Verification Activities-Inspection, Nondestructive Examination, Testing, and Quality Assurance and Quality Control Introduction.

Now Piping and Fabrication will comes to an explanation about Quality Control and Quality Assurance and everything connecting with them, including NDE (Non Destructive Examination), NDT (Non Destructive Test) and many others, and we start from Verification Activities-Inspection.

Activities involved in verifying that fabrication meets the specified quality level may be broadly categorized as inspection, NDE, testing and QA and QC. The terms inspection, examination, and testing are still often used interchangeably. The ASME Boiler and Pressure Vessel Codes have begun to establish specific definitions for these terms. The B31 Codes present a mixture of usages, some following the ASME Boiler and Pressure Vessel Code lead, while others are less definitive. The reader is directed to the individual codes to see how these terms are used. In general, the ASME Boiler and Pressure Vessel Code practice will be followed in this section.

Inspection relates to those activities performed by the owner, the owner’s agent, or a third party. All other activities are usually performed by fabricator personnel. The term examination is applied to nondestructive methods of examination, while testing refers to traditional hydrostatic and pneumatic tests for leakage. QA and QC relate to in-plant or on-site programs, whose function is to control the various activities which affect quality. Inspection. Inspection, as used in ASME Section I, III and B31.1 for Boiler External Piping, covers those activities which the authorized inspector (AI) or authorized nuclear inspector (ANI) performs in verifying compliance with the applicable code. The AI or ANI is employed by a third party; is independent of the owner, fabricator, or installer; is an employee of a state or municipality in the United States, a Canadian province, or an insurance company authorized to write boiler insurance; and is qualified by written examination as required by state or provincial rules. In the B31 Piping Codes, inspection is the verification activity performed by the owner or the owner’s agent. Specific requirements for qualification of inspectors are outlined in the individual code sections.

The manner in which an inspector verifies compliance is generally left to the discretion of the individual. It may take the form of detailed visual examinations; witnessing of actual operations such as bending, welding, heat treatment, or NDEs; review of records; or combinations thereof. Much relies on the degree of confidence the inspector has in the fabricator’s programs and personnel. B31.3 has mandatory sampling requirements for this activity.

In the next post we will enter the chapter of Examinations including the Type of Examinations it self. Thanks for reading and visiting, hope this article useful.

Code Requirements on Piping & Fabrication

Code Requirements, something that Piping & Fabrication will explain to all of you, after I'm back from my duty on South Pacific Viscose, and now this is the detail.s

Postbending and Postforming Requirements. The designer of the piping system should specify the type of heat treatment required to assure appropriate physical, metallurgical, or corrosion-resistant properties. As an example, a normalize or normalize and temper may be required to assure certain notch toughness properties for nuclear or low-temperature applications, or a carbide solution heat treatment for cold worked austenitic stainless steel may be required to preclude IGSCC. This should be agreed upon well before any fabrication starts.

The codes have certain mandatory heat treatment requirements which must be observed as a minimum, normally a stress-relieving treatment. Such heat treatment is usually in accordance with the postweld heat treatment tables given in the applicable code. Differing requirements apply depending on whether the bending or forming was performed hot or cold. According to B31.3, cold bending is performed at a temperature below the transformation range (below the lower critical), and hot bending is performed at a temperature above the transformation range (above the upper critical). B31.1 and ASME Section III make the break between hot and cold bending at a temperature 100°F (38°C) below the lower critical.

B31.3 requires heat treatment after cold bending when (1) specified in the engineering design, (2) the calculated elongation will exceed 5 percent for materials requiring notch toughness properties, and (3) the calculated elongation will exceed 50 percent of the specified minimum elongation indicated in the material specification for P-No.1 through P-No.6 materials. For hot bending and forming, heat treatment
is required for all thicknesses of P-Nos.3, 4, 5, 6, and 10A materials. B31.1 and ASME Section III on the other hand require heat treatment after bending or forming in accordance with the postweld heat treatment table of the applicable code for P-No.1 materials with a nominal wall thickness exceeding 3/4 in unless the bending or forming was completed above 1650°F (900°C). All ferritic alloy materials of NPS 4 (DN 100) or larger or with a nominal wall thickness of 1/2 in or greater which are hot bent or formed must receive an annealing, normalizing and tempering, or a tempering heat treatment to be specified by the designer, or if cold bent or formed, the heat treatment at the required time and temperature cycle specified in the postweld heat treatment table for the material involved.

