8/12/2019 Stress Relieving as per IS 2825
3/4
6. MANUFACTURE AND WORKMANSHIP6.1 Approval of Design - Refore
commencingmanufacture, the manufacturer, if so required,shall
submit for approval by the purchaser a fullydimensioned drawing
showing the pressureportions of the vessel and carrying the
followinginformation:4
b)C4
4f)g)
h)
A statement that the vessel is to he con-structed to this
standard.Specification(s) to which materials shallconform.Welding
process(es) to be adopted for allparts of the vessel.Large-scale
dimensional details of theweld preparation for the longitudinal
andcircumferential seams and details of thejoints for branch pipes,
seatings, etc, andthe position of these joints relative to
thelongitudinal and circumferential seams andother openings.Design
pressure(s) and temperature(s) andmajor structural loadings.Test
,pressure s) .Amount and location of corrosion allowance.
No modification shall be made to theapproved design except with
prior agree-ment between the purchaser and the
manu-facturer.Additional requirements, if any, specifiedby the
purchaser.
i.2 Welded J oints General Considerations6.2.1 Welded
construction of pressure vessels1s subjected to the following
general conditions.
6.2.1.1 All details of design and constructionshall generally
conform to the provisions of thiscode. ( Examples of typical
designs of weldedconnections are given in Appendix G. )6.2.1.2 The
materials shall conform to therequirements of the appropriate
Indian Standardsor shall be any other approved material.6.2.1.3 The
welders shall be qualified for the
type of welding concerned in conformity withthe welders
performance qualification ( see 7.2 ).6.2.2 Nozzles, pads;
branches, pipes, tubes, etc,and non-pressure parts may be welded to
pressureparts provided that the strength and the character-istics
of the material of the pressure parts are notaffected
adversely.
If heat treatment is mandatory under therequirements of this
code, the attachment of partsmentioned above by welding shall take
placebefore the final heat treatment.6.2.3 The manufacturer of a
pressure vessel
built according to this code, shall be responsiblefor all the
welding work done under this code.
IS : 2825 - 1969The manufacturer shall conduct the testsrequired
in this code ( see 7.1 anJ 7.2 ) to qualifythe welding procedure
employed and to judgeperformance of the welders who apply
thisprocedure.
6.2.4 The manufacturer shall maintain a recordof the results
obtained in welding procedure quali-location tests ( see Appendix H
).These records giving an acctuate descriptionof all the
particulars of the materials and procedureconcerned shall be
certified by him and shall beaccessible to the inspecting authority
who shouldbe permitted to witness the tests if he so desires.
6.2.5 Any person who wishes to qualify for awelders performance
test under this code shallnot be below the age of 18 years and
shall havebeen employed as a welder in a workshop or firmfor a
period of not less than two years.A record shall be kept to show
that the welder
has been employed on work of the kind covered byhis performance
tests, during the previous sixmonths.These records shall contain
the results of thewelders performance tests and the
identificationmark assigned to each welder. T rey shall becertified
by the manufacturer and be accessible tothe inspecting authority (
see Appendix H ).The welds made by each welder shall he markedwith
a stamp showing the welders identity atintervals of one metre or
less, Care shall be takento avoid notching or stress concentration
due todeep stamping of welders identity. Deep stamp-ing as a means
of identifying welded seam is notrecommended on carbon steel plates
less than7 mm thick or vessels subject to low temperaturesor on
austenitic and alloy steels. When deepstamping is not permitted, a
record shall be keptby the manufacturers of welders and
weldingoperators employed on each joint which shall beavailable to
the inspecting authority; suitablestencil or other surface markings
may be usedadditionally.
