The section should not be taken from the weld area. Drill a 6 mm hole through the coating down to the steel substrate. Then, centre the electroyte cell with the electrodes around the hole. Using a suitable sealant, form a seal between the electroyte cell and the polyethylene coating. Add distilled water to make up for loss of electrolyte during the test period.
Table C. Using a suitable tool, chip off a sufficiently large area of the coating around the drilled hole. For each segment determine, to an accuracy of 0,5 mm, the maximum length of disbondment measured from the edge of the artificial defect to the edge of original adhered area For system testing, calculate the arithmetic mean of three samples, and express the maximum length of disbondment expressed as the cathodic disbondment in mm.
NOTE Using a suitable cutting tool, cut out and then remove a square area of the coating the size of the sealed cylinder. The loss of adhesion is recognizable as a nearly circular area and is to be determined as follows.
Divide the circle into eight segments. The main criterion for three-layer coatings is the cohesive failure of the PE adhesive layer, i. The peel strength of the polyethylene coating shall be determined using the test assemblies shown in Figures D. Furthermore, a twin-blade saw or a suitable cutting device is required to prepare the samples.
Then, make another cut perpendicular to the axis of the previous cut to isolate the strip and lift a length of about 20 mm from the pipe. The sample shall be cut in the cold state. Record and document the force required to peel the strip. For system testing, evaluations should be based on a continuously recorded force-time diagram. If the polyethylene coating strip breaks during the test, the tensile force recorded at the time of the break applies. The dielectric strength of defect-free coatings is not tested.
Normally a metal brush or conductive rubber is used as the scanning electrode. The presence of defects is indicated by the sound of the spark or by a signal generated by the testing equipment. The voltage should not exceed 25 kV. Pass the scanning electrode over the entire surface of the coating with the electrode touching the surface.
A noticeable air gap will distort the result. If there is a spark, mark the defective area. For testing, the polyethylene layer may be applied without adhesive to make sampling easier. After sampling, the underside of the samples surface which was previously in contact with the steel substrate may be mechanically smoothed. Elongation is measured between two gauge marks within the test area. The following test speeds apply: Table F. The arithmetic mean of five results shall be determined.
Care shall be taken that coating samples are free of adhesives. The weight shall be guided to minimize friction. The a hemispherical head with a diameter of 25 mm. The drop height shall be about 1 m. Table H. The specimen shall be supported in such a manner that its elastic response is eliminated.
The distance between two impacts should be at least 30 mm. The polyethylene coating shall be checked for defects holidays as in Annex E using spark testing equipment.
No holidays shall be detected. The total mass shall be 2,5 kg. Furthermore, a penetrometer with a dial gauge having an accuracy of 0,1 mm is needed. The test piece shall be conditioned, depending on the required test temperature. If necessary, the bottom side of the test piece can be ground down to the desired thickness.
Set the zero value within 5 s. Then, attach the additional weight to the indenter and, after 24 h, read the depth of indentation indicated on the penetrometer scale. The gap between the container and pipe shall be closed with a suitable sealant.
Furthermore, a direct current supply having a minimum output voltage of 50 V and an ammeter and a voltmeter are necessary. For the purposes of measurement, the positive pole of the direct current source shall be connected to the steel substrate and the negative pole shall be connected to the counter electrode.
During measurement the counter electrode shall be immersed in the test medium. The voltage is to be applied only at the time of measurement. Standard Poster ParaType. Grunge Standard Scholtz Fonts. Stylo Standard Fonts of Chaos. Nuclear Standard Zang-O-Fonts. NotaBene Wiescher Design.
Normalise Din Mecanorma Collection. Standard Shaded Slab Yes Please. There are two kinds of procession by winding-wrap and full-coated.
Prior to coating application, the metal surface of the steel pipe shall be free of all contaminants and deleterious matter such as dirt, oil, grease, weld beads, etc. DIN 3 layers polyethylene coating Spiral welded pipe Chinese supplier. DIN PE coatings Furthermore, a penetrometer with a dial gauge having an accuracy of 0,1 mm is needed. On each pipe being inspected carry out at least 12 measurements. Coating pipe is the pipe that is by the processing after the corrosion, which can effectively prevent or don the steel pipe occurs in the course of transport and chemical or electrochemical reaction corrosion phenomena.
Tubing and Casing Coupling. Stainless Steel Welded Pipe. If the document is revised or amended, you will be notified by email. Experience gained in the transport and ein of pipes and pipelines with polyethylene coatings has shown that a high bond strength is necessary to reduce possible mechanical damage to the pipes. Other design temperatures may be agreed between the purchaser and the coater. Care shall be taken that coating samples are free of adhesives. GTS-PE is developed as per unique technology of adhesion directly to main PE coating that provides characteristics not worse than the main coating.
Using a suitable tool, chip off a sufficiently large area of the coating around the drilled hole. Table 1 — Types of coating Type Design temperatures for sintered polyethylene coatings Design temperatures for extruded polyethylene coatings Area of application N from?
Blast cleaning and any necessary subsequent work shall not result in the reduction of the minimum wall thickness specified in the technical delivery standards for the steel pipe.
The measurements shall be made at points distributed along four equally spaced longitudinal lines at the intersection with three equally spaced circumferential lines and at a distance of at least mm from the end of the coating. This website uses cookies to improve your experience while you navigate through the website.
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