PACKING RINGS
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Spec. TU 5728-001-93978201-2008
Graphite packing rings and sets made thereof are used for sealing gland joints of pipeline accessories and other industrial, marine, automotive mechanisms, and also as hollow-carrier seals in technology savvy equipment.
Packing rings may be made of thermally expanded graphite of various purity or other materials depending on application field. The most common versions of rings are die formed, braided and sandwich-type. Packing rings are made by pressing pretreated material with its mass accurately measured whereby constant sealing characteristics are achieved. As compared to a traditional method of sealing gland joints with braided packing, packing rings are more reliable, and provide for easy and rapid installation. The sizes of packing rings and sets made thereof correspond to the sizes of stuffing box of typical lock valves and multipurpose valves of Russian and foreign make. The Company “Sealur” manufactures packing rings of non-standard sizes at special orders in compliance with customer drawings (sketches).
Properties
≤ 40 MPa
Permissible pressure the environment
-253 ÷ +650°С
Acceptable temperature range
0 ÷ 14
Permissible acidity of environment
Types
Die formed graphite rings are made by pressing a graphite foil until the required density is obtained, usually within the limits of 1.2 ÷ 1.8 g/cm3 (standard density: 1.5 ÷ 1.7 g/cm3). The cross-section of the ring is usually a square, but it can be a rectangular or a trapezium. Die formed rings have a high axial compression-to-radial pressure transformation coefficient 0.8 ÷ 0.9, unlike asbestos-containing packs which have this value not exceeding 0.3. Therefore to provide an equal contact pressure on sealed surfaces, it is necessary to apply at least a half tightening torque. Twine rings may be made of graphite foils of various purity including rings for using in atomic industry. Twine rings may be used both independently and as part of sets where they are used as main rings to provide sealing.
Sandwich-type rings are made by blanking or cutting the multilayered MGL as per spec. TU 5728-004-93978201 followed by pressing until a graphite component attains the density of 1.6 ÷ 1.8 g/cm3. Sandwich-type rings have a low axial compression-to-radial pressure transformation coefficient, and therefore they are usually used as a closing element to prevent extrusion of material of the main rings into gaps of a gland-packing chamber. The sandwich-type rings may be also used as distant rings in deep gland-packing chambers.
Woven rings are made by cold pressing in the press-mold for woven gland packing as per spec. TU 2573-002-93978201. The required cross-section of the packing is selected on the basis of diametrical sizes of gland-packing chamber and piston-rod. The density of the finished ring depends on material and density of the initial packing. For graphite packing rings, the density of 1.4 ÷ 1.6 g/cm3 is considered standard. In case of independent usage, woven rings provide a more even distribution of radial pressure along the height of the gland-packing chamber, unlike the packing sealing, where 70% of load is taken by two rings, the nearest to the press-on bushing.
Woven rings are also used as part of sets, as closing elements to protect the main rings against abrasive particles of the operating environment and to prevent extrusion of material into a gap. Made to the sizes of the gland-packing chamber and packed separately, the molded woven rings or the sets thereof can considerably reduce the time of installation and gland settlement.