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What is sensitization? Causes and remedies? Sensitization refers to the precipitation (too quickly) of carbides at grain boundaries in a stainless steel or alloy, causing the alloy to be subject to intergranular corrosion or intergranular intergranular stress corrosion cracking Intergranular Intergranular corrosion is caused by the isolation of impurities at the grain boundaries by reduction of one of the alloying elements in the grain boundary What is sour service? "Sour Service" refers to a well environment containing containing Hydrogen Sulfide ( H2S), which is hazardous to human health and could significantly impact steel drilling tubulars performance. What is the sweet gas? Sweet gas is the natural gas that contains very little or no the hydrogen sulfide. The H2S is undesirable due to its toxicity in addition to being corrosive to all metals used in the equipment for gas processing, handling and transportation. What is an acid gas? Acid gas is a particular type of natural gas or any other gas mixture containing significant quantities of hydrogen sulfide (H2S), carbon dioxide (CO2), or similar acidic gases. What is the difference between sweet and sour natural gas? Sour gas refers to natural gas that contains significant amounts of acidic gases such as hydrogen sulfide and carbon dioxide (CO2). It is preferable instead to have sweet gas because it does not contain such amounts of these contaminants. How will you check hardness values? "75 HB 10/500/30" which means that a Brinell Hardness of 75 was obtained using a 10mm diameter hardened steel with a 500 kilogram load applied for a period of 30 seconds. The Vickers hardness test method consists of indenting the test material with a diamond indenter, in the form of a right pyramid with a square base and an angle of 136 degrees between opposite faces subjected to a load of 1 to 100 kgf. The full load is normally applied for 10 to 15 seconds. What is HIC? Causes for HIC? Hydrogen-Induced Cracking During hydrogen embrittlement, hydrogen is introduced to the surface of a metal and individual hydrogen atoms diffuse through the metal. ... This pressure can increase to levels where the metal has reduced ductility, toughness, and tensile strength, up to the point where it cracks open (hydrogen-induced cracking, or HIC) What is a crater crack? Transverse cracks are perpendicular to the direction of the weld. These are generally the result of longitudinal shrinkage stresses acting on weld metal of low ductility. Crater cracks occur in the crater when the welding arc is terminated prematurely What is hydrogen embrittlement? Hydrogen embrittlement is the process by which metals such as steel become brittle and fracture due to the introduction and subsequent diffusion of hydrogen into the metal. This is often a result of accidental introduction of hydrogen during forming and finishing operations. What do you mean by ductility and brittleness? What is necking in tensile testing? material's ability to deform under tensile stress Ductility is a solid material's deformation A material is brittle if, when subjected to stress, it breaks without significant plastic deformation How are electrodes classified? electrodes are classified based classified based on “Minimum tensile strength, strength, position, position, electric electric characteristic characteristic and coating coating type” Did you heard about high hydrogen electrodes? no Can we use cellulosic electrode for Fillet welding? Why?
No, The electrode coating has moisture content which on heating, gives off hydrogen. hydrogen formation may cause hydrogen cracking due to which they cannot be applied on materials that are susceptible to hydrogen induced cracking. Before applying cellulosic electrodes following points must be considered in order to avoid cracking. cracking.
