GB/T 8163 is a widely used Chinese standard for seamless steel pipes designed for fluid transportation applications. It is mainly used in the transportation systems of water, oil, natural gas, steam, and other industrial fluids. The standard specifies requirements for pipe materials, dimensions, tolerances, mechanical properties, hydrostatic testing, and surface quality to ensure the safety, stability, and long-term durability of pipelines operating under pressure.

Compared to ordinary structural steel pipes, GB/T 8163 places greater emphasis on pressure-bearing performance and fluid conveyance safety, making it widely used in fields such as petrochemicals, municipal water supply, natural gas pipelines, boiler piping, and industrial pipeline engineering. Common materials include 10#, 20#, and Q345B, among which 20# seamless steel pipes are the most widely used due to their stable overall performance.

For purchasers and engineering projects, understanding the GB/T 8163 standard helps ensure the correct selection of pipe specifications, pressure ratings, and suitable materials, thereby enhancing the operational safety of piping systems and reducing long-term maintenance costs.

II. Comparison Table of Main Materials/Grades in GB/T 8163

Material Grade	Type	Chemical Composition Features	Mechanical Properties Features	Key Differences / Remarks
10#	Carbon Structural Steel	Low carbon content, few impurities	Lower strength, good plasticity, easy to process	Suitable for low-pressure, cost-sensitive applications; lowest strength, best ductility
20# (Most Common)	Carbon Structural Steel	Medium strength, stable composition	Tensile strength ~410–550 MPa, good weldability	Most commonly used in GB/T 8163; cost-effective with balanced performance
Q345 (A/B/C)	Low-Alloy High-Strength Steel	Contains trace Nb/V/Ti, increased strength	Yield ≥345 MPa, high pressure resistance	Significantly stronger than 10# and 20#; thinner wall can be chosen for same specifications to reduce weight
Q390 / Q420	Low-Alloy High-Strength Steel	More alloying, higher strength	Yield 390–420 MPa, higher pressure resistance	Higher strength, but reduced weldability and machinability; higher cost
15CrMo (Alloy Steel)	Cr-Mo Alloy Steel	Heat and pressure resistant	High-temperature strength, creep resistance	Suitable for high-temperature service; preferred for high-temperature, high-pressure environments
12Cr1MoV	Alloy Steel	Contains Cr, Mo, V; excellent temperature resistance	Good long-term high-temperature stability	Better temperature resistance than 15CrMo; slightly higher cost
35 / 45#	Structural Steel	High strength	High tensile strength, poor weldability	Often used for structural parts; not recommended for long-distance fluid pipelines
ST45 / ST52 (Equivalent foreign grades)	High-Strength Steel	Refer to DIN/EN composition	High strength, moderate plasticity	Commonly matched with GB/T 8163 in export projects

III. GB/T 8163 Chemical Composition and Mechanical Properties of Seamless Steel Pipes for Fluid Transportation

i. Chemical Composition Table

Material	C (%)	Mn (%)	Si (%)	S (%) ≤	P (%) ≤	Cr (%)	Mo (%)	V (%)
10#	0.07–0.13	0.35–0.65	≤0.35	0.035	0.035	—	—	—
20# (Most Common)	0.17–0.23	0.35–0.65	≤0.35	0.035	0.035	—	—	—
Q345	≤0.18	1.0–1.6	0.20–0.50	0.035	0.035	—	—	Nb/V/Ti trace
15CrMo	0.12–0.18	0.40–0.70	0.30–0.60	0.030	0.030	0.80–1.10	0.45–0.60	—
12Cr1MoV	0.08–0.15	0.40–0.70	0.17–0.37	0.030	0.030	0.90–1.20	0.25–0.35	0.15–0.30

ii. Mechanical Properties Table

Material	Yield Strength ReL (MPa) ≥	Tensile Strength Rm (MPa)	Elongation A (%) ≥	Features
10#	195	315–430	32	Soft, easy to bend and process
20# (Most Common)	245	410–550	26	Suitable for water, oil, and gas pipelines
Q345	345	470–630	20	High strength, used for higher pressure or structural applications
15CrMo	310	470–630	17	Good high-temperature and high-pressure performance
12Cr1MoV	275	440–600	18	Best high-temperature creep performance