6.2.6 The inspecting authority shall have theright to disqualify
a welder any time during thefabrication of a vessel, when there is
a specificreason to question his ahility to make welds thatmeet
this code requirements. Such a disquali-fied welder at the option
of the manufacturer maybe put up for retests, under the
conditionsspecified in 7.2.8.1.6.3 Design of Welded J oints
6.3.1 Single fillet welded lap joints should notbe used without
previous consent of the inspectingauthority.6.3.2 In the design of
all details the aim shall beto avoid disturbances in the flow of
the lines offorce, in particular in constructions subjected to
fatigue stresses. Holes and openings shall not bepositioned on
or. in the heat affected zones of65
8/12/2019 Stress Relieving as per IS 2825
4/4
IS:2825 969welded joints. Where such openings are un-avoidable?
such holes can be located on circum-ferential Joints provided the
weld is radiographi-tally solmd for a length of three times
thediameter of the hole on either side.
6.3.2.1 Further, welded joints should bepositioned in such a
manner that they are subjectedto lowest possible bending stresses.
*Joints betweencylindrical shells and domed end plates shall notbe
located in the curved part of the domed endgee Table 6.2 ). When
dished end plates areassembled from a number of plates, the
weldedjoints bettveen these plates shall preferahly crossthe corner
curvature for the shortest possiblelength.6.3.2.2 Attachment of
parts by weldingwhich cross or which are in the immediate vici-nity
of existing main welds in pressure parts should,as far as possible,
be avoided. If such welds can-not he avoided, they should cross the
main weldcompletely rather than stop abruptly near themain weld so
that stress concentrations in theseareas are avoided. Further, such
a part should besubjected to local radiographic examination orother
approved non-destructive tests and stressrelief, where
necessary.
6.3.3 The entire assembly as well as the indivi-dual welded
joints shall be designed after giving
T I---+--4cA) PREFERRED
L TAPER MN BE INSlOE OR OUTSILX uCC) PREFERRED
not possible to comply with this requirement,the intersection of
the welds should be radio-graphed, 100 mm on each side of
intersectionSM 8.7.1 and 8.7.2 ). This involves among otherthings
that the longitudinal joints should be,wherever possible, staggered
when assembling acylindrical shell from two parts by meansof a
circumferential joint. The distance shallhe at least five times the
thickness of thicker plate.6.3.5 Where a butt joint is required
betweenplates which differ in thickness y more than one-fourth the
thickness of thinner plate or more than3 mm, the thicker plate
shall have a tapered transi-tion section as shown in Fig. 6.1 see
soTable 6.2 ). The transition section shall havea minimum length of
four times the offsetbetween the abutting plate edges, The
transi-tion section may be fnrmcd by any process
that will provide a uniform taper. The weldmay be partly or
entirely in the tapered section oradjacent to it.It is recommended
that width of the parallelportion may not be less than 32 mm when
thebutt weld is to be radiographically examined.
6.3.6 The types of butt joints recommended forfusion welding
processes arc and gas welding 1,their shapes and dimensions are
given in Table6.1. The dimensions and shape of the edges shall
4CP ct2 6 1 t1i f--- cd
LTAPERAr BE IWM OR oulsloE0) PERMISSIBLE
Fro. 6.1 BUTT WELDING PL TES OF UNEQU L THICKNESSdue
consideration to the method of welding andthe specific character of
the joints. The aim shallbe to avoid welding in dificult positions.
Fur-ther, welded joints shall be so positioned that theypermit
visual and other methods of inspectionand re-welding of the root
side of the weldswherever posslblb. Welded joints should be
freefrom undue restraint.
6.3.4 Concentration of welded joints should beavoided and the
design should he made in sucha way that no two main seams come
together underan acute angle or cross each other. Where it ir
permit complete fusion and penetration. Qualifi-cation of
welding procedure as required under 7.1is acceptable aq proof that
the welding groove issatisfactory.6.3.6.1 Where butt joints welded
from oneside only are credited with a joint factor equal tothat
permitted for butt joints with backing strips,the procedure of
welding should be such asto obtain the same quality of deposited
weld metalon the inside and outside. The joint shall havecomplete
joint penetration and complete fusionfor the full length of the
weld and shall be free
