Steel Tube Handbook - 2018

104 The tightness of tubes under the ASTM (ASME) regulations Within limits it is necessary to use in preference the methods of NDE (NDT), especially for cold finished tubes. If hydrostatic test is agreed, for the test pressure value calculation is valid: ASTM A450 and ASTM A 1016 (Tube) Minimum hydrostatic test pressure is determined by the following formula: Inch - Pound units: P = 32000 t / D (psi) SI units (mm): P = 220,6 t / D (MPa) The minimum hydrostatic test pressure need not exceed these values: D (in., mm) Pressure P (psi, MPa) Under 1 (25,4) 1 000 (7) 1- under11/2 (25,4 - under38,1) 1 500 (10) 11/2 - under 2 (38,1- under 50,8) 2 000 (14) 2 - under 3 (50,8 - under 76,2) 2 500 (17) 3 - under 5 (76,2 - under 127) 3 500 (24) 5 and over (127 and over) 4 500 (31) The values are valid for ASTM A 450, for ASTM A 1016 is valid value 1000 psi - 7 MPa Higher pressure according to agreement. The tube wall stress shall be determined by the following equation: S = PD / 2t (psi, MPa). (The standards do not specify the amount of tension S as a share of 60% min. yield strength) ASTM A 530 and A999 (Pipe) Each length of pipe shall be tested to a hydrostatic pressure which will produce in the pipe wall a stress not less that 60% of the minimum specified yield strength for C-steel pipe: P = 2 St / D (inch or mm, psi or MPa) S = PD / 2t The minimum hydrostatic test pressure need not exceed 2500 psi (17,0 MPa) for pipe 3,5in or 2800 psi (19,0 MPa) for pipe over 3,5 in (88,9 mm) Upon agreement it is possible to test with higher pressure too. The values of pressures are also in tables of relevant standards TDC - ASTM A. For comparison – pressure according to formulas based on EN is in bars. Definition of status and nomenclature of heat treatment Delivery conditions and heat treatment according to DIN and EN Precision tubes are delivered in following conditions (first symbol lists previous designation, the new one according to EN is in brackets): +C (BK) Cold finished/hard (cold finished as drawn). No heat treatment after last cold forming process. +LC (BKW) Cold finished/soft (lightly cold worked). After last heat treatment there is a light finishing pass (cold drawing). +SR (BKS) Cold finished/stress relieve annealed. After the final cold forming process the tubes are stress relieve annealed. +A (GBK) Annealed. After the final cold forming process the tubes are annealed in a controlled atmosphere. +N (NBK) Normalized. After the final cold forming process the tubes are annealed above the upper transformation point in a controlled atmosphere. Material condition designation depending on heat treatment according to ČSN and STN (first supplemen- tary number behind steel grade): 0 – without heat treatment 1 – normalized 2 – annealed (kind stated) 3 – soft annealed 4 – quenched and tempered 5 – normalised and tempered 6 – heat treatment with the object of achieving a minimum tensile within a specified range 7 – heat treatment with the object of achieving a average tensile within a specified range 8 – heat treatment with the object of achieving a maximum tensile within a specified range 9 – specific (upon agreement) Steel condition designation according to ASTM A519: CW – ColdWorked A – Annealed N – Normalized SR – Stress Relieved or Finished Annealed QT – Quenched and Tempered