The codes have no requirements for postbending or forming heat treatments of austenitic stainless steels or nonferrous materials. Postwelding Heat Treatment Requirements. Before applying any post-welding
heat treatment (PWHT), it should be noted that for work under ASME Section IX, postwelding heat treatment is an essential variable for welding procedure qualification. For ferritic materials there are five possible conditions of heat treatment, each requiring separate qualifications. These are:

1. No PWHT
2. PWHT below the lower critical temperature (stress relief)
3. PWHT above the upper critical temperature (normalize or anneal)
4. PWHT above the upper critical temperature, followed by heat treatment below the lower critical temperature (normalize and temper)
5. PWHT between the upper and lower critical temperatures.

For other materials, two conditions apply: no PWHT or PWHT within a specified temperature range.
Accordingly, for shop work, it may be necessary to qualify welding procedures for several possible heat-treatment situations. For field work only the no heat treatment or stress-relieving situations will normally apply.

When required by the codes, heat treatment consists of a stress-relieving operation. Other heat treatments such as annealing, normalizing, or solution heat treatment may be applied but are not mandatory. However, the welding procedure must have been qualified for the heat treatment applied.
Each code has its own definition regarding governing thicknesses, its own exemptions, differing temperature and holding requirements, heating and cooling rates, etc., reflecting the differing concerns and needs of individual industries. The codes are also constantly evolving as the committees obtain and review new data. Accordingly, the reader should refer to the applicable edition of the code of interest
for requirements. At the time of this writing, the following is a comparison of the heat treatment
requirements for carbon steel materials.

B31.1 requires heat treatment of P-No. 1 Gr.Nos. 1, 2, and 3 in the temperature range of 1100 to 1200°F (600 to 650°C) for 1 h/in (1 h/25 mm) of thickness for the first 2 in (50 mm) plus 15 min for each additional inch over 2 in (50 mm), with a 15-min minimum. Exempted are welds with a nominal thickness of 3/4 in (19 mm) or less, and a 200°F (95°C) preheat must be applied when either of the base metals exceed 1 in (25 mm). The nominal thickness is defined as the lesser of the thickness of the weld or the thicker of the base metals being joined at the weld. The thickness of the weld is further defined as the thicker of the abutting edges in a groove weld, the throat of a fillet weld, the depth of a partial penetration weld, and the depth of the cavity for repair welds. Thickness as it relates to branch welds is a function
of the header thickness, the branch thickness, and reinforcing pad thickness.

