Piping on Pipe Rack

It's been almost the end of April, but our progress on the Pipe Rack Line 5 at South Pacific Viscose still far far away from the target. The target should be 60% in the end of this month, but we only reach 48.98% for over all job on the Pipe Rack. I know there is so many problem on the field when we doing Piping and Fabrication for this job. For example, there is too many Pipe Rack doesn't suit to with the drawing, or too small support, so it's not possible if we put 24" Inch Pipe on that Pipe Rack and also the other problem such as unfinished pipe rack and support. Because all the Pipe Rack and support is doing by Civil.

We can't joint straight because the limitation of pipe rack

We who doing the Piping Job, it's really face the hard situation here, because only one week left but we have to chase 10% delay from the target. We hope everything will be fine as our planning. By the way, today Piping and Fabrication only post about this, because this is very important to me to catch everything on time.

Thanks for visiting and Good Luck.

Cutting, Bending, Welding, Heat Treatment, and Examination

Cutting, Bending, Welding, Heat Treatment, and Examination

Cutting, bending, and welding operations in the field parallel those used in the shop. See the section ‘‘Fabrication’’ in this Piping and Fabrication blog in the older post. and also Mechanical and oxyfuel gas cutting are most commonly used in the field. Plasma cutting may occasionally be used in Piping. 

Bending, if used at all, is limited to small-diameter piping using relatively simple bending equipment at ambient temperatures. Occasionally in order to correct for misalignment, larger-diameter ferritic piping is bent at temperatures below the lower critical. Please note that this procedure is limited to ferritic materials. Any application of heat to austenitic materials will result in sensitization and loss of corrosion properties. See the section ‘‘Bending.’’ For smaller pipe sizes, torches may be used to supply heat, but for larger, heavier-wall materials and where better temperature control is warranted, heat may be applied by induction or resistance heating units in the same manner as local stress relieving. See the section ‘‘Local Heat Treatment.’’ The heating units are applied to the section of the pipe to be bent. The section of the line upstream of the area to be bent should be anchored to preclude translation or rotation of the installed portion of the line. The anchor should preferably be not more than one or two pipe diameters from the area to be heated. Once the bend area has attained the required temperature, a bending force can be applied on the downstream leg of the pipe until the required bend arc has been obtained. Since most ferritic materials still have reasonably high

yield strengths even at lower critical temperatures, care should be exercised. Large bending forces may damage the building structure or crack the line being bent.

Apply a reasonable force for the conditions and allow the imposed stress in the bend arc to be relieved by the heat. Then repeat. Progress in this fashion until the required bend is accomplished. Some small amount of overbending may be required to offset the deflection which will occur in the unheated section of pipe between the heated arc and the pulling device. When the bend is completed and allowed to cool, all restraints may then be removed. Little if any force should be needed to align the downstream joint; otherwise additional bending may be needed to further correct the situation. No further heat treatment of the bend arc is needed since the temperatures applied in this bending method are below the lower critical temperature. Corrections to lines with large section modulus or where the required bend arc is large should preferably be made in a shop since better controls can be exercised.

Field welding is more often than not in a fixed position. Welders should be qualified in the 6G position since this qualifies for all positions. Welding will be done using SMAW,GMAW,FCAW, and GTAW. Somewelding processes can be automated using orbital welding techniques. Such practice can result in fewer repairs, provided the bevels and alignment are within tolerance and the welding parameters are carefully selected.

Field postweld heat treatment also follows the practices outlined in the section ‘‘Heat Treatment’’ for local stress-relieving of ferritic materials. This usually involves induction or resistance heating units with recording devices. For small pipe welds, torch heating using temperature-sensitive crayons to control temperature is sometimes used. Exothermic heating to stress-relieve welds is still used on occasion for outdoor applications where heating rates are not required to be controlled.

Exothermic materials are preformed to pipe contour and sized to reflect the wall thickness and desired stress-relieving temperature. They are placed around the weld and ignited, attaining temperature in 5 or 10 min. The actual maximum temperature attained may vary. NDE in the field will follow the practices outlined in the section ‘‘Verification Activities.’’ Radiography is usually limited to radioactive isotopes, although occasionally X-ray equipment may find a use. Most surface examination is conducted using liquid-penetrant methods, since magnetic particle equipment is not as convenient in the field. Ultrasonics are used for thickness verification and in certain situations as an alternative to radiography of welds when permitted by the governing code.

