DIN 2445-2 (2)

DIN 2445 Part-2 SEAMLESS STEEL TUBES FOR DYNAMIC LOADS SUPPLEMENT BASIS FOR CALUCULATION OF STRAIGHT TUBES DIN2445 1. General ination During the operation of hydraulic installations, when the control valve is operated the pressure and velocity of the flow medium change. As the valve is switched on and off, the pressure changes with each working stroke for P A0 to the maximum nominal pressure in each case. In addition, by reason of the changes in velocity, pressure surges arise which are superimposed on this pressure. The pipeline is dynamically stressed. The pressure surge can be approximately determined according to DIN 2413, Jone 1972 edition, Section 4.4 or according to the rteatise by Paul Boss Untersuchungen uber den druckstoss in den zuleitungen von hydraulichen pressanlagen investigations of the pressure surge in the supply lines of hydarulic pressing plants VDI-Zeitschriftjournal of the associatoon of German Engineers,Vol. 1041962No. 20,pp903-909. The calcuiation is carried out differently there for presses the working stroke of which is controlled by a valve or limited by a stop. The calculations with valve control, since it is only for these that generally valid assumptions arc possible. In the case of presses limited by a stop, the load must be recalculated after a dimension is chosen to allow for the water contained in the press cylinder. Tube Wall- Tube Deign Weight Tube Wall- Tube Deign Weight o. d. thick i. d. pressures o. d. thick i. d. pressures mm ness mm bar kg/m mm ness mm bar kg/m mm mm 4 0.5 3 313 0.043 20 1.58 17 212 0.684 4 0.75 2.5 409 0.063 20 2 16 282 0.888 4 1 2 522 0.074 20 2.5 15 353 1.079 5 0.75 3.5 376 0.083 20 3 14 373 1.258 5 1 3 432 0.099 20 3.5 13 426 1.424 6 0.75 4.5 333 0.103 20 4 12 478 1.578 6 1 4 389 0.123 22 1 20 128 0.518 6 1.5 3 549 0.166 22 1.5 19 192 0.758 6 2 2 692 0.197 22 2 18 256 0.986 6 2.25 1.5 757 0.208 22 2.5 17 320 1.202 8 1 6 333 0.173 22 3 16 385 1.406 8 1.5 5 431 0.24 25 2 21 226 1.134 8 2 4 549 0.296 25 2.5 20 282 1.387 8 2 4 549 0.296 25 3 19 338 1.628 8 2.5 3 658 0.339 25 4 17 394 2.072 10 1 8 282 0.222 25 4.5 16 432 2.275 10 1.5 7 373 0.341 25 5 15 478 2.466 10 2 6 478 0.395 28 1.5 25 151 0.98 10 2.5 5 576 0.462 28 2 24 201 1.282 10 3 4 666 0.518 28 2.5 23 252 1.572 12 1 10 235 0.271 28 3 22 302 1.85 12 1.5 9 353 0.383 28 4 21 403 2.368 12 2 8 409 0.493 28 5 18 434 2.836 12 2.5 7 495 0.586 30 2 26 188 1.381 12 3 6 576 0.665 30 2.5 25 235 1.695 12 3.5 5 69 0.734 30 3 24 282 1.998 14 1 12 20 0.321 30 4 22 376 2.565 14 1.5 11 302 0.462 30 5 20 409 3.083 14 2 10 403 0.592 35 2 31 161 1.628 14 2.5 9 434 0.709 35 2.5 30 201 2.004 14 3 8 507 0.814 35 3 29 242 2.367 14 3.5 7 576 0.906 35 4 27 322 3.058 14 4 6 64 0.986 35 5 25 403 3.699 15 1 13 188 0.345 35 6 23 419 4.291 15 1.5 12 282 0.499 38 2.5 33 186 2.189 15 2 11 376 0.641 38 3 32 223 2.589 15 2.5 10 409 0.771 38 4 30 297 3.354 15 3 9 478 0.888 38 5 28 371 4.069 16 1 14 176 0.37 38 6 26 390 4.735 16 1.5 13 264 0.536 38 7 24 446 5.352 16 2 12 353 0.691 42 2 38 134 1.973 16 2.5 11 386 0.832 42 3 36 201 2.885 16 3 10 452 0.962 42 4 34 269 3.749 18 1 16 157 0.419 50 6 38 338 6.511 18 1.5 15 236 0.61 50 9 32 437 9.103 18 2 14 313 0.789 65 8 49 347 11.246 18 2.5 13 392 0.956 80 10 60 353 17.263 18 3 12 409 1.11 2. Design pressures The pumps and accumulators of a hydraulic installation are designed for a pressure, the nominal pressure, as specified in DIN 2401 Part 1. This is the design pressure