An Introduction To Pipe And Tube Types . Selection .Calculation .uses And Specifications
Introduction:
A pipe: is round tubular section or hollow cylinder used mainly to convey media. It may also be used for structural applications; however, in this instance we will concentrate on its use in the process industry. Pipe is generally manufactured to several long-standing and broadly applicable industrial standards. While similar standards exist for specific industry application tubing,
A tube: is often made to custom sizes and a broader range of diameters and tolerances. Many industrial and government standards exist for the production of pipe and tubing. The term "tube" is also commonly applied to non-cylindrical sections (i.e. square or rectangular tubing).
Fig 1
1- Difference Between Pipe and Tube
In general practice the designations pipe and tube are almost interchangeable, but in the pipe fitting industry and engineering discipline the terms are uniquely defined. The main difference between a pipe and a tube is the way the diameter of the pipe or tube is designated. Pipe is normally designated by a ‘Nominal Pipe Size’ (NPS) based upon the ID (inside diameter) of the most common wall thickness while the tube is designated by the measured OD (outside diameter). FIG 2Pipe
Depending on the applicable standard to which it is manufactured, pipe is specified by the internal diameter (ID) and a wall thickness, the inside diameter called the nominal diameter may not exactly match the pipe size as it varies with the wall thickness. For example, the ID of an 8” pipe varies from 213.54mm ID for Sch5 pipe to 193.68mm for Sch40 pipe.
Tube
Tube is most often defined by the outside diameter (OD) and a wall thickness. Therefore 8” tube would have an outside diameter of 203.2mm
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| Fig 2 |
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.
2-1 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,
- pressure pipe. Standard pipe, available in ERW or seamless, is produced in three weight (wall-thickness) classifications:
- standard, (std)
- extra strong, (xs)
- double extra strong (either seamless or welded). ( xxs )
ASTM and the American Petroleum Institute (API) provide specifications for the many categories of pipe according to the end use.
2-1-1 Common types of steel pipes
The common types of steel pipes are described below.
Standard pipe – It is standard weight, extra strong, and double extra strong welded or seamless pipe of ordinary finish and dimensional tolerances, produced in sizes up to 660 mm in nominal diameter, inclusive. This pipe is used for fluid conveyance and some structural purposes.
Conduit pipe – It is welded or seamless pipe intended especially for fabrication into rigid conduit, a product used for the protection of electrical wiring systems. Conduit pipe is not subjected to hydrostatic testing unless so specified. It can be galvanized or bare, as specified. It is furnished in standard weight pipe sizes from 6 mm to 150 mm in lengths of around 3 m to 6 m with plain ends or threaded ends.
Piling pipe – It is welded or seamless pipe for use as piles, with the cylinder section acting as a permanent load-carrying member or as a shell to form cast-in-place concrete piles. There are normally three grades, which have different minimum tensile strengths, a variety of diameters, ranging from 150 mm to 610 mm, and a variety of wall thicknesses. Ends can be plain or beveled for welding.
Pipe for nipples –It is standard weight, extra strong, or double extra strong welded or seamless pipe, produced for the production of pipe nipples. Pipe for nipples is normally produced in random lengths with plain ends and in nominal sizes from 3 mm to 300 mm. Close OD tolerances, sound welds, good threading properties, and surface cleanliness are essential in this product. Pipe for OCTG couplings are to be manufactured from seamless pipe. It is normally coated with oil or zinc and is well protected in shipment.
Transmission or line pipe – It is welded or seamless pipe presently produced in sizes ranging from 3 mm nominal to 1.2 m actual OD and is used principally for conveying gas or oil. Line pipe is produced with ends plain, threaded, beveled, grooved, flanged, or expanded, as required for various types of mechanical couplers or for welded joints. When threaded ends and couplings are needed, recessed couplings are used.
Water main pipe – It is welded or seamless steel pipe used for conveying water for municipal and industrial purposes. Pipe lines for such purposes are normally designated as flow mains, transmission mains, force mains, water mains, or distribution mains. The mains are generally laid underground. Sizes ranges from 40 mm to 2.45 m in nominal diameter in a variety of wall thicknesses. Pipe is produced with ends suitably prepared for mechanical couplers, with plain ends beveled for welding, or with bell and spigot joints for field connection. Pipe is produced in double random lengths of around 12 m, single random lengths of around 6 m, or in specified lengths. When required, it is produced with a specified coating or lining, or both.
Oil country tubular goods – OCTG is a collective term applied in the oil and gas industries to three kinds of pipe used in oil wells namely
(i) drill pipe,
(ii) casing, and
(iii)tubing.
The drill pipe is used to transmit power by rotary motion from ground level to a rotary drilling tool below the surface and to convey flushing media to the cutting face of the tool. Drill pipe is produced in sizes ranging from 60 mm to 170 mm in OD. Size designations refer to actual OD and weight per meter. Drill pipe is normally upset, either internally or externally, or both, and is prepared to accommodate welded-on types of joints.
4-1 Metallic Pipes
The pipes made of metal are known as metallic pipes. They can be grouped into two categories: Pipes made from ferrous materials, and Pipes made from non-ferrous materials.
4-1-1Type of Pipes made from ferrous materials:
These types of pipes are stronger and heavier. These pipes have iron as their main constituent element. Common examples of pipes made from ferrous materials are
9- 1 What is Nominal Pipe Size?
Nominal pipe size (NPS) is the number that defines the size of the pipe. For example, when you say 6” pipe, the 6” is the nominal size of that pipe. However, for the pipe sizes, NPS 14 and above Outside Diameter is the same as NPS. To understand this concept, you have to learn the way pipes are manufactured.
