ASME STP-PT-004:2005 pdf free download

ASME STP-PT-004:2005 pdf free download.IMPREGNATED GRAPHITE FOR PRESSURE VESSELS.
Because of the resin. impregnated graphite is likely to be less sensitive to notches than nonimpregnated graphite. The industry espenence by the SWG-GPE members is that the simple rule “No sharp inside corners” and rounding the inside corners to 14 in. (6.3 mm) or larger radius virtually eliminates the risk of crack initiation in those areas of impregnated graphite components.
3.7 Corrosion Resistance
Impregnating graphite with resins to reduce its porosity inariabIy produces a composite material with unique corrosion resistance and thermal stability characteristics, especially when compared to the original characteristics of the graphite. The selection of the most appropriate grade from the many available and use in combination with the most eflective resin is perhaps the most crucial aspect of Graphite Process Equipment design. In essence, the chemical resistance of the composite part is determined by how long the resin will maintain its imperviousness. This is greatly affected by the size and availability of the porosity within the graphite part, which to a large degree determines how well the selected resin will penetrate and render it impervious
3.8 Coefficient of Thermal Expansion
Graphite has a low Coefficient of thermal expansion, which reduces the effect of thermal stresses in this material. tSee Table 2.)
4.1 Existing Codes for Graphite Pressure Vessels
Currently there arc no rules in the ASME Boiler and Pressure Vessel (‘ode for the design and construction of graphite pressure vessels. Most of the recently constructed graphite pressure vessels follow the design and construction practices of the Gennan pressure vessel code Al) Merkblatt N2 [XJ, as well as experience driven proccdurcs. These include rcquiremcnts for materials, testing of graphite materials, marking. certification of quality, allowable stresses, tolerances and surface finish, and design calculations (including factors of safety fof design and for pressure tests). Annex 3 to Al) Merkblatt includes requirements for tension testing of graphite materials and the details of the tension test specimen. However, the acceptance criteria for mechanical properties to be used in design in AD Merkhlatt N2 is less restrictive than that proposed for Part UIG.
The Dutch Rules for pressure vessels include Specification D 140183-12, Graphite Block Heat Exchangers II. and NI 0X07E3-12, Impregnated Graphite (10]. and reference AD Merkblatt N2 as part of the requirements for impregnated graphite.
4.2 Permissible Design Temperature
The German Technical Supersisoty Board (Technische Uberwachungsserein. or TUV) permits a maximum design temperature of 200°C (3929:) for impregnated graphite vessels. AD Merkblatt N2 limits the minimum design temperature to -60°C (-769:). The design temperature for impregnated graphite vessels to be designed and constructed to the proposed Part UIG is limited to the same salues
4.3 Properties for Design of Impregnated Graphite Vessels and Components
Pressure vessels and pressure components of impregnated graphite shall at least meet the requirements listed in Table I.
4.4 Design Margins
In the rnid-1970s, Union Carbide performed a series of tests to confirm the validity of the design margin of 5 on tensile strength that had been used for impregnated graphite since the l930s (see section 3.2). Some additional testing has also been performed to confirm again the validity of the design margin of 5. Although this design margin has prus’c41 to be adequate, a design margin of 6 is proposed for part UIG.
4.5 Buckling of Cylindrical Shells
According to the German Pressure Vessel Code AD-Merkblatt N2 [Xj, paragraph 8.4. elastic buckling from external pressure need not be considered in the design. Because of low design stresses compared to those for ferrous and nonferrous materials) and low D’t ratios, elastic buckling of graphite shells is not of concern. However, calculations need to be performed for plastic deformation, in which case the tensile strength value K used in the design is increased by a factor of 2.5 in Equation 4. which takes into account the higher compressive strength of impervious graphite compared to the tensile strcnglh, In design of tubes under external pressure, the tensile strength value K may be increased by a factor of 2.