The undersea line pipe inspection

The undersea line pipe inspection

 

Over the past decade, with the development of U.S. offshore oil fields, the domestic demand for subsea pipeline steel pipe in increasing. Now domestic steel industrial enterprises have been able to mature mass production of subsea pipeline steel pipes of different diameter and wall thickness. The author through participation in the work of the inspection that the the subsea pipeline pipe inspection should focus on the following aspects:

 

Inspection of equipment and processes

 

1 the checking pipeline steel pipe factory in the necessary production equipment is complete.

 

(1) Smelting equipment: electric furnace, converter furnace refining, continuous casting, die casting

 

(2) heating the device

 

(3) Rolling equipment: hot-rolled, hot expanded, cold drawn units, sizing machine, Jiao straightening machine

 

(4) Heat treatment equipment

 

(5) Non-destructive testing equipment: ultrasonic, eddy current, magnetic flux leakage, and magnetic

 

(6) The hydrostatic test equipment

 

(7) Sand (pill) equipment

 

(8) the tube end processing equipment

 

(9) The physical and chemical testing equipment

 

Check line pipe production process is perfect.

 

Main mode of production of seamless steel tubes for hot-rolled, hot expansion, hot extrusion, cold-rolled, cold- drawn and cold spinning, check following the two most commonly used in the production process of the production process is perfect, has important to ensure quality role.

 

(1) hot-rolled General Production lines:

 

Smelting (furnace / BOF - refining furnace) → the billets → blank preparation (grinding, testing, surface treatment) → heating (stepper / annular furnace) → perforation (two rolls or roller ramp roller punch) → reaming → rolling → whole (main deformation is flaring / reducing and less wall) → sizing → shear → reheated → quenching (or normalized) → tempering → again all → thermal straightening → cooling → The cold straightening → performance test → sandblasting (steel shot or quartz sand) → storage → → tube-side blind spot testing → → measuring the length of the pipe end processing, weighing → print logo destructive testing → water pressure.

 

(2) thermal expansion (mainly used in the production of large-diameter steel pipe  pipeline ) production line:

 

The smelting → billet → heating → → → rolling → the perforated → reaming sizing (blooming tube) → heating → thermal expansion expansion bell → → Sizing → quenching (or normalized) → tempering heat straightening → → nondestructive testing the cold straightening → performance test → (sandblasting) → the hydrostatic → → measuring the length of the pipe end processing, weighing → print identification → storage.

 

Factory data / qualification and technical documentation review

 

Offshore engineering products producers inspection certification by the U.S. Classification Society, CCS factory must hold recognized certificates.

 

Production line pipe specification "(44) business at the same time need to hold the steel pipe manufacturing certificate validity period issued by the API.

 

3 review of the quality system of the factory and technical documents related to the products of the project. Check to make sure the factory quality system running ability the factory can effectively control the quality of the product. Factory quality audit record forms, compliance with the contract's technical requirements and standards.

 

4 of inspections process documents (important step process card, operating procedures, etc.) meets the requirements of Order Agreement and the relevant standards. Check that the plant personnel are familiar with the technical documentation and related standards.

 

Variety of testing equipment and measuring instruments for inspection of factories, whether to meet the production requirements of the contract, whether it is approved. Check the validity of Audit shall comply with the regulations of relevant national measurement test units.

 

Review of NDT operator qualification certificates. NDT operator should hold the appropriate level of qualification.

 

Review of the commissioning party or factory orders technical agreement. Unclear or objection of the technology agreement, should be timely feedback to the commissioning party.

 

Common defects and treatment

 

Destructive testing found trauma (refers to defects in the steel tube outer surface) from the centerline of the pipe wall thickness or internal injuries, should comply with the relevant requirements.

 

Outside the fold: present spiral sheet folded steel pipe outer surface can be used grinding wheel grinding, grinding depth and width ratio should be> 6:1 "smooth transition, according to the amount of grinding necessary The mill thickness measurements at the grinding large impact surface quality, need to entrust agree. Conversely, internal injuries, in principle, should be commuted. For trauma after manual grinding flaw, if qualified, should be grinding at the pipe wall thickness measurement, if the wall thickness beyond the negative tolerance, then commuted.

