Non-essential variables, as the name suggests, are those variables that are not regarded as affecting the quality or mechanical properties of the welded joint and comprise such variables as the weld preparation, shield gas flow rate, method of back gouging, shield gas nozzle size etc. Supplementary variables are only invoked when toughness requirements are specified by the application code, eg ASME VIII or ASME B31.3. ASME IX in addition identifies supplementary and non-essential variables. A change to an essential variable outside of its range of approval requires the welding procedure to be re-qualified.
ASME BPVC SECTION IX ISO
Other alloys and joining processes are covered by additional specifications within the ISO 15614 series.īoth specifications identify essential variable (although ISO 15614 Pt1 does not describe them as such) to each of which is assigned a range of approval. ISO 15614 Pt1 covers the welding procedure qualification of arc and gas welds in steel and nickel alloys only. Such flexibility may allow the manufacturer to submit to the client or inspecting authority procedure qualification records (PQR) to ISO 15614 Part 1 for approval that can be shown to be technically equivalent to an ASME PQR.ĪSME IX covers the qualification of welders and welding operators, welding procedures, brazing operatives and brazing procedures for the complete range of ferrous and non-ferrous engineering metals (steels, copper, nickel, aluminium, titanium and zirconium alloys) and oxy-gas, arc, power beam, resistance and solid phase welding processes.
ASME BPVC SECTION IX CODE
All the requirements of the ASME specifications MUST be complied with, even to the extent of dimensions of the mechanical test pieces and the calibration of testing equipment.ĪSME intent is used where the item is not to be code stamped but is perhaps only designed to the relevant ASME code and some flexibility is possible with respect to the manufacturing aspects of specification compliance. If the welded item is to be ASME stamped this can only be done by a manufacturer who has a quality system accredited by ASME and who holds an appropriate stamp, N stamp for nuclear components, U for unfired pressure vessels, S for power boilers etc. With respect to ASME IX the specification requirements can be applied in two ways ASME intent and ASME stamp. Where compliance is required then reference MUST be made to the appropriate specification. It will not be possible in this short article to cover every welding variable and its range of approval in the two specifications. The two most frequently encountered specifications are ISO 15614 Part 1 and ASME IX and whilst these are written with the same purpose (that of giving assurance that a welding procedure will provide the desired joint properties) there are major differences between the two specifications that mean that they are not equivalent. This is particularly relevant when substantial costs and/or delays will be incurred if re-qualification of the welding procedures is necessary. The question is sometimes asked ‘Can I use our existing welding procedure qualifications?’ where the qualification specification required by the contract is one that has not previously been used by the organisation. National Structural Integrity Research Centre.Structural Integrity Research Foundation.
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