Mechanical Joints

Threaded joints probably represent the oldest method of joining piping systems. The dimensional standards for taper pipe threads are given in ASME B1.20.1. This document gives all required dimensions including number of threads per inch, pitch diameter, and normal engagement lengths for all pipe diameters. Thread cutting should be regarded as a precise machining operation. For steel pipe the lip angle should be about 25,

but for brass it should be much smaller. Improper lip angle results in rough or torn threads. Since pipe threads are not perfect, joint compounds are used to provide leak tightness. The compounds selected, of course, should be compatible with the fluid carried and should be evaluated for possible detrimental effects on system components. Manufacturers’ recommendations should be followed.

Threading Die

Where the presence of a joint compound is undesirable, dryseal pipe threads in accordance with ASME B1.20.3 may be employed. These are primarily found in hydraulic and pneumatic control lines and instruments. Flanged joints are most often used where disassembly for maintenance is desired. Agreat deal of information regarding the selection of flange types, flange tolerances, facings and gasketing, and bolting is found in B16.5. The limitations regarding castiron-to-steel flanges, as well as gasket and bolting selection, should be carefully observed. The governing code will usually have further requirements. Gasket surfaces should be carefully cleaned and inspected prior to making up the joint. Damaged or pitted surfaces may leak. Appropriate gaskets and bolting must be used. The flange contact surfaces should be aligned perfectly parallel to each other. Attempting to correct any angular deviation perpendicular to the flange faces while making up the joint may result in overstressing a portion of the bolts and subsequent leakage. The proper gasket should be inserted making sure that it is centered properly on the contact surfaces. Bolts should be tightened hand-tight.

Compression sleeve (Dresser) coupling for plainend cast-iron or steel pipe

If necessary for alignment elsewhere, advantage may be taken of the bolt hole tolerances to translate or rotate in the plane of the flanges. In no case should rotation perpendicular to the flange faces be attempted. When the assembly is in its final location, bolts should be made up wrench-tight in a staggered sequence. The bolt loading should exert a compressive force of about twice that generated by the internal pressure to compensate not only for internal pressure but for any bending loads which may be imposed on the flange pair during operation. For a greater guarantee against leakage, torque wrenches may be employed to load each bolt or stud to some predetermined value. Care should be exercised to preclude loading beyond the yield point of the bolting. In other cases, special studs that have had the ends ground to permit micrometer measurement of stud elongation may be used. Flange pairs which are to be insulated should be carefully selected since the effective length of the stud or bolt will expand to a greater degree than the flange thicknesses, and leakage will occur. Thread lubricants should be used, particularly in high-temperature service to permit easier assembly and disassembly for maintenance. There are a great variety of mechanical joints used primarily for buried castiron pipelines carrying water or low-pressure gas. They are primarily of the bell and spigot type with variations involving the use of bolted glands, screw-type glands, and various types of gasketing. The reader is referred to AWWA Standards C 111, C 150, and C 600, and to catalogs for proprietary types. For reinforced concrete pipe,AWWAStandards C 300, C 301,51 and C 302, should be consulted. Compression-sleeve couplings such as the Dresser coupling and the Victualic coupling are widely used for above- and below-ground services, both with cast-iron and steel pipe. Consult the manufacturers’ catalogs for more information. 

INSTALLATION PROCESS ON PIPING AND FABRICATION

INSTALLATION ON PIPING AND FABRICATION

I think everyone who work and involved in the Piping, Maintenance, Fabrication and Mechanical on Piping and Fabrication must know about the whole process from the beginning what the piping system is and here we will talk start from drawing, erection, cold spring, joint alignment and etc.

Drawings

Drawings used for piping system installation may vary greatly. Often orthographic projections of the building showing several systems or single systems, depending on complexity, are used. In many cases single or multiple isometric drawings of a single system are used. These of course are not to scale but are convenient for planning, progress recording, or record keeping when required by quality programs. In all cases where prefabricated subassemblies are being erected, these drawings will have been marked up to show the locations and mark numbers of the individual subassemblies, the location and designations of field welds, and the locations and markings of hangers.