B31.1 also requires controlled heating and cooling at temperatures above 600°F (316°C). The rate shall not exceed 600°F/h (335°C/h) or 600°F/h (335°C/h) divided by one-half the maximum thickness at the weld in inches, whichever is less. Section III requires heat treatment of P-No. 1 materials in the temperature range of 1100 to 1250°F (600 to 675°C) for 30 min when the thickness is 1/2 in (12.7 mm)
or less, for 1 h/in (1 h/25 mm) of thickness for thickness over 1/2 to 2 in (12.7 mm to 50 mm), and 2 h plus 15 min for each additional inch of thickness over 2 in (50 mm). In this case the thickness is defined as the lesser of (1) the thickness of the weld, (2) the thinner of the pressure retaining parts being joined, or (3) for structural attachment welds, the thickness of the pressure retaining material. ASME Section III exempts P-No. 1 materials in piping systems from mandatory heat treatment based on thickness and carbon content. When the materials being joined are 11/2 in (38 mm) or less, the following exemptions apply: (1) a carbon content of 0.30 percent or less with a nominal thickness of 11/4 in (32 mm) or less,
(2) a carbon content of 0.30 percent or less with a nominal wall thickness of 11/2 in (38 mm) when a preheat of 200°F (95°C) is applied, (3) a carbon content over 0.30 percent with a nominal wall thickness of 3⁄4 in (19 mm) or less, and (4) a carbon content over 0.30 percent and a nominal wall of 11/2 in (38 mm) or less when a preheat of 200°F (95°C) is applied. ASME Section III also requires controlled heating and cooling. Above 800°F (430°C) the rate shall not exceed 400°F/h (225°C/h) divided by the maximum thickness in inches but not to exceed 400°F/h (205°C/h). The rate need not be less than 100°F/h (55°C/h).
Time and temperature recordings must be made available to the Authorized Nuclear Inspector. B31.5 requires heat treatment of P-No. 1 material greater than 3/4 in (19 mm) in the temperature range of 1100 to 1200°F (600 to 650°C) for 1 h/in (1 h/25 mm) of wall thickness with a 1 h minimum. The governing thickness is the thicker of the abutting edges for butt welds and the throat thickness for fillet socket and seal welds. Controlled heating and cooling rates are specified. B31.3 has similar requirements except that differing thickness definitions are applied to branch, fillet, and socket welds, and there are no specified heating or cooling rates. B31.4 and B31.11 both require stress relieving when the wall thickness exceeds
11⁄4 in (32 mm), or 11⁄2 in (38 mm) if a 200°F (95°C) preheat is applied. No specific temperature is specified. B31.8 on the other hand requires stress relief if the carbon content exceeds 0.32 percent, the carbon equivalent (C + 1⁄4 Mn) exceeds 0.65 percent, or the wall thickness exceeds 11⁄4 in (32 mm). Carbon steels are to be heat treated at 1100°F (600°C) or higher as stated in the qualified welding procedure. Requirements for postweld heat treatment of many different ferrous alloy steels are given in the various codes. As in the case of the carbon steels, there are variations in requirements from code to code. In the case of welding dissimilar metals, the codes most often specify that the heat treatment which invokes the higher temperature requirement be applied to the weld joint. In applying this criteria many factors should be considered. See the section ‘‘Dissimilar Metals’’ for some options. Another possibility is to take advantage of longer-time and lower-temperature heat treatments permitted by some codes.
In the end, the best source of information for specific requirements regarding heat treatment is the particular code mandated by law or contract. Where none is invoked, the various codes can be used as guides.

Anyway, thanks for all the support and start from today, I will try to continue post this blog, just to share the knowledge from Piping and Fabrication.

Begin For Pipe Rack Line 5 Project at South Pacific Viscose

It's long time ago that I've been abandoned this blog, but seems I miss to blog once a in a while, and in this opportunity I will wrote a little about the project in the South Pacific Viscose at Purwakarta, which is Pipe Rack for Line 5, where this project is need a full concentration from all the teams.

Even this is only an introduce for me on this Pipe Rack Line 5 Project, but I really learn a lot from it, and I hope I will keep going and going, until I can manage my own project in the future.

Piping & Fabrication will end this post for today, because I really have to go now. Thanks anyway to visit this blog and bye.

Furnace Heat Treatment

Furnace Heat Treatment. To assure that heat treatments attain the results intended (i.e., correct heating and cooling rates, desired holding temperature in all parts, etc.), it is very important that all controlling and recording instruments be calibrated on a regular basis. The furnace should be inspected and a temperature survey made to assure that all locations within it are capable of attaining and maintaining specific temperatures within some reasonable tolerance. This is particularly important if the zone temperatures are used as the basis for acceptance of the heat treatment. If there is any concern, it might be advisable to attach thermocouples directly to the parts being heat-treated. When piping subassemblies are placed in the furnace, they should be supported to permit exposure of the underside to the radiant and convection heating surface. Supports should be located so as to avoid sagging. Care should be taken to avoid any flame impingement directly on surfaces being heat-treated. The ends of assemblies being heat-treated should be closed but not sealed to minimize oxidation of the inside surfaces. Occasions may arise where special surface finishes on the pipe inside surface or on flow meter sections could be adversely affected by oxidation caused by heat treatment. In such cases the inside of the assembly can be purged with an inert gas to minimize oxidation.

