The high frequency vibration of high pressure piping has strict requirements on the assembly of the lens gasket of the high pressure flange. Before the assembly should be inside pipeline, pipe threaded end and tapered sealing surface, gaskets, high pressure flange and bolts, nuts and all the clean up, and check the appearance, when necessary, then coloring, magnetic or ultrasonic flaw detection. Any seals shall have crack; surface defects, which the pipe threaded end, high pressure flange, bolt and nut thread of the effective part of tooth high corrosion and wear shall not exceed 10% of the standard tooth height, each lap mechanical damage length should not be more than 1 / 5 of the perimeter, each circle and not larger than the circumference of a circle, bolt rod section shall not corrosion or mechanical damage; overproofed defects should be replaced in a timely manner. In the assembly process, attention should be paid to maintain a clean sealing surface, and strictly control the bolt of flange preload, the hydraulic tightening device or measuring torque wrench symmetric fastening.
Stud bolt tightening after the elongation control in general is not more than 3 / 10 000 bolt length, high temperature control between the 3 / 10 000 ~ 5 / 10 000 bolt length, bolt ends exposed outside the nut thread length should be equal as far as possible and not less than 2 times the pitch, to remove more than twice the bolt pre tightening force of around 6% increase. Installation shall not use forced assembly and a requirement to keep two flanges parallel to the end surface, the parallel deviation control within 0.3mm, keep the two flanges on the axial center line of the coaxial, coaxiality error depending on the diameter size control in less than 0.3 ~ 0.5mm range, to really confidential cover good contact and prevent bad moment. Keep a good surrounding environment, do a good job of dampproof, dustproof and anti rust and other maintenance work, and according to the working temperature of the level of discretion in the high pressure bolt coated powder lubricating oil or grease molybdenum disulfide. Pipeline running at high temperatures, the general should be in keeping the temperature test operation 24h after, tube pressure relief to 0.5MPa (gauge) following then moderate fastening force will flange bolts in hot tight to seal the pretightening force; pipeline running at low temperatures, in keeping the temperature test operation 24h after unloading despite internal pressure and with methanol on the surface of the bolts of flanges.
Source: Yaang Pipe Industry Co., Limited (www.yaang.com)