INTRODUCTION OF PIPES

PIPES HISTORY
Pipes are hollow structure, usually cylindrical, for conducting fluids. It is used primarily to convey liquids, gases, or solids suspended in a liquid, e.g., slurry. It is also used as a conduit for electric wires.

The earliest pipes were probably made of bamboo, used by the Chinese to carry water c.5000 B.C. The Egyptians made the first metal pipe of copper c.3000 B.C. Until cast iron became relatively cheap in the 18th cent. Most pipes were made of bored stone or wood, clay, lead, and, occasionally, copper or bronze. Modern materials include cast iron, wrought iron, steel, copper, brass, lead, concrete, wood, glass, and plastic. Welded steel pipe is made by bending strips of steel into the form of a tube and welding the longitudinal seam either by electric resistance, by fusion welding, or by heating the tube and pressing the edges together. Seamless pipe is made from a solid length of metal pierced lengthwise by a mandrel with a rounded nose.

Steel pipe, introduced in the early 20th cent., is widely used for conducting substances at extremely high pressures and temperatures. Cast-iron pipes, which came into common use in the 1840s, resist corrosion better than steel pipes and are therefore frequently used underground. Clay and concrete pipes usually carry sewage, and concrete pipes are also used to carry irrigation water at low pressures; for moderate pressures, the concrete is reinforced with steel or mixed with asbestos. Seamless copper and brass pipes are used for plumbing and boilers. Because of its softness and resistance to corrosion, lead is used for flexible connections and for plumbing that does not carry drinking water. The chemical and food industries use glass pipes. During World War II manufacturers developed plastic pipe to replace metals that were in short supply. Today PVC pipe is widely used to carry waste water as well as certain corrosive liquids.

A pipeline carries carry the lifeblood of modern civilization. In a modern city they transport water from the sources of water supply to the points of distribution; convey waste from residential and commercial buildings and other civic facilities to the treatment facility or the point of discharge. Similarly, pipelines carry crude oil from oil wells to tank farms for storage or to refineries for processing. The natural gas transportation and distribution lines convey natural gas from the source and storage tank forms to points of utilization, such as power plants, industrial facilities, and commercial and residential communities. In chemical plants, paper mills, food processing plants, and other similar industrial establishments, the piping systems are utilized to carry liquids, chemicals, mixtures, gases, vapors, and solids from one location to another.

PIPING

Piping includes pipe, flanges, fittings, bolting, gaskets, valves, and the pressure- containing portions of other piping components. It also includes pipe hangers and supports and other items necessary to prevent over pressurization and overstressing of the pressure-containing components. It is evident that pipe is one element or a part of piping. Therefore, pipe sections when joined with fittings, valves, and other mechanical equipment and properly supported by hangers and supports, are called piping

Pipes

Pipes can be defined as a pressure tight cylinder used to convey a fluid. The pipes are available in standard length of 20feet (6m).The media conveyed may be of different pressure temperature. Various types of pipes are used depending upon the nature of fluid, quantity to be transported, service condition, and cost of production and installation deterioration, liability of failure and result of such failure, its pressure and velocity.

● ASME B36.10M Welded and Seamless Wrought Steel Pipe

● ASME B36.19M Stainless Steel Pipe

The word “pipe” is used as distinguished from “tube” to apply to tabular products of dimensions commonly used for piping systems. The pipes dimensions of sizes 12” (300mm) and smaller have outside diameter numerically larger than corresponding sizes. In contrast, the out side diameter of tubes is numerically identical to the size number for all sizes.

The tubes and pipes can compare on the following lines:

Tubes:

1) Lower thickness and higher ductility of the tubes permits rolling into coils without higher differential stress between inside and outside of coils.

2) Tubes are specified by outside diameter and actual thickness in mm or inch or wire gauge.

3) Uniform thickness in tubes means less chances of failure due to hot spot.

4) Low roughness factor and low pressure drop.

5) Normally used in heat exchanger and coils for heat transfer.

Pipes:

1) Lower ductility makes it unsuitable to coil. Due to higher moment of inertia larger bending moment is required for the same radius. This means larger residual stress.

2) Specified by NOMINAL BORE and thickness by SCHEDULE.

3) Variation in thickness can cause hot spot and consequent failure.

4) Higher roughness factor and higher pressure drop.

5) Normally used in straight length for fluid transfer.

DIAMETER AND WALL THICKNESS OF PIPE:

The size of all pipe is identified by the Nominal Pipe Size (NPS) which is seldom equal to the true bore (internal diameter) of the pipe, the difference is some instance is larger. 14 inch NPS and larger pipes has out side diameter equal to the nominal pipe size

Initially Pipes were manufactured as Iron Pipe Size (IPS) was established to designate the pipe size. The size represented the approximate inside diameter of the pipe in inches. An IPS 6 pipe is one whose inside diameter is approximately 6 inches (in). Users started to call the pipe as 2-in, 4-in, 6-in pipe and so on. To begin, each pipe size was produced to have one thickness, which later was termed as standard (STD) or standard weight (STD. WT.). The outside diameter of the pipe was standardized. As the industrial requirements demanded the handling of higher-pressure fluids, pipes were produced having thicker walls, which came to be known as extra strong (XS). The higher pressure requirements increased further, requiring thicker wall pipes. Accordingly, pipes were manufactured with double extra strong (XXS) walls while the standardized outside diameters are unchanged.