Erection Planning

Planning is vitally important in installing a piping system. Many factors must be considered, among them accessibility to the building location, coordination with other work, availability and accessibility of suitable welding and heat treatment equipment, availability and qualification of welders and welding procedures, rigging, scaffolding, and availability of terminal equipment. Each of the system components should also be carefully checked to assure correctness. Valves and other specialty items in particular should be checked to assure they are marked with flow arrows, that the handwheels or motor operators are properly oriented, and that the material to be welded is compatible with the material of the piping. Special valves for use in carbon steel systems are sometimes furnished as 5 percent chrome material, and thermowells are often not of the same chemical composition as the pipe. This may not be apparent from the drawings Such a preliminary check will indicate the need for alternate welding procedures and preclude problems later.

The location of the work and accessibility to it should be viewed. It may not be possible to install an overly long subassembly after other equipment or building structure is in place. A common practice in the power field is to have large, heavy assemblies often found in the main steam and reheat lines of large central stations erected with the structure. In other cases, a preliminary review may show interferences from an existing structure, cable trays, ducts, or other piping which are not apparent from the drawings. The locations of the terminal points on equipment should be checked to assure that they are correct. The type, size, rating, or weld preparation of the connection should be checked to assure that it will match the piping. Solutions to any problems can be devised with the designer before work starts.

The ideal way to begin erection is to start at some major piece of equipment or at a header with multiple outlets. Install the permanent hangers if possible. If these are to be welded to the structure, some prudence should be exercised, since the final location of the line may warrant some small relocation to assure that the hanger is properly oriented relative to the piping in its final position. Obviously a certain number of temporary supports will be needed. Welding of temporary supports to the building structure or to the piping itself should be avoided or used only with the approval of the responsible engineers. Variable spring and constantsupport type hangers should normally be installed with locking pins in place, assuring that they function as a rigid support during the erection cycle. Where welded attachments to the pipe are involved, it is preferred that they be installed in the shop as part of the subassembly. If possible, the major components of the system should be erected in their approximate final position prior to the start of any welding. This will reveal any unusually large discrepancies which may result from equipment mislocation, fabrication error, or tolerance accumulations. Adjustments or corrections can then be decided upon. Long, multiplane systems can absorb considerable tolerance accumulation without the need to modify any part. Short, rigid systems may not be able to accommodate any tolerance accumulation, and it may be necessary to rework one or more parts.

Cold Spring

Both the B31.1 and B31.3 Codes address cold springing in detail. Cold spring is the intentional stressing and elastic deformation of the piping system during the erection cycle to permit the system to attain more favorable reactions and stresses in the operating condition. The usual procedure is to fabricate the system dimensions short by an amount equal to some percentage of the calculated expansion value in each direction. The system is then erected with a gap at some final closure weld, equal to the ‘‘cut shorts’’ in each direction. Forces and moments are then applied to both ends as necessary to bring the final joint into alignment. Once this is done, it is usually necessary to provide anchors on both sides of the joint to preserve alignment during welding, postweld heat treatment, and final examination. When the weld is completed and the restraining forces are removed, the resulting reactions are absorbed by the terminal points, and the line is in a state of stress. During start-up the line expands as the temperature increases, and the levels of stress and terminal reactions resulting from the initial cold spring will decrease. For the 100 percent cold sprung condition, the reactions and stress will be maximum in the cold condition and theoretically zero in the hot condition. It should be borne in mind that it is very difficult to assure that a perfect cold spring has been attained and for this reason the codes do not permit full credit in the flexibility calculations. Also remember that lines operating in the creep range will ultimately attain the fully relaxed condition. Cold spring merely helps it get there faster. Cold spring was historically applied to high-temperature systems such as main steam and hot reheat lines in central power stations, but this practice is not as prevalent anymore.

For those involved with the repair of lines which have been cold sprung, or which have achieved some degree of creep, caution should be exercised when cutting into such lines since the line will be in a state of stress when cold. The line should be anchored on either side of the proposed cut to prevent a possible accident.

Joint Alignment

In aligning weld joints for field welding it may be necessary to compromise between a perfect weld fit-up and the location of the opposite (downstream) end of the assembly. The weld bevel may not be perfectly square with the longitudinal axis of the assembly. Even a 1/32-in (0.8 mm) deviation across the face of the weld bevel can result in an unacceptable deviation from the required downstream location if the joint is aligned as perfectly as possible. Often such a small gap can be tolerated in the welding. If, in order to maintain the downstream location, the gap at the joint is excessive, the joint should be disassembled, and the land filed or ground as needed to attain the required alignment of the weld joint while still maintaining the required downstream position. Flanged connections should be made up handtight so that advantage can be taken of the bolt-hole clearances to translate or rotate the assembly for better alignment of downstream connections.

