1. The structure and characteristics of old insulated flange
The old type I insulation flange is composed of two pairs of butt welding flange flange between the installation of insulating pads and fastening bolts on the installation of insulation and insulation bolts and gasket composition. The structure of the assembly diagram shown in Figure 1, the flange insulation gasket material selection of oil-resistant rubber asbestos, chloroprene rubber sheet, fabric-based chloroprene rubber sheet and Teflon and other materials. Insulated bolts and bolts Insulating gaskets are made of high strength phenolic laminates and presses. Its characteristics are: good steel, insulation performance and stability, the need for a special installation location dedicated installation, high cost.
2 new type of insulation flange development
We have improved the structure of the old insulated flange. In the city gas transmission and distribution project, for the city gas transmission and transportation project pressure is low (PN ≤ 2.5MPa), pipe network pressure PN ≤ 0.4MPa to improve the characteristics. In the pipe network distribution project in the use of steel flat flange instead of butt welding flange, flange insulating gasket with PTFE, oil-resistant rubber asbestos, chloroprene rubber and other materials, and tighten the bolt insulation Sets and insulation pads will be two, and shorten the insulating sleeve half made of integral high-strength insulation pads. Figure 2, will be inserted through the pad flange flange bolt holes can be extended to wear insulation pads; to ensure that the sleeve diameter suitable for the original steel flange bolts required, so that made a special role in the steel method Blue, after assembly has become a new type of insulating flange, the structure of the installation shown in Figure 3 It can be installed separately, or can be installed with the connection valve; both to save the cost of the project, but also save the site installation location, is a simple and applicable new insulation flange.
Insulation principle and performance
Insulation flange works is the use of insulating flange insulation pads and high-strength insulation pad insulation properties of the insulation flange on both sides of the electrical insulation to work. According to the engineering practice, our insulation performance of the insulation flange according to "insulation flange design technical requirements" (SY / T0516--1997) in the relevant requirements and "buried steel pipe cathodic protection parameters test method" (SYJ23- 86), the test results show that: insulation pads and fastening bolts insulation pads in the insulation between the working surface of the resistance value to meet the regulatory requirements.