IV. GB/T 8163 Specifications and Dimensions of Seamless Steel Pipes for Fluid Transportation

i. Small Diameter Fluid Pipes (10.3–60.3 mm)

Outer Diameter OD (mm)	Wall Thickness WT Range (mm)
10.3	1.8–3.0
13.7	1.8–3.0
17.2	1.8–3.5
21.3	2.0–4.0
26.9	2.0–4.5
33.4	2.5–5.0
42.3	2.5–6.0
48.3	2.5–6.0
60.3	3.0–8.0

ii. Commonly used medium-diameter sizes (73–168 mm)

Outer Diameter OD (mm)	Wall Thickness WT Range (mm)
73.0	3.5–10
76.1	3.5–10
88.9	4.0–12
101.6	4.0–14
108	4.0–14
114.3	4.0–14
121	4.0–14
133	4.5–16
139.7	4.5–16
159	5–18
168.3	5–20

iii. Large-diameter fluid pipes (≥ 219 mm)

Outer Diameter OD (mm)	Wall Thickness WT Range (mm)
219	6–25
245	6–25
273	6–30
325	6–30
355.6	8–30
377	8–32
406.4	8–36
426	8–36
457	8–40
508	8–45
530	8–50
559	10–50
610	10–60

V. Production Process

Round tube blank → Heating → Piercing → Rolling → Sizing/Reduction → Cooling → Cutting → Heat treatment (if required) → Surface treatment → Inspection → Finished product

VI. GB/T 8163 Quality Inspection Standard for Seamless Steel Pipes for Fluid Transportation

Inspection Item	Test Method / Standard	Acceptance Criteria (According to GB/T 8163)
Chemical Composition	Spectral Analysis (OES) or Chemical Analysis	Must meet the chemical composition requirements of the corresponding steel grade (10#, 20#, Q345, 15CrMo, etc.)
Mechanical Properties	Tensile Test (GB/T 228)	Yield strength, tensile strength, and elongation must meet the standard values of the corresponding steel grade (e.g., 20#: ReL ≥245 MPa, Rm 410–550 MPa)
Impact Test (for Low Alloy Steel)	Charpy Impact Test (GB/T 229)	Q345 and similar grades must meet the specified impact energy (room temperature ≥27 J)
Hydrostatic Test / Pressure Test	GB/T 241	Must withstand the specified pressure without leakage or rupture (P ≥ standard value, generally ≥20 MPa, calculated according to WT/OD)
Nondestructive Testing (UT/ET)	Ultrasonic Test or Eddy Current Test (GB/T 7735, GB/T 5777)	No cracks, slag inclusions, delaminations, or harmful defects are allowed
Surface Quality	Visual Inspection (GB/T 8163)	Pipe surface must be free of cracks, folds, laps, delaminations, weld overlaps, scars, etc.; minor scratches allowed locally but must be within tolerance
Dimensional Measurement	Calipers, Wall Thickness Gauge, Steel Tape	OD, WT, length, and tolerances must comply with GB/T 8163 requirements (OD ±1%, WT -12.5% or ±10%, etc.)
Ovality Check	OD Measurement	Ovality must be within OD tolerance range (usually ≤1%)
End Inspection	Visual + Caliper	Plain ends must be smooth and burr-free; bevel angle 30° ±2.5°, blunt edge 1.6 ±0.8 mm
Straightness (Bending)	GB/T 8163 Straightness Test	Overall bending ≤1.5‰; local bending ≤3 mm/m
Weight Deviation	Theoretical Weight Comparison	Weight deviation must meet the standard (generally ±10%)
Pipe End Seal (Threaded Pipe)	Thread Gauge Inspection	Threads must meet G pressure thread requirements; no cross-threading or damage

