Seamless Steel Pipe Sizes

What is Seamless Steel Pipe

Seamless steel pipe is a continuous metal steel tube manufactured through hot rolling, cold rolling, or cold drawing. Solid steel billets are processed into hollow tubes through perforation or extrusion. No welding is involved in the entire production process, hence the name "seamless." Compared to welded steel pipe, seamless pipe has higher structural integrity and pressure-bearing capacity.

1. Seamless steel pipe outer diameter

1/2 inch - 36 inch (21.3mm-914.4mm)

2. Seamless steel pipe thickness

2.11mm-60mm ( SCH10, SCH20, SCH40, SCH80, STD, SCH120, SCH160, XXS)

Dimensional Parameters of Seamless Steel Pipe

The dimensions of seamless steel pipe are primarily determined by three parameters: outer diameter, wall thickness, and length.

 

1. Outer Diameter Range

Small Diameter Seamless Steel Pipe: The outer diameter is typically 6mm to 89mm.

Medium Diameter Seamless Steel Pipe: The outer diameter is typically 89mm to 219mm.

Large Diameter Seamless Steel Pipe: The outer diameter is typically 219mm or greater.

 

2. Wall Thickness Range

Conventional wall thicknesses are categorized into three types:

SCH5S to SCH160 Standard Wall Thickness Series

XS/XXS Thickened Series

ST Special Thin Wall Series

Thin-Wall Seamless Steel Pipe: The wall thickness is typically 1mm to 6mm. Thick-walled seamless steel pipe: Wall thickness is typically 6mm or thicker, with some reaching 50mm or thicker.

 

3. Length Specifications

Fixed Lengths: Commonly available in three standard lengths: 6m, 9m, and 12m.

Multiple Lengths: Specific multiples of length produced to order.

Special Lengths: Determined based on production conditions, generally ranging from 4 to 12m.

4. Common Specifications

Small Diameters: Examples include Φ25×2.5, Φ32×3, and Φ57×3.5.

Medium Diameters: Examples include Φ89×4, Φ108×4.5, and Φ159×6.

Large Diameters: Examples include Φ219×8, Φ273×10, and Φ325×12.

Seamless Pipe Size in Different Types

1. Seamless Carbon Steel Pipe 

API 5L GR.B, X42,X52,X60,X65 PSL1 & PSL2
Seamless carbon steel pipe size range: 2" - 24"
Seamless carbon steel pipe schedules: STD,SCH100,SCH120,SCH160,XXH
utilized for the water and petroleum industry to transport liquids or as platforms on off-shore rigs.

ASTM A53 GR.B, ASTM A106 GR.B
Seamless carbon steel pipe Size range:  1/8" - 26"
Seamless carbon steel pipe Schedules: SCH20, SCH30, SCH40, STD, SCH100, SCH120,SCH160,XXH
utilized for services ranging from structural supports to steam drum headers with temperature ranges up to 800°F

2. Seamless Boiler Tube

Seamless boiler tube outer diameter (OD): 10.2 - 139.7 mm
(from 26.9 mm manufactured as hot rolled)
Seamless boiler tube wall thickness (WT): 0.5 - 16.0 mm

(from 2.6 mm manufactured as hot rolled)

3. Seamless Heat Exchanger Tube

Seamless heat exchanger tube outer diameter (OD): 6.00 - 101.00 mm
Seamless heat exchanger tube thickness: 0.85 - 12.7mm 
Seamless heat exchanger tube length: 1.0 - 27.0 MTR

4. Seamless Precision Tube

Seamless precision tube outer diameter (OD): 10 - 120 mm
Seamless precision tube wall thickness (WT): 0.5 - 5 mm
Seamless precision tube length: 4 - 8m

5. Seamless Hydraulic Tube

Seamless hydraulic tube outer diameter (OD): 4 - 130mm 
Seamless hydraulic tube material: E355 (ST52.4),E235 (ST37.4)
Seamless hydraulic tube standard: DIN 2391/C (DIN EN 10305-1),DIN 2445/2 (DIN EN 10305-4)
Seamless hydraulic tube finishing: NBK (Phosphate and Normalized)

