Tolerances, Procedures and Travelers

After the holiday is finished, I will try to make another post about fabrication and today Piping & Fabrication will talk about Tolerances, Procedures and Travelers. I hope that would be enough for today.

Tolerances. In order to assure installation of a system within a reasonable degree of accuracy, all the components involved must be fabricated to some set of tolerances on those dimensions which affect the system length. Tolerances on valve dimensions are given in B16.34, those of welding fittings in B16.9, and those for flanges and flanged fittings in B16.5, B16.1, etc. The assembly of these components will result in ‘‘tolerance stack-up,’’ which could have a significant impact on the overall dimensions, particularly in a closely coupled system.

Dimensioning

Piping subassembly tolerances normally conform to PFI-ES-3 ‘‘Fabricating Tolerances.’’ Usually the terminal dimensions are held to + 1/8 in, but can be held more closely upon agreement with the fabricator. In order to assure that tolerance stack-up is held to a minimum, the manner in which shop details are dimensioned should be carefully studied. As an example, assemblies with multiple nozzles can result in large deviations if these are dimensioned center to center. A better way is to select a base point and dimension all nozzles from this location. This assures that all nozzles are + 1/8 in (3.0 mm) from the base point.

For angle bends, terminal dimensions and often a chord dimension are required, since a small variation in angle with long ends can result in serious misalignment.  Sometimes assemblies which have been fabricated within tolerance may not fit in the field because of tolerance stack-ups on equipment to which they are attached. This will be addressed in the section, ‘‘Installation.’’

Procedures and Travelers. The need to assure better control of fabrication processes has led the use of written procedures for most operations. Fabricators will have a library of written procedures controlling cutting, welding, bending, heat treatment, nondestructive examination, and testing. Welding procedures in most codes are qualified under ASME Section IX, which requires written Welding Procedure Specifications (WPSs) backed up by Procedure Qualification Records (PQRs).

Similarly ASME Section V requires NDE to be performed to written procedures. Frequently, piping fabricators use a system of travelers to control flow through the shop. This practice is well-suited to fabrication of piping subassemblies under QA or QC programs, where record keeping is required. It also affords the purchaser and the third-party inspector opportunities for establishing ‘‘hold points’’ where they may wish to witness certain operations or review certain records.

FABRICATION & DRAWING

FABRICATION
Drawings
Installation Drawings. Current industry practice is for the designer to prepare plans and sections or isometric drawings of the required piping system. These, together with line specifications, outline all the requirements needed for the fabrication and installation. Usually the weld bevel requirements for field welds are specified to assure compatibility between all the system components to be field welded.
Frequently the shop welding bevels are left to the discretion of the fabricator, provided, of course, the required weld quality is attainable. Location and numbers of field welds are an economic consideration of available pipe lengths, shipping or heat-treating limitations, and field installation limitations.

Shop Details. A piping system prefabricated at a commercial pipe fabrication shop is usually divided into subassemblies or spools. The manner in which a system is divided depends on many factors: available
lengths of straight pipe, dimensional and weight limitations for shipping and heat treatment, field welding clearance requirements, and sometimes scheduling needs. Bending, forging, special heat treatment, cleaning, and as much welding as possible are normally performed in the shop. Every attempt is made to minimize the number of field welds, but this must be balanced economically against the added costs of transportation and greater field rigging problems because of larger, heavier, more complex assemblies. Where the site conditions are adverse to normal field erection practices, much of the plant can be fabricated in modules for minimal onsite installation work. Once the number and locations of field welds have been decided, the fabricator will prepare detailed drawings of each sub assembly.

Each sub assembly drawing will show the required configuration; all necessary dimensions required for fabrication; reference to auxiliary drawings or sketches; size, wall thickness, length, alloy, and identification of the materials required; code and classification; reference to special forming, welding, heat treatment, NDE, and cleaning requirements; need for third-party inspection; weight and piece identification
number.

Materials Considerations

In Indonesia this week is a busy week, because we have to prepare for lebaran or a long holiday, and that's why piping & fabrication maybe will post only for few days, and after those post, will take a long holiday.

