action of strong acids. Resistance to corrosive agents may be in- creased by combining these two fiber types with binders such as rubber. The character- istics of the particular binder and of the as- bestos will determine the properties of the resulting c
10、omposition, The most common type of asbestos combination is the asbestos- rubber composition. It is considered the principal asbestos material, although woven or braided asbestos and mill board or paper are also used. Each of these three groups of asbestos materials is analyzed in the fol- lowing pa
11、ragraphs. The rubber-asbestos compositions include “compressed asbestos” and several other forms of asbestos sheeting or composition with similar characteristics and applicabil- ity. Of the three groups of asbestos ma- terials, this group is produced in greatest quantity and has the widest range of
12、use. Rubber-asbestos sheets vary according to the formula and process of manufacture : and some forms are pigmented while others are given some external after-treatment. The type known as “compressed asbestos” is made by calendering a dough of asbestos Provided by IHSNot for ResaleNo reproduction or
13、 networking permitted without license from IHS-,-,-MIL-HDBK-2 12 26 SEPTEMBER 1958 TABLE 1. GENERAL PROPERTIES AND USES OF GAsKET MATERIALS Classification Asbestos, Compressed Cork-and- Rubber Cork Composition Rubber and Plastic Paper, Untreated Paper, Treated Leather Combination Constructions Data,
14、 courtesy Special Characteristics Tough and durable. Dimensionally stable. Relatively incompressible. Good steam and hot water resistance. Oil and solvent re- sistance determined by characteristics of rubber binder. Provides fluid barrier and resilience of rubber with compressibility of cork. Prop-
15、erties of flow versus compression subject to controlled variation according to pro- portions of cork and rubber. Some sacrifice of rubbers tensile and elongation proper- ties. Chemical properties about same as base polymers. Higher in cost than cork com- position or fiber types, but lower than strai
16、ght rubbers. Does not extrude from joint. Die cuts easily. High coefficient of friction. Versatile, dependable general-purpose ma- terial. Variable as to binder, texture and hardness (density). Truly compressible. High friction whether dry, wet or oily. Low cost. Excellent oil and solvent resist- an
17、ce. Poor resistance to alkalies and cor- rosive acids. Highly variable according to compound- ing, hardness, modulus, fabric reinforce- ment, etc. Generally impervious, but en- tirely incompressible. Low in cost; may induce corrosion. General-purpose material having better tensile strength than cork
18、 composition, but less compressibility. Good oil, gasoline and water resistance, but alternate wet and dry cycles may cause shrinkage and hard- ening of some types. Tough, porous, abrasion resistant, flexible at extreme low temperatures. Tanning and impregnation are important variables. Can be molde
19、d to simple shapes - cups, Vs, Us. Innumerable modifications available, de- pending on materials used and methods of combining. Engineekg. 4 . I 0- /“ 1.: General Uses For heavy duty bolted and threaded joints, as in water and steam pipe fit- tings, manifold connections. Tempera- tures to 500F. For
20、general-purpose gasketing, except steam lines, combustion chambers, etc. Enables design of metal-to-metal joints with gasket positioned in channel or counter-bore and with no allowance for flow. High friction keeps gasket positioned even where closing pressure is not per- pendicular to flange faces.
21、 For mating rough or irregular parts, as glass, light stampings, unfinished cast- ings. Oil sealing at lowest cost in normal range of temperatures and pressures. For installations involving sfxetching over projections, or where flow of gas- ket into threads or recesses is desired. For lowest compres
22、sion-set and maxi- mum resistance to fluids such as alka- lies, hot water and certain acids. Ability to be molded permits use for special de- sign and assembly conditions. Spacers, dust barriers, splash seals, where breathing and wicking not objec- tionable. For machined or r.easonably uniform flang
23、es where adequate bolt pressures can be applied. Relative firmness and high tensile strength permit use of thin gaskets to give good alignments of cov- ers and connected parts. Widely used in dynamic packing appli- cations and as back-up for rubber 0- Rings in high pressure joints. Avoid steam, acid
24、s, alkalies. Usually employed for extreme conditions and special purposes. I Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-HDBK-212 53 m 7779970 0006874 7 W fibers and rubber cement. It has a pro- nounced grain and usually contains clumps of un
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