Seamless Pipe Size Chart

OMINAL PIPE SIZE	OD (mm)	NOMINAL WALL THICKNESS
DN	NB (inch)	ASME	SCH10	SCH20	SCH30	STD	SCH40	SCH60	XS	SCH80	SCH100	SCH120	SCH140	SCH160	XXS
15	1/2"	21.3	2.11		2.41	2.77	2.77		3.73	3.73				4.78	7.47
20	3/4"	26.7	2.11		2.41	2.87	2.87		3.91	3.91				5.56	7.82
25	1"	33.4	2.77		2.9	3.38	3.38		4.55	4.55				6.35	9.09
32	1.1/4"	42.2	2.77		2.97	3.56	3.56		4.85	4.85				6.35	9.7
40	1.1/2"	48.3	2.77		3.18	3.68	3.68		5.08	5.08				7.14	10.15
50	2"	60.3	2.77		3.18	3.91	3.91		5.54	5.54				8.74	11.07
65	2.1/2"	73	3.05		4.78	5.16	5.16		7.01	7.01				9.53	14.02
80	3"	88.9	3.05		4.78	5.49	5.49		7.62	7.62				11.13	15.25
90	3.1/2"	101.6	3.05		4.78	5.74	5.74		8.08	8.08
100	4"	114.3	3.05		4.78	6.02	6.02		8.56	8.56		11.13		13.49	17.12
125	5"	141.3	3.4			6.55	6.55		9.53	9.53		12.7		15.88	19.05
150	6"	168.3	3.4			7.11	7.11		10.97	10.97		14.27		18.26	21.95
200	8"	219.1	3.76	6.35	7.04	8.18	8.18	10.31	12.7	12.7	15.09	18.26	20.62	23.01	22.23
250	10"	273	4.19	6.35	7.8	9.27	9.27	12.7	12.7	15.09	18.26	21.44	25.4	28.58	25.4
300	12"	323.8	4.57	6.35	8.38	9.53	10.31	14.27	12.7	17.48	21.44	25.4	28.58	33.32	25.4
350	14"	355.6	6.35	7.92	9.53	9.53	11.13	15.09	12.7	19.05	23.83	27.79	31.75	35.71
400	16"	406.4	6.35	7.92	9.53	9.53	12.7	16.66	12.7	21.44	26.19	30.96	36.53	40.19
450	18"	457.2	6.35	7.92	11.13	9.53	14.27	19.05	12.7	23.83	39.36	34.93	39.67	45.24
500	20"	508	6.35	9.53	12.7	9.53	15.09	20.62	12.7	26.19	32.54	38.1	44.45	50.01
550	22"	558.8	6.35	9.53	12.7	9.53		22.23	12.7	28.58	34.93	41.28	47.63	53.98
600	24"	609.6	6.35	9.53	14.27	9.53	17.48	24.61	12.7	30.96	38.89	46.02	52.37	59.54
650	26"	660.4	7.92	12.7		9.53			12.7
700	28"	711.2	7.92	12.7	15.88	9.53			12.7
750	30"	762	7.92	12.7	15.88	9.53			12.7
800	32"	812.8	7.92	12.7	15.88	9.53	17.48		12.7
850	34"	863.6	7.92	12.7	15.88	9.53	17.48		12.7
900	36"	914.4	7.92	12.7	15.88	9.53	19.05		12.7

Factors Affecting Seamless Steel Pipe Sizes

1. Rolling Process Parameters

The piercing mill's rolling angle and rolling speed directly affect the pipe's outer diameter accuracy. The reduction and number of rolling passes during cold rolling determine wall thickness variation. Fluctuations in process parameters can also lead to dimensional deviations.

2. Raw Material Quality

The diameter, roundness, and material uniformity of the tube billet are all transferred to the finished product. If the tube billet exhibits ovality, it can easily result in an out-of-round outer diameter of the steel pipe.

3. Temperature Control

Excessively high or uneven heating temperatures can cause inconsistent tube billet deformation, and differences in cooling rates can cause dimensional shrinkage deviations, especially in high-precision cold-drawn tubes.

4. Equipment Accuracy

Mechanical clearances and die wear in equipment such as rolling mills and sizing mills directly affect the consistency of pipe diameter and wall thickness. Older equipment can exacerbate dimensional fluctuations.

5. Subsequent Processing

Improper operation in processes such as straightening and cutting can lead to deviations in pipe straightness or length.

 

Dimensional Requirements for Seamless Steel Pipes in Different Industries

1. Oil and Gas Industry

Large-diameter (219-1422mm) and thick-walled (6-20mm) seamless steel pipes meet high-pressure, long-distance transportation requirements and reduce joints.

 

2. Chemical Industry

Mostly medium-diameter (25-377mm) with a wall thickness of 5-16mm. Seamless stainless steel pipes are often used for corrosive media, while small-diameter (10-50mm) pipes can be used for low-pressure applications.

 

3. Power Industry

Seamless boiler pipes have an outer diameter of 32-426mm and a wall thickness of 2.5-20mm. High-pressure boilers require thicker wall thicknesses, complying with GB5310 standards.

 

4. Mechanical Manufacturing

Mainly seamless precision pipes with an outer diameter of 6-200mm and a wall thickness of 0.5-10mm. Dimensional tolerances are strictly required (within ±0.1mm).

 

5. Construction Industry

Small-diameter (20-50mm, wall thickness 1-3mm) seamless pipes are used for decoration, while large-diameter (159-630mm, wall thickness 5-15mm) seamless pipes are used for structural support.

 

How to Choose Seamless Steel Pipes

1. Clarify Your Usage Requirements

When purchasing seamless steel pipes, first clarify your usage requirements, including the operating pressure, temperature range, and other requirements, so you can select the appropriate outer diameter, wall thickness, and material.

 

2. Choose a Reputable Brand

When purchasing seamless steel pipes, be sure to choose products from reputable manufacturers to ensure that their quality and performance meet standard requirements.

 

3. Check Product Certificates

When purchasing, review the product's quality certificate, certificate of conformity, and other relevant documents to ensure that the product is qualified and complies with national standards.

Read more: Seamless pipe weight calculation formula