The elbow and the elbow pipe basic difference is the elbow shorter. R=1 or 2 times is the elbow, then big multiples is the elbow pipe. The cold bend pipe can be bend by straight pipe, finished with one procedure, not need to do secondary corrosion in the production.  However, the production process of the elbow is much complicated compare to the elbow pipe.  It is manufacturers custom-made, corrosion, which means it has long order cycle. The cost efficient of the elbow higher than the elbow pipe and the price is much higher too. It is know to people that the elbow pipe easily damaged due to no corrosion prevention. because inexpensive so that it is widely used in the project that not have high demands.

Construction technology of the cold bend pipe has a oil standard, West-East natural gas transmission project have its enterprise standard. Both are good at plain area, considering the cost, the elbow pipe is better. But the elbow is must at narrow sector , like stonework trench segment . The curvature semidiameter of the elbow are small , usually 6D, and the the elbow pipe is 40D.