What Are API Steel Pipe Technical Requirements and Testing Phase?

The time of issue:2013-11-25 9:03:34       Author:

The main technical requirements of high intensity API steel pipe are: the steel grade is X70, the OD is 1016mm, the wall sickness is from 14.6 to 26.2mm; the pipeline steel uses the acicular ferrite microstructure mostly; has the corrosion resistance; in the -20℃, the mean charpoy absorbed energy should be bigger than 190J, in the weld and heat affected zone, the mean charpoy absorbed energy should be bigger than 90J; the OD tolerance of the steel end is +2.0mm/-0.5mm, the roundness should be less than 0.6%; the inner wall of the steel should be coated with drag reduction internal coating, the outer wall should be coated with 3 layers polyethylene coating.

The molding methods of manufactured abroad large-caliber LSAW API steel pipe mainly are: JCOE, UOE, CFE, CE and some other methods. Use the full board ultrasonic testing machine to review the possible internal or external defects of the plates, such as cracks, inclusions, depressions an so on, all the defects can be found, in this way can avoid unqualified plates going to the next process. Before the construction, we should pay attention to clean the plates surface, in order to avoid misjudgment. If it alarms during the testing, we need to repeat testing the alarm area, confirm the defect type, examine if it is qualified, it should be control continuously.

There are some questions have occurred in the testing phase:
1. Energy selection is not suitable, it results that we can't test defects;
2. The probe position is incorrect, we can't check out all the surface problem comprehensively;
3. The mode of setting up alarm is incorrect, that results the inspectors can't find problems timely.
During the manufacturing, the plates need two processing operations: pipe pre-suppression and expanding to make the plates thinner, the thickness reduction is about 5-7%, so we'd better consider the thickness reduction before order plates, avoid wast.

Edge planing craft is easy, but it influents welding a lot, we usually inspect the following indexes:
1. The accuracy of edge planing angle;
2. The parallelism of the edge planing;
3. The knife shock phenomenon during the planing process, if the knife loose or not sharp, strong knife shock will make the planing undulating, affect the welding quality and waste plates. By multistep to make the plates round. This process is the stamping step design, according to the OD to get logical steps, such as 20, 28, 30 and so on. The key factors are the followings:
1. Each plate starts stamping from middle , the bazel machine moves coordinated with stamping machine;
2. Keep the stamping area flat and linked firmly;
3. The feed amount should be uniform. If the stamping tubes are qualified, they can turn to the welding process. The welding process includes pre-soldering, internal welding and outside welding. The basis are PQR, WPS and welding procedure specification.

The welded steel pipe and black steel pipe are also available.

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