S.S Mesh Roll,Stainless Steel Mesh Roll,Stainless Steel Wire Mesh Roll,Stainless Steel Insect Mesh Roll ANPING COUNTY HUAXING WIRE MESH CO.,LTD , https://www.huaxingwire.com
Key words: Leakage; Seal with pressure; Fixture CLC number: TK26 Document code: A Article ID: 2095-2945 (2017) 32-0141-02
1 There is a problem that the main steam pressure of the company's No. 6 steam turbine inlet is 3.8 MPa, 435°C is a medium-pressure high-temperature steam, and the electric main bypass bypass secondary valve (DN65 PN10.0 MPa) found a leak in December 2014. The inspection revealed that the bonnet flange surface of the valve was leaking and the bonnet gasket was ineffective. There was no sign of leakage after the bonnet bolts were tightened. Due to the heavy load of production operation, the conditions for immediate shutdown and maintenance are not available.
2 Solution In order to avoid the further expansion of the leakage and thus affect the normal operation of the production, the maintenance personnel of the public machinery carried out analysis and research on the site, and formulated a program for implementing pressure sealing to seal the leakage of the flange of the valve bonnet flange.
2.1 design fixture 2.2.1 on-site measurement of various dimensions as shown in Figure 1
2.2.2 Flange Grip Body Thickness Calculation The fixture thickness S is determined by the strength calculation and rigidity as well as the thread size requirements of the installed injection valve. Fixture with hole for injection agent, minimum wall thickness not less than 14mm (fluid valve and clamp connection screw length 12mm, screw thread not less than 6 teeth)
(1) The determination of the calculation formula refers to the wall thickness calculation formula of GB150 "Fixed Pressure Vessel":
(2) Selection of formula parameters when applied to the calculation of fixture thickness According to GB150, the selection of the most severe conditions and the characteristics of the pressure sealing fixture, the design pressure was corrected. The maximum pressing force on the action jig is selected as the design pressure Pc.
General design pressure Pc = system pressure PL + correction value 5MPa
(3) Incorporate on-site measurement and known data into the formula so use 15mm thick 20R steel plate to make jig body 2.2.3 Boss Width CC = Flange Pair Minimum Connection Clearance - 0.3mm
2.2.4 Boss inner diameter d
2.2.5 Fixture width B. Generally, the inner side of the leaking flange extends to not less than 10 to 20 mm from both sides, and the amount of clearance increases the seal reinforcing structure appropriately.
Because the thickness of the lower flange is 28mm, the outer flange of the flange is adopted when the fixture is fabricated. Therefore, the width of the fixture is calculated as 28×2+4=60mm, that is, B=60mm.
2.2.6 The calculation of the number of bolts and specifications determines the bolts corresponding to the selection of M8, and the bolts are stressed due to temperature difference. The single bolt is 1.4 times that of the stud bolts. When the bolts are used above 250°C, the bolts for the fixture should be bolted. The stud bolts with a performance rating of not less than 8.8 are specified in accordance with the minimum specifications of the connecting bolts: The minimum specifications for the actual application of connecting bolts shall not be less than M12. Based on:
(1) No yield deformation occurs during initial tightening of the control bolt.
(2) During the injection process, tighten the bolts. Overloading the bolt may cause the bolt to be overloaded. Small bolts may cause yield deformation or damage.
To sum up: select two M12 8.8 stud bolts 2.2.7 The design of the ear plate thickness of the fixture is calculated according to the minimum thickness of the fixture ear plate: The thickness of the fixture ear plate is not less than the thickness of the body.
When the fixture is manufactured and the body is welded to the lug plate, the angle of the double-sided V-shaped groove is about 35 to 50 degrees.
3 When the clamp fixture is used to implement the upper fixture and plastic injection work, it shall be in strict accordance with GB/T 26467-2011 "Technical Specifications for Pressurized Equipment with Pressure Seal" 7.3.1 Fixture Method Sealing to ensure safety.
4 Results and Benefits The pressure sealing operation successfully sealed the leakage point without affecting the normal operation of the company's boiler and other equipment, eliminated the leakage and successfully ensured the safe and normal operation of the 6# steam turbine system. Until October 2016. In short, the pressure sealing technology is a kind of sealing technology that integrates knowledge of various disciplines such as mechanics and materials, and has a wide range of application fields. It plays a significant role in maintaining the normal operation of the device and preventing leakage. It will bring great economic benefits, and it will help save resources and protect the environment.
references:
[1] Wang Jinrong. Pressurized Vessel Pressure Pipe Sealing Technology [M]. Tianjin: Tianjin University Press, 2007.
[2] China National Standardization Management Committee. GB/T26467-2011. Technical specifications for pressure sealing of pressure equipment [S]. Beijing: China Standard Press, 2011.
[3] China National Standardization Management Committee. GB150.1 ~ 150.4-2011. Pressure Vessels [S].
[4]LI Xue, LIU Weiwei. Analysis of Control Points for Pressure Vessel Manufacturing Quality Management [J]. Science and Technology Innovation and Application, 2017(18):140.
Abstract: Under the conditions of high temperature medium pressure steam valve leakage without shutdown inspection, according to the state of the valve leakage point designed and manufactured to meet the requirements and reliable fixtures, under the premise of ensuring safety, the implementation of the sealing leakage of the valve leaking successfully implemented Plugging eliminates leaks, ensures the normal operation of the turbine system, brings certain economic benefits to the company, and is advantageous for resource conservation and environmental protection.