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Material type Material Composition Material thickness Material Resistance to hydrogen cracking Why cellulosic electrodes for roots? Cellulosic (E6010) is much more of a "digging" arc, giving better penetration. What is DSS, ASS, and FSS? Difference b/w them? Properties? Ferritic – Ferritic – These These steels are based on Chromium with small amounts of Carbon usually less than 0.10%. These steels have a similar microstructure to carbon and low alloy steels. They are usually limited in use to relatively thin sections due to lack of toughness in welds. However, where welding is not required they offer a wide range of applications. They cannot be hardened by heat treatment. High Chromium steels with additions of Molybdenum can be used in quite aggressive conditions such as sea water. Ferritic steels are also chosen for their resistance to stress corrosion cracking. They are not as formable as austenitic stainless steels. They are magnetic. Austenitic - These steels are the most common. Their microstructure is derived from the addition of Nickel, Manganese Manganese and Nitrogen. Nitrogen. It is the same structure as occurs in ordinary steels steels at much much higher temperatures. This structure gives these steels their characteristic combination of weldability and formability. Corrosion resistance can be enhanced by adding Chromium, Molybdenum and Nitrogen. They cannot be hardened by heat treatment but have the useful property of being able to be work hardened to high strength levels whilst retaining a useful level of ductility and toughness. Standard austenitic steels are vulnerable to stress corrosion cracking. Higher nickel austenitic steels have increased resistance to stress corrosion cracking. They are nominally non-magnetic but usually exhibit some magnetic response depending on the composition and the work hardening of the steel. Martensitic - These steels are similar to ferritic steels in being based on Chromium but have higher Carbon levels up as high as 1%. This allows them to be hardened and tempered much like carbon and low-alloy steels. They are used where high strength and moderate corrosion resistance is required. They are more common in long products than in sheet and plate form. They have generally low weldability and formability. They are magnetic. Duplex - These steels have a microstructure which is approximately 50% ferritic and 50% austenitic. This gives them a higher strength than either ferritic or austenitic steels. They are resistant to stress corrosion cracking. So called “lean duplex” steels are formulated to have comparable corrosion resistance to standard austenitic steels but with enhanced strength and resistance to stress corrosion cracking. “Superduplex” steels have enhanced strength and resistance to all forms of corrosion compared to standard austenitic steels. They are weldable but need care in selection of welding consumables and heat input. They have moderate formability. They are magnetic but not so much as the ferritic, martensitic and PH grades due to the 50% austenitic phase. Precipitation hardening (PH) - These steels can develop very high strength by adding elements such as Copper, Niobium and Aluminium to the steel. With a suitable “aging” heat treatment, very fine particles
form in the matrix of the steel which imparts strength. These steels can be machined to quite intricate shapes requiring good tolerances before the final aging treatment as there is minimal distortion from the final treatment. This is in contrast to conventional hardening and tempering in martensitic steels where distortion is more of a problem. 16) Can you heat treat 304 stainless steel? A. 300 series of stainless steels are known as austenitic grades not hardenable by heat treatment. Some hardening can be obtained by mechanical work. A. 304 is an austenitic stainless steel. You can't throughharden it. 17) Two PQR – PQR – one one with GTAW qualified for 8 mm thickness and other with SMAW for 16 mm thickness. What are the thickness ranges qualified for both of them? Is it possible to make a WPS in combination process to weld a 32 mm thk pipe? yes 18) What do you check in an RT film before interpretation? The interpreter must make an overall observation before interpretation a) Processes b) Type of Technique c) Was the proper film used? d) Is the part and rediograph properly identified? identified? e) Have location mark properly used? f) Was the proper IQI or penetramiter used? g) Was it properly positioned? h) Is the density differential with in limites? i) Type of discontinuities discontinuities 19) What are the density ranges as per ASME Sec V? Density as per ASME Sec V X-ray: (Min 1.8, Maximum 4) γ-ray (Min 2 , Maximum 4) 20) Three different Density values obtained in a RT film like 2.5 at penetrameter, 2 and 3.2 @ different location of weld area? Do you accept this? Why? Density required as per ASME Sec V γ-ray (Min 2 , Maximum 4), hence the above I will accept 21) What is dead zone in UT? The Dead Zone is a zone where it is not possible to detect defect 22) What method gives better results DP or MPI? Why? when the component ismagnetic and both methods can be applied, the application of MPI is generally preferred to that of dye penetrant penetrant for a number number of reasons. reasons. MPI has the capability capability to detect defects defects through thin coatings. Dye penetrant is less tolerant of poor surface condition condition and its effectiveness effectiveness can also be adversely affected by any material within a defect. In addition MPI is much quicker to apply than dye penetrant. 23)
Checklist for attending repair? If a part requires rework, a thorough welding procedure should be established established to minimize the effect of the repair on the remaining portion of the weld. This procedure must consider the procedure used to create the original weld. It must also consider the following: • the condition of the base metal and weld • the type of filler metal to be used in the repair • the welding sequence
• any in-process in-process inspection required during the repair • tooling required for the repair • the final weld’s mechanical properties Incomplete consideration of any of these factors may result in further rejection of the weld repair and possible failure failure of the weld when when placed into service. service.
