What does SCH mean?
SCH is the abbreviation of Schedule, which usually appears in the American steel pipe standard. It is a prefix of a series number. For example: SCH10,
SCH40, SCH80, etc. Corresponding to the above series numbers, you will find the wall thickness of each specification of steel pipe in the steel pipe size table. This is stipulated by the 1938 American National Standards Association ANSIB36.10 (welded and
seamless steel pipe) standard.
What is NPS?
NPS (Nominal Pipe Size) is a dimensionless ordinal number used to indicate the size of a pipe. The number following NPS indicates the size of the standard pipe. The NPS system originated from the IPS (Iron Pipe Size) system, which was introduced to distinguish different pipe sizes. These sizes were originally in inches and represented the approximate inside diameter of the pipe. For example, a pipe marked as IPS 6" has an inner diameter of approximately 6 inches.
Early pipes had fixed wall thicknesses for each size, which were later called standard wall thicknesses (STDs), and the outer diameter of the pipes was also standardized. The basic definition of NPS is based on the outer diameter of the pipe. For pipes of NPS12 and below, the outer diameter will be slightly larger than the number of inches marked after the NPS; for pipes of NPS14 and above, the outer diameter is equal to the number of inches attached to the NPS. For example, the outer diameter of steel pipes represented by NPS 6 is uniformly 168.3mm. However, NPS does not completely correspond to the inner diameter of the pipe, especially for different wall thickness series, the change in inner diameter will be more obvious.
Sch series pipe size, wall thickness comparison table (Sch wall thickness and millimeter comparison table)
(GB standard) Steel pipe wall thickness grade (Sch) expression method
The expression method of the wall thickness grade series of steel pipes varies in different standards. There are three main expression methods:
1. By pipe number (Sch) indicates:
For carbon steel pipe wall thickness, there are 10 grades: Sch10, 20, 30, 40, 60, 80, 100, 120, 140, 160 (if s is added after the number, it means stainless steel pipe); for stainless steel wall thickness series, there are four grades: 5S, 10S, 40s, 80S
2. Expressed by pipe weight, such as STD (standard weight), XS (thickened pipe), XxS (extra thick pipe)
3. Expressed by steel pipe wall thickness size, that is, "pipe outer diameter x wall thickness", such as 89x4
For carbon steel pipe wall thickness, there are 10 grades: Sch10, 20, 30, 40, 60, 80, 100, 120, 140, 160
DN15 - DN1200 NPS1/2" - 48" American Standard Pipe Sch Wall Thickness Grade Corresponding Millimeters (mm)
|
NPS
|
DN
|
Tube OD.
|
SCH5s
|
SCH10s
|
SCH10
|
SCH20
|
SCH30
|
STD
|
SCH40
|
SCH40s
|
|
1/2"
|
15
|
21.3
|
1.65
|
2.11
|
2.11
|
|
2.41
|
2.77
|
2.77
|
2.77
|
|
3/4"
|
20
|
26.7
|
1.65
|
2.11
|
2.11
|
|
2.41
|
2.87
|
2.87
|
2.87
|
|
1"
|
25
|
33.4
|
1.65
|
2.77
|
2.77
|
|
2.9
|
3.38
|
3.38
|
3.38
|
|
1-1/4"
|
32
|
42.2
|
1.65
|
2.77
|
2.77
|
|
2.97
|
3.56
|
3.56
|
3.56
|
|
1-1/2"
|
40
|
48.3
|
1.65
|
2.77
|
2.77
|
|
3.18
|
3.68
|
3.68
|
3.68
|
|
2"
|
50
|
60.3
|
1.65
|
2.77
|
2.77
|
|
3.18
|
3.91
|
