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Inspection method of threaded flange for pressurized opening

2022-04-06 09:50:08   COMMENT:0 HITS:
1. Open the product package, check whether the main parts are consistent with the products in the list or contract, and count the quantity of products.
2. Inspect the surface of threaded flange for pits, scratches, rust fragments and oil quality, and the roughness of flange surface shall not be greater than 6.3 μ m. If the roughness is inconsistent, trim the flange surface, check the flange and bolt hole, and clean the flange surface.
3. The flange sealing surface shall be flat and smooth without burrs and radial grooves; The threaded part of threaded flange shall be complete without damage; The sealing surface in the form of concave convex seal shall be able to fit naturally, and the height of the convex surface shall not be lower than the depth of the groove.
4. Check and clean bolts and nuts, and apply insulating grease to the threads of all bolts and nuts.
5. Align the flanges to keep them parallel to the shaft center, and carefully install the gasket. It is forbidden to use lubricant, grease and adhesive on the gasket and flange surface to prevent damage to the sealing ring on the gasket.
6. Insert bolts, nuts and washers. The nuts coated with lubricating oil should be first assembled with stainless steel washers, and pre tighten the bolts until the flange and gasket contact each other.
7. Use micrometer, flashlight and other tools to check the gap between flange and gasket. If the gap exists, it indicates that the flange assembly is not parallel.
8. If there is a gap, unscrew the nut a little, and then retighten it until the two flanges are in contact with the gasket. This method is necessary to prevent the alignment offset caused by the contact between the flange and the gasket; If the method is improper, the sealing ring of the gasket will be damaged when the bolt load is too large when the flange is in contact with the gasket.
9. Tighten the loose nut again according to the bolt torque pre tightening torque recommended above (10-15% bolt torque), remove the perforated nail, replace the bolt, nut and washer, and pre tighten with the same torque.
10. Continue to tighten the bolts and increase the preload to 50% of the bolt torque; Continue to tighten the bolts to the final torque.

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