of the installation pA. It is possible to calculate a pressure surge which brings about an increase in pressure. This calculated pressure p pA p is the maximum pressure in the installation. The calculation of the continuous pulsating fatigue strength of the tubes was hased on the maximum pressure p. When there are unusually long supply lines, the greater pressure surge fluctuates around the pressure permanetly present in the installatior. The fatigue strength of such tubes can be calculated from the amplitude of fluctuation p - p 2 p. Correlation of the pressures All pressures are overpressures in bar Alternation of pressure on which the calculation is based Maximum applicable pressure calculatedpressure for Nominal pressure of the installation design pressure for water hydraulic installations with l 30 m w 10 m/s Ts 0.1 s for oil hydraulic installations with l 7 m w 9 m/s Ts 0.025 s bot finished tubes according to DIN 2445 Part 1 for water hydraulicinstallations preision steel tubes according to DIN 2445 Part 2 for oil hydraulic installations Nominal pressure of pipeline components d.g. flanges, fitted appliances pA p p PN 64 - 45 - - 125 100 60 45 160 145 160 160 60 45 220 205 250 250 60 45 310 295 320 320 60 45 380 365 400 400 60 45 460 445 500 3. Types of fluctuating stress Various types of change in pressure arise in a hydraulic installation during operation. Pressure changes from 0to p occur in the control line, depending on the number of working strokes. A pressure change equal to the pressure surge around the installation pressure pA p also occurs as a multiple of the number of workin g strokes. It is mostly not possible to give more precise ination as to the nature of the actual collectives stresses. The overall rise in pressure from 0 to p should therefore be taken into account in calculating pulasting gatigue strength. 4. Calculation assumptions Sections 4.1 and 4.2 list calculation assumptions which are valid for most cases in practice. The calues can be varied, although p cannot be made lager than the pressure change on which the calculation is based as shown in the Table. 4.1 Hot finished tubes for hydraulic installations according to DIN 2445 Part Length of pipeline l 30 m Rate of flow w 10m/s Closing time of contorl element Ts 0.1 s Number of working strokes n 2 10 Pressure propagation velocity a 1300 m/s Density of water O 1000 kg/m Surhe effect factor Z 2 l / a T5 2 30 / 1300 0.1 0,45 Pressure increase from pressure surge p ZO a w / 10 0,45 1000 1300 10 / 10 4.2 Precision steel tubes for oil hydraulic installations according to DIN 2445 Part 2 Length of pipeline l 7 m Rate of flow w 9 m/s Closing time of contorl element Ta 0,025 s Number of working strokes n 2 10 Pressure propagation velocity a 1300 m/s Density of water O 880 kg/m Surhe effect factor Z 2 l / a T5 2 7 / 1300 0,025 0,43 Pressure increase from pressure surge p ZO a w / 10 0,43 880 1300 9/10 4,45 N/mm 45 bar 5.Calculation The tubes should be calculated in accordance with DIN 2431, June 1972 edition, scope for deation and for fatigue failure over a given number of cycles or overall. The larger of the resulting tube wall thickneses should be chosen. 5.1 Calculation for deation s da p / 2 Ozul c1 P Pa P Ozul K / S y K Materials St 35,4 and St 52.4 Yield strength in N/mm da 30 mm wall thickness da30mm wall thickness Range of application Grade of steel 3 3 16 16 30 30 50 50 Part St 35.4 225 235 235 - - - Part St 52.4 - 355 355 345 335 315