3.91
|
3.91
|
|
2-1/2"
|
65
|
73
|
2.11
|
3.05
|
3.05
|
|
4.78
|
5.16
|
5.16
|
5.16
|
|
3"
|
80
|
88.9
|
2.11
|
3.05
|
3.05
|
|
4.78
|
5.49
|
5.49
|
5.49
|
|
3-1/2"
|
90
|
101.6
|
2.11
|
3.05
|
3.05
|
|
4.78
|
5.74
|
5.74
|
5.74
|
|
4"
|
100
|
114.3
|
2.11
|
3.05
|
3.05
|
|
4.78
|
6.02
|
6.02
|
6.02
|
|
5"
|
125
|
141.3
|
2.77
|
3.4
|
3.4
|
|
|
6.55
|
6.55
|
6.55
|
|
6"
|
150
|
168.3
|
2.77
|
3.4
|
3.4
|
|
|
7.11
|
7.11
|
7.11
|
|
8"
|
200
|
219.1
|
2.77
|
3.76
|
3.76
|
6.35
|
7.04
|
8.18
|
8.18
|
8.18
|
|
10"
|
250
|
273
|
3.4
|
4.19
|
4.19
|
6.35
|
7.8
|
9.27
|
9.27
|
9.27
|
|
12"
|
300
|
323.8
|
3.96
|
4.57
|
4.57
|
6.35
|
8.38
|
9.53
|
10.31
|
9.53
|
|
14"
|
350
|
355.6
|
3.96
|
4.78
|
6.35
|
7.92
|
9.53
|
9.53
|
11.13
|
|
|
16"
|
400
|
406.4
|
4.19
|
4.78
|
6.35
|
7.92
|
9.53
|
9.53
|
12.7
|
|
|
18"
|
450
|
457.2
|
4.19
|
4.78
|
6.35
|
7.92
|
11.13
|
9.53
|
14.27
|
|
|
20"
|
500
|
508
|
4.78
|
5.54
|
6.35
|
9.53
|
12.7
|
9.53
|
15.09
|
|
|
22"
|
550
|
558.8
|
4.78
|
5.54
|
6.35
|
9.53
|
12.7
|
9.53
|
|
|
|
24"
|
600
|
609.6
|
5.54
|
6.35
|
6.35
|
9.53
|
14.27
|
9.53
|
17.48
|
|
|
26"
|
650
|
660.4
|
|
|
7.92
|
12.7
|
|
9.53
|
|
|
|
28"
|
700
|
711.2
|
|
|
7.92
|
12.7
|
15.88
|
9.53
|
|
|
|
30"
|
750
|
762
|
6.35
|
7.92
|
7.92
|
12.7
|
15.88
|
9.53
|
|
|
|
32"
|
800
|
812.8
|
|
|
7.92
|
12.7
|
15.88
|
9.53
|
17.48
|
|
|
34"
|
850
|
863.6
|
|
|
7.92
|
12.7
|
15.88
|
9.53
|
17.48
|
|
|
36"
|
900
|
914.4
|
|
|
7.92
|
12.7
|
15.88
|
9.53
|
19.05
|
|
|
38"
|
950
|
965.2
|
|
|
|
|
|
9.53
|
|
|
|
40"
|
1000
|
1016
|
|
|
|
|
|
9.53
|
|
|
|
42"
|
1050
|
1066.8
|
|
|
|
|
|
9.53
|
|
|
|
44"
|
1100
|
1117.6
|
|
|
|
|
|
9.53
|
|
|
|
46"
|
1150
|
1168.4
|
|
|
|
|
|
9.53
|
|
|
|
48"
|
1200
|
1219.2
|
|
|
|
|
|
9.53
|
|
|
Common Sch Series Wall Thickness Grades
The wall thickness grades of carbon steel pipes are mainly the following: SCH10, SCH20, SCH30, SCH40, SCH60,
SCH80, SCH100, SCH120, SCH140, SCH160. These grades cover the range from thinner wall thickness to ultra-thick wall thickness, which can meet the needs of different application scenarios. For example, SCH10 is usually used for lower pressure applications, while SCH80 or SCH160 is used in situations that require higher strength and pressure resistance.
The wall thickness grades of stainless steel pipes are 5S, 10S, 40S and 80S. Stainless steel pipes are widely used and are often used in industrial fields with high corrosion requirements.
Summary
The SCH series of pipe wall thickness grades provides a standardized way to indicate the wall thickness of steel pipes of different specifications. This system originated from the American steel pipe standard and is widely used in pipeline projects around the world. NPS (nominal size) is used to identify the specifications of the pipe, while SCH is used to indicate the wall thickness of the pipe. Understanding the basic concepts of SCH and NPS is essential for selecting the appropriate pipe type and wall thickness. In practical applications, according to different pipe standards, pressure levels and use environments, selecting the appropriate SCH level can ensure the safety and reliability of the pipeline system.
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