Materials Considerations
Piping systems are fabricated from a great variety of metals and nonmetals, material selection being a function of the environment and service conditions. Materials must conform to the standards and specifications outlined in the governing code. Some codes such as ASME Section III impose additional requirements on materials beyond those in the material specifications. All fabrication and installation practices applied to these materials must be conducted so as to assure that the final installation exhibits all of the properties implicit in the design. For example, hot bending of certain austenitic stainless steels in the sensitization range will reduce their corrosion resistance if they are not subsequently heat-treated. Accordingly, a heat treatment to restore these properties should be specified.

Consideration must also be given to the various types of piping products, their tolerances, alloys, heat-treated conditions, weldability, and formability. Pipe is made by a variety of processes and depending on the method of manufacture can have differing tolerances.

Most product forms also come in a variety of alloys, and the choice of a fabrication process may be governed by the alloy. ASME Section IX has developed a system of P Numbers and Group Numbers. This system groups material specifications by chemical composition and/or physical properties. Those with like compositions and properties are grouped together to minimize the number of welding procedure qualifications required. This method of grouping can also be applied to other fabrication processes as well.

Happy Holiday to all of you and thanks!

FABRICATION AND INSTALLATION OF PIPING SYSTEMS

Now we entering the new chapter of this blog, which is Piping & Fabrication blog and I wish this information will be useful to all of us and thanks for every support to this blog.

FABRICATION AND INSTALLATION OF PIPING SYSTEMS

INTRODUCTION
Background
The term fabrication applies to the cutting, bending, forming, and welding of individual pipe components to each other and their subsequent heat treatment and nondestructive examination (NDE) to form a unit (piping subassembly) for installation.
The term installation refers to the physical placement of piping subassemblics, valves, and other specialty items in their required final location relative to pumps, heat exchangers, turbines, boilers, and other equipment; assembly thereto by welding or mechanical methods; final NDE; heat treatment; leak testing; and cleaning and flushing of the completed installation.
Depending on the economics of the particular situation, fabrication may be accomplished in a commercial pipe fabrication shop, or a site fabrication shop, where portions of the piping system are fabricated into subassemblies or modules for transfer to the location of the final installation.
Commercial pipe shops have specialized equipment for bending and heat treatment which is not normally available at installation sites. They also have certain types of automatic welding equipment which permits welding to be performed more efficiently and economically than in field locations where fixed position, manual arc welding is most often employed.
As a general rule piping NPS 21⁄₂ (DN 65) and larger for nuclear and fossil power plants, chemical plants, refineries, industrial plants, resource recovery, and cogeneration units are most often shop fabricated. Piping NPS 2 (DN 50) and smaller is often shop fabricated where special heat treatment or cleaning practices may be required; otherwise it is field fabricated. Pipelines and other systems involving long runs of essentially straight pipe sections welded together are usually field assembled.
In recent years, the infusion of new bending technologies, new welding processes, new alloys, fracture toughness limitations, and mandatory quality assurance (QA) programs have made piping fabrication and installation much more complex than in the past. Greater emphasis is being placed on written procedures for QA and quality control (QC) programs, special processes, and qualification and certificationof procedures and personnel.
Improper selection of fabrication or installation practices can result in a system which will not function properly or will fail before its expected life span. Accordingly, fabrication and installation contractors must work closely with the designer and be aware of the mandatory requirements of the applicable codes, the unique requirements and limitations of the materials, and those of the fabrication and installation techniques being applied.

Codes and Standards Considerations
A great many codes and standards apply to piping. These are discussed in detail in Chap. A4. It is incumbent on the fabricator and/or installer to be familiar with the details of these codes and standards since some codes have the force of law. As an example, the ASME B31.1 Power Piping Code1 is referenced by ASME Section I Power Boilers2 for piping classed as Boiler External Piping. The latter, which is law in most states and Canadian provinces, contains rules for code stamping, data reports, and third-party inspection. Piping under ASME Section III3 also has legal standing.
Most other piping codes are used for contractual agreements. Most codes reference ASME SectionV4 for nondestructive examination methodology and ASME Section IX5 for welding requirements. Each of the codes covers a different piping application, and each has evolved in a different way over the years. For specific practices, some have mandatory requirements, while others only have recommendations. Heat treatment requirements may vary from one to another. The manner in which the code-writing bodies have perceived the hazardous nature of different applications has led to differing NDE requirements.

