Pipeline failure and maintenance-15

Answer: Construction of pipeline thermal insulation metal protective layer: the pipeline thermal insulation metal protective layer is generally made of ordinary steel sheet, galvanized steel sheet and aluminum alloy sheet. The protective layer should be connected with self tapping screws by inserting, and the ring seam should be started before the sheet rolling, and the line seam should be overlapped.

Construction requirements for common thermal insulation protective layer of pipeline: a. the protective layer on the outer layer of thermal insulation structure shall be tight and firm, without water seepage, crack, loose joint or falling under the condition of environmental change and vibration. B. The metal material should be used as the protective layer, and the corrosion-resistant metal material should be used as the protective layer in corrosive environment. C. According to the specific situation, the joint form of metal protective layer can be selected as lap joint, socket joint or bite joint, which shall meet the following requirements: a. the longitudinal joint of metal protective layer of hard thermal insulation products can be bite joint without damaging the inner products and damp proof layer. The longitudinal joints of the metal protective layer of semi-rigid and soft thermal insulation products can be spliced or lapped, and the spigot joints can be connected with self tapping screws or pop rivets, while the lap joints should be connected with pop rivets. The spacing between nails is 200mm. b. The circular seam of the metal protective layer can be spliced or lapped. The overlapping width is 30 ~ 50mm. In addition to the vertically installed protective layer with fall protection requirements, the horizontal pipeline should not be fixed with self tapping screws or pop rivets on the lap or inserted ring joints of the protective layer. c. The joint of metal protective layer of cold insulation structure should be bound with snap or steel belt, and it is not allowed to connect with screws or bell nails. d. The metal protective layer shall have the overall water (rain) proof function. For the parts where the water is easy to penetrate into the insulation layer, apply Marui grease or cement weir joint. D. The lap size of the metal protective layer on the elbow and straight pipe section is 75-150 mm for high temperature pipes, 50-75 mm for medium and low temperature pipes and 30-50 mm for cold insulation pipes. The lap joint shall not be fixed. E. When using portable electric drill to drill holes, measures must be taken to fix the metal protective layer of cold insulation structure. It is strictly prohibited to damage the damp proof layer. F. The circumferential joint of the metal protective layer of the horizontal pipeline shall be along the slope direction of the pipeline and towards the lower part. The longitudinal joint shall be arranged 150 ~ 45 ° below the horizontal centerline with the joint facing down. The laying of metal protective layer of vertical pipeline shall be carried out from top to bottom, and the joints shall be built up and down. G. The circumferential joint position of the metal protective layer of the straight pipe section, the position of the expansion joint of the metal protective layer of the stationary equipment and rotating machinery, and the joint size of the protective layer shall meet the requirements of thermal expansion. No fixed parts shall be added, and the movable joint shall be made, and the interval shall meet the following requirements: it shall be consistent with the expansion joint set by the thermal insulation layer. The circular movable joint spacing of metal shell of semi hard and soft insulation layer shall comply with the provisions in table 7-10. H. Expansion joint shall be reserved for the thermal insulation layer according to the specification requirements

The metal protective layer shall also be reserved at the gap part. 1. For the metal protective layer on the thermal insulation layer of equipment or large diameter pipeline, when one end is fixed by bolts, the welding of bolts shall be perpendicular to the wall surface. The fixed bolts on each metal protective layer shall not be less than 2, and the other end shall be supported by plug-in or S-shaped hook.