Planning & projects |
material indicates the extent to which its length and volume change when subjected to a change in temperature under constant pressure conditions. Piping, which is subjected to a variety of operating conditions, generally undergoes repeated expansion and contraction as a result of temperature changes. Therefore, composite materials used to restore the mechanical strength of pipe materials must also be able to cope with thermal strain. The linear expansion coefficient of Belzona SuperWrap II materials cured at ambient temperature are between 9.40 and 11.26 x 10-6
/K, which is close to that of ordinary steel (11-12.5 x 10-6 /K).4 This means that the stress effect
Top: Damaged pipeline after suffering from Corrosion Under Insulation (CUI)
Above: After rebuilding the pipe to original profile using Belzona 1111, several wraps of Belzona 9381 were applied
j
that of steel. This means that when a typical steel pipe is subjected to compressive or tensile loads, the accompanying SuperWrap II repair reacts similarly to the base metal. Young’s modulus (tensile modulus) is a measure of the stiffness of a material, and the SuperWrap II materials have high Young’s modulus of 37-39 GPa, meaning that the repair will have good stiffness and bending moment. From a practical point of view, when assessing the performance of a composite pipe repair, it is reported that a standard modulus of elasticity of 6,895 MPa or higher is desirable,3 and the values of SuperWrap II materials are well above this. On the other hand, considering that the Young’s modulus of ordinary steel is about 200 GPa, SuperWrap II materials, which have about one-fifth, are far more elastic than steel, and in this sense, it can be said that SuperWrap II repair has excellent elasticity and can easily follow the movement of the base metal. The thermal expansion coefficient of a solid
Table 4 – Testing conditions for composite performance Test items
Belzona 1981 resin
Short-term survival Long-term survival Impact
39.2 MPa 60.0 MPa 5 J
Belzona 1982 resin
39.2 MPa 60.0 MPa 5 J
(thermal strain) on the adhered surface caused by the difference in thermal expansion between the composite materials and the base metal is minimal. Table 4 shows the conditions for durability testing of the SuperWrap II composite materials. The short-term pressure test evaluates the performance of Belzona SuperWrap II against wall thinning defects (no penetration). The objective is to determine the maximum level of wall thinning that can be repaired. The test is carried out on a short carbon steel spool with a pseudo-defect (wall loss) of a specified size. The repair is designed to restore the yield strength of the original pipe wall. The test pressure was calculated as the yield pressure of the test spool in its original sound condition (test pressures indicated in Table 4). The difference in test pressure between the Belzona 1981/1982 resins and Belzona 1983 resin is due to the different test spools used. All the resins passed the test and the results demonstrate that the repair conforms to the design specification and is able to restore the durability of the pipe material. The long-term pressure test also evaluates the performance of Belzona SuperWrap II against thin-wall defects. Here, the durability of the repair is assessed after 1000 hours of sustained loading by maintaining the pipe internal pressure at a constant level (test pressures indicated in Table 4). As a result, no cracks, delamination or any other degradation was observed and the test was therefore deemed a pass. The impact endurance test examines the effect on
the repair of a low velocity 5 J impact, simulating a tool drop such as a spanner being dropped on the repair. The objective of this test is to determine the minimum thickness of the repair layer where external impact is concerned. In accordance with ISO 24817 Annex F, an impact of 5 J was applied to the pipe repair by dropping a weight from a height of 1m, followed by a pressure test. The results showed that there was no difference between the measured and calculated energy release rates, and it was concluded that this level of impact did not affect the integrity of the SuperWrap II repair system.
Requirements for application The repair design of Belzona SuperWrap II is
Belzona 1983 resin
28.4 MPa 36.0 MPa 5 J
determined by strength calculations based on actual defective conditions of pipes in accordance with the ISO/ASME standards, which also take into account factors such as surface preparation method, pipe geometry, environmental conditions, operational/ design pressures, etc. The repair is then carried out following the design, but there are certain conditions that must be adhered to during the application. Firstly, to ensure the quality of the work, all Belzona
46 | March 2023 |
www.waterpowermagazine.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53