Weld shrinkage of field welds may or may not be important in field assembly. In long flexible systems, they may be ignored. For more closely coupled systems, particularly those using GTAW root-pass welding, this factor should be considered. The degree of longitudinal shrinkage across a weld varies with welding process, heat input, thickness, and weld joint detail. See the section ‘‘Layout, Assembly, and Preparation for Welding.’’ In extreme cases closure pieces may be used. Here, the system is completed except for the final piece. A dummy assembly is then fabricated in place and the closure assembly is fabricated to match the dimensions of the dummy assembly with weld shrinkage of the final welds taken into account.

Just to remembering, that what we explain here is according to the ASME Standard.

Cleaning and Packaging

Cleaning and Packaging. Cleaning and Packaging is one of the important aspect that we have to know in Piping and Fabrication, because we need to know what is the best material and way to make good Cleaning and Packaging. Cleanliness of piping subassemblies is a matter of agreement between the fabricator and purchaser. As a minimum the fabricator will clean the inside of the subassembly of loose scale, weld spatter, machining chips, etc., usually with jets of compressed air. For those systems which require a greater degree of cleanliness several options are available. For specific information refer to PFI Standard ES-5 ‘‘Cleaning of Fabricated Pipe.’’39 See also the following specifications published by the Steel Structures Painting Council:

SSPC—SP 2 Hand Tool Cleaning
SSPC—SP 3 Power Tool Cleaning
SSPC—SP 6 Commercial Blast Cleaning
SSPC—SP 8 Pickling
SSPC—SP 10 Near-white Blast Cleaning

For ferritic steels the inside surfaces may be cleaned by turbinizing to remove loosely adhering mill scale and heavy rust. Wire brushing and grinding may also be employed for removal of more tightly adhering scale, rust, etc.; however, the most effective method for removal of tight scale is blasting with sand, shot, or grit.

For guidance on blasting methods and degrees of cleanliness refer to PFI Standard ES-29 ‘‘Abrasive Blast Cleaning of Ferritic Piping Materials.’’ Pickling is an equally effective method of cleaning. It is most often used for cleaning large quantities of straight tubes prior to fabrication or small-size (about NPS 4) subassemblies where blasting is not as effective. Its application is limited by the availability and size of pickling tanks. A hot solution of sulfuric acid (H2SO4) is most commonly used, although cold hydrochloric acid (HCl) is also recommended. See SSPC—SP 8 ‘‘Pickling.’’

For the 9Cr-1Mo-V materials, aluminum-oxide or silicon-carbide grit, sand or vapor blasting is preferred. Steel shot or grit which has been previously used to clean iron-bearing materials should be avoided. Acid pickling should also be avoided since damaging hydrogen embrittlement may occur. Austenitic stainless steels normally do not require cleaning except for a degreasing with solvent-saturated cloths to remove traces of greases or cutting oils. Subassemblies which have been heated for bending or which have been given a carbide solution heat treatment will have a tightly adhering chromic oxide scale. Pickling and passivating in a solution of hydrofluoric and nitric acid will remove the scale and passivate the exposed surface. Here again, the equipment for pickling may limit the size of the subassembly. See ASTM A 380 published by the American Society for Testing Materials.42 Blasting may also be used, but new silica sand or aluminum-oxide grit is required. Sand or grit previously used on ferritic pipe will contaminate the pipe surface with iron particles, and it will subsequently rust. The blasted surface should be treated with a solution of nitric acid to passivate the surface.

For extreme cleanliness, steam degreasing and rinsing with demineralized water may be employed. The external surfaces of pipe may be left as is, painted, or otherwise preserved. See PFI Standard ES-34 ‘‘Painting of Fabricated Piping.’’ Depending on the need for maintaining rust-free interior surfaces, the pipe inside diameter may be coated with different preservatives, or desiccants may be employed during shipping and storage. For shipping, the ends of subassemblies are equipped with some type of end protection to preclude damage to weld end bevels or flange faces during shipment and field handling. See PFI Standard ES-31 ‘‘Standard for Protection of Ends of Fabricated Piping Assemblies.’’