NPS is frequently referred as an NB (Nominal Bore). As such, there is no difference between NB and NPS. NB is also an American way to refer to pipe dimensions. I have also seen that when pipe dimensions are shown in mm (DN) people refer to pipe sizes in NB. So when someone says 25nb pipe or 50nb pipe, basically they are talking about DN.
9-3 What is DN (Diameter Nominal) Pipe Size?
DN or Diameter Nominal is an international designation (SI or Matric Designator) and a European NPS equivalent to show pipe sizes. Here, you have to note that DN shows pipe sizes differently than NPS.
Calculation formula for nominal pipeline wall:
9-4 What is Pipe Schedule?
Pipe Schedule Number is the standard method to define the thickness of the pipes used in Process Plants.
Standardization of wrought steel Pipe schedule and pipe sizes began with the mass production era. At that time, pipes were available in only three sizes standard weight (STD), extra-strong (XS), and double extra-strong (XXS), based on the iron pipe size (IPS) system.
With the modernizing of various industries and the use of pipes in different pressure and temperature conditions, three sizes are insufficient to meet the requirement. This will result in the concept of the schedule number that combines wall thickness and diameter of the pipe.
In current practice, pipe size defines by two sets of numberPipe bore/nominal diameter
The pipe schedule is nothing but the wall thickness of the pipe.
The pipe schedule (fig 14) is the way pipe wall thickness is mentioned. To simplify the ordering of the pipe ASME committee has developed Schedule Number, which is based on modified Barlow’s wall thickness formula.
10- Standard Color Codes of Piping Pipes in factories, plants
11- Steel Pipe Tolerances and Dimensional Standard
Why Are Dimensional Tolerances So Important?
Accurate dimensional control plays a crucial role in the structural stability, safety, and efficiency of steel pipe applications: Ensures Structural Integrity: Smaller deviations allow tighter fits and stronger overall structures.
Improves Weld Quality: Greater roundness and accurate alignment lead to more stable welds with reduced residual stress.
Facilitates Automated Assembly: Especially in projects like wind turbine towers and bridge supports, dimensional accuracy directly impacts assembly efficiency.
Enhances Post-Processing: Stable diameters and roundness support uniform galvanizing and coating distribution.
Water well pipe – It is a collective term applied to four types of pipes which are used in water wells, and these are
(i) type I, drive pipe,
(ii) type II, reamed and drifted pipe,
(iii) type III, driven well pipe,
(iv) type IV, casing pipe.
Drive pipe is used to transmit power from ground level to a rotary drill tool below the surface and to convey flushing media to the cutting face of the tool. The lengths of pipe have specially threaded ends that permit the lengths to butt inside the coupling. Drive pipe is produced in nominal sizes of 150 mm, 200 mm, 300 mm, 350 mm, and 400 mm OD. Driven well pipe is threaded pipe in short lengths used for the manual driving of a drill tool or for use with short rigs. It can be furnished in random lengths ranging from 0.9 m to 1.8 m or in random lengths ranging from 1.8 m to 3.0 m. Casing is used both to confine and conduct water to ground level and as a structural retainer for the walls of water wells. It is produced as threaded pipe in random lengths from 4.9 m to 6.7 m and in sizes from 90 mm to 220 mm in OD.
Pipe and tube designations may also indicate the method of final finishing, such as:
- hot finished
- cold finished.
2-2 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.
3- Pipe and tube types according to manufacturing:
1- Integrated Steel Manufacture2-Seamless pipes & tubes (Mannesmann process)
3-Seamless pipe pipes & tubes (hot extrusion ･ hot hollow forged)
4-Electric resistance-welded pipes & tubes
5-Hot electric resistance-welded pipes & tubes
6-Arc-welded pipes & tubes (SAWH pipe (by Spiral process))
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| Fig3 |
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| Fig 4 |
4- Pipe Types based on Material.
Pipes are normally classified based on the material which is used to produce the pipe during manufacturing. In general, there are two types of pipes fig 5:
Pipes are normally classified based on the material which is used to produce the pipe during manufacturing. In general, there are two types of pipes fig 5:
1-Metallic Pipes
2- Non-metallic Pipes
2- Non-metallic Pipes
3- clad pipes
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| Fig 5 |
4-1 Metallic Pipes
The pipes made of metal are known as metallic pipes. They can be grouped into two categories: Pipes made from ferrous materials, and Pipes made from non-ferrous materials.
4-1-1Type of Pipes made from ferrous materials:
These types of pipes are stronger and heavier. These pipes have iron as their main constituent element. Common examples of pipes made from ferrous materials are
* Carbon steel pipes
* Stainless steel pipes
* Alloy steel pipes
* DSS pipes
* Cast Iron pipes
* Galvanized Steel Pipes
* Ductile Iron pipes, etc
This category of pipes is suitable for higher temperature and pressure applications. Most of the pipes used in oil and gas, refineries, chemical, petrochemical, power plants, etc. are made of ferrous materials
* Stainless steel pipes
* Alloy steel pipes
* DSS pipes
* Cast Iron pipes
* Galvanized Steel Pipes
* Ductile Iron pipes, etc
This category of pipes is suitable for higher temperature and pressure applications. Most of the pipes used in oil and gas, refineries, chemical, petrochemical, power plants, etc. are made of ferrous materials
4-1-2 Type of Pipes made from Non-ferrous materials:
In this group of pipes, iron is not the main constituent element. They are usually made of copper, aluminum, brass, etc. Common pipes made from non-ferrous materials are
- Aluminum and Aluminum alloy pipes.
- Copper and copper alloy pipes.
- Nickel and Nickel alloy pipes.
- Titanium and titanium alloy pipes.
- Zirconium and Zirconium alloy pipes.
5-1 The most common types of seamless pipes are:
ASME B36.10 : Welded and Seamless Wrought Steel Pipe.
ASME B36.19 : Stainless Steel Pipes.