Generally, the codes are reasonably similar, but the owner, designer, fabricator, and installer must meet the specifics of the applicable code to ensure a satisfactory installation. It is essential that the designer be very familiar with the code being used and that purchasing specifications for material, fabrication, and installation be very specific. Reference to the code alone is not sufficient. In the design, a particular allowable stress for a specific material, grade, type, product form, and/or heat-treated condition was selected. The specifications issued for material purchase and fabrication must reflect these specifies to assure that the proper materials and fabrication practices are used.

As an example: Type 304 stainless steel has a specified carbon content of 0.08 percent maximum. There is no specified minimum. Footnotes in the B31.1 Code Allowable Stress Tables for Type 304 indicate that for use over 1000°F (538°C), the allowable stresses apply only when the carbon content is 0.04 percent or higher.

It is essential that this requirement be put in the purchasing specification if the design temperature exceeds 1000°F (538°C). Similarly, in the B31.1 Code, low chrome alloy electric fusion welded pipe has
differing allowable stresses depending upon whether the plate from which it was made was annealed or normalized and tempered. If this material is to be heated above the lower critical temperature during fabrication by hot bending or forming, the designer should specify a postbending heat treatment appropriate for the allowable stress level used in the design.

It is also incumbent upon the fabricator and/or installer to be very familiar with the applicable code. Each project should be reviewed in detail. ‘‘Standard shop practices’’ may not always produce the desired result. Communication between the designer, fabricator, and installer is essential. All should be familiar with the various standards used in piping design. Most piping systems are composed of items which conform to some dimensional standards such as ASME B36.10M6 and ASME B36.19M for pipe, B16.57 for flanges, etc. Other dimensional standards are issued by the Manufacturers Standardization Society (MSS)8 and the American Petroleum Institute (API).

The Pipe Fabrication Institute (PFI)10 publishes a series of Engineering Standards which outline suggested practices for various fabrication processes. These standards give excellent guidance for many aspects of piping fabrication not covered by the codes.

The American Welding Society (AWS)11 publishes a number of recommended practices for welding of pipe in various materials.

COMMERCIAL PIPE AND TUBE SIZES AND TUBULAR PRODUCT CLASSIFICATION

Finally Piping & Fabrication has finish this chapter about Manufacturing of Metallic Pipe and this is the last post of this chapter.

COMMERCIAL PIPE AND TUBE SIZES
The standard pipe sizes and other pipe properties are given in App. E2 and E2M, and the standard tube sizes and other tube properties are given in App. E3 and E3M.

TUBULAR PRODUCT CLASSIFICATION
Pipe and tubing are considered to be separate products, although geometrically they are quite similar. ‘‘Tubular products’’ infers cylindrical products which are hollow, and the classification of ‘‘pipe’’ or ‘‘tube’’ is determined by the end use.

Piping Classification
Tubular products called pipe include standard pipe, conduit pipe, piling pipe, transmission (line) pipe, water-main pipe, oil country tubular goods (pipe), water-well pipe, and pressure pipe. Standard pipe, available in ERW or seamless, is produced in three weight (wall-thickness) classifications: standard, extra strong, and double extra strong (either seamless or welded). ASTM and the American Petroleum Institute (API) provide specifications for the many categories of pipe according to the end use. Other classifications within the end use categorization refer to the method of manufacture of the pipe or tube, such as seamless, cast, and electric resistance welded. Pipe and tube designations may also indicate the method of final finishing, such as hot finished and cold finished.