During shop operations, it is common practice to move piping assemblies with overhead or floor cranes, usually with chain or wire rope slings. For austenitic stainless steels and nonferrous materials which could be damaged or contaminated, use of nylon slings is recommended.

Methodology on Piping and Fabrication

Methodology is one of the important thing that we have to know in Piping and Fabrication Systems. There is so many thing and knowledge that we can read here only on Piping & Fabrication.

The ASME Boiler and Pressure Vessel, B31.1 and B31.3, require certain NDEs to be performed in accordance with the methods described in ASME Section V Nondestructive Examination. The pipeline codes, B31.4, B31.8, and B31.11, refer to API-1104 for Radiographic Procedures. In some cases, particularly in visual examination, requirements are given but no specific methodology is stated. In others, alternative parameters or qualification requirements are given. The specific requirements of the individual codes should be consulted.

Qualification Requirements. Qualification of procedures and personnel used in NDEs are required by most codes. When ASME Section V orAPI-1104 are invoked by the referencing code, a written procedure is required and it must be demonstrated to the satisfaction of the AI, ANI, owner, or owner’s agent, whichever is applicable.

Similarly personnel who perform NDEs must be trained, qualified, and certified. The most frequently invoked qualification document is SNT-TC-1A; it is also accepted by B31.1 for qualification of personnel performing visual examinations. Some codes permit alternatives, such as AWS-QC-1

Table A
Acceptance Standards for Visual Examination
The following indications are unacceptable:
1. Crack(s) on external surfaces
2. Undercut on surface greater than 1⁄32 in (1.0 mm) deep
3. Weld reinforcement greater than specified in ASME Table 127.4.2
4. Lack of fusion on surface
5. Incomplete penetration (applies only when inside surface is readily accessible)
6. Any other linear indications greater than 3⁄₁₆ in (5.0 mm) long
7. Surface porosity with rounded indications having dimensions greater than 3⁄16 in (5.0 mm) or 4 or more rounded indications separated by 1⁄16 in (2.0 mm) or less edge to edge in any direction. Rounded indications are indications which are circular or elliptical with their length less than 3 times their width

Source: From ASME B31.1 1995 ed.

Extent of Examination. The applicable code will define the extent of examination required for piping systems under its coverage. The degree of examination and the examination method and alternatives are a function of the degree of hazard which might be expected to occur in the event of failure. Pressure, temperature, toxicity of the fluid, and release of radioactive substances are some of the considerations. Added layers of examinations may be required as the perceived hazard increases.

Accept-Reject Criteria. The applicable code will also define the items to be examined and the accept-reject criteria to be applied. Table A shows the acceptance standards applicable to the visual examination of butt welds under B31.1. Other piping codes have similar but not necessarily identical criteria.

Table B shows acceptance standards for radiographic examination. Indications interpreted as cracks, incomplete penetration, or lack of fusion are not permitted. Porosity and elongated indications are kept within certain limits. The acceptance standards for ultrasonic examination are similar.

Table B
Acceptance Standards for Radiography
Welds that are shown by radiography to have any of the following types of discontinuities are unacceptable:
1. Any type of crack or zone of incomplete fusion or penetration
2. Any other elongated indication with a length greater than
a. 1⁄4 in (6.0 mm) for t up to 3⁄₄ in (19.0 mm)
b. 1⁄3 t for t from 3⁄4 in (6.0 mm) to 21⁄4 in (57.0 mm) inclusive
c. 3⁄4 in (19.0 mm) for t over 21⁄4 in (57.0 mm) where t is the thickness of the thinner portion of the weld
3. Any group of indications in a line that have an aggregate length greater than t in a length of 12 t, except where the distance between successive indications exceeds 6L where L is the longest indication in the group
4. Porosity in excess of that shown as acceptable in Appendix A-250 of Section I of the Boiler and Pressure Vessel Code
5. Root concavity when there is an abrupt change in density indicated on the radiograph

Table C
Acceptance Standards for Magnetic Particle and Liquid Penetrant Examinations
The following relevant indications are unacceptable:
1. Any cracks or linear indications
2. Rounded indications with dimensions greater than 3⁄16 in (5.0 mm)
3. Four or more rounded indications in a line separated by 1⁄16 in (2.0 mm) or less edge
to edge
4. Ten or more rounded indications in any 6 in2 (3870 mm2) of surface with the major dimension of this surface not to exceed 6 in (150 mm) with the area taken in the most unfavorable location relative to the indications being evaluated

Both magnetic particle and liquid penetrant examinations have identical limits. See Table C, Other types of NDEs, such as acoustic emission, bubble testing, and mass spectrometer testing, are not required by the various codes. They can be invoked by contract and the acceptance standards must be a matter of agreement between the contracting parties.

