PIPE

Pipe is a tube or hollow cylinder for the conveyance of fluid, gas and sometimes other materials. The terms 'pipe' and 'tubing' are almost interchangeable. 'Pipe' is generally specified by the internal diameter (ID) whereas 'tube' is usually defined by the outside diameter (OD) but may be specified by any combination of dimensions (OD, ID, wall thickness), depending upon which are considered the most important to the designer. 'Tube' is often made to custom sizes and may often have more specific sizes and tolerances than pipe. Also the term "tubing" can be applied to tubes of a non-cylindrical nature (i.e. square tubing). The term 'tubing' is more widely used in the USA and 'pipe' elsewhere in the world.
Both "pipe" and "tube" imply a level of rigidity and permanence, whereas a 'hose' is usually portable and flexible. Pipe may be specified by standard pipe size designations, such as Nominal Pipe Size (in the US), or by nominal, outside, or inside diameter and wall thickness. Many industrial and government standards exist for the production of pipe and tubing.

Nominal Pipe Size (NPS) is a set of standard pipe sizes used for pressure piping in North America. The same pipe dimensions are used with different names in Europe. It is often incorrectly called National Pipe Size, due to confusion with National pipe thread. For other pipe size standards, see pipe (material).
Pipe size is specified with two non-dimensional numbers: a Nominal Pipe Size (NPS) and a schedule (SCH). The relationship of these numbers to the actual pipe dimensions is a bit strange. The NPS is very loosely related to the inside diameter in inches, but only for NPS 1/8 to NPS 12. For NPS 14 and larger, the NPS is equal to the outside diameter (OD) in inches. For a given NPS, the OD stays constant and the wall thickness increases with larger SCH. For a given SCH, the OD increases with increasing NPS while the wall thickness increases or stays constant. Pipe sizes are documented by a number of standards, including API 5L, ANSI/ASME B36.10M in the US, BS 1600 and BS EN 10255 in the United Kingdom and Europe, and ISO 65 internationally. The ISO and European standard uses the same pipe ID's and wall thicknesses, but labels them with a Diametre Nominal (DN) instead of NPS. For NPS of 5 and larger, the DN is equal to the NPS multiplied by 25 (not 25.4).
The most commonly used schedules today are 40, 80, and 160. There is a commonly held belief that the schedule number is an indicator of the service pressure that the pipe can take. For example, the McGraw Hill Piping Handbook says the schedule number can be converted to pressure by dividing the schedule by 1000 and multiplying by the allowable stress of the material (Ref. #2). However, this is not true. Using equations and rules in ASME B31.3 Process Piping, it is easily shown that pressure rating actually goes down with increasing NPS and constant schedule.
The various standards for pipe schedule are not identical. Frequently some sizes—or even entire schedules—are present in some standards but not others. When different standards do overlap, they usually have the same dimensions. For this reason, the source of the schedules is not distinguished in the table below. Beyond NPS 8, however, there are two different versions of schedules 5, 10, 40, and 80. In newer standards and in the table below, the distinction is denoted by the presence or absence of an 'S' suffix after the schedule number. The 'S' was originally meant to indicate Stainless Steel Schedule (Ref. #3, pp B-16 and B-17), but in practice, pipe of any material may be available in either schedule depending on the manufacturer.
Some specifications use pipe schedules called Standard Wall (STD), Extra Strong (XS), and Double Extra Strong (XXS), although these actually belong to an older system called iron pipe size (IPS). The IPS number is the same as the NPS number. STD is identical to SCH 40S, and 40S is identical to 40 for NPS 1/8 to NPS 10, inclusive. XS is identical to SCH 80S, and 80S is identical to 80 for NPS 1/8 to NPS 8, inclusive. Different definitions exist for XXS, but it is generally thicker than schedule 160.
Copper plumbing tube for residential plumbing follows an entirely different size system; see domestic water system. Both polyvinyl chloride pipe (PVC) and chlorinated polyvinyl chloride pipe (CPVC) are made in NPS sizes. CPVC has a roughly 50°C higher temperature limit which makes it suitable for use in domestic hot water service.