With the development of stronger and corrosion-resistant piping materials, the need for thinner wall pipe resulted in a new method of specifying pipe size and wall thickness. The designation known as nominal pipe size (NPS) replaced IPS, and the term schedule (SCH) was invented to specify the nominal wall thickness of pipe. Nominal pipe size (NPS) is a dimensionless designator of pipe size. It indicates standard pipe size when followed by the specific size designation number without an inch symbol. For example, NPS 2 indicates a pipe whose outside diameter is 2.375 in. The NPS 12 and smaller pipe has outside diameter greater than the size designator (say, 2, 4, 6,.). However, the outside diameter of NPS 14 and larger pipe is the same as the size designator in inches. For example, NPS 14 pipe has an outside diameter equal to 14 in. The inside diameter will depend upon the pipe wall thickness specified by the schedule number. Refer to ASME B36.10 or ASME B36.19.

Diameter nominal (DN) is also a dimensionless designator of pipe size in the metric unit system, developed by the International Standards Organization (ISO). It indicates standard pipe size when followed by the specific size designation number

1. Nominal Bore (NB): It indicates standard pipe size designation number with mm or inch symbol E.g.:- 2” NB or 50mm NB.

2. Nominal Pipe Size (NPS): This is dimensionless designator in USCS. It indicates standard pipe size designation number without inch symbol. E.g.:-NPS 2, NPS12

3. Nominal Diameter (DN): this is dimensionless designation in metric system; it indicates standard size designation number without millimeter. E.g.:-DN 50, DN 300, etc.

Pipe size NB(inch)	Eq.Metric Pipe Size NB(mm)	Outside Dia (inch)	Outside Dia (mm)
1/8	6	0.405	10.3
1/4	8	0.540	13.7
3/8	10	0.675	17.1
1/2	15	0.840	21.3
3/4	20	1.050	26.7
1	25	1.315	33.4
*1 ¼	32	1.660	42.2
1 ½	40	1.900	48.3
2	50	2.375	60.3
*2½	65	2.875	73.0
3	80	3.500	88.9
*3 ½	90	4.000	101.6
4	100	4.500	114.3
*5	125	5.563	141.3
6	150	6.625	168.3
8	200	8.625	219.1
10	250	10.750	273.0
12	300	12.750	323.9
14	350	14.000	355.6
16	400	16.000	406.4
18	450	18.000	457.2
20	500	20.000	508.0
*22	550	22.000	558.8
24	600	24.000	609.6

In Indian standard IS 1239, the thicknesses of pipes are specifies as:

1. Light

2. Medium

3. Heavy

The medium and heavy pipes are only used for fluid handling. In IS 3589, the thicknesses are specified in actual dimension in mm.

The pipe thickness is designated by Schedule Number and corresponding thickness is specified in the ASME B 36.10 for carbon steel pipes and ASME B 36.19 for stainless steel pipes.

Stainless steel pipes are available in schedule 5S, 10S, 40S and 80S whereas carbon steel pipes are available in schedule 5, 10, 20, 30, 40 ,60, 80, 100, 120, 140, 160, STD, XS, XXS.

· Thickness standard weight and schedule 40 are identical for nominal pipe size up to 10 inch (250mm) inclusive.

· All larger size of STD has 3/8 inch (9.53mm) wall thickness.

· Extra strong and schedule 80 are identical of nominal pipe size up to 80 inch (200mm) inclusive.

· All larger size of extra strong has ½ inch (12.7mm) wall thickness.

· The thickness of double extra strong is more than schedule 160 in pipe sizes up to 6 inch (150mm) NB.

· This thickness is specified for pipe up to 12 inch (300mm) NB.

· For 12 inch (300mm) NB the thickness matches to that of schedule 120 and for 10 inch (250mm) NB it schedule 140.

Generally the thickness specified by schedule number of B36.10 and B 36.19 matches except in the following:

10” SCH80/SCH80S

12” SCH40/SCH40S

12” SCH80/SCH80S

14” SCH10/SCH10S

16” SCH10/SCH10S

18” SCH10/SCH10S

20” SCH10/SCH10S

22” SCH10/SCH10S

PIPES END

Based on the material of construction and the pipe to pipe joint, the end specified as:

1. Beveled End: Bevel ends are specified when pipe to pipe and/or fittings joints are done by butt welding.

2. Plain End: Plain ends are specifies where pipe to pipe or fittings joints are done by fillet welding.

3. Screwed End: Screwed joints are specified when pipe to pipe and fittings joints are done by thread connections.

4. Flanged End: Flanged ends are specified to provide bolted connections between pipe to pipes or fittings.

5. Spigot/Socket End: Spigot / Socket ends are specified when lead caulked / cemented joints are provided between pipes and between pipes and fittings.

6. Buttress End: Buttress ends are used in glass piping and are joined by bolting with the use of backing flanges.