VII. GB/T 8163 Application Areas of Seamless Steel Pipes for Fluid Transportation

Application	Typical Medium / Working Condition	Why Choose GB/T 8163 (Advantages)	Common Steel Grades
Industrial Fluid Transport	Water, oil, gas, compressed air, inert gases	Seamless structure provides stability, high pressure resistance, good weldability	20, Q345
Boiler Room & Heat Exchange Piping	Hot water, steam systems (≤350°C)	Good pressure and temperature resistance, suitable for thermal cycles	20, Q345B
Petrochemical Pipelines	Chemical media, light oils, water injection systems	High strength, corrosion resistance can be enhanced with internal coatings	20, Q345, Q345E
Urban Infrastructure	Tap water, fire-fighting networks, pressurized water supply	High reliability and long service life of seamless steel pipes	20
Mechanical Equipment Piping	Hydraulic oil, lubricating oil, machine cooling water	Uniform wall thickness, good machinability, suitable for mechanical piping	20, Q345
Mining & Tunnel Engineering	High-pressure water supply, drainage, grouting systems	Impact and pressure resistant, suitable for harsh environments	Q345B / Q345E
Marine & Port Engineering	Seawater pipelines, anti-corrosion transport systems	High strength and corrosion resistance, external anti-corrosion layer can be applied	Q345E
Power Plant Auxiliary Piping	Industrial water, circulating water, oil systems	Moderate cost, stable performance	20, Q345B

VIII. Selection Guide

1. Select material based on the conveying medium

Different fluids have different requirements for the performance of steel pipes, therefore the material should be determined based on the conveying medium.

Transported Medium	Recommended Material	Features
Water, air, and general fluids	10# / 20#	Low cost and widely used
Oil and natural gas	20#	Good strength and weldability
Medium- and high-pressure industrial fluids	Q345B	Higher strength and better pressure resistance
Corrosive media	Anti-corrosion coated steel pipe	Improved corrosion resistance and longer service life

Among these, 20# seamless steel pipe is the most widely used grade in GB/T 8163 and is suitable for most standard fluid conveyance projects.

2. Select Wall Thickness Based on Operating Pressure

Generally speaking:

Standard wall thickness (SCH40) is suitable for low-pressure conveyance systems.
For medium- and high-pressure systems, it is recommended to use thicker walls (SCH80 or higher).
Long-distance conveyance pipelines typically require higher strength and thicker wall designs.

If the wall thickness is too thin, the following issues may occur:

Pipe deformation
Risk of leakage
Reduced service life

Conversely, excessive wall thickness will increase procurement and construction costs.

Therefore, it is recommended to select the appropriate wall thickness based on a comprehensive evaluation of:

Operating pressure
Transportation temperature
Pipe diameter
Operating environment

3. Select the outer diameter based on the installation method

Application	Common Sizes
Indoor industrial piping systems	DN15 – DN100
Municipal water supply systems	DN100 – DN400
Oil and natural gas transmission	DN200 and above
Large industrial projects	Customized large-diameter sizes

When placing an order, please confirm the following:

Outer Diameter (OD)
Wall Thickness (WT)
Length
Whether custom lengths are required

This will help prevent compatibility issues during installation.

4. Is Corrosion Protection Required?

GB/T 8163 is a standard for bare steel pipes. If the pipes are to be used in:

Underground pipelines
Humid environments
Marine environments
Chemical engineering projects

it is recommended to apply a corrosion protection system, such as:

3PE coating
FBE epoxy coating
Hot-dip galvanizing
Epoxy coal tar coating

This can significantly improve the pipe’s corrosion resistance and service life.