 

 

 

 

 

 

 

 

NPS 1/8 to NPS 3-1/2

NPS	DN	OD (inches)	Wall Thickness (inches)
			SCH 5	SCH 10	SCH 30	SCH 40	SCH 80	SCH 120	SCH 160
1/8	6	0.405	0.035	0.049	0.057	0.068	0.095	?	?
3/16	7	?	?	?	?	?	?	?	?
1/4	8	0.540	0.049	0.065	.073	.088	.119	?	?
3/8	10	0.675	.049	.065	.073	.091	.126	?	?
1/2	15	0.840	.065	.083	.095	.109	.147	.170	.188
5/8	18	?	?	?	?	?	?	?	?
3/4	20	1.050	.065	.083	.095	.113	.154	.170	.219
1	25	1.315	.065	.109	.114	.133	.179	.200	.250
1-1/4	32	1.660	.065	.109	.117	.140	.191	.215	.250
1-1/2	40	1.900	.065	.109	.125	.145	.200	.225	.281
2	50	2.375	.065	.109	?	.154	.218	.250	.344
2-1/2	65	2.875	.083	.120	?	.203	.276	.300	.375
3	80	3.500	.083	.120	?	.216	.300	.350	.438
3-1/2	90	4.000	.083	.120	?	.226	.318	?	?

 

 

 

 

 

 

 

 

 

NPS 4 to NPS 8

NPS	DN	OD (inches)	Wall Thickness (inches)
			SCH 5	SCH 10	SCH 20	SCH 30	SCH 40	SCH 60	SCH 80	SCH 100	SCH 120	SCH 140	SCH 160
4	100	4.500	.083	.120	?	?	.237	.281	.337	?	.437	?	.531
4-1/2	115	5.000	?	?	?	?	.247	?	.355	?	?	?	?
5	125	5.563	.109	.134	?	?	.258	?	.375	?	.500	?	.625
6	150	6.625	.109	.134	?	?	.280	?	.432	?	.562	?	.719
8	200	8.625	.109	.148	.250	.277	.322	.406	.500	.593	.718	.812	.906

NPS 10 to NPS 24

NPS	DN	OD (inches)	Wall Thickness (inches)
			SCH 5s	SCH 5	SCH 10s	SCH 10	SCH 20	SCH 30	SCH 40s	SCH 40	SCH 60	SCH 80s	SCH 80	SCH 100	SCH 120	SCH 140	SCH 160
10	250	10.75	.134	.134	.165	.165	.250	.307	.365	.365	.500	.500	.593	.718	.843	1.000	1.125
12	300	12.75	.156	.165	.180	.180	.250	.330	.375	.406	.500	.500	.687	.843	1.000	1.125	1.312
14	350	14.00	.156		.188	.250	.312	.375	.375	.437	.593	.500	.750	.937	1.093	1.250	1.406
16	400	16.00	.165		.188	.250	.312	.375	.375	.500	.656	.500	.843	1.031	1.218	1.437	1.593
18	450	18.00	.165		.188	.250	.312	.437	.375	.562	.750	.500	.937	1.156	1.375	1.562	1.781
20	500	20.00	.188		.218	.250	.375	.500	.375	.593	.812	.500	1.031	1.280	1.500	1.750	1.968
24	600	24.00	.218		.250	.250	.375	.562	.375	.687	.968	.500	1.218	1.531	1.812	2.062	2.343

MATERIAL
The manufacturing of pipe uses many materials including ceramic, metal, concrete, and plastic.
Pipe may be made from a variety of materials. In the past, materials have included wood and lead (Latin plumbum, from which we get the word plumbing).
Metal pipes are commonly made from unfinished, black (lacquer), or galvanized steel, brass, and ductile iron. Copper tubing is popular for plumbing systems.
Plastic tubing is widely used for its light weight, chemical resistance, non-corrosive properties, and ease of making connections. Plastic materials include polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), polyethylene (PE), cross-linked high-density polyethylene (PEX), polybutylene (PB), and acrylonitrile butadiene styrene (ABS), for example.
Pipe may also be made from concrete or ceramic. These pipes are usually used for low pressure applications such as gravity flow or drainage.

Joining

Pipes are commonly joined by welding or by using pipe threads. The most common pipe thread in North America is the National Pipe Thread (NPT) or the Dryseal (NPTF) version. Other pipe threads include the British standard pipe thread (BSPT), the garden hose thread (GHT), and the fire hose coupling (NST).
Copper pipes are typically joined by soldering, brazing, compression, flaring, or crimping. Plastic pipes may be joined by solvent welding, heat fusion, or elastomeric sealing.
If frequent disconnection will be required, gasketed pipe flanges or union fittings provide better reliability than threads. Some thin-walled pipes of ductile material, such as the smaller copper or flexible plastic water pipes found in homes for ice makers and humidifiers, for example, may be joined with compression fittings.
Mechanical grooved couplings or Victaulic joints are also frequently used for frequent disassembly & assembly. Developed in the 1920s, these mechanical grooved couplings can operate up to 1,200psi working pressures and available in materials to match the pipe grade.