Kamis, 08 November 2007
WPS
weld defect
Rabu, 07 November 2007
Diposting oleh NOV di 11:26 PM
सर्तिफिकाते एक्साम ई
Question Paper 8 1 Bs 499 part II communicates by the use of symbols the type of joint preparation to be used. Listed below are four symbols: which of these indicates the depth of penetration of the weld required on the joint. 2 Which of the following symbols would indicate that a weld has to be finished flush on the other side of the weld 3 what two factors in arc welding must be in equilibrium to enable a stable arc to be established A arc voltage B current C wire /electrode feed rate D metal burn off rate 4 in mma welding what parameter is used for the control of penetration into the base material A voltage B welding speed C iron powders in the coating D current 5 in the welding of a butt joint made from one side which of the following controls the profile of the root bead A root face B bevel angle C root gap D none of the above 6 what type of power source characteristic is required for manual welding A constant voltage B flat characteristic C drooping characteristic D motor generator 7 which one of the following destructive tests would indicate the toughness of weld parent metal – haz A macro B nick break C hardness D charpy v notch 8 degreasing components is essential for quality welding but some agents may A cause corrosion problems B gives off phosgene gas C leaves residuals D all of the above 9 which of the following chemical elements has the greater effect on the hardenability of steel plate Molybdenum B chromium C titanium D carbon 10 in mag / co2 welding which parameters give the greatest control of weld appearance during dip transfer or short circuit welding A wire stick out length B amperage C wire feed speed D inductance 11 in mma welding the slags produced can be varied to suit the welding position which type of slag would be required for welding in the hv position A fluid B viscous C none of the above D semi fluid 12 the weld metal deposit of mma electrodes achieves its mechanical strength through A the core wire B the flux coating C iron powders with the flux coating 13 what constituent is needed in a coating to prevent the formation of porosity when welding rimming steel A iron powders B calcium fluoride C silicon D calcium carbonate 14 welds made with high heat inputs show a reduction in one of the following properties A ductility B toughness C fatigue strength D mechanical strength 15 in the welding of austenitic pipe work the bore is usually purged with argon to A prevent the formation porosity in the weld B prevent burn through in the root run C prevent oxidation of the root bead D eliminate the formation of hydrogen 16 in x-ray work the quality of the image is assessed by the A density of the film B iqi indicator C kva available D stand off distance 17 a steel described as qt will have improved tensile properties because it has A had control of chemical composition B been heat treated C been quality tested D been vacuum melted 18 which one of the following type of steels would give rise to the formation of porosity when autogenously welded with an arc process A fully killed steel B semi killed steel C rimming steel D fine-grained steel 19 in submerged arc welding the use of excessively high voltage would result in A insufficient flux melting B excessive flux melting C slag removal difficulties D spatter 20 the use of cellulosic electrodes is often made when welding root pass of pipes in the field A hydrogen control is needed B iron powders in the elecrode C higher arc voltage can be obtained D shorter arc lrngth can be achieved 21 in the welding of austentic stainless steels the electrode and the plate material can be purchased with low carbon contents the reason for this is to prevent A cracking in the haz B the formation of chromium carbides C cracking in the weld material D distortion 22 submerged arc fluxes can be supplied in two forms these are A sintered and agitated B agitated and fsued C crushed and agglomerated D fused and agglomeraterd 23 in a steel which has improved creep properties at an elevated temperature whish one of the following elements helps in this improvement A tungsten B manganese C molybdenum D carbon 24 welding a steel plate of ceq of .45 would require preheating to A prevent formation of sulphides B prevent hardening in the haz C prevent formation for carbides D to improve mechanical properties of the weld 25 which one of the following process uses the keyholing system of fusion A FRICTION WELDING B diffusion bonding C electron beam welding D autogenous tig welding 26 in friction welding is the metal at the interface in the A liquid state B solid state C plastic state D elastic state 27 welding procedures may require weld to be deposited at a controlled rate of heat input high heat inputs would A have poor profile B have larger grain size C have high hardness in the haz D have low elongation properties 28 in a tensile test a brittle material would be indicated if the fracture surface A shows areduction in size B is flat and featureless C breaks in the weld metal D breaks in the parent metal 29 what destructive test would be required to ascertain the likelihood of cracking in the haz of a weld A nick break B side bend test C charpy impact D macro test 30 in submerged arc welding excessive arc voltage may cause A excessive penetration B change in weld metal properties C narrow weld width D excessive bead profile
Diposting oleh NOV di 11:26 PM
CERTIFICATION EXAM 1
Diposting oleh NOV di 10:55 PM
MENCARI EMAS HITAM
Diposting oleh NOV di 5:56 PM
SMAW WELDING PROSES
Diposting oleh NOV di 5:44 PM
Minggu, 04 November 2007
RIG MAP ASEAN dan Kebutuhan ENERGI
Oil prices Dengan terus naiknya hargaminyak dunia yang selalu berfluktuasi telah membeikan dampak buruk bagi Indonesia dalam mengendalikan APBN dan pertumbuhana ekonomi secara makro. Indonesia mendapatkan tantangan baru untuk mencukupi kebutuhan akan sumber energi guna mengimbangi kebutuhan dalam negri. Pencarian sumber ladang minyak baru menjadi suatu alternatif yang mendesak untuk dilakukan oleh bangsa Indonesia. Sebebnarnya masih banyak ladang minyak Indonesia yang potensial yang mesti digarap secara intensif. Disamping mencarikan solusi alternatif dalam penghematan sumber energi itu sendiri
Diposting oleh NOV di 8:29 PM
WELDING INSPECTOR DUTIES
Diposting oleh NOV di 7:22 PM
WPS BASED ON ASME IX
Diposting oleh NOV di 5:29 PM
Diposting oleh NOV di 5:19 PM
OIL PRICES
Oil DashboardNovember, Sunday 4 2007 - 05:35:19 Crude Oil $95.75 0.18 0.19% 5:35 AM EST - 2007.11.04 To get the oil price, please enable Javascript.
