Technical Requirements Of Pipeline Valves

Pipeline valve’s strength and toughness

In addition to bearing the internal medium pressure, the valve also needs to bear the foundation load, the axial tension and pressure caused by the change of environmental temperature, the external load caused by a landslide, land subsidence, and flood, and the low-temperature impact toughness of materials in cold regions and frozen regions should be considered to prevent low-temperature brittle fracture. The fracture toughness (CTOD) of all-welded body ball valves, weld, and heat-affected zones should be considered according to the fracture mechanics theory.

Zero-level sealing requirements

The valve requires a zero-level seal to ensure the effective interception of the downstream pipeline. Considering the influence of metal particles in the medium on the zero-level seal, the metal-to-metal seal is the primary seal PTFE/ rubber is the secondary seal, and emergency sealing measures should be taken once the seal fails.

Pipeline valves have fire safety and anti-static functions.

Fire safety should be considered in the design of the pipeline ball valve. In case of fire, the external leakage and internal leakage of the valve should not exceed the leakage standard specified in API607. The ball is clamped by nonmetallic materials, which may generate static electricity and must be connected to the valve body. At 24VDC, the resistance value is less than 10 ohms.

DBB function

When the valve cavity is drained, the upstream end valve seat and the downstream end valve seat should be automatically cut off at the same time to ensure safety when draining.

Prevent the clamping of valve cavity pressure.

No matter whether the valve is in the open or closed position, the medium should be prevented from being clamped in the valve cavity. If the medium may be clamped, the pressure in the valve cavity should be automatically relieved for gas medium or liquid medium. The maximum pressure relief in the valve cavity should not exceed 1.33 times the valve pressure rating, and the diameter of the external pressure relief valve should be DN15 or larger.

Pipeline valves excrete

The medium in the valve cavity can be discharged; And through this drain hole, the online sealing detection of the valve is carried out.

Position indication

Whether manual or power-driven, there should be an obvious valve position indication indicating whether the valve is in the open position or the closed position.

Transmission chain

The design torque of the transmission chain should be at least 2 times of the maximum torque of the ball valve.

Vulcanization condition

The materials of pressure-bearing components and bolts shall have the ability to resist stress cracking and meet the requirements of nace NACE, MR0175.

Emergency cut-off function

The long-distance pipeline transportation system adopts the SCADA System. When the pressure drop rate or duration of the pipeline reaches a certain set value, the valve should be cut off urgently.

Consider the potential corrosion and stress corrosion of groundwater.

All-welded valve body structure, pipeline cathode grounding, and external surface anticorrosion are adopted to prevent potential corrosion and stress corrosion.