nd钢管外径和承受压力求壁厚计算方法：nd钢管外径、规格、壁厚求能承受压力计算方法(钢管不同材质抗拉强度不同) 压力=(壁厚*2*钢管材质抗拉强度)/(外径*系数) 二：nd钢管外径和承受压力求壁厚计算方法：
Method for calculating wall thickness of ND steel pipe by external diameter and bearing pressure: method for calculating external diameter, specification and wall thickness of ND steel pipe to be able to withstand pressure (different tensile strength of different materials of steel pipe) pressure= (wall thickness*2*tensile strength of steel pipe material)/(external diameter*coefficient). 2: method for calculating wall thickness of ND steel pipe by external diameter and bearing pressure:
壁厚=(压力*外径*系数)/(2*钢管材质抗拉强度)三：nd钢管压力系数表示方法：
Thickness = (Pressure * Outer Diameter * Coefficient)/(2 * Tensile Strength of Steel Tube Material) 3:nd Pressure Coefficient of Steel Tube:
钢管压力P<7Mpa 系数S=8
Steel pipe pressure P<7Mpa coefficient S=8
7<钢管压力P<17.5 系数S=6
7<Steel Tube Pressure P<17.5 Coefficient S=6
钢管压力P>17.5 系数S=4
Steel pipe pressure P>17.5 coefficient S=4 怎样判断nd钢管的好坏
How to judge the quality of ND steel pipe

首先要看nd钢管的表面。观察亮度和表面有无漏焊和脱皮等表面问题。好的nd钢管表面色泽光亮，一般情况下不会生锈。
First of all, we should look at the surface of ND steel pipe. Observe the brightness and surface problems such as welding leakage and peeling. A good ND steel pipe has a bright surface and will not rust in general.

第二点就是看材质。化学成分是nd钢管的基础。检查化学成分是否达标是nd钢管很重要的检查方式。还有就是检查是否精炼炉的材料。
The second point is to look at the material. Chemical composition is the basis of ND steel pipe. Checking whether the chemical composition is up to the standard is an important inspection method for ND steel pipes. The other is to check whether the material of the refining furnace is available.

第三点就是要看做工。圆管的圆度、方管的方度、表面的处理、nd钢管两端的处理、还有很重要的一点就是整只钢管的平直度。
The third point is to look at the workmanship. Roundness of circular pipe, squareness of square pipe, surface treatment, treatment of both ends of ND steel pipe, and a very important point is the flatness of the whole steel pipe.

最后，好的nd钢管厂家拥有好的管理层、好的操作工、好的制度、有一定的知名度和信誉度，产出来的产品自然也能满足客户的高端要求。而一些小的或者不正规的钢管厂家生产出来nd钢管不仅在外观上与好的nd钢管有差距，其坚硬程度、韧性，也有很大的差距。
Finally, a good ND steel pipe manufacturer has good management, good operators, good system, a certain degree of popularity and credibility, and the products can naturally meet the high-end requirements of customers. And some small or irregular steel pipe manufacturers produced ND steel pipe not only in appearance and good ND steel pipe has a gap, its hardness, toughness, but also a big gap.