Diposting oleh NOV di 2:28 AM
PREHEAT WELDING
The purpose of preheat:- 1. Reduce the risk of hydrogen cracking 2. Reduce the hardness of the weld heat affected zone 3. Reduce shrinkage stresses during cooling and improve the distribution of residual stresses. If preheat is locally applied it must extend to at least 75mm from the weld location and be preferably measured on the opposite face to the one being welded. Got To The Pre-Heat Calculator Background To Preheating When hydrogen diffusing from a solidified weld meets a hard microstructure under a tensile stress a crack is likely! Hydrogen cracking normally occurs in the heat affected zone where hard microstructure is to be found, occasionally it can occur in weld metal. HydrogenThis is a very searching gas that can be liberated by oil, grease, rust etc. and water under the right conditions. The greatest risk comes from hydrogen generated within the arc from damp or contaminated welding consumables, mainly fluxes or electrode coatings. Contamination on the parent metal can also be a risk unless the heat from the welding arc can drive it away. Moisture from condensation on the parent metal will normally be driven off by the heat from the arc before it can get into the weld pool. Hydrogen in the atmosphere is unlikely to penetrate the arc envelope unless welding is carried out in very damp and humid conditions. A hydrogen crack can take anything from a few hours to 24 hours to occur. After 24 hours cracking is still possible but less likely, although there have been some reported cases of cracking at 72 hours. It is therefore good practice to allow at least 48 hours before carrying out any NDE. Hydrogen will eventually disperse from the parent metal, within a few days at room temperature or a few hours if held at around 200°C. Hydrogen cracking is only possible at room temperature, this is why it is also referred to as cold cracking Parent MetalA hydrogen crack requires a hard microstructure which is created by a hardenable material subject to fast cooling from 800°C to 500°C. Cooling can be slowed down by:- applying preheat, maintaining a high interpass temperature, increasing welding power and reducing travel speed. The heat sink caused by the parent metal thickness and the number of available paths the heat can take to escape, also influence cooling rate. (However once the heat sink reaches a certain size further increases have a negligible effect on cooling rate.). This is why when determining preheat the term combined thickness is used, for a butt weld it is twice the thickness of the parent material and for a T fillet weld three times the thickness. The hardening of a carbon manganese steel/low alloy steel is influenced primarily by carbon content and to a lesser extent other constituents such as manganese, chrome, silicone etc. The Carbon Equivalent is a formula used to express the harden-ability of a particular alloy steel in terms of an equivalent plain carbon steel. Several such formula exist, the one favoured for low alloy steel is the IIW formula: CEIIW = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15 Current steel specification do not restrict or limit the Carbon Equivalent and as most steel specs permit a wide range of composition it is possible that one batch of steel may require pre-heat and another may not. Very low sulphur ( <>
Label: HEAT TREATMENT Diposting oleh NOV di 2:18 AM
Heat Treatment
1 INTRODUCTION Various codes and specifications require that welded structures such as pressure vessels and offshore platforms be post weld heat treated (PWHT), depending on the type and thickness of the welded joint. Post weld heat treatment reduces the effect of any stresses induced by the welding process and tempers the heat-affected zone. The PWHT may be performed several times on a structure during fabrication and after weld repairs, resulting in an accumulation of the total time at soaking temperature. In some instances, the original welds of the structure or vessel may be subjected to cumulative PWRT cycles which exceed the amount of time qualified for by the original welding procedure qualification tests. Because PWHT, in some instances, may result in the loss of both the heat-affected zone and weld metal strength and toughness,1 the mechanical properties of the weld-joint may deteriorate, as the vessel is repaired repeatedly. This may be undesirable, since it is not known whether the mechanical properties of a weldment are still acceptable. Studies1,2 have been conducted to study the effect of a long PWHT on the properties of constructional and pressure vessel steel weldments. Post weld heat treatment may have a beneficial, detrimental or negligible effect on the properties (especially toughness) of the weidments, depending on the chemical composition of the steel, welding procedure used and PWHT time and temperature. The purpose of the current study is to provide detailed information on the effect of a long PWHT on the microstructure and mechanical properties of a welded joint in ASTM A302 Gr B pressure vessel steel. Weld-joints of the steel in the as-welded and post weld heat treated conditions were studied. The mechanical properties of the weldments were determined by heat-affected zone (HAZ) and weld metal Charpy impact and hardness tests, HAZ fracture toughness tests and transverse weld tensile tests. Tests on the HAZ were supplemented by Charpy impact and hardness tests on HAZs generated from thermal simulation techniques. Metallographical examination included optical and transmission electron microscopy. 2 EXPERIMENTAL PROCEDURE 2.1 Materials and welding procedure Normalized ASTM A302 Gr B plate material from manufacturers A and B, with dimensions of approximately 500 x 500 x 30 mm was used. The test steels had a ferrite-pearlite/bainite microstructure. Welds were deposited using the submerged-arc welding (SAW) process; the materials used were a commercial SD3-Mo wire (3.2 mm dia.) in combination with an OERLIKON OPl2lTT basic welding flux. The chemical compositions of the base metal and weld metal
Label: HEAT TREATMENT Diposting oleh NOV di 2:08 AM