METHOD FOR FASTENING HEAT EXCHANGE TUBES IN CHAMBER-TYPE HIGH-PRESSURE PRE-HEATERS Russian patent published in 2021 - IPC B21D39/06 

FIELD: heat exchange.

SUBSTANCE: invention relates to processing of metals by pressure and can be used for tube expanding in tube grids of heat exchange equipment assemblies. The ends of the heat exchange tubes are preliminarily distributed in the interval of L₁=4⁺¹ mm from the outer surface of the tube sheet with a roller expander until the radial gap between the tube and the tube sheet is removed. The ends of the tubes are then welded to the tube sheet and the tubes are hydraulically expanded with a liquid pressure of 254.8±9.8 MPa over a length of L_gp in the range of L₁ ≤ L_gp ≤ L_d-(10÷15) mm. The "pocket" in the area adjacent to the outer surface of the tube sheet is removed by rolling with a roller expander. The "pocket" in the area adjacent to the inner surface of the tube sheet is removed by rolling with a roller expander in two passes. Radial normal stresses in the area of contact of the tube with the wall of the hole in the tube sheet are therein provided at σ_k1=(0.25÷0.27)σ_m^0.9±2.5, σ_k2=(0.3÷0.32)σ_m^0.9±2.5 MPa, wherein σ_m is the yield strength of the material of the tube, at a torque value determined by the above formula.

EFFECT: reliability of fastening tubes in the tube sheet is increased as a result.

1 cl, 1 dwg, 1 ex