 

3. Hemp / linen surface: abrasions inside the furnace due to equipment reasons, the pipe rolling mill or sizing mill roll groove wear; steel pipe for too long time to stay in the furnace, the heating temperature is too high so that the surface generate thick oxide; rolling pressed into the steel surface; the steel surface bonding reheating furnace foreign body;, or high-pressure water pressure is not enough (or nozzle clogging), high-pressure water phosphorus removal, did not play its due role cause surface pitting / Ma surface affect the surface quality.

 

Partial manual grinding under the premise of obtaining the consent of the Principal, the factory should be carried out, but artificial grinding at excessive grinding, and should steel pipe wall thickness measurement.

 

4. Within the fold: steel pipe surface showing spiral, half spiral or irregular distribution serrated folding, folding pipe end local. Grinding to clear the necessary thickness measurements at the grinding, Central or full-length of steel pipe body exists within folding should be commuted.

 

Within straights: rolling, head stick steel is not timely cleaning, or serious head wear, steel pipe inner surface to form numerous longitudinal grooves along the length direction of the steel pipe. Deal with such defects, the removal of part of the steel pipe, until no defects or commuted.

 

6. Within helix pits: the surface of the tube surface of the body, found by artificial lighting can spiral steel pipe inner surface bump phenomenon, or within was local pit (the outer surface of the check basic does not appear). Choose a typical steel pipe anatomy. Touch, no obvious bump transitional sense, and measured with a ruler concave depth <0.5 mm, the spiral height of <0.2mm wall thickness (ultrasonic thickness) to meet the requirements, you can accept.

 

7 Stratification: billets nonmetallic inclusions, or the presence of severe osteoporosis, compression can not be welded together in the pipe ends, or inner surface appears spiral or lumps of metal separation or break. Handle layered defects, should be the removal of part of the steel pipe, until no defects.

 

8. Cracks: pided into three, crack direction generally vertical or diagonal.

 

(1) penetrating crack (tear): rare such cases, the cause is the tube end cracks; cutting head and cut the tail is not enough; rolling metal debris is rolled into a tube. Such cracks have a certain length and width, and visible to the naked eye, testing, and the hydraulic pressure can also be detected defect. Products such defects, local excision, if the length does not comply with the requirements of the agreement, is the substandard products, or commuted.

 

(2) general surface cracks: Tube pinhole exists or subcutaneous inclusions; tube surface hairline cracks have a certain length and width, such cracks visually generally can not be found, but the defects can be detected by magnetic detection. The manual method such defects can be used to eliminate the need for steel pipe wall thickness measurement, grinding capacity.

 

(3) superficial cracks (also known as the hairline): Such cracks naked eye generally can not be found, but can be detected by magnetic particle inspection, defect. The length of such cracks, generally less than 10mm, the depth of generally less than 0.1mm, little grinding, the defect can be eliminated.

 

Green Line 9.: Steel tube outer surface presented symmetric or asymmetric linear rolling marks along the vertical distribution. Allowed the depth of the "the <0.1mm blue line.

 

10. Ears: in one or both sides of the steel pipe outer surface, there is the longitudinal rectilinear metal protrusions formed burrs. Such defects, eliminate artificial methods available.

 

11. Concave (touch deflated): steel pipe surface local inward depression, wall presented within the outer concave convex, no damage. If the outside diameter and roundness does not exceed the size tolerance range, ultra-source excision.

 

12 overcorrection concave: cold straightening straightening are angle improperly adjusted, under pressure caused by excessive; the steel surface rendering spiral recessed. The apparent angular or inner surface is not raised, acceptable, and vice versa commuted.

 

13. Overfiring: the heating temperature is too high, or the long residence time of the high-temperature section (often caused by equipment failure), the steel surface is very thick oxide, the internal organization of coarse grains and grain boundary oxidation occurs, plastic value is low. Of such products should be commuted.

 

14. Defects (lack of existing quality, the product does not meet the relevant specifications or technical requirements of the agreement), or defect (by manual or mechanical methods to get rid of, and comply with the requirements of the specification or technical agreement) distinguish and disposal according to ANSI / API SPECIFICATION 5L (44 Edition) P29 9.10 handling.

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