API 6D Vs. BS 5351: In-depth Analysis of International Design Standards for Floating Ball Valves

API 6D is a standard for pipeline valves formulated by the American Petroleum Institute (API). It is mainly used for the design and manufacturing of valves in long-distance