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What is A 106 Gr-b, A 333 gr-6, 105 N, A234? A106 Gr-b: This specification covers carbon steel pipe for high-temperature service. A 333 gr-6: This specification covers wall seamless and welded carbon and alloy steel pipe intended for use at low temperatures. temperatures. A105 N: This specification specification covers covers standards standards for forged forged carbon steel steel piping components, components, that is, flanges, fittings, Valves, and similar parts, for use in pressure systems at ambient and higher-temperature service conditions. A234: This specification specification covers wrought carbon steel and alloy steel fittings of seamless seamless and welded construction. What is PSL? The two specs under API 5L are PSL-1 and PSL-2. These specs cover seamless and welded steel line pipe from grades X42 through X80. API 5L is suitable for transporting gas, water, water, and oil, oil, and is usually found in the hydrocarbon petroleum and natural gas industry. What is E-6010, E 7010-P1? E7010-P1 electrode is suitable for vertical down welding and backing welding for root passes, hot passes, filler filler and cover cover passes as as well as capping of of high press pipelines pipelines and similar similar structures. structures. E7010-P1 give x-ray quality welds. Design temperature of 106 Gr-b? can it be used at -20° C? A106 Gr B can use -29° C without impact test as per Fig. 323.2.2A , ASME B31.3 Which is more ductile? SS or CS? Why? C% increase -brittleness increase C% decrease – decrease – ductility ductility increase SS metal having Carbon % up to 0.1% (.035 to 0.1)% CS metal having Carbon % up to 2% (0.3 to 2)% So SS is more ductile What will happen if SS and DSS stored together? It will start Galvanic Corrosion DSS is more noble (Cathodic) than Less nobel SS (Anodic) What is super duplex stainless steel? Super Duplex Stainless Steel. 25% chromium copper-free super duplex (austenitic/ferritic) steel (also known as 2507). Good strength and ductility combined with high marine corrosion resistance. Primarily used for Oil & Gas and marine applications. What is a duplex material? Duplex stainless steels are so called “duplex” because they have a two -phase microstructure consisting of grains of ferritic and austenitic stainless steel. Duplex stainless steels are about twice as strong as regular austenitic or ferritic stainless steels. Can SS be used in Low temperatures? Why? SS can be used temp -257° C to 538° C
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Difference between On-plot and Off Plot? The main difference between "on-plot" and "off-plot" is the construction codes. On-plot usually refers to plant piping (ASME B31.1 B31.1 or B31.3)whereas, B31.3)whereas, off off plot refers refers to cross country country pipelines pipelines (API-1104, (API-1104, B31.4 and B31.8). on plot is comming under process area (process piping )and off plot in Hydrocarbon area ( flow lines ). What is class -1, 2 & 3 pipeline? Class 1: refers to any location within 220 yards of the pipeline that contains 10 or fewer dwellings Class 2: refers to any location within 220 yards of the pipeline that contains more than 10 and fewer than 46 dwellings Class 3: refers to 1) any location within 220 yards of the pipeline that contains 46 or more dwellings, or 2) an area where the pipeline lies within 100 yards of a building or a small, welldefined outside area (such as playgrounds, recreational areas, outdoor theater, or places of assembly) that is occupied for a specified number of days per year. Class 4: refers to any location within 220 yards of the pipeline where buildings with four or more stories above ground are prevalent. What will you check in an MTC? One MTC must contain the following information: steel mill's name, heat number, batch number, final test result, dimension (steel pipe diameter, wall thickness, length), quantity, steel grade, standard/specification, chemical analysis composition results, mechanical test properties results. If applicable, applicable, there also should be hydro test result, UT result, hardness test result, CVN impact results, metal graphic result etc. Hardness value for sour and non sour service-SP 1173? Hardness for sour < 22 HRC (average) < 24 HRC (individual)
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Formula for density? geometric unsharpness? Radiographic density (AKA optical, photographic, or film density) is a measure of the degree of film darkening.