Tubing Classification
Pressure tubes are differentiated from pressure pipe in that they are used in externally fired applications while carrying pressurized fluid inside the tube. Structural tubing is used for general structural purposes related to the construction industry. ASTM provides specifications for this type of tubing. Mechanical tubing is produced to meet particular dimensional, chemical, and mechanical property and finish specifications which are a function of the end use, such as machinery and automotive parts. This category of tubing is available in welded (ERW) and seamless form.

SPECIALTY TUBULAR PRODUCTS
There are many specialty tubular products designed for special applications requiring unique manufacturing methods for production. Examples are the rifled boiler tube, the finned heat-exchanger tube, the duplex tube, and the double-wall tube.

FIGURE A5.10 Single rifled boiler tube

The rifled boiler tube (Fig. A5.10) is used to provide an improved heat transfer surface on the inner surface of a boiler tube. The rifling twist, similar to that of a rifle, is produced by specially shaped mandrels over which the tube is drawn. The finned heat exchanger (Fig. A5.11) tube provides improvement in thermal efficiency by providing an extended surface from the base tube surface. The extended surface is produced by turning the tube through special sets of dies which raise fins from part of the base tube material. These fins can be coarse or fine depending on the equipment developed for producing fins.

Duplex or composite tubes have been developed to provide a different material on the inside and outside of the tube to meet the requirements of a different environment on either side of the tube. One method of producing a composite tube is by providing a bimetal mother tube before the extrusion or drawing process. Careful development of this process will yield a composite tube with an excellent bond between the two materials.

FIGURE A5.11 Finned heat-exchanger tube

Double-wall tubes (Fig. A5.12) are used in applications requiring leak detection to avoid a catastrophic mixture of the fluids on either side of the tube. An inert detecting gas can be placed in the annulus between the two tubes to sense very small amounts of leakage from either tube so as to allow careful shutdown of the system. This tube is manufactured by inserting one tube inside the other, then drawing the combined tube through dies or over mandrelswhich provide a calibrated prestress between the two tubes. This type of tube was developed for application to a fast breeder reactor sodium-water steam generator.

FIGURE A5.12 Double-wall leak-detecting tube

ENGINEERING SELECTION OF PIPE MANUFACTURING METHODS
The selection of the appropriate pipe manufacturing method by the design engineering specification deserves consideration. For many applications, the codes and standards specified in the procurement contract provide for little room to select an optimal manufacturing method. The safest procedure is to obtain the price and schedule from suppliers before firming the piping specifications. At times the selection of the pipe with the best manufacturing process might be tempered by project cost or delivery considerations. In such cases, much is required of the engineer to consider whether lesser quality will be able to meet the desired reliability standard.
It therefore is essential that the engineer is aware of the alternates and their operating history of success and failure before an appropriate alternative decision can be accepted. It must also be recognized that choices based on economic considerations alone may prove to be the more costly in the face of the downtime costs of failure.

Nickel and Nickel-Alloy Pipe and Tube

Nickel and Nickel-Alloy Pipe and Tube
Nickel and nickel-alloy pipe and tube, because of their high strength and generally good resistance to oxidation and corrosion, are used in the chemical industry and in steam-generation equipment for nuclear power-generation plants. Applications of nickel are found in tubes and pipe of pure nickel and binary and tertiary alloys of nickel, such as Ni-Cu (Monel 400 and Monel K-500), Ni-Mo and Ni-Si (Hastelloy B), Ni-Cr-Fe (Inconel 600 and Inconel 800), and Ni-Cr-Mo (Hastelloy C276 and Inconel 625) alloys. The alloys are used in applications requiring corrosion resistance to water, acids, alkalis, salts, fluorides, chlorides, and hydrogen chloride. The alloy must be carefully selected to provide for resistance to the specific corrosion media found in the environment.

Nickel and nickel-alloy pipe and tube are produced by the Ugine-Sejournet extrusion process, in which a shell is formed by hydraulic piercing of a billet by a ram and subsequent extrusion. Alternately, the billet may be initially pierced by means of drilling.