Y : Coefficient from Table 304.1.1,
Valid for t < D/6 and for materials shown. The value of Y may be interpolated for intermediate temperatures.
Calculated Design Wall Thickness should be added with Corrosion Allowance, Mechanical Allowance for Grooving, Threading etc and Manufacturing Tolerance to arrive at final value. Next higher standard thickness value from Pipe Standards such as ASME B36.10 and ASME B36.19 is used.
Designer should select a thickness from schedules of nominal thickness contained in Table 1 specified in ASME B36.10 and B36.19, to suit the value computed to fulfill the conditions for which the pipe is desired.
7-1 Force Main Pipe Material Selection and Sizing
The discharge pipe, commonly called a force main, is sized to convey the effluent economically from the pump to its ultimate point of discharge. The pipe material selected is based on flow rate, friction loss of the fluid in the pipe, chemical resistance to the effluent, and fluid velocity.
where:
In this group of pipes, iron is not the main constituent element. They are usually made of copper, aluminum, brass, etc. Common pipes made from non-ferrous materials are
- Aluminum and Aluminum alloy pipes.
- Copper and copper alloy pipes.
- Nickel and Nickel alloy pipes.
- Titanium and titanium alloy pipes.
- Zirconium and Zirconium alloy pipes.
4-1-3 Non-metallic Pipes
Non-metallic pipes are widely used for services where the temperature is not significant. Non-critical services like water industries and drainage systems make use of most of the non-metallic pipes. Common non-metallic and widely used pipes are:
- PE/HDPE Pipes
- uPVC/PVC/CPVC Pipes
- PP pipes
- Reinforced thermoplastic pipes or RTPs.
- ABS Pipes
- Composite pipes like GRE/GRP/FRP Pipes
- Cement and Asbestos Cement Pipes
- Vitrified clay pipes
5- Materials used for pipe and tube
Pipe can be made from a variety of materials. In the past, materials have included wood and lead (Latin for lead is plumbed; from this, the word plumbing has come). Nowadays several materials are used for the production of pipes. These materials are ceramics, fiberglass, concrete, plastics, and metals.
Concrete and ceramic pipes – Pipes can be made from concrete or ceramic materials. These pipes are normally used for low pressure applications such as gravity flow or drainage underground. Concrete pipes normally have a receiving bell or a stepped fitting, with various sealing methods applied at installation. Ceramic pipes are used for underground drainage which can be exposed to corrosive chemicals. These types of pipes are relatively inexpensive for the diameters in question and allow for ease of installation in rough site conditions.
Plastic pipes – Plastic pipe is widely used for its light weight, chemical resistance, non-corrosive properties, and ease of making connections. Plastic materials include PVC, CPVC, FRP, RPMP, PP, PE, PEX, PB, and ABS etc.
Metal pipes and tubes – Metallic pipes are commonly made from iron or steel with the metal chemistry and its finish being peculiar to the use fit and form. Typically metallic piping can be made of steel or iron, such as unfinished, black (lacquer) steel, carbon steel, stainless steel, or galvanized steel, brass, and ductile iron. Aluminum pipe or tube can be used where iron is incompatible with the service fluid or where weight is a concern. Aluminum is also used for heat transfer tubes such as in refrigerant systems. Copper tube is popular for domestic water (potable) plumbing systems. Copper can also be used where heat transfer is desirable (i.e. radiators or heat exchangers). Inconel, chrome molybdenum, and titanium steel alloys are used for high temperature and pressure piping in process systems where corrosion resistance is important.
Stainless steel pipes and tubes – Stainless steel pipes and tubes are used for a variety of reasons namely
(i) to resist corrosion and oxidation,
(ii) to resist high temperatures,
(iii) for cleanliness and low maintenance costs, (iv) to maintain the purity of materials which come in contact with pipe material. There are more than 60 grades of stainless steel available. The ability of stainless steel to resist corrosion is achieved by the addition of a minimum of 12 % chromium to the iron alloy. Additions of other elements affect other properties. The inherent characteristics of stainless steel permit the design of thin wall piping systems without fear of early failure due to corrosion. Because of the thinner wall thickness of stainless steel tube, it is not possible to thread tube and hence this is overcome by fusion welding to join such pipe and tube.
5- Materials used for pipe and tube
Pipe can be made from a variety of materials. In the past, materials have included wood and lead (Latin for lead is plumbed; from this, the word plumbing has come). Nowadays several materials are used for the production of pipes. These materials are ceramics, fiberglass, concrete, plastics, and metals.
Concrete and ceramic pipes – Pipes can be made from concrete or ceramic materials. These pipes are normally used for low pressure applications such as gravity flow or drainage underground. Concrete pipes normally have a receiving bell or a stepped fitting, with various sealing methods applied at installation. Ceramic pipes are used for underground drainage which can be exposed to corrosive chemicals. These types of pipes are relatively inexpensive for the diameters in question and allow for ease of installation in rough site conditions.
(i) to resist corrosion and oxidation,
(ii) to resist high temperatures,
(iii) for cleanliness and low maintenance costs,
Type 304 stainless is the most widely used analysis for general corrosive resistant pipe and tube applications. It is used in chemical plants, refineries, paper mills, and food processing industries. Type 304 has a maximum carbon content of 0.08 %. It is not recommended for use in the temperature range between 400 deg C and 900 deg C due to the carbide precipitation at the grain boundaries which can result in inter-granular corrosion and early failure under certain conditions. Type 304L is the same as 304 except that a 0.03 % maximum carbon content is maintained which precludes carbon precipitation and permits the use of this analysis in welded assemblies under more severe corrosive conditions. Type 318 is much more resistant to pitting than other chromium nickel alloys due to the addition of 2 % to 3 % of molybdenum. It is particularly valuable wherever acids, brines, sulphur water, seawater or halogen salts are encountered. Type 316 is widely used in the sulphite paper industry and for manufacturing chemical plant equipment, photographic equipment, and plastics. Type 316L, like 304L, is held to a maximum carbon content of 0.03 %. This permits its use in welded assemblies without the need of final heat treatment. It is used extensively for pipe assemblies with welded fitting.
