Forum Replies Created
-
Posts
-
im not a design engineer but it seems strange to just leave 4mm of incomplete penetration, its not really goin to save time or money
i had a look in as 1101.3 “graphic symbols for general engineering – welding & nde”
i found clause 4.2.4 “depth of preparation specified, design throat thickness (DTT) not specified, or specified eleswhere”
this just shows the symbol and says nothing about size of weld.
the “specified elsewhere” might be worth checking, the DTT may be written somewhere else on the drawing eg: “all welds to be complete penetration unless noted otherwise” but when they do this they usually leave preparation size and shape to the choice of the fabricator.the usual way to draw a weld symbol for an incomplete penetration butt weld with penetration depth equal to the preparation depth is to just specify the DTT (xx) and desired preparation shape eg: double vee, single vee, etc
for depth of prep different to DTT the symbol requires both size of prep and DTT to be displayed
it could also just be an error on the drawing, it may be worth checking with the client just to be sure.
i have recently seen a drawing with symbols for a fillet weld in a corner joint with the symbol on the wrong side of the reference line,it was obvious what they wanted but wrong none the less, hope this helpsfor pressure equipment It depends on what hazard level the vessel is classed and what materials are to be weld repaired
before proceeding with weld repairs on pressure equipment classed hazard level “A” if the vessel is to be subjected to external fabrication inspection, the fabrication inspection body must be informed .
the inspection body must approve the repair if it is greater than 20mm deep and 300mm long in base metal groups A1,A2,A3,K and M. Greater than 10mm deep and 200mm long in base metal groups D,E,J and any repair in base metal groups F,G,H
for equipment of other hazard levels relevent consent should be granted by the inspector to the fabricator to conduct repairs as necessary.
All repairs must be documented and made available if requested.
a qualified procedure and welding operator must be used for the repair. a previously qualified procedure and operator may be used but a new procedure tested and qualified may be required (if the weld has failed something may be wrong with the original procedure).
repairs should be prior to heat treatment or the repair may need to be reheat treated, more info on this in section 14 of AS4458if the production test plate fails additional tests may be taken from the test piece if these fail the test piece shall be rejected.
If a production test plate is rejected all welds which it represents on the vessel will have to be removed.done a little a CuNi pipe work awhile back. Used single vee no gap or very small gap (less than 1mm) and no root face because the weld pool isn’t very fluid (compared to stainless and carbon steels) so it makes bridging with GTAW difficult. clean area to be welded thoroughly. Use a short arc and try and keep the filler wire tip in the gas shield while welding to avoid the tip oxidizing while its hot this helps to keep oxygen out of the pool which can cause small sub surface porosity. Generally use amps a bit higher than you’d use for s/s or carbon steel as the heat dissipates quickly due to the thermal conductivity of the copper.
Its not difficult but it does look and feel a bit different when welding to compared to your stainless and carbon steels.1. Requires a high level of training to use and interpret results.
2. Traditionally doesn’t keep a permenent record. ( modern ut machines do these days)
3. Expensive machines and probes
4. Limitated to specific joint geometrys and shapes and surface cobditions (very small very thin very rough and non homogeneous materials are difficult)
5. linear defects orientated parallel to the sound beam may go undetectedthe fcaw 8F ticket requires you to do 4 welds they are:
3 pass horizontal fillet (2F)
vertical up fillet (3F)
horizontal butt weld (2G)
and 1G rotating butt weld on pipe1. its cheap
2. requires little training
3. can be used on most materials aslong as they are non pourous
4. very portable, can be taken from job to job easily
5. defects are made visible and can be photgraphed to be recordedG.P welds are selected for static loaded or low stressed members. S.P are selected for dynamic loaded or higher stressed members. Using s.p welds gives a higher quality assurance in the weld due to the
1. Stricter tolerances on the level of discontinuities accepted.
2. Requires greater nde
3. Weld procedures require greater extent of testing prior to being approvedAS 2812 glossary of terms for welding clause 2.072
Defines weldability as – The ability of a metal to be welded under given fabrication conditions in a specific weldment, and to perform satisfactorily in the intended service.Similar to your answer but a bit more generic.