Titanium and Titanium-Alloy Tube and Pipe
Titanium and its alloys have provided the engineering designer with an important alternative to aluminum. They are lightweight and have high strength at moderately elevated temperatures, good toughness, and excellent corrosion resistance. Their applications have been found in a wide range of industries, including aerospace, heat-exchange equipment, chemical plants, and power-generation facilities.

There is a wide range of alloying systems to which titanium may be produced. The alloying elements possibly include aluminum, molybdenum, nickel, tin, manganese, chromium, and vanadium. UNS numbers are used to identify the many available alloys and forms of titanium. Titanium and alloys of titanium pipe and tube are produced from a melt of raw titanium ‘‘sponge’’ and alloying metals in a vacuum electric arc furnace. An ingot is obtained which is reduced to a billet. The billet provides the stock for the extrusion process, from which the tube or pipe is formed. The process consists of initially piercing the billet, then passing a heated shell through a die and over a mandrel.

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NONFERROUS PIPE-MAKING PROCESSES

Well, I think it's true that I've been a little bit lazy for few months and that's really make myself not good at all and I think today is the right time to stop all the lazyness in me because I really want to change this way of life and make a better ones, and I will start with publish this piping and fabrication blog and the rest will coming.

NONFERROUS PIPE-MAKING PROCESSES
Aluminum and Aluminum Alloy Tube and Pipe
Aluminum tubular products include both pipe and tube. They are hollow-wrought products produced from a hollowed ingot by either extrusion or by welding flat sheet, or skelp, to a cylindrical form. General applications are available in alloys 1100, 2014, 2024, 3003, 5050, 5086, 6061, 6063, and 7075. For shell and tube heat exchanger applications, alloys 1060, 3003, 5052, 5454, and 6061 are available. Pipe is available only in alloys 3003, 6061, and 6063. The designation numbers indicate the particular alloying element contained in the aluminum alloy (such as copper, manganese, silicon, magnesium, and zinc) and the control of the impurities. The numerical designation system consists of four numbers, abcd, where a designates the major alloying element in the aluminum alloy: 1 for 99 percent pure aluminum, 2 for copper, 3 for manganese, 4 for silicon, 5 for magnesium, 6 for magnesium and silicon, 7 for zinc, and 8 for another element. Digit b designates an alloy modification for groups 2 through 8 and an impurity limit for group 1. Digits c and d indicate the specific alloy for groups 2 through 8 and the purity of group 1.

Copper and Copper Alloy Tube and Pipe
Copper tube and pipe have a wide range of application throughout the chemical, process, automotive, marine, food and beverage, and construction industries. Unified Numbering System (UNS) designations (CXXXXX) have been established for many alloys of copper. ASTM and ASME specifications have been developed for copper tube and pipe. Seamless pipe and tube are covered by ASTM B466, B315, B188, B42, B302, B75, B135, B68, B360, B11, B395, B280, B306, B251, B372, and B88. ASME specifications include SB466, SB315, SB75, SB135, SB111, SB395, and SB359.

Tubes and pipe of copper and copper alloys are produced by either of two processes—piercing and extrusion, or welding skelp formed into cylindrical shape. The seamless pipe or tube produced through the extrusion process is the most common commercial form of copper and copper alloy tubular products.

Hot Piercing Process. In theMannesmann piercing process, a heated copper billet is first pierced, then rolled over a mandrel which determines the inside diameter of the pipe. Following the piercing operation, the pierced shell is drawn through a die and over a plug to obtain the finished outside and inside diameters. Extrusion Process. In the extrusion process, the heated copper or copper alloy billets are formed into shells by heavy hydraulic presses. The hollowed-out billet is then extruded through a die and over a mandrel to form the outside and inside diameters of the pipe.

Cold-Drawing Process. The cold-drawing process uses mother pipe which is placed on a draw bench which pulls a cold tube through one or a multiplicity of dies and over a mandrel to reduce the pipe gradually to its finished dimensions.

Other Processes. Other processes of significance are the cup-and-draw process for large-diameter pipe and the tube-rolling process which reduces copper tubing by means of cold-working over a mandrel with oscillating tapered dies.