Testing. All of the piping codes outline some type of pressure test to determine leak tightness. Since the completed piping system is usually subjected to some type of test in the field after installation, shop testing of subassemblies is infrequent. In those cases where the assembly cannot be field tested, where welds in the assembly will not be exposed for examination during the field test, and in other special situations, shop testing may be required. Shop testing must meet all of the requirements for field testing. See the section ‘‘Installation’’ for particulars.

Quality Assurance and Quality Control. ASME Section III has very specific requirements for QA programs. ASME Section I has requirements for QC programs. The B31 Piping Codes do not require any formal written program at this time. Refer to these codes for detailed information on this subject.

Examination on Piping and Fabrication

Examination, this chapter like I promise in the last post, Piping and Fabrication will gave to you, I think the description and explanation about The Examination on Piping & Fabrication is detail enough, enjoy your self.
Types of Examinations. When used in the various codes, examination refers to the verification work performed by employees of the fabricator, much of which falls into the category of NDE. NDEs most often referenced by code and applied to the fabrication and installation of piping components and systems are:
•    Visual
•    Radiographic
•    Ultrasonic
•    Liquid penetrant
•    Magnetic particle
Eddy current examination is often used to evaluate the quality of straight lengths of pipe as they are manufactured but is not often used in fabrication activities. Although not referenced by most codes, bubble testing, halogen diode probe testing, or helium pass spectrometer leak testing may be invoked by contract when, in the opinion of the designer, they will contribute to the integrity of the system. While these methods are referred to as leak tests, their methodology is outlined in Article 10 of ASME Section V Nondestructive Examination.

Accept-reject criteria and the extent to which the various NDEs are to be applied are in the applicable code. The following are brief descriptions of NDEs as they apply to piping. For much more detailed information the reader is referred to various publications of the American Society for Nondestructive Testing (ASNT),36 particularly the Nondestructive Testing Handbooks.

1. Visual examination: Visual examination is probably the oldest and most widely used of all examinations. It is used to ascertain alignment of surfaces, dimensions, surface condition, weld profiles, markings, and evidence of leaks, to name a few. In most instances the manner of conducting a visual examination is left to the discretion of the examiner or inspector, but more recently, written procedures
outlining such things as access, lighting, angle of vision, use of direct or remote equipment, and checklists defining the observations required are being used. Visual examination takes place throughout the fabrication cycle along with QA and QC checks. At setup, this would consist of verifying materials, weld procedures, welder qualifications, filler metal, and weld alignment, and on completion of fabrication, such things as terminal dimensions, weld profile, surface condition, and cleanliness.

2. Radiographic examination: When the need for greater integrity in welding must be demonstrated, the most frequently specified examination is radiography. Since the internal condition of the weld can be evaluated, it is referred to as a volumetric examination.

Radiographic sources used for examination of piping are usually X-rays or gamma rays from radioactive isotopes. While X-ray equipment is often used, it has limitations in that it often requires multiple exposures for a single joint, and special equipment, such as linear accelerators, are needed for heavier thicknesses. Although X-ray machines produce films with better clarity, they are not as practical in the field because of space limitations and portability. In the field, radioactive isotopes are used almost exclusively because of their portability and case of access. For wall thicknesses up to about 21⁄₂ in (63.5 mm) of steel, the most commonly used isotope is iridium 192. Beyond this cobalt 60 is used for wall thickness up to about 7 in (179 mm).

Radioactive sources normally used in piping work range in intensity from a few curies up to about 100 curies. Each source decays in intensity in accordance with its particular half-life. As the intensity decays, longer exposure times are required. Iridium 192 has a half-life of 75 days, while cobalt 60 has a 5.3-year half-life. Radioactive sources have finite dimensions and as a result produce a shadow effect on the film. This is referred to as geometric unsharpness, and it is directly proportional to the source size and inversely proportional to the distance between the source and the film. ASME Section V has established limits for geometric unsharpness.