Assemblies should be so placed as to assure the uniform application of heat. Heating and cooling rates must be selected to assure heating through the full thickness and to minimize distortion caused by uneven heating. The faster the rate of heating or cooling, the more probability of distortion. Assemblies with massive flanges, fittings, or other unusual configurations should be treated more carefully than those with butt welds only. Many of the codes have specified heating and cooling rates which are considered reasonable. Local Heat Treatment. When an assembly is too large for a furnace to accommodate, it may be fabricated in sections which are individually furnace heat-treated and later joined by welding. The final butt welds may then be locally heat-treated
in the same fashion as field welds. The most common practice is the use of induction or resistance heating. When preheating is an essential part of the welding operation, the induction or resistance equipment can be used for preheating, maintaining preheat during welding, and, finally, stress relieving.

A proper stress-relieving operation will assure that the weld and HAZ through the full thickness will attain the required temperature for the required time. The B31.1 Code requires that the heated band be at least 3 times the thickness of the thickest part being joined. With induction or resistance heating the heating elements themselves often have greater coverage. Depending on the massiveness of the joint being heated, one or more pieces of heating equipment may be needed. Controlling and recording thermocouples are located on or adjacent to the weld. Usually locally heat-treated shop welds are in the 5G position (pipe horizontal, weld vertical). For small pipe sizes, a single thermocouple located at the 12 o’clock position may suffice, but for larger diameters and heavier walls at least two and preferably four, located at 90° intervals, should be employed to assure uniformity of heating. Judicious use of insulating material should be employed to minimize heat loss. When joining parts of differing masses, concentrate more heating effort on the more massive part.

If it is necessary to locally stress-relieve a branch connection, not only the branch weld itself but the entire circumference of the header for a distance of at least 2 times the header thickness on either side of the branch should be heated. Heating of the weld alone, while resulting in a satisfactory stress relief, could distort the header significantly. Heating and cooling during local stress relief of pipe to pipe joints can be more rapid than for furnace applications since there is less chance of distortion unless, of course, the heating is not applied uniformly. Ends of the assembly should be closed but not sealed to reduce heat loss on the inside surface due to air flow. The main concern is assurance that the inside surface of the weld attains the required temperature for the required time. Local stress relieving with torches or gas ring burners can be effectively employed but must be limited to situations where controlled heating and cooling rates are not a factor.

I think thats' all what Piping & Fabrication can distribute to all of you and thanks!

Nonferrous Material & Heat Treatment Methods

Still I try to focus with this Piping & Fabrication blog, even I post this blog rarely, but I think that would be enough to gave some information about Piping System.

Nonferrous Materials. Bending and forming of nonferrous materials may result in undesirable work-hardening. Some nickel alloys may be subject to carbide precipitation when hot bent or formed. Materials that can be hardened by precipitation require other considerations. Depending on the final use, it may be desirable to perform some type of postbending or forming heat treatment. Because of the great many new materials being developed and used, it is suggested that the user contact the material manufacturers or material associations for their recommendations on the specific material and service.

Heat Treatment Methods. Shop heat treatments are most often carried out in specifically designed heat treatment furnaces, but local stress relieving of welds may also involve induction, resistance, or torch heating. Above critical heat treatments, such as annealing, normalizing, and normalizing and tempering for ferritic steel and carbide solution heat treatment for austenitic stainless steels, are performed in large heat-treatment furnaces. These same furnaces are also used for stress-relieving heat treatments of ferritic steels. Such furnaces are generally fired with natural gas, propane, or low-sulfur oil. Depending on their design, they may attain temperatures up to 2300°F (1260°C) which covers the entire spectrum of temperatures commonly encountered in piping applications. Heating and cooling rates and holding temperatures are automatically controlled. Larger furnaces may have two or more zones, each independently controlled. Records of furnace zone temperatures and material temperatures are obtained using recording potentiometers.