5-1 The most common types of seamless pipes are:
ASTM A106, A333, A53, and API 5L (CS and LTCS pipes)
ASTM A312 Series 300 and 400 (SS pipes with grades 304, 316, 321, 347)
ASTM A335 Grades P5 to P91 (Alloy steel pipes)
ASTM A790/A928 (DSS and SDSS pipes)
Nickel alloys (Inconel, Hastelloy, Cupronickel, Monel, Nickel 200)
In general, pipes with a diameter of less than 16 inches are seamless, and larger-diameter pipes are welded. Seamless pipes are preferred due to the absence of the weld seam which is considered a weak point. However, they are costlier than welded pipes. Also, For large-diameter pipes, producing seamless pipes becomes difficult.
Carbon steel pipes (A53, A333, A106, and API 5L) have the largest market share due to the fact that they are cheaper and suitable for a wide range of applications ranging from -29 Deg C to 427 Deg C.
6- Pipe End Types
The pipes come in following end types.
7- calculations
ASTM A312 Series 300 and 400 (SS pipes with grades 304, 316, 321, 347)
ASTM A335 Grades P5 to P91 (Alloy steel pipes)
ASTM A790/A928 (DSS and SDSS pipes)
Nickel alloys (Inconel, Hastelloy, Cupronickel, Monel, Nickel 200)
In general, pipes with a diameter of less than 16 inches are seamless, and larger-diameter pipes are welded. Seamless pipes are preferred due to the absence of the weld seam which is considered a weak point. However, they are costlier than welded pipes. Also, For large-diameter pipes, producing seamless pipes becomes difficult.
Carbon steel pipes (A53, A333, A106, and API 5L) have the largest market share due to the fact that they are cheaper and suitable for a wide range of applications ranging from -29 Deg C to 427 Deg C.
6- Pipe End Types
The pipes come in following end types.
- Plain Ends
- Beveled Ends
- Threaded Ends
- Socket & Spigot Ends
- Flanged Ends
- Buttress Ends
- Beveled Ends
- Threaded Ends
- Socket & Spigot Ends
- Flanged Ends
- Buttress Ends
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| Fig 6 |
7- calculations
As we know, ASME B31.3 Provides formula and guidelines for calculation of pipe under pressure.
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| Fig 7 |
304.1.2 (a) equation 3a :For t < D/6, the internal pressure design thickness for straight pipe shall be not less than that calculated in accordance with either eq. (3a) or eq. (3b)
Seamless Pipes: Design Thickness
t = (PD)/2(SE+PY)
Welded Pipes: Design Thickness t = (PD)/2(SEW+PY)
For t ≥ D/6 or for P/SE > 0.385, calculation of pressure design thickness for straight pipe requires special consideration of factors such as theory of failure, effects of fatigue, and thermal stress.
Where:
P : Internal Design Guage Pressure
D : Outside diameter of pipe
outside diameter is taken from American Pipe Standards for the selected nominal pipe diameter
ASME B36.10 : Welded and Seamless Wrought Steel Pipe.
ASME B36.19 : Stainless Steel Pipes.
S : Allowable Stress value for material from Table A-1
These are allowable stress values for different materials at different temperatures. Provided in Table A-1 of ASME B31.3
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| Fig 8 |
E : Longitudinal Weld Joint Quality Factor Applicable as per ASME B31.3 Table A-1A or A-1B .
1 For Seamless Pipes.
0.60 for Furnace Butt Welded Pipes.
0.85 for Electric Resistance Welded Pipes.
1 For Seamless Pipes.
0.60 for Furnace Butt Welded Pipes.
0.85 for Electric Resistance Welded Pipes.
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| Fig 9 |
W : Weld Joint Strength Reduction Factor Applicable as per Para 302.3.5(e) of ASME B31.3
It is applicable only for Welded pipes. W is Take as 1 for Seamless Pipes.
Value of W is taken as 1.0 at temperatures of 510°C (950°F) and below, and 0.5 at 815°C (1500°F) for all materials.
Value is linearly interpolated for intermediate temperatures.
It is applicable only for Welded pipes. W is Take as 1 for Seamless Pipes.
Value of W is taken as 1.0 at temperatures of 510°C (950°F) and below, and 0.5 at 815°C (1500°F) for all materials.
Value is linearly interpolated for intermediate temperatures.
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| Fig 10 |
Y : Coefficient from Table 304.1.1,
Valid for t < D/6 and for materials shown. The value of Y may be interpolated for intermediate temperatures.
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| Fig 11 |
Required Thickness = Design Thickness + Allowances
c : sum of the mechanical allowances (thread or groove depth) plus corrosion and erosion allowances. For threaded components, the nominal thread depth (dimension h of ASME B1.20.1, or equivalent) shall apply. For machined surfaces or grooves where the tolerance is not specified, the tolerance shall be assumed to be 0.5 mm (0.02 in.) in addition to the specified depth of the cut.
tm =t +C
tm = minimum required thickness, including mechanical, corrosion, and erosion allowances
c : sum of the mechanical allowances (thread or groove depth) plus corrosion and erosion allowances. For threaded components, the nominal thread depth (dimension h of ASME B1.20.1, or equivalent) shall apply. For machined surfaces or grooves where the tolerance is not specified, the tolerance shall be assumed to be 0.5 mm (0.02 in.) in addition to the specified depth of the cut.
Addition of Allowances
Calculated Design Wall Thickness should be added with Corrosion Allowance, Mechanical Allowance for Grooving, Threading etc and Manufacturing Tolerance to arrive at final value. Next higher standard thickness value from Pipe Standards such as ASME B36.10 and ASME B36.19 is used.
