steel tube pipe

Another problem is if a buyer know that he wants 1000 meters carbon steel pipe
,but how can he know the weight of it weight , commonly due to the density is fixed . so the it is easy to calculate the weight from its dimension . here we can give you a predigested formula. let us have an example for a round shape seamless tube
. suppose its outside diameter (OD) is” D” mm and the wall thickness of the seamless steel pipe
is “r” mm , and its length is “L” meters ,so we can calculate its bulk and then multiple its density and then you can got its weight . it is easy to know its weight formula is : [π (D/2) ^2-π(D/2-r)^2]*L*ρ , after predigest ,we can got the final formula is : (D-r)*r*πρ*L, due to: ρ=7.85 kg/m3 π=3.1415 . and then the formula should be (D-r)*r*L*24.66
But consider the unit for D and r is millimeter not meters ,so final result is : (D-r)*r*0.02466*L .remember the unit for D and r is
So if the pipe is weld carbon steel tube ,you can direct use this formula , for example you want a pipe with 48.3MM OD ,2.5MM wall thickness , 6 meters length ,and totally 3000 pcs ,then the weight should be (48.3-2.5)*2.5*0.02466*6*3000=50824 kg , totally about 51tons ,and you also know the goods can be delivery via 2 pcs of 40 ft containers .
The story is not over till now , if the pipe is seamless steel tube ,and it comply standard with ASTM A 106 Gr B standard or ASTM A 213 standard ,these two standard is commonly used in boiler industry ,and the tube must bear high pressure ,so the standard need the pipe have positive tolerance for its wall thickness to guarantee that the minimal capability of the tube is larger than its requirement for boiler . in fact the these two standard request the tolerance to be -0/+22% , so the weight is not a fixed data . currently there are two methods commonly used to deal with the problem . the first one is the pipe producer just tell you the price per ton ,and the real value of the goods will be available after the pipe is been produce ,and the weigh the tube and then let you know how much you have to pay . the second methods is that the supplier fixed the weight will 11% higher than its theoretic weight , for example the above mentioned tube is 50.8tons and further more suppose the pipe is seamless steel tube and apply to standard ASTM A 106 Gr B ,and the seller will fixed the tube value based on 50.8*1.11=56.388 tons , if the goods is larger in its weight after it was been produce ,then the seller will bear the risk .if finally the pipe is 53 tons ,then the seller will earn more , if the weight is less than 50.8 tons for example 49 tons ,needless to say the tube is unqualified .due to cold draw pipe is difficult to control the tolerance for pipe .so the weight is not fixed ,but according to our experience the manufacturer in China now can control its weight within 8% area , that means if the theoretic weight is 100 tons .commonly the real goods is within 108 tons .
Some standard do not need tolerance for -0/+22% ,for example ASTM A 312 and ASTM A 269 , The standard acceptable for negative tolerance ,then the buyer should take care of its weight .
So we know that seamless tube have larger tolerance and weld pipe due to the tolerance is according to the thickness of the steel sheet , and steel sheet commonly have small tolerance in thickness ,so commonly weld tube do now have larger tolerance in weight . tube some buyer want to by galvanized steel tube ,then the weigh again will be an issue and need to be talked about .
Some buyer need the tube to be hot dip galvanized pipe
and ask for the zinc layer must be 50 microns thickness , then how can we know its real weight of the tube , the density of zinc is 7.14g/cm3 , if the thickness is 50 microns then it can also be express as 50*7.14=357g/m2 , so different express methods have the same meaning .
Commonly if the zinc layer is small than 320 g/m2 or 45 microns thickness ,then the weight should be 6% higher then the un-galvanized tube ,for example if the tube is 100 tons ,after galvanization the tube maybe be 106 tons . but if the tube made by galvanized steel sheet or galvanized steel strip ,then the tube will not have so much increase in weight .but the tube need to reinforce the zinc in the welding line ,due to welding rod is not galvanized rod ,so the part of seam surface is not galvanized . need to additional process to add zinc in this place .

This entry was posted on Saturday, December 19th, 2009 at 3:55 pm and is filed under Steel Tube. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.