FAQs

SCH (Schedule) stands for the wall‑thickness series designation for American‑standard steel pipes. It represents a specification system instead of fixed numerical values. With a fixed outer diameter, a higher SCH number means a thicker pipe wall. SCH 40 is widely used for general‑purpose fluid pipes, while SCH 80 is applied in high‑pressure service.

NPS (Nominal Pipe Size) is the nominal bore designation for American‑standard steel pipes, measured in inches. Larger NPS values correspond to larger wall‑thickness figures. According to American‑standard wall‑thickness tables, NPS does not stand for actual outer diameter; it is merely a standard size code. For instance, NPS 2 literally means 2‑inch nominal size, yet its actual OD is 60.3 mm (approximately 2.375 inches), rather than 50.8 mm.

Specifications are stated by Outer Diameter (OD) and Wall Thickness (WT), marked in millimeters or inches. Inner‑diameter marking is also acceptable. A common format is OD 50.8mm x WT 2.65mm.

Adopt the format of NPS (Nominal Pipe Size) + SCH (Schedule wall‑thickness number), e.g. NPS 2 SCH 40. The OD x WT format is also acceptable on occasion.

API 5L pipe refers to fluid‑transport pipe governed by API 5L specification issued by the American Petroleum Institute, designed for conveying petroleum, natural gas, water and other media. It has two grades: PSL 1 for regular service and PSL 2 for more stringent requirements.

Hot‑rolled pipe is steel pipe formed by rolling under high‑temperature conditions. It features low internal stress and suits mass‑volume production at competitive cost, making it the mainstream product. It covers seamless fluid‑transport pipes and general structural steel pipes.

Cold‑drawn pipe is manufactured by drawing hot‑rolled pipe stock at ambient temperature to reduce diameter. It delivers superior surface finish, high dimensional accuracy and elevated yield strength, and falls into the category of precision or mechanical tubing.

ERW pipe is High‑Frequency Electric‑Resistance Welded pipe, the most prevalent longitudinal welded pipe. Round, square, rectangular and elliptical pipes are mostly produced via the ERW process with low manufacturing costs.

LSAW pipe is Longitudinal Submerged‑Arc Welded pipe. It boasts reliable weld quality, heavy wall thickness and large nominal diameter. It is primarily used for large‑bore high‑pressure fluid transportation instead of structural applications.

CDS Tubing means Cold‑Drawn Seamless Tubing. Using hot‑rolled seamless pipe as raw material, it achieves extremely tight dimensional tolerances and fine surface finish, commonly applied in precision machinery and hydraulic systems.

CDW Tubing means Cold‑Drawn Welded Tubing. Together with CDS Tubing, it forms the two major categories of cold‑drawn tubing. Its raw stock is ERW welded pipe. It costs considerably less than CDS tubing, and is fit for mechanical structural components, but not for high‑pressure hydraulic circuits.

SSAW pipe is Spiral Submerged‑Arc Welded pipe. It is produced by spirally forming steel strip and performing welding. Large‑diameter pipes can be made from narrow steel strip, and it is widely used for long‑distance large‑bore oil and gas transmission.

Conventional steel pipes are carbon‑steel products. Chinese national‑standard grades include Q235B, Q355B and 20#. American‑standard grades cover ASTM A36, A53 Grade B and A106 Grade B. Common European‑standard grades are S235JR and S355JR.

Conventional electro‑galvanizing produces a zinc coating of 8‑20 μm. Hot‑dip galvanizing yields 45‑85 μm. Chinese national standards generally require a minimum zinc coating weight of 275 g/㎡, equivalent to roughly 40 μm coating thickness.

Aluminum tubes are identified by alloy series. Main strength grades are: 1000‑series pure aluminum (e.g. 1060), 3000‑series Al‑Mn alloy (e.g. 3003), 5000‑series Al‑Mg alloy (e.g. 5052), and 6000‑series Al‑Mg‑Si alloy (e.g. 6061, 6063, the most widely‑used grades).

Precision tubes refer to seamless or welded tubes made by cold‑drawing or cold‑rolling. Typical materials include carbon steel, alloy steel and stainless steel such as 20#, 45#, Q355B, 40Cr, 42CrMo, 20CrMo, 304, 316L and 321. They are characterized by ultra‑high dimensional accuracy and tight tolerances.

Black pipe denotes steel pipe in its original as‑produced condition with no post‑processing treatment. It receives no pickling or surface coating; its dark surface consists of iron oxide scale. It serves as base tube for galvanized pipe and powder‑coated pipe.

Hexagonal or square bundling methods are standard. Thinner‑walled small‑size pipes may have 100‑200 pieces per bundle, while large‑size pipes may have only 10‑20 pieces per bundle. Bundle quantities can be customized upon request.

ASTM A53 covers steel pipes for fluid services such as water, gas and steam. ASTM A500 governs cold‑formed welded steel pipes for structural purposes. A500 focuses on load‑bearing capacity and mechanical properties, whereas A53 emphasizes pressure resistance and sealing performance.

By traditional definition, Pipe is designated for fluid transportation of water, gas and oil. Tube is intended for structural applications such as support posts and frameworks.

ASTM A53 is the specification for American‑standard carbon‑steel seamless and welded pipes for fluid service. It includes Type S (seamless) and Type E (electric‑resistance welded). Hydrostatic testing is mandatory at factory. Grade B is the most widely‑used commercial grade.

ASTM A500 is the specification for cold‑formed welded and seamless carbon‑steel structural tubing. Factory hydrostatic testing is not required; priority is given to mechanical strength and load‑bearing performance.

• For fluid transportation: ASTM A53 / A106 (US standard), EN 10217 (European standard).
• For structural load‑bearing: ASTM A500 (US standard), EN 10219 (European standard).
• For oil & gas service: API 5L (US standard).
• For mechanical finishing: GB/T 8162 / GB/T 3639 (Chinese national standard).
• For stainless‑steel pipe: ASTM A312 (US standard).