Cryogenic Top Entry Ball Valve API 6D Top Entry Ball Valve Cryogenic Valves

I. Product Overview

II. Key Attribute Specifications

A. Dimensional and Pressure Parameters

• Nominal Diameter: Spanning from DN25 to DN300, it caters to the diverse flow demands of pipelines. In LNG transfer setups, a DN50 valve can adeptly manage a flow rate of up to 80 m³/h, striking a harmonious balance between flow capacity and system compactness.
• Pressure Rating: Adhering to API 6D, it supports pressure classes including Class 150, 300, and 600. A Class 300 valve, for instance, can bear a working pressure of 5.17MPa, making it a perfect fit for medium – pressure cryogenic storage and transportation systems.
• Temperature Range: Engineered to operate steadily between – 196℃ (the boiling point of liquid nitrogen) and 100℃. Special thermal insulation designs are integrated to curtail cold energy loss and fend off external moisture condensation on the valve surface.

B. Material Composition

• Valve Body and Ball:
  • For standard cryogenic applications, low – temperature carbon steel like ASTM A352 LCB is employed. LCB boasts exceptional toughness at low temperatures, with a Charpy impact energy of ≥27J at – 46℃, effectively warding off cold brittleness.
  • In more corrosive cryogenic environments, stainless steels such as ASTM A351 CF8 (304 stainless steel) or CF8M (316 stainless steel) are utilized. These materials offer superior corrosion resistance against cryogenic media laced with impurities, such as wet LNG.
• Sealing Components:
  • Primary seals leverage polytetrafluoroethylene (PTFE) with spring pre – loading. PTFE retains good elasticity at low temperatures and has a low coefficient of friction, ensuring a dependable seal even amid thermal contraction.
  • For high – pressure cryogenic scenarios, metal – to – metal seals (e.g., Inconel 625 coating) are available. These seals can withstand higher pressure differentials and exhibit remarkable wear resistance.

C. Structural and Operational Features

• Top – Entry Design: The valve body is furnished with a top – mounted access flange. During maintenance, there’s no need to disconnect pipeline flanges; instead, internal components like the ball, stem, and seals can be directly removed and replaced from the top. This design slashes maintenance downtime by over 50% compared to side – entry valves.
• Stem Sealing: A multi – layer sealing structure, combining graphite packing and O – rings, is adopted. It effectively thwarts the leakage of cryogenic media and the ingress of external air, preserving the low – temperature environment inside the valve.
• Operation Mode: It can be outfitted with manual, pneumatic, or electric actuators. For remote – controlled LNG terminals, electric actuators with explosion – proof certification are often chosen, enabling precise flow regulation.

III. Feature Description

A. Top – Entry Design for Efficient Maintenance

B. Cryogenic – Resistant Sealing Technology

• The primary seal uses PTFE with a spring pre – load. The spring compensates for the volume contraction of PTFE at low temperatures, ensuring continuous contact between the seal and the ball.
• The secondary metal backup seal springs into action when the primary seal fails (such as during a fire or extreme temperature fluctuations), preventing large – scale leakage of cryogenic media.
  In tests simulating – 196℃ conditions, the leakage rate of the valve is less than 1×10⁻⁶ cm³/s, far below the API 6D leakage standard.

C. API Compliance and Safety Assurance

• Pressure Testing: It endures a hydrostatic test at 1.5 times the rated pressure and a pneumatic test at 1.1 times the rated pressure to ensure structural integrity.
• Cryogenic Performance Testing: The valve is cooled to – 196℃ using liquid nitrogen and subjected to multiple opening and closing cycles to verify its operational prowess at low temperatures.
• Fire – Safe Design: An optional fire – safe certification (API 607) is available. In the event of a fire, the metal backup seal and graphite packing can maintain temporary sealing, preventing the leakage of flammable cryogenic media such as LNG.

D. Material Toughness at Low Temperatures

• LCB Steel: Through quenching and tempering heat treatment, the grain structure is refined, and the impact toughness at low temperatures is significantly enhanced. In a Charpy impact test at – 46℃, the impact energy can reach 40J, far surpassing the standard requirement of 27J.
• Stainless Steel: For media containing corrosive components (such as LNG with high sulfur content), 316L stainless steel is used. Its molybdenum content bolsters corrosion resistance, and it still maintains good toughness at – 196℃.