管的最重要的特征是外径和壁厚。外径减去两倍的壁厚得到内径。而内径决定了管能通过流体的能力。其公称管径与实际直径并不一致，只是一个粗略的指标。The most important dimensions for a pipe is the outer diameter (OD) together with the wall thickness (WT). OD minus 2 times WT (SCHEDULE) determine the inside diameter (ID) of a pipe, which determines the liquid capacity of the pipe. The NPS does not match the true diameter, it is a rough indication
金属管子最重要的特征是外径和壁厚。这些参数一般用英寸或者毫米作为单位，标识的外径也就是实际外径。The most important dimensions for a steel tube are the outside diameter (OD) and the wall thickness (WT). These parameters are expressed in inches or millimeters and express the true dimensional value of the hollow section.
Wall Thickness 壁厚
金属管的壁厚会被指定一个"schedule"值 （最常见的是 sch.40，Sch. STD., Sch. XS, Sch. XXS等等）。两种公称管径不一样的管但有同样的 schedule值时，其壁厚不一样。The thickness of a steel pipe is designated with a "Schedule" value (the most common are Sch. 40, Sch. STD., Sch. XS, Sch. XXS). Two pipes of different NPS and same schedule have different wall thicknesses in inches or millimeters.
The wall thickness of a steel tube is expressed in inches or millimeters. For tubing, the wall thickness is measured also with a gage nomenclature.
Types of Pipes and Tubes (Shapes) 形状
Round only 仅圆管
Round, rectangular, square, oval 圆形、矩形、方形、椭圆形
Production range 量产规格的范围
Extensive (up to 80 inches and above) 可以高到80英寸和更高
A narrower range for tubing (up to 5 inches), larger for steel tubes for mechanical applications 范围较窄，最高只有5英尺
Tolerances (straightness, dimensions, roundness, etc) and Pipe vs. Tube strength 公差
Tolerances are set, but rather loose. Strength is not the major concern. 设置有公差，但比较宽松，强度不是主要的考虑点。
金属管子则有严格公差。管子需要在制造的过程中对各方面的尺寸进行质检，比如直度，圆度，壁厚，以及检查表面等等。机械强度是管子的主要考虑点。Steel tubes are produced to very strict tolerances. Tubulars undergo several dimensional quality checks, such as straightness, roundness, wall thickness, surface, during the manufacturing process. Mechanical strength is a major concern for tubes.
Production Process 生产工艺
管一般是由高度自动化的高效工艺来批量生产的，比如管厂一般连续生产并将其分销到全球各地。Pipes are generally made to stock with highly automated and efficient processes, i.e. pipe mills produce on a continuous basis and feed distributors stock around the world.
管子的制造流程更长并且消耗更多人工 Tubes manufacturing is more lengthy and laborious
Delivery time 交期
Can be short 短
Generally longer 长
Market price 市场价格
比管子相对低 Relatively lower price per ton than steel tubes
高，由于生产成本和严格的要求 Higher due to lower mills productivity per hour, and due to the stricter requirements in terms of tolerances and inspections
Materials 材料
可选的材料很多 A wide range of materials is available
管子主要采用碳钢，低碳合金，不锈钢，镍合金，一般的机械方面应用使用的管子是碳钢的Tubing is available in carbon steel, low alloy, stainless steel, and nickel-alloys; steel tubes for mechanical applications are mostly of carbon steel
End Connections 连接方式
坡口，平口和螺纹 The most common are beveled, plain and screwed ends
Threaded and grooved ends are available for quicker connections on site 螺纹和槽型以便于快速连接