Ideally for pipe, the source is placed inside the pipe and at the center of the weld being examined, with film on the outside surface of the weld, thus permitting one panoramic exposure. Where geometric unsharpness precludes this practice, the source may be placed on the inside on the opposite wall and a portion of the weld is shot. Several exposures will be needed. The source may also be placed outside the pipe and the exposure made through two walls. Again this requires multiple exposures and longer exposure times. A radiograph is considered acceptable if the required essential hole or wire size information on this subject.

3. Ultrasonic examination: Ultrasonic examination is used in piping for the detection of defects in welds and materials as well as for determining material thickness. A short burst of acoustic energy is transmitted into the piece being examined and echoes reflect from the various boundaries. An analysis of the time and amplitude of the echo provides the examination results.

A clock in the equipment acts to initiate and synchronize the other elements. It actuates a pulsar to send a short-duration electrical signal to a transducer, usually at a frequency of 2.5 MHz. The transducer converts the electrical signal to mechanical vibration. The vibration as ultrasound passes through a couplant (such as glycerine) and through the part at a velocity which is a function of the material. As the
sound reflects from various boundaries, it returns to the initiating transducer or sometimes to a second one where it is converted back to an electrical signal which is passed to a receiver amplifier for display on a cathode-ray tube. The horizontal axis of the display relates to time and the vertical axis relates to amplitude. The indication on the extreme left will show the time and amplitude of the signal transmitted from the transducer. Indications to the right will show the time and degree of reflection from various boundaries or internal discontinuities. The ability of an ultrasonic examination to detect discontinuities depends a great deal on the part geometry and defect orientation. If the plane of the defect is normal to the sound beam, it will act as a reflecting surface. If it is parallel to the sound beam, it may not present a reflecting surface and accordingly may not show on the oscilloscope. Therefore, the search technique must be carefully chosen to assure that it will cover all possible defect orientations.

The most serious defect in a pipe butt weld is that which is oriented in the radial direction. The most commonly used technique for detecting such defects is the shear wave search. In this procedure, the transducer is located to one side of the weld at an angle to the pipe surface. The angle is maintained by a lucite block which transmits the sound from the transducer into the pipe. The sound will travel at an angle through the pipe and weld. Being at an angle, it will reflect from the pipe surfaces until it is attenuated. Any surface which is normal to the beam, however, will reflect a portion of the sound back to the transducer and show as an indication on the oscilloscope. If the beam angle and the material thickness are known, the reflecting surface can be located and evaluated.

Prior to and periodically during each search, the equipment is calibrated against artificial defects of known size and orientation in a calibration block. The block must be representative of the material being searched (i.e., an acoustically similar material, with appropriate thickness, outside contour, surface finish, and heattreated condition). A variation of ultrasonic examination can be used to measure material thickness. If the speed of sound within the material is known, the time it takes for the signal to traverse the thickness and return can be converted to a thickness measurement.

4. Liquid penetrant examination: Penetrant-type examinations are suitable for surface examinations only but are very sensitive. They require a fairly smooth surface, since surface irregularities such as grinding mark indications can be confused with defect indications. The surface to be examined is thoroughly cleaned with a solvent and then coated with a penetrating-type fluid. Sufficient time is allowed to permit the fluid to penetrate into surface discontinuities. The excess penetrant is removed by wiping with cloths until all evidence of the penetrant is removed. A developer which acts somewhat like a blotter is then applied to the surface. This an indication. Obviously, the success of the examination depends on the visibility of the indication. To enhance this, the penetrant contains colored dyes which can be seen under normal light, or fluorescent dyes which are viewed under ultraviolet light. The most common case is a red dye penetrant with a white developer.

        FIGURE A6.26 Ultrasonic shear wave search. (a) Search arrangement; (b) oscilloscope

5. Magnetic particle examination: Magnetic particle examination is essentially a surface-type examination, although some imperfections just below the surface are detectable. This type of examination is limited to materials which can be magnetized (paramagnetic materials), since it relies on the lines of force within a magnetic field.

The item to be examined is subjected to a current which will produce magnetic lines of force within the item. The surface is then sprayed with a fine iron powder. The powder will align itself with the lines of force. Any discontinuity normal to the lines of force will produce a leakage field around it and a consequent buildup of powder which will pinpoint the defect. The examination must be repeated at 90° to detect discontinuities which were parallel to the original field. There are a great many variations of magnetic particle examination depending on the manner in which the field is applied and whether the particles are wet or dry and fluorescent or colored.

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.