Designer should select a thickness from schedules of nominal thickness contained in Table 1 specified in ASME B36.10 and B36.19, to suit the value computed to fulfill the conditions for which the pipe is desired.
7-1 Force Main Pipe Material Selection and Sizing
The discharge pipe, commonly called a force main, is sized to convey the effluent economically from the pump to its ultimate point of discharge. The pipe material selected is based on flow rate, friction loss of the fluid in the pipe, chemical resistance to the effluent, and fluid velocity.
Q=A XV
where:
A = Internal pipe area
V = Fluid velocity
Charts for standard pipe sizes and schedules are available to determine velocities
V = Fluid velocity
Charts for standard pipe sizes and schedules are available to determine velocities
8- Carbon steel pressure and temperature ratings
Maximum allowable pressure and temperature ratings for petroleum refinery piping and chemical plant piping systems grade B with plane ends according ANSI/ASME B31.3 Process Piping.
Pressure and Temperature Ratings of A-53 B, A-106 B, A333, A334 and API 5L Carbon Steel Pipes -
Maximum allowable pressure and temperature ratings for petroleum refinery piping and chemical plant piping systems grade B with plane ends according ANSI/ASME B31.3 Process Piping.
Pressure and Temperature Ratings of A-53 B, A-106 B, A333, A334 and API 5L Carbon Steel Pipes -
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| Fig12 |
9- NPS - IPS
9- 1 What is Nominal Pipe Size?
Nominal pipe size (NPS) is the number that defines the size of the pipe. For example, when you say 6” pipe, the 6” is the nominal size of that pipe. However, for the pipe sizes, NPS 14 and above Outside Diameter is the same as NPS. To understand this concept, you have to learn the way pipes are manufactured.
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| Fig 13 |
NPS is frequently referred as an NB (Nominal Bore). As such, there is no difference between NB and NPS. NB is also an American way to refer to pipe dimensions. I have also seen that when pipe dimensions are shown in mm (DN) people refer to pipe sizes in NB. So when someone says 25nb pipe or 50nb pipe, basically they are talking about DN.
9-3 What is DN (Diameter Nominal) Pipe Size?
DN or Diameter Nominal is an international designation (SI or Matric Designator) and a European NPS equivalent to show pipe sizes. Here, you have to note that DN shows pipe sizes differently than NPS.
Calculation formula for nominal pipeline wall:
THK = (OD – ID) ÷ 2
9-4 What is Pipe Schedule?
Pipe Schedule Number is the standard method to define the thickness of the pipes used in Process Plants.
Standardization of wrought steel Pipe schedule and pipe sizes began with the mass production era. At that time, pipes were available in only three sizes standard weight (STD), extra-strong (XS), and double extra-strong (XXS), based on the iron pipe size (IPS) system.
With the modernizing of various industries and the use of pipes in different pressure and temperature conditions, three sizes are insufficient to meet the requirement. This will result in the concept of the schedule number that combines wall thickness and diameter of the pipe.
In current practice, pipe size defines by two sets of numberPipe bore/nominal diameter
The pipe schedule is nothing but the wall thickness of the pipe.
The pipe schedule (fig 14) is the way pipe wall thickness is mentioned. To simplify the ordering of the pipe ASME committee has developed Schedule Number, which is based on modified Barlow’s wall thickness formula.
Definition of Schedule Number: The schedule number indicates an approximate value of the expression
1000 x P/S
where:
P is the service pressure and S is the allowable stress, both expressed in pounds per square inch.
You can see the pipe schedule calculation formula below.
P is the service pressure in (psi)
S is the allowable stress in (psi)
You can see the pipe schedule calculation formula below.
Schedule number = P/S
where:P is the service pressure in (psi)
S is the allowable stress in (psi)
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| Fig 14 |
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| Fig 15 |
11- Steel Pipe Tolerances and Dimensional Standard
Why Are Dimensional Tolerances So Important?
Accurate dimensional control plays a crucial role in the structural stability, safety, and efficiency of steel pipe applications: Ensures Structural Integrity: Smaller deviations allow tighter fits and stronger overall structures.
Improves Weld Quality: Greater roundness and accurate alignment lead to more stable welds with reduced residual stress.
Facilitates Automated Assembly: Especially in projects like wind turbine towers and bridge supports, dimensional accuracy directly impacts assembly efficiency.
Enhances Post-Processing: Stable diameters and roundness support uniform galvanizing and coating distribution.
