Long-distance pipeline is global, is an energy supply line, from the Arctic Circle to the equator, from the mountains to the sea, from the plateau to the desert, during which through the seismic zone, wetlands, permafrost, rivers, lakes, hillsides. Have set up, there are direct-buried underground, in the field operation, maintenance difficulties, asked 30-year service life. General transportation of crude oil, natural gas, despite dealing with the content, including rust and metal particles, and zero-order sealing requirements, the actual conditions of use and the importance of energy supply line, the ball valve on the pipeline has strict technical requirements.
1, strength and toughness
In addition to the valve under the pressure of the internal medium, the need to bear the foundation bearing, due to changes in ambient temperature caused by axial tension and pressure, taking landslides, ground subsidence, floods caused by the external load, and frozen in cold areas still need to be considered low-temperature impact toughness of the material to prevent the low-temperature brittle fracture. Ball valve for the entire welding, weld and heat affected zone, in accordance with fracture mechanics theory, its fracture toughness (CTOD)
2, the sealing requirements of zero-order
Requirements of zero-order sealing the valve to ensure that the downstream end of the effective cut-off line, consider the medium of metal particles on the impact of zero-sealed, metal to metal seal as the primary seal, PTFE / rubber on the metal as a secondary seal, and once the seal Seal Failure to take urgent measures should be.
3, with the fire safety and anti-static function;
Pipeline ball valve design would need to consider fire safety (fire safe), if a fire breaks out inside the valve leakage and leakage can not exceed the provisions of the leakage API607 standards; ball was gripping non-metallic materials and may generate static electricity, must be on-Valve in 24VDC, the resistance value of <10 ohms.
4, DBB function (Double Brock & Bleed)
Excretion in the valve chamber, the upstream side and downstream side valve seat should be automatically cut off at the same time in order to ensure the safety of emissions.
5, to prevent the clamping pressure valve cavity;
Whether the valve is open or closed position, should be in the valve chamber to prevent the media has been gripping, if the medium may be gripping, the medium for the gas or liquid media are necessary to ensure that the automatic discharge valve cavity pressure vent valve cavity pressure release valve the maximum pressure rating of not more than 1.33 times the external pressure for the discharge valve DN15-caliber or greater.
6, excretion
Valve cavity medium can be excreted; and through the discharge hole of the valve seal testing line.
7, position-indicating
Whether manually or power-driven, have clear instructions show that the valve position valve in the open position or closed position;
8, transmission chain
The design of torque transmission chain for the ball valve should be at least 2 times the maximum torque.
9, Chemical state of sulfur
Pressure components and bolt material should have the ability to stress cracking, in line with the NACE, MR 0175 requirements.
10, the emergency cut off function
Long-distance pipeline transportation system uses satellite monitoring system (SCADA System), when the pipeline pressure drop rate or duration of a certain set value, the valve should be an emergency cut off;
11, to consider the potential of underground water corrosion and stress corrosion.
The use of all-welded body structure, pipeline and grounding the outer surface of the cathode anti-corrosion, to prevent potential corrosion and stress corrosion. valve ball valve gate valve check valve globe valve butterfly valve
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