Can’t be done unfortunately, need to use a multimeter or the welding machines own readouts if it is calibrated and reliable but multimeter will give a better reading
if the two 65mm plates are being joined 1st the combined joint thickness would be 130mm and then when 25mm plate is to be attached the combined joint thickness would be 155mm, adding the 25mm. If all plates are to be joined/welded at once the combined joint thickness is 155mm, that is i’m assuming that all the plates are longer than 75mm. if they are shorter the equation changes.
Preheat is required because without preheat the heat from welding is rapidly quenched from the welding zone through the parent material thickness which can cause undesirable microstructures in the HAZ. so any material that is in sufficient contact to act as a “heat travel path” within 75mm of the joint centre when the weld is being laid can be added to the combined joint thickness.mmm yes forgot to add backing bars are not usually added to the C.J.T
Carburising flame adds carbon to the weld metal and metal surface which depending upon application can lead to undesired hardening. It can be used for no ferrous materials and high carbon steels in which higher hardness levels are required.
Neutral flame is used for cutting and welding most steels
Oxidising flame Is used for welding copper based and zinc based materials and some cast irons.
The main reason propane lpg isn’t used, although it can be, is because it has a lower flame temperature and requires more oxygen to get a flame heat which is still cooler than the oxy acetylene flame. The cooler flame makes it slower and difficult to melt thicker materials.check AS 1554.1 clause 4.2 (a) note 1
procedures qualified to AS 3992 can be used for AS 1554.1 providing you’ve got records/evidence of the tests done when qualifying the WPS to 3992. The WPS also has to be within the essential variables of AS 1554.1 so you’ll have to check through that. note there is a new AS 1554 – 2011 some variables have changed and been added.AS 1554.1 doesn’t really have a clear yes or no answer for deleting a process. not that i can find anyway.
Propane and natural gas are usually limited to heating and cutting because of its relative low temperature low heat flame
g’day wazza
in AS 3992 – pressure equipment – welding and brazing qualifications which covers welding qualification for AS 4041. if you look in the essential variables and the notes to those variables it states a process can be deleted from a WPS providing the joint thickness is within the thickness range for the remaining process.
That being said trying to do the root run with flux core is extremely difficult its not really suited for root run, i don’t know what position your actual job is in but i remember doing 8f flux core ticket with 1g rotating pipe was hard enough, the slightest wobble or travel speed change and you can say goodbye to root fusion or blow through. It can be done but i would personally qualify a new WPS and go through all the testing again if your going to do it.
Fillets wouldn’t have the same problem but often a procedure qualified as a butt weld lacks the “power” amps and volts to get the adequate root penetration, it depends on your procedure. i personally qualify butt welds as butt only and do a separate fillet WPS and welding personnel qualification, but i work in a small company in a big company this might get expensiveg’day
second class welder is the term used for welding operators who have had informal training and have learnt skills through work and employers. A second class welding operator may be highly skilled but just doesn’t have the “piece of paper” to show it.The standards such as AS1554 and AS3992 state basically without going into great detail that all welds must be made to a proven Qualified Welding Procedures, that welding operators must be competent to complete the required weld and that employers must provide proof that the welding operator is competent.
If the welding operator is certified through formal training and has welding tickets “1st class” the employer can chose to use these certifications as proof to comply with the code. If the welding operator does not have tickets the employer must show that the person is competent and this is done through weld tests. A lot of employers tend to test all operators 1st or second Class before hiring anyway but the 1st class welder may be called to the job interview/weld test first.As far as the mines are concerned if you get welding certifications it will obviously increase your chances. Some Tafe collages also run mine specific induction courses which cover subjects like O.H&S for working in mines, confined space working and working at heights. these would also help your case.