12- STANDARDS FOR STEEL PIPES
ASTM STANDARDS FOR STEEL PIPES
A53 Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless
A74 Standard Specification for Cast Iron Soil Pipe and Fittings
A106 Standard Specification for Seamless Carbon Steel Pipe for High-Temperature Service
A126 Standard Specification for Gray Iron Castings for Valves, Flanges, and Pipe Fittings
A134 Standard Specification for Pipe, Steel, Electric-Fusion (Arc)-Welded (Sizes NPS 16 and Over)
A135 Standard Specification for Electric-Resistance-Welded Steel Pipe
A139 Standard Specification for Electric-Fusion (Arc)-Welded Steel Pipe (NPS 4 and Over)
A182 Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service
A252 Standard Specification for Welded and Seamless Steel Pipe Piles
A312 Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes
A333 Standard Specification for Seamless and Welded Steel Pipe for Low-Temperature Service
A335 Standard Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service
A338 Standard Specification for Malleable Iron Flanges, Pipe Fittings, and Valve Parts for Railroad, Marine, and Other Heavy Duty Service at Temperatures up to 650°F (345°C)
A358 Standard Specification for Electric-Fusion-Welded Austenitic Chromium-Nickel Stainless Steel Pipe for High-Temperature Service and General Applications
A369 Standard Specification for Carbon and Ferritic Alloy Steel Forged and Bored Pipe for High-Temperature Service
A376 Standard Specification for Seamless Austenitic Steel Pipe for High-Temperature Central-Station Service
A377 Standard Index of Specifications for Ductile-Iron Pressure Pipe
A409 Standard Specification for Welded Large Diameter Austenitic Steel Pipe for Corrosive or High-Temperature Service
A426 Standard Specification for Centrifugally Cast Ferritic Alloy Steel Pipe for High-Temperature Service
A451 Standard Specification for Centrifugally Cast Austenitic Steel Pipe for High-Temperature Service
A523 Standard Specification for Plain End Seamless and Electric-Resistance-Welded Steel Pipe for High-Pressure Pipe-Type Cable Circuits
A524 Standard Specification for Seamless Carbon Steel Pipe for Atmospheric and Lower Temperatures
A530 Standard Specification for General Requirements for Specialized Carbon and Alloy Steel Pipe
A648 Standard Specification for Steel Wire, Hard Drawn for Restressing Concrete Pipe
A674 Standard Practice for Polyethylene Encasement for Ductile Iron Pipe for Water or Other Liquids
A691 Standard Specification for Carbon and Alloy Steel Pipe, Electric-Fusion-Welded for High-Pressure Service at High Temperatures
A694 Standard Specification for Carbon and Alloy Steel Forgings for Pipe Flanges, Fittings, Valves, and Parts for High-Pressure Transmission Service
A716 Standard Specification for Ductile Iron Culvert Pipe
A733 Standard Specification for Welded and Seamless Carbon Steel and Austenitic Stainless Steel Pipe Nipples
A742 Standard Specification for Steel Sheet, Metallic Coated and Polymer Precoated for Corrugated Steel Pipe
A746 Standard Specification for Ductile Iron Gravity Sewer Pipe
A760 Standard Specification for Corrugated Steel Pipe, Metallic-Coated for Sewers and Drains
A761 Standard Specification for Corrugated Steel Structural Plate, Zinc-Coated, for Field-Bolted Pipe, Pipe-Arches, and Arches
A762 Standard Specification for Corrugated Steel Pipe, Polymer Precoated for Sewers and Drains
A790 Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe
A796 Standard Practice for Structural Design of Corrugated Steel Pipe, Pipe-Arches, and Arches for Storm and Sanitary Sewers and Other Buried Applications
A798 Standard Practice for Installing Factory-Made Corrugated Steel Pipe for Sewers and Other Applications
A807 Standard Practice for Installing Corrugated Steel Structural Plate Pipe for Sewers and Other Applications
A810 Standard Specification for Zinc-Coated (Galvanized) Steel Pipe Winding Mesh
A813 Standard Specification for Single- or Double-Welded Austenitic Stainless Steel Pipe
A814 Standard Specification for Cold-Worked Welded Austenitic Stainless Steel Pipe
A849 Standard Specification for Post-Applied Coatings, Pavings, and Linings for Corrugated Steel Sewer and Drainage Pipe
A861 Standard Specification for High-Silicon Iron Pipe and Fittings
A862 Standard Practice for Application of Asphalt Coatings to Corrugated Steel Sewer and Drainage Pipe
A865 Standard Specification for Threaded Couplings, Steel, Black or Zinc-Coated (Galvanized) Welded or Seamless, for Use in Steel Pipe Joints
A872 Standard Specification for Centrifugally Cast Ferritic/Austenitic Stainless Steel Pipe for Corrosive Environments
A885 Standard Specification for Steel Sheet, Zinc and Aramid Fiber Composite Coated for Corrugated Steel Sewer, Culvert, and Underdrain Pipe (Withdrawn 2006)
A888 Standard Specification for Hubless Cast Iron Soil Pipe and Fittings for Sanitary and Storm Drain, Waste, and Vent Piping Applications
A926 Standard Test Method for Comparing the Abrasion Resistance of Coating Materials for Corrugated Metal Pipe
A928 Standard Specification for Ferritic/Austenitic (Duplex) Stainless Steel Pipe Electric Fusion Welded with Addition of Filler Metal
A929 Standard Specification for Steel Sheet, Metallic-Coated by the Hot-Dip Process for Corrugated Steel Pipe
A930 Standard Practice for Life-Cycle Cost Analysis of Corrugated Metal Pipe Used for Culverts, Storm Sewers, and Other Buried Conduits
A943 Standard Specification for Spray-Formed Seamless Austenitic Stainless Steel Pipes
A949 Standard Specification for Spray-Formed Seamless Ferritic/Austenitic Stainless Steel Pipe
A972 Standard Specification for Fusion Bonded Epoxy-Coated Pipe Piles
A978 Standard Specification for Composite Ribbed Steel Pipe, Precoated and Polyethylene Lined for Gravity Flow Sanitary Sewers, Storm Sewers, and Other Special Applications
