I. Overview: With the continuous improvement of supporting measures and measures of urban gas pipe network, insulation joints in pipeline & GT; More and more cases are used at the outlet of the pipeline, and the protective effect of the insulation joint is obvious. But with the application of insulation joint, there are also some safety risks, among which the over-voltage breakdown of insulation joint is one of the most easy fault points. The existing overvoltage protection products include metal oxide arrester, zinc grounded battery and discharge gap products, and the discharge gap product is the best protection scheme by functional comparison.

The main way to cause the surge overvoltage is lightning discharge, industrial operation and electrostatic discharge. The surge overvoltage caused by different reasons is different in amplitude, energy, waveform and repetition times. The amount of energy contained in a surge voltage is often enormous and can cause severe damage to even very reliable industrial installations and other equipment.

The following are some typical overvoltage types and their hazards. 1, direct lightning lightning directly hit the external device of the building, such as lightning rod, lightning belt, outdoor antenna, satellite receiving device, water pipe & GT; Pipeline, natural gas pipeline & GT; Pipeline, etc. 2, inductive lightning even if the building is not subjected to direct lightning, the lightning discharge around may also be induced by the coupling line surge overvoltage, general long wire loop or long natural gas pipeline & GT; Piping is particularly easy to induce surge overvoltage. 3, switch surge switch surge voltage from the circuit closed and open the switch operation, inductive, capacitive load switch operation. The breaking of large power supply systems or transformers and other motor equipment will produce surge overvoltage in the equipment line. Any surge or overvoltage will cause these devices to become more potential. In particular, some equipment has a lot to introduce indoor, such as outdoor antenna and natural gas pipeline & GT; Pipeline, so it is very easy to direct lightning current or induction over voltage into indoor, resulting in threats to the safety of staff and equipment.

3. Natural gas pipeline & GT; The necessity of over-voltage protection of pipe insulation joint natural gas pipeline & GT; The necessity of over-voltage protection of pipe insulation joints is mainly reflected in the following two aspects: 1. The overvoltage discharge of the pipeline is put into the ground, so that the overvoltage and lightning current can not enter the room, so as to protect the safety of indoor staff and reduce the interference of electromagnetic interference to indoor equipment. 2, reduce the pipeline & GT; Pipeline insulation flange two real potential difference, so that its value is reduced to the insulation tolerance range of insulation joint, to avoid overvoltage breakdown insulation, resulting in system failure, and prevent the arc caused by the breakdown of insulation joint when the natural gas pipeline is ignited & GT; The pipe.

Four, over-voltage protection products compared to 1, zinc grounding battery zinc batteries are the most widely used insulation joint drainage products, has many characteristics, such as installation, then, reliable operation, but zinc grounding battery also has a lot of defects, like, the starting voltage is too low, often exist misprint flow, and have limited service life, increase the maintenance capital. 2, metal oxide lightning arrester metal oxide lightning arrester with high action potential, large current capacity and other characteristics, has been in the long transport pipeline & GT; There are a lot of use on the pipeline, but the metal oxide arrester has a particularly bright disadvantage, that is, the residual voltage after the arrester conduction is high, nearly 2000V or so, the residual voltage value can protect the insulation joint from overvoltage damage, only can not guarantee the safety of the operator is not threatened. 3, spark gap type equipotential protector

At present, explosion-proof discharge gap (LPD equal potential connector) is generally referred to the national scale GB18802.1 related technical indicators of production and structure through four departments: 1, high-current capacity of gas discharge gap, the nominal discharge is 100kA, can effectively protect the direct lightning and induced overvoltage damage to the insulation joint, and high starting voltage, low voltage after conduction characteristics. 2, high strength glass cloth tube, is the first layer of explosion-proof function guarantee. 3, high temperature epoxy resin seal, increase the insulation of the discharge gap side, and is the second layer of explosion-proof function guarantee. 4, silicone rubber in one vulcanization, so that the connection cable and the main body of the product are reliably connected in one, and the connection is seamless, waterproof, dustproof, arc leakage, is the third layer of explosion-proof function guarantee. The spark gap type equipotential protector can effectively protect the safety of insulated joints and employees, and is the best over-voltage protection product.

1, bonded at both ends of the insulation connector will be bonded to the product in the pipeline & GT; At both ends of the pipe insulation joint, when there is a surge of overvoltage, the product will respond within nanosecond time, limit the surge of overvoltage within the range of 50V, to protect the insulation joint from overvoltage and breakdown damage. 2. Connect the product to the ground, ground pipeline & GT; When there is a surge overvoltage in the pipeline, the product instantly conduction, the surge overvoltage leakage into the ground, the insulation joint two real overvoltage to insulation tolerance level below, and will not lead the current into the underground pipeline & GT; Pipeline, to avoid overvoltage damage underground pipeline & GT; The occurrence of pipeline anticorrosion layer.

Six, summarize with discharge gap products in natural gas pipeline & GT; Pipeline application, believe natural gas pipeline & GT; The chance of pipeline failure will become smaller and smaller, and the safety of people's lives and property will be more comprehensively protected.