Development and use of new insulating flanges

Since the reform and opening up, with the continuous and stable development of my country’s socialist economic market, the application of pipeline gas industry in urban construction has gradually become popular. The construction and protection of gas pipeline projects is becoming more and more important, and the application of matching pipeline insulating flanges is becoming more and more common. How to find an insulating flange with good insulation performance and low cost is particularly important. This article introduces a new type of insulating flange with new structure, low cost, flexible and convenient use.
1 Structure and characteristics of old-fashioned insulating flange
The composition of the old type I insulating flange is to install a flange insulating gasket between two butt-welded flat flanges, and to install an insulating sleeve and insulating bolt gasket on the fastening bolts. The structural assembly diagram is shown in Figure 1. The flange insulation gasket material is made of oil-resistant rubber asbestos board, chloroprene rubber board, fabric-based chloroprene rubber board and polytetrafluoroethylene. The insulating bolt sleeves and bolt insulating gaskets are made of high-strength phenolic laminated cloth boards and pressed cloth tubes. Its characteristics are: good steel and stable insulation performance. It requires a special installation location and high cost.
2 Development of new insulating flange
We have made suitable improvements to the structure of the old insulating flange. In urban gas transmission and distribution projects, improvements are made based on the characteristics of low pressure (PN ≤ 2.5MPa) and pipeline network pressure PN ≤ 0.4MPa. In pipeline network transmission and distribution projects, steel flat flanges are used instead of butt welded flat flanges. The flange insulation gaskets are made of polytetrafluoroethylene, oil-resistant rubber asbestos sheets, neoprene and other materials, and the insulation of the fastening bolts is The cover and insulating pad are combined into one, and the insulating cover is shortened by half to make an integral high-strength insulating cover pad. As shown in Figure 2, the bolt holes of the steel flange that pass through the sleeve gasket are enlarged to be able to pass through the insulating sleeve gasket; thereby ensuring that the inner hole diameter of the sleeve gasket meets the requirements of the bolts used in the original steel flange, thus creating a special steel method The flange becomes a new insulating flange after assembly. Its structure and installation are shown in Figures 3 and 4. It can be installed alone or together with the connecting valve; it not only saves engineering costs, but also saves on-site installation locations. It is a simple and applicable new insulating flange with a particularly low cost.
3 Insulation principles and performance
The working principle of the insulating flange is to use the electrical insulation properties of the insulating gasket in the insulating flange and the high-strength insulating bushing to perform electrical insulation on both sides of the insulating flange. According to the actual project, the insulation performance of this insulating flange is based on the relevant requirements in the “Technical Regulations for the Design of Insulating Flanges” (SY/T0516–1997) and the “Testing Method for Cathodic Protection Parameters of Buried Steel Pipelines” (SYJ23- 86), the test results show that: the resistance value between the insulating gasket and the insulating sleeve of the fastening bolt between the insulating working surface can meet the specification requirements.
4 Usage
This type of insulating flange is used at building valves in cathodicly protected transmission and distribution pipeline networks and in buried pipe valve wells that require potential segmentation (zone) isolation. Isolating the segments (areas) of the buried transmission and distribution pipeline network can clearly grasp the cathodic protection situation of each segment (area); evaluate the cathodic protection segments (areas) and deal with different cathodic protection situations ; When the protection potentials of adjacent pieces (areas) are the same (or similar) and meet the protection potential requirements, a cross-bar can be used to connect both sides of the insulating flange for unified protection; when the protection potentials of adjacent pieces (areas) are greatly different. And when there are slices (areas) that cannot meet the protection potential requirements, the slices (areas) that cannot meet the protection potential requirements can be specially processed until they meet the requirements, and then the slices (areas) can be operated continuously.
5. Strong applicability
The insulating flanges produced by this method are still suitable for the insulating flanges used in long-distance pipelines and stations with pressure PN ≥ 2.5MPa in oil and gas fields. Just change the flange to a special flange of the corresponding level, and the usage method is exactly the same.
6 Conclusion
(1) This new type of insulating flange has a new structure, strong applicability and low cost.
(2) It is not only suitable for electrical insulation isolation in urban gas transmission and distribution projects; it is also suitable for long-distance pipelines, gas gathering pipelines, transmission and distribution stations and other places that require electrical insulation isolation.
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