A984 Standard Specification for Steel Line Pipe, Black, Plain-End, Electric-Resistance-Welded
A998 Standard Practice for Structural Design of Reinforcements for Fittings in Factory-Made Corrugated Steel Pipe for Sewers and Other Applications
A999 Standard Specification for General Requirements for Alloy and Stainless Steel Pipe
A1005 Standard Specification for Steel Line Pipe, Black, Plain End, Longitudinal and Helical Seam, Double Submerged-Arc Welded
A1006 Standard Specification for Steel Line Pipe, Black, Plain End, Laser Beam Welded
ASTM STANDARDS FOR STEEL TUBES, BOILER, SUPERHEATER, AND MISCELLANEOUS TUBES
A74 Standard Specification for Cast Iron Soil Pipe and Fittings
A106 Standard Specification for Seamless Carbon Steel Pipe for High-Temperature Service
A126 Standard Specification for Gray Iron Castings for Valves, Flanges, and Pipe Fittings
A134 Standard Specification for Pipe, Steel, Electric-Fusion (Arc)-Welded (Sizes NPS 16 and Over)
A135 Standard Specification for Electric-Resistance-Welded Steel Pipe
A139 Standard Specification for Electric-Fusion (Arc)-Welded Steel Pipe (NPS 4 and Over)
A182 Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service
A252 Standard Specification for Welded and Seamless Steel Pipe Piles
A312 Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes
A333 Standard Specification for Seamless and Welded Steel Pipe for Low-Temperature Service
A335 Standard Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service
A338 Standard Specification for Malleable Iron Flanges, Pipe Fittings, and Valve Parts for Railroad, Marine, and Other Heavy Duty Service at Temperatures up to 650°F (345°C)
A358 Standard Specification for Electric-Fusion-Welded Austenitic Chromium-Nickel Stainless Steel Pipe for High-Temperature Service and General Applications
A369 Standard Specification for Carbon and Ferritic Alloy Steel Forged and Bored Pipe for High-Temperature Service
A376 Standard Specification for Seamless Austenitic Steel Pipe for High-Temperature Central-Station Service
A377 Standard Index of Specifications for Ductile-Iron Pressure Pipe
A409 Standard Specification for Welded Large Diameter Austenitic Steel Pipe for Corrosive or High-Temperature Service
A426 Standard Specification for Centrifugally Cast Ferritic Alloy Steel Pipe for High-Temperature Service
A451 Standard Specification for Centrifugally Cast Austenitic Steel Pipe for High-Temperature Service
A523 Standard Specification for Plain End Seamless and Electric-Resistance-Welded Steel Pipe for High-Pressure Pipe-Type Cable Circuits
A524 Standard Specification for Seamless Carbon Steel Pipe for Atmospheric and Lower Temperatures
A530 Standard Specification for General Requirements for Specialized Carbon and Alloy Steel Pipe
A648 Standard Specification for Steel Wire, Hard Drawn for Restressing Concrete Pipe
A674 Standard Practice for Polyethylene Encasement for Ductile Iron Pipe for Water or Other Liquids
A691 Standard Specification for Carbon and Alloy Steel Pipe, Electric-Fusion-Welded for High-Pressure Service at High Temperatures
A694 Standard Specification for Carbon and Alloy Steel Forgings for Pipe Flanges, Fittings, Valves, and Parts for High-Pressure Transmission Service
A716 Standard Specification for Ductile Iron Culvert Pipe
A733 Standard Specification for Welded and Seamless Carbon Steel and Austenitic Stainless Steel Pipe Nipples
A742 Standard Specification for Steel Sheet, Metallic Coated and Polymer Precoated for Corrugated Steel Pipe
A746 Standard Specification for Ductile Iron Gravity Sewer Pipe
A760 Standard Specification for Corrugated Steel Pipe, Metallic-Coated for Sewers and Drains
A761 Standard Specification for Corrugated Steel Structural Plate, Zinc-Coated, for Field-Bolted Pipe, Pipe-Arches, and Arches
A762 Standard Specification for Corrugated Steel Pipe, Polymer Precoated for Sewers and Drains
A790 Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe
A796 Standard Practice for Structural Design of Corrugated Steel Pipe, Pipe-Arches, and Arches for Storm and Sanitary Sewers and Other Buried Applications
A798 Standard Practice for Installing Factory-Made Corrugated Steel Pipe for Sewers and Other Applications
A807 Standard Practice for Installing Corrugated Steel Structural Plate Pipe for Sewers and Other Applications
A810 Standard Specification for Zinc-Coated (Galvanized) Steel Pipe Winding Mesh
A813 Standard Specification for Single- or Double-Welded Austenitic Stainless Steel Pipe
A814 Standard Specification for Cold-Worked Welded Austenitic Stainless Steel Pipe
A849 Standard Specification for Post-Applied Coatings, Pavings, and Linings for Corrugated Steel Sewer and Drainage Pipe
A861 Standard Specification for High-Silicon Iron Pipe and Fittings
A862 Standard Practice for Application of Asphalt Coatings to Corrugated Steel Sewer and Drainage Pipe
A865 Standard Specification for Threaded Couplings, Steel, Black or Zinc-Coated (Galvanized) Welded or Seamless, for Use in Steel Pipe Joints
A872 Standard Specification for Centrifugally Cast Ferritic/Austenitic Stainless Steel Pipe for Corrosive Environments
A885 Standard Specification for Steel Sheet, Zinc and Aramid Fiber Composite Coated for Corrugated Steel Sewer, Culvert, and Underdrain Pipe (Withdrawn 2006)
A888 Standard Specification for Hubless Cast Iron Soil Pipe and Fittings for Sanitary and Storm Drain, Waste, and Vent Piping Applications
A926 Standard Test Method for Comparing the Abrasion Resistance of Coating Materials for Corrugated Metal Pipe
A928 Standard Specification for Ferritic/Austenitic (Duplex) Stainless Steel Pipe Electric Fusion Welded with Addition of Filler Metal
A929 Standard Specification for Steel Sheet, Metallic-Coated by the Hot-Dip Process for Corrugated Steel Pipe
