In the natural gas pipeline there is a relatively common valve, gas ball valve, gas ball valve because of its special use occasions, so the requirements for sealing performance is also relatively high, it is specifically how to ensure its sealing performance?
In the gas ball valve on its seat structure design, there will generally be two ways, such as downstream seat self-release design and double piston effect design.
For the first type of seat design, in its closed state, when the line pressure acts on the outer surface of the upstream seat ring, it will press the seat towards the ball, and if the medium leaks into the valve cavity from its upstream, when the pressure inside the cavity is higher than the downstream line pressure, the relevant downstream seat will press the pressure of the cavity downstream to release it.
In the case of the second form of valve seat, the pressure is normally applied to the outside of the end of the seat seal, which presses the seal against the body to produce a corresponding squeezing pressure, thus forming a more reliable sealing structure between the seal and the body.
Even in the case of leakage of the valve seat, the pressure will directly enter the inside of the valve body, acting directly on the inner side of the upstream sealing surface, and generating squeezing pressure on the seat seal, so that the seat seal will slowly approach the valve body, thus forming a more reliable and effective sealing structure to ensure its sealing performance.
What type of valve is used for gas lines?
1, natural gas ball valve anti-static, fire prevention device; with gas special ball valve has a spring electrostatic export device, that is, in the ball and stem, stem and body between the conductive spring, so that the ball and stem and stem and body between the formation of electrostatic channel, to achieve the purpose of removing static electricity. Avoid ignition of flammable media by electrostatic firing to ensure system safety. In the unlikely event of a fire and the soft sealing ring such as polytetrafluoroethylene burned, the ball valve can still operate reliably and has good sealing performance to prevent the expansion of the fire, specially designed for gas, liquefied gas pipeline special ball valve with anti-static, fire prevention devices.
2, natural gas ball valve using PTFE (polytetrafluoroethylene) as a seal, with good lubrication and elasticity, and the ball friction system is small, long service life.
3, natural gas ball valve by the configuration of manual, worm gear drive, pneumatic, electric (explosion-proof) can achieve remote automatic control, can meet the user's various working conditions and requirements.
4, to ensure that the natural gas ball valve can not leak; natural gas pipeline network is mostly built in the edge of the city, operation and management unlike the general plant, there are often workers to operate, maintenance and inspection.
Generally urban natural gas pipelines are over hundreds of kilometres and can only be patrolled and inspected regularly, and sometimes the pipelines need to pass through areas where the situation is complex and leakage of media may bring about serious fire accidents.
It is particularly important to prevent leakage from valves on pipelines that are closer to the city. The leakage requirements for natural gas valves are very strict and usually buried and more important valves have a fully welded body construction.
In order to ensure the sealing performance of the pipeline valve, the seal is required to have excellent corrosion resistance, wear resistance, self-lubrication and elasticity. In recent years, the development of polymer materials for pipeline valve sealing material selection provides a wide selection of materials, such as polytetrafluoroethylene, nylon, special synthetic rubber (VITON), etc.
5, natural gas ball valve material selection to choose corrosion-resistant sulfur-resistant materials; because the pipeline transmission of natural gas before desulfurization contains a large amount of hydrogen sulfide (which is a toxic and corrosive gas, it reacts with iron to generate iron sulfide, can be flaky flaking, wear corrosion of machinery and equipment). Even after desulphurisation and other processes, there is still residual hydrogen sulphide in the natural gas. Therefore, the selection of materials for pipeline valves should be corrosion-resistant sulphur-resistant materials.
6, natural gas ball valves of the main sealing wear parts such as valve seats and other parts require a long life; once the pipeline is put into operation, it is not allowed to stop running for a few years, the longer the operation, unlike general chemical plants or refineries, there is an overhaul period.
The natural gas transported by the pipeline faces a large number of users throughout the city, including residents, businesses and factories, especially those that use natural gas as a raw material and do not allow for a momentary break.
The consequences of a failure of a pipeline valve in series on a pipeline are unthinkable. Therefore, the main seal of the pipeline valve wearing parts such as valve seats and other parts require a long life. General main line pipeline valves require a service life of 30 years or more.
7,Natural gas ball valve is suitable for medium and small diameter pipeline of various pressure, temperature and media under the control of connecting or truncating pipeline media opening and closing device; rely on media pressure to press the ball on the valve seat at the outlet end, its use of pressure and diameter of passage is limited to a certain extent, the switch is convenient and rapid.
8,The natural gas ball valve is packed with PTFE, the handle is operated with smooth torque, the driving method can be manual, worm wheel drive, pneumatic, electric, etc. The O-shaped sealing ring is used to prevent external impurities from entering the valve and maintain the long-term sealing performance of the valve, the ball valve larger than DN150 adopts worm wheel drive.
Suitable for gas pipeline, liquefied petroleum gas pipeline, natural gas pipeline, gas pipeline and other general working media. The stainless steel valve body is also suitable for media with harsh working conditions, such as oxygen, hydrogen peroxide, ethylene, etc.