When assemblies are too large or furnaces are not available, local stress relieving of individual welds may be accomplished in the shop using electrical induction, electrical resistance, or gas torch heating. Induction equipment involves alternating current frequencies of the order of 60 to 400 Hz. Induction generates heat within the wall of the pipe. This has the advantage of amore uniform temperature through the thickness with greater uniformity at the lower frequencies. The heat treatment cycle is controlled automatically with thermocouples attached directly on or adjacent to the weld. The weld and

thermocouple are covered with insulating material. The induction field is generated in copper cables or solid or water-cooled copper coils external to the insulation.

Resistance heating involves the use of direct current in suitable lengths of nichrome heating wire. Various configurations and sizes of prefabricated heating elements consisting of heating wires separated by ceramic beads are available commercially. Depending on the size, wall thickness, and desired heating temperature, multiple heating units and combinations of elements may be needed. The weld and heating elements are covered with insulating blankets to retain the heat. Since heating is from one side, a somewhat wider heating band on the outside may be needed to assure that the inside of the pipe attains the required temperature. Thermocouples attached directly to the weld or adjacent to it are used to control heating, holding, and cooling temperatures. Torch heating can often be used for stress relieving, but where controlled heating and cooling rates are mandated, it may be less than satisfactory. Single torches may be used for pipe up to about NPS 3 (DN 80), but ring burners are needed for larger sizes. Exothermic heating has been used in the field and is discussed in the section ‘‘Installation.’’

Austenitic Stainless Steels

Austenitic Stainless Steels. Today Piping & Fabrication will talk about and this is the rest of post. Austenitic stainless steels do not undergo phase changes like the ferritic steels. They remain austenitic at all temperatures and so heat treatments usually do not apply. When austenitic stainless steels are to be used in corrosive services, cold working and heating for bending may significantly lower their corrosion resistance. Cold working may result in residual stresses, and heating operations can result in sensitization. Both factors contribute to intergranular stress corrosion cracking (IGSCC). When austenitic stainless steels are heated in the range of about 800 to 1600°F (430 to 870°C), carbon in excess of about 0.02 percent will come out of solution and diffuse to the grain boundaries where it will combine with adjacent chromium to form chromium carbide (Cr23C6). This phenomenon is called sensitization. These grain boundaries are then preferentially attacked by corrosive media. The heat treatment often applied to cold-worked and sensitized stainless steels to restore corrosion resistance is a carbide solution heat treatment. In this procedure, the material is heated to a temperature above the sensitization range, usually about (1950 to 2100°F (1065 to 1150°C), and held there sufficiently long to permit the carbides to dissolve and the carbon to go back into solid solution. The material is then removed from the furnace and rapidly cooled through the sensitization range, preferably by quenching in water. The rapid cooling does not give the carbon sufficient time to come out of solution, and corrosion resistance is restored to the sensitized area.

Heat treatment cycles

Obviously carbide solution heat treatment is limited by the furnace size and quenching facilities. It is most freqently applied to bends but is also useful in reducing sensitization and residual stresses in welds.

HEAT TREATMENT

Now after all the busy time I had pass, so I'll try to post this Piping & Fabrication with the topic Heat Treatment.

Purpose. Heat treatment during piping fabrication is performed for a variety of reasons (i.e., to soften material for working, to relieve fabrication stresses, to restore metallurgical and physical properties, etc.). During fabrication, ferritic steels undergo phase changes during heating and cooling, while the austenitic stainless steels and nonferrous piping materials do not; consequently differing criteria must be applied.