A930 Standard Practice for Life-Cycle Cost Analysis of Corrugated Metal Pipe Used for Culverts, Storm Sewers, and Other Buried Conduits
A943 Standard Specification for Spray-Formed Seamless Austenitic Stainless Steel Pipes
A949 Standard Specification for Spray-Formed Seamless Ferritic/Austenitic Stainless Steel Pipe
A972 Standard Specification for Fusion Bonded Epoxy-Coated Pipe Piles
A978 Standard Specification for Composite Ribbed Steel Pipe, Precoated and Polyethylene Lined for Gravity Flow Sanitary Sewers, Storm Sewers, and Other Special Applications
A984 Standard Specification for Steel Line Pipe, Black, Plain-End, Electric-Resistance-Welded
A998 Standard Practice for Structural Design of Reinforcements for Fittings in Factory-Made Corrugated Steel Pipe for Sewers and Other Applications
A999 Standard Specification for General Requirements for Alloy and Stainless Steel Pipe
A1005 Standard Specification for Steel Line Pipe, Black, Plain End, Longitudinal and Helical Seam, Double Submerged-Arc Welded
A1006 Standard Specification for Steel Line Pipe, Black, Plain End, Laser Beam Welded
ASTM STANDARDS FOR STEEL TUBES, BOILER, SUPERHEATER, AND MISCELLANEOUS TUBES
A178 Specification for Electric-Resistance-Welded Carbon Steel and Carbon-Manganese Steel Boiler and Superheater Tubes
A179 Specification for Seamless Cold-Drawn Low-Carbon Steel Heat-Exchanger and Condenser Tubes
A192 Specification for Seamless Carbon Steel Boiler Tubes for High-Pressure Service
A209 Specification for Seamless Carbon-Molybdenum Alloy-Steel Boiler and Superheater Tubes
A210 Specification for Seamless Medium-Carbon Steel Boiler and Superheater Tubes
A213 Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes
A249 Specification for Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes
A250 Specification for Electric-Resistance-Welded Ferritic Alloy-Steel Boiler and Superheater Tubes
A254 Specification for Copper-Brazed Steel Tubing
A268 Specification for Seamless and Welded Ferritic and Martensitic Stainless Steel Tubing for General Service
A269 Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service
A270 Specification for Seamless and Welded Austenitic Stainless Steel Sanitary Tubing
A334 Specification for Seamless and Welded Carbon and Alloy-Steel Tubes for Low-Temperature Service
A423 Specification for Seamless and Electric-Welded Low-Alloy Steel Tubes
A450 Specification for General Requirements for Carbon, Ferritic Alloy, and Austenitic Alloy Steel Tubes
A608 Specification for Centrifugally Cast Iron-Chromium-Nickel High-Alloy Tubing for Pressure Application at High Temperatures
A618 Specification for Hot-Formed Welded and Seamless High-Strength Low-Alloy Structural Tubing
A632 Specification for Seamless and Welded Austenitic Stainless Steel Tubing (Small-Diameter) for General Service
A688 Specification for Welded Austenitic Stainless Steel Feedwater Heater Tubes
A771 Specification for Seamless Austenitic and Martensitic Stainless Steel Tubing for Liquid Metal-Cooled Reactor Core Components
A778 Specification for Welded, Unanneled Austenitic Stainless Steel Tubular Products
A789 Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing for General Service
A803 Specification for Welded Ferritic Stainless Steel Feedwater Heater Tubes
A822 Specification for Seamless Cold-Drawn Carbon Steel Tubing for Hydraulic System Service
A826 Specification for Seamless Austenitic and Martensitic Stainless Steel Duct Tubes for Liquid Metal-Cooled Reactor Core Components
A847 Specification for Cold-Formed Welded and Seamless High Strength, Low Alloy Structural Tubing with Improved Atmospheric Corrosion Resistance
A908 Specification for Stainless Steel Needle Tubing
A953 Specification for Austenitic Chromium-Nickel-Silicon Alloy Steel Seamless and Welded Tubing
ASTM STANDARDS FOR HEAT-EXCHANGER AND CONDENSER TUBES
A179 Standard Specification for Seamless Cold-Drawn Low-Carbon Steel Heat-Exchanger and Condenser Tubes
A213 Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Super heater, and Heat-Exchanger Tubes
A214 Specification for Electric-Resistance-Welded Carbon Steel Heat-Exchanger and Condenser Tubes
A249 Specification for Welded Austenitic Steel Boiler, Super heater, Heat-Exchanger, and Condenser Tubes
A498 Specification for Seamless and Welded Carbon, Ferritic, and Austenitic Alloy Steel Heat-Exchanger Tubes with Integral Fins
A851 Specification for High-Frequency Induction Welded, Unannealed, Austenitic Steel Condenser Tubes
ASTM STANDARDS FOR MECHANICAL TUBING
A511 Specification for Seamless Stainless Steel Mechanical Tubing
A512 Specification for Cold-Drawn Buttweld Carbon Steel Mechanical Tubing
A513 Specification for Electric-Resistance-Welded Carbon and Alloy Steel Mechanical Tubing
A519 Specification for Seamless Carbon and Alloy Steel Mechanical Tubing
A554 Specification for Welded Stainless Steel Mechanical Tubing
ASTM STANDARDS FOR STRUCTURAL TUBING
A500 Specification for Cold-Formed Welded and Seamless Carbon Steel Structural Tubing in Rounds and Shapes
A501 Specification for Hot-Formed Welded and Seamless Carbon Steel Structural Tubing
A847 Specification for Cold-Formed Welded and Seamless High Strength, Low Alloy Structural Tubing with Improved Atmospheric Corrosion Resistance
A618 Specification for Hot-Formed Welded and Seamless High-Strength Low-Alloy Structural Tubing
ASME – American Society of Mechanical Engineers
BPVC – Boiler and Pressure Vessel Code
B31.1 – Power Piping
B31.3 – Process Piping
B31.1 – Power Piping
B31.3 – Process Piping
American Water Works Association
AWWA C-900 - 4 to 12 in PVC
AWWA C-901- 1⁄2 to 3 in PE
AWWA C-902 - 1⁄2 to 3 in PB
AWWA C-903 - Deleted
AWWA C-904 - Fittings for C-900 pipe
AWWA C-905 - 14 to 36 in PVC
AWWA C-906 - Larger diameter PE pipe