5. Verification of Testing and Compliance with Standards

For export or engineering projects, it is recommended to focus on verifying the following:

Hydrostatic testing
Ultrasonic testing (UT)
Chemical composition testing
Mechanical property testing
Third-party inspection

If the project has higher requirements, the following may be requested:

EN 10204 3.1 Material Test Certificate (MTC)
SGS / BV / TÜV inspection

to ensure that the products comply with engineering standards.

6. Choose a Reliable Manufacturer

High-quality manufacturers typically possess:

A complete production line
A stable supply of raw materials
A rigorous quality control system
Extensive export experience

When making a purchase, you should not focus solely on price, but also consider:

Actual quality consistency
Delivery lead times
Testing capabilities
After-sales service

For long-term projects, a stable and reliable supply chain is often more important than a low price.

IX. GB/T 8163 Seamless Steel Pipe Selection FAQs

1. What is the difference between GB/T 8163 and GB/T 8162 seamless steel pipes?

Although both are standards for seamless steel pipes, they are intended for different applications.

GB/T 8163: Used for fluid conveyance, with greater emphasis on pressure-bearing performance, hydrostatic testing, and conveyance safety.
GB/T 8162: Used for general structural and machining applications, with lower requirements for fluid pressure.

If the project involves:

Water
Petroleum
Natural gas
Steam
Industrial fluids

GB/T 8163 should generally be the preferred choice.

2. How do I choose the appropriate steel pipe wall thickness?

Wall thickness primarily depends on:

Working pressure
Transportation temperature
Pipe diameter
Operating environment

Generally speaking:

SCH40 is suitable for low-pressure conveyance
SCH80 or thicker is recommended for medium- to high-pressure systems
Long-distance conveyance typically requires higher strength and thicker walls

If uncertain, ask the supplier to calculate the recommended wall thickness based on:

Working pressure (MPa)
Temperature
Conveyed medium
Design life

Help calculate the recommended wall thickness.

3. How should I choose between 20# and Q345B?

This is one of the most common questions in procurement.

20#

Suitable for:

General fluid conveyance
Water pipelines
General industrial projects

Features:

Lower cost
Good weldability
Adequate market supply

Q345B

Suitable for:

Medium- and high-pressure systems
Large-diameter pipelines
High-strength engineering projects

Features:

Higher yield strength
Greater pressure-bearing capacity
Better suited for heavy-duty applications

If the project does not involve high pressure, 20# is usually sufficient.

4. Do GB/T 8163 seamless steel pipes require corrosion protection?

In most cases, corrosion protection is recommended.

This is because bare steel pipes are prone to corrosion in the following environments:

Underground environments
Damp areas
Coastal environments
Chemical environments

Common corrosion protection methods include:

3PE coating
FBE epoxy coating
Hot-dip galvanizing
Epoxy coal tar

For long-term projects, corrosion protection is typically more cost-effective than subsequent repairs.

5. Are seamless steel pipes always better than welded pipes?

Not necessarily.

Advantages of seamless steel pipes:

More stable pressure-bearing capacity
No risk of weld defects
Suitable for high-pressure systems

However, welded pipes (ERW/SSAW) also have advantages:

Lower cost
Easier to produce in large diameters
Faster delivery

Generally:

High-pressure systems → Seamless steel pipes are preferred
Low-pressure water supply → Welded pipes are also acceptable
Large-diameter long-distance pipelines → SSAW is more common

The key is to select based on the specific operating conditions, rather than simply comparing which is “better.”

6. What parameters need to be confirmed when purchasing GB/T 8163 seamless steel pipes?

At a minimum, the following information should be confirmed:

Outer Diameter (OD)
Wall Thickness (WT)
Length
Material
Applicable Standard
Surface Treatment
Whether corrosion protection is required
Inspection Requirements
Quantity
Operating Conditions

For export projects, it is also recommended to confirm:

EN 10204 3.1 Material Test Certificate (MTC)
Third-party inspection
Hydrostatic testing
Ultrasonic testing (UT)

The more clearly defined the complete set of parameters is, the better you can avoid delivery and installation issues later on.