Ferritic Steels. Ferritic steels undergo a phase change on heating and cooling during fabrication operations because their principal component (iron) is allotropic; that is, it undergoes a change in crystalline structure with temperature. At room temperature iron favors a body-centered cubic (BCC) structure called alpha iron, but on heating to 1670°F (910°C) it changes to a face-centered cubic (FCC) structure called gamma iron and subsequently at 2534°F (1390°C) it reverts to a BCC called delta iron. The addition of carbon to the iron to form steel and additions of other elements such as chromium, manganese, molybdenum, and nickel to form alloys modify the temperatures at which transformation occurs and the manner in which the crystalline structure forms into grains.

As an example, a melt of 0.30 percent carbon steel will first begin to solidify as delta iron and a liquid, then at about 2680°F (1479°C) to an interstitial solid solution of carbon in gamma iron called austenite.At about 1500°F (815°C) this will transform into a mixture of austenite and ferrite, which at 1333°F (721°C) becomes ferrite and pearlite. Ferrite is alpha iron which contains small amounts of carbon (up to a maximum of about 0.02 percent) in solid solution. The excess carbon not in solid solution with the ferrite forms as iron carbide (Fe3C) or cementite. The cementite forms as thin plates alternating with ferrite. This structure is known as pearlite. The temperatures at which the transformations occur are called critical temperatures or transformation temperatures. The lower critical temperature, usually designated A1, is that point on heating where the BCC ferrite and pearlite phase begins to transform to FCC austenitic structure, and the upper critical temperature, A3, is the temperature at which the transformation is complete. Between these two points the structure is a mix of ferrite-pearlite and austenite. These temperatures are of importance in postbending and postwelding heat treatments as well as qualification of welding procedures.

The critical temperatures are a function of chemical composition and as such will vary with alloy. As an example, for 9Cr-1Mo-V, the lower critical is located between 1525 and 1560°F (830 and 850°C), and the upper critical is between 1650 and 1725°F (900 and 940°C). Some approximate methods of calculating critical temperature are found in Welding Metallurgy34 and The Making, Shaping and Treating of Steel.

Critical temperatures are affected by heating and cooling rates. An increase in heating rate will serve to increase the transformation temperatures, while an increase in cooling rate will tend to depress them. The more rapid the rate of heating or cooling, the greater the variation from the critical temperature at equilibrium conditions. Most sources will indicate the lower and upper critical temperatures on heating as Ac1 and Ac3, respectively, and the upper and lower on cooling as the Ar3 and Ar1, respectively. In the case of our 0.30 percent carbon steel, cooling from the austenite phase through the critical range at a rate of 50°F/h (28°C/h) or less will result in the soft, ductile ferrite-pearlite structure. On the other hand, extremely rapid cooling from the austenite phase down to temperatures 600°F (316°C) or lower can result in an extremely hard structure called martensite. This is because the austenite FCC crystals did not have time to transform to BCC ferrite and cementite.

Heat treatments which are applied to ferritic steels are related to the critical temperatures and depending on which is applied will have differing results. These are annealing, normalizing, normalizing and tempering, and stress relieving.  Annealing is used to reduce hardness, improve machinability, or produce a more uniform microstructure. It involves heating to a temperature above the upper critical or to a point within the critical range, holding for a period of time to assure temperature uniformity, then following with a slow furnace-controlled cooling through the critical range. Normalizing is used to refine and homogenize the grain structure and to provide more uniform mechanical properties and higher resistance to impact loadings. It involves heating to a temperature above the upper critical temperature, holding for a time to permit complete transformation to austenite, and cooling in still air from the austenitizing temperature. A normalized structure may be pearlitic, bainitic, or even martensitic depending on the cooling rate. If there is a concern for excessive hardness and attendant low ductility, a tempering treatment may follow the normalizing treatment. Tempering involves heating to a temperature below the lower critical and slowly cooling to room temperature, much like a stress relief. The degree of tempering depends on the tempering temperature selected. The higher the tempering temperature, the greater the degree of softening.

A stress-relieving heat treatment is primarily intended to reduce residual stresses resulting from bending and welding. It involves heating to a temperature below the lower critical; holding for a predetermined time, depending on thickness and material, to permit the residual stresses to creep out; and then slowly cooling to room temperature.