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An unexposed and processed film will have a density of about? An unexposed film density 0.1 to 0.2 and unexposed film density is 3
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What is NACE and NON-NACE pipes? CS Normal pipe will be meeting the Specification(ASTM/ASME) standard requirements. NACE Pipes will be having additional restriction in Chemical Composition,Hardness,Carbon Equivalent and Heat treatment requirements.This additional requirements to ensure the usability of material in Sour services Sensitivity formula? You have to radiograph a plate to plate welded joint of 8mm thickness. The specification asks for 2% sensitivity .Now 2% of 8mm=0.16mm. What do you know about piping class (ANSI) ? What does ANSI 300 means? A pipe class is a document (normally prepared by an operating or engineering company) for use within its confines and which contains the definition of pipe and all related components that are to be used under a specific pressure, temperature condition – condition – including including sometimes the service they are in. we will convert the classes to megapascals (Mpa), another pressure measure which relates better to the class system: Class 150 equals 2.0Mpa; Class 300 is 5.0Mpa; Class 400 is 6.3Mpa;
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What is difference b/w A 333 gr 6 and A 106 gr b? ASTM A333 — standard standard of Seamless and Welded Steel Pipe for Low-Temperature Service. ASTM A106 — standard standard of seamless carbon steel pipe for high -temperature service A333 gr.6 = TS-478 mpa , Normalised at 920 degree C A106 gr.b = TS-515 mpa, Hot finished finished C material
V Mn
Si (min)
Cu
Ni
(max)
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P
S
Cr
Mo
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A333 Gr.6
0.30
0.29-1.06
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0.40
0.08
0.025
0.025
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0.12
A106 gr.b
0.30
0.29 –1.06
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0.4
0.40
0.08
0.035
0.035
0.4
0.15
Which electrode gives more hydrogen in weld? Moisture content of these electrodes is quite high, typically 4 to 5%. The cellulose (EXX10) burns in the arc to form a gas shield of carbon monoxide, carbon dioxide and, in conjunction with the moisture in the coating, produces a large amount of hydrogen, typically 30 to 45ml hydrogen/100gm weld metal
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Which electrode gives deeper penetration? Deeper penetration is obtained with cellulosic electrodes (EXX10) 5) Which electrode gives smooth arc? Rutile Electrode (EXX13) 6) What is downhill welding and what electrodes are used? E6010 is traditionally used for downhill. these have a thin highly fluid slag which makes makes slag inclusions much less likely. 7) What are tests required for sour service materials? 1)All materials specified for sour service shall, as a minimum, meet the requirements of NACE MR0175 / ISO 15156 – 15156 – latest latest edition. 2) All welded pipes / fittings in sour service shall be HIC tested, if required by the project specification. It shall be conducted for one pipe / fitting per heat in accordance with NACE TM-0284 Solution – A A with acceptance criteria as specified in NACE MR-0175. 8) Why spatter can be removed easily? There is a oxide layer 9) What is lamellar tearing? Lamellar tearing can occur beneath the weld especially in rolled steel plate which has poor through-thickness ductility. The characteristic features, principal causes and best practice in minimising the risk of lamellar tearing are described 10) What is through thickness ductility? Ductility in the “Z “ Z” Direction (through ( through thickness). 11) Why fatigue crack occur in outside surface of materials? Fatigue crack occur in outside surface of materials because where bending stress are highest.and because material material defect such such as corrosion corrosion pitting pitting on the surface,
1) Which side IQI gives good image? Why?
Correct, IQI(s) is (are) required to be placed on source side with given RT set up conditions to verify detectability and then sensitivity of near surface indications, as the y are impaired due to increased OFD. Alternatively, indications within the test object have a better chance of detectability / sensitivity due to decreased OFD.
I just received a calculations with the results bellow and I dont know how to interpretate the results,my need is pipe to nozzel neck in A106 and MDMT -29ºC, the calculations is fine to this condition? Minimum Design Metal Temperature Temperature (Noz. Neck to Flange Weld), Weld), UCS Curve: B Nozzle, tg = 14.980 , tr = 3.397 , c = 3.0000 mm , E* = 1.00 Stress Ratio = tr * (E*) / (tg - c) = 0.284 Minimum Temp. w/o impact per UCS-66 Minimum Temp. at required thickness Minimum Temp. w/o impact per UG-20(f)
-16 C -94 C -29 C
Degas: No, this calculation does not appear to be correct. If you review ASME Section VIII, Div 1 UCS 66.2, the equation for determining the MDMT without impact testing is based on a similar equation except there is no t g. The variable is t n, which is nominal noncorroded thickness. You need to review UCS-66.
If your vessel or portions of your vessel satisfies ALL the requirements of UG-20(f), MDMT is good to -29°C with no impact testing. If not exempted by the rules of UG-20(f), you are now bound by the rules of UCS-66. For a 17.12 mm nominal thick pipe, the governing thickness would be 17.12 x 0.875 = 14.98 mm. Using Curve B at this thickness, you would get MDMT = -16.725°C from Fig. UCS-66M UCS-66M or Table UCS-66. -16.725°C is the "unadjusted" "unadjusted" MDMT. You can further reduce this MDMT using the rules of UCS-66(b). Now assuming assuming the tr and coincident ratio (stress ratio as you called it) in your original post are correct, go to Fig. UCS-66.1M and see what you end up with your coincident ratio. Since your coincident ratio (0.284) is less than 0.35, Figure UCS-66.1M tells you to see UCS66(b)(3). Your pipe's MDMT is good for -155°C with no impact testing. But that does not end there. Your nozzle is a welded assembly composed of more than 2 components (e.g. pipe to shell joint and repad, pipe to flange). You need to follow the rules of UC S-66(a) and determine the MDMT of each welded component. The warmest MDMT should be the MDMT of your nozzle assembly.
