【正文】 ansverse baffles and support plates to form a continuous sliding surface. kid bars shall protrude 0,8 mm (1/32 in) beyond the outside diameter of baffle and support plates. The leading and trailing edges of skid bars and seal strips shall be provided with a radius or a bevel to prevent damage to the shell when inserting or removing the bundle.Unless otherwise specified by the purchaser, the tubetotubesheet joint shall be expanded only. If welded joints are specified, the joint shall be welded by one of the following methods: a) strengthwelded only。 b) strengthwelded and expanded。 c) sealwelded and expanded.Flanged connections shall be of one of the following types: a) forged or centrifugallycast long welding neck (integrally flanged)。 b) pipe welded to a forged or centrifugallycast weldingneck flange。 c) pipe welded to a forged slipon flange.Slipon flanges shall not be used under any of the following conditions: a) if the pressure exceeds 2 070 kPa (20,7 bar) (300 psi) gauge。 b) if the design temperature exceeds 400 176。C (750 176。F)。 c) if the corrosion allowance exceeds 3 mm (1/8 in)。 d) if hydrogen is present at a partial pressure exceeding 690 kPa (6,9 bar) (100 psi) absolute。 e) in cyclic service, if the pressure design code requires fatigue analysis.Integrally reinforced nozzles shall be designed so that standard spanners (wrenches) fit the nuts without interference from nozzle neck reinforcement. Flanged external girth joints Channel and shell external girth joints shall be of throughbolted construction. The nominal clearance between flanges after assembly shall be not less than 3 mm (1/8 in). The clearance between flanges shall extend within the bolt circle to allow flanges to be checked for radial distortion caused by an excessive bolt load. Flanges shall be spotfaced or backfaced to the extent required by ASME B or the pressure design code. Hardened washers shall be provided under nuts for all bolts having diameters of 38 mm (1189。 in) or larger. The washers shall be at least 6 mm (1/4 in) thick. External protective covers shall be provided for thinwall bellowstype expansion joints in the shell.Internal floating head expansion joints shall have permanent stays to prevent damage during maintenance and hydrostatic testing with the shell cover removed. Stays shall be designed to permit the full movement of which the expansion bellows are capable. Bellowstype expansion joints should be designed for at least 1 000 cycles during normal operation. Gaskets in hydrocarbon service shall be doublejacketed fibrefilled metal, solid metal, serrated metal with soft gasketseal facing, or spiralwound fibrefilled metal. A means shall be provided to prevent overpression of spiralwound gaskets.The lifting device shall be a weldon lug or ring provided with a hole not less than 38 mm (1189。 in) in diameter. Wherever possible, the lug or ring shall be located at the top of the ponent, above its centre of gravity。 otherwise, two suitably located lugs or rings shall be provided. The lifting device shall be designed to support at least twice the mass of the ponent. For stacked heat exchangers, two lifting lugs or rings shall be provided on all covers, located at the top, approximately 45176。 from the vertical centreline. Pulling lugs or tapped holes for the insertion of eyebolts shall be provided on the outer face of the stationary tubesheet to aid removal of the bundle from the shell. Pulling lugs and tapped holes shall be designed for a pulling force equal to at least 150 % of the bundle mass. Each tapped hole shall be fitted with a threaded plug of the same material as the tubesheet face. The exposed section of the plug shall be at least 50 mm (2 in) long. All vertical heat exchangers shall be provided with lifting devices for the entire heat exchanger unit. The lifting devices shall be provided above the centre of gravity of the heat exchanger unit.Nozzles and couplings shall not protrude beyond the inside surface of the shell, channel or head to which they are attached. Gaskets shall not contain asbestos. Material for metaljacketed, serratedmetal or solidmetal gaskets shall have a corrosion resistance at least equal to that of the gasket contact surface material. Welds attaching insulation support rings need not be continuous. Welds attaching other nonpressure attachments (such as lugs or structural steel supports) shall be continuous.Fullpenetration welds shall be used for those ponents that will be exposed to hydrogen at a partial pressure (absolute) exceeding 690 kPa (6,9 bar) (100 psi). Machined contact surfaces, including any threaded connections, shall be suitably protected to prevent scaling or loss of finish during heat treatment. For stacked heat exchangers, mating nozzle flanges shall not be out of parallel with each other by more than 0,8 mm (1/32 in), measured across any diameter. Separation of mating nozzle flanges shall not exceed 3 mm (1/8 in) after installation of the gasket. Bolts shall be capable of being inserted and removed freely without binding. Shims shall be installed as required between the supports and shall be tackwelded in place.The magneticparticle examination method, extent and acceptance criteria shall ply with the pressure design code. For nonmagnetic materials, a liquidpenetrant examination shall be used in place of any required magneticparticle exami nation. The liquidpenetrant examination method and acceptance criteria shall ply with the pressure design code. Weld hardness testing shall be in accordance with the pressure design code, or the following requirements, whichever is the more stringent: a) the weld metal and heataffected zone of pressureretaining welds in ponents shall be tested。 b) Examination shall be made after any required postweld heat treatment。 c) Brinell hardness limits shall be in accordance with Table 5。 d) Hardness shall be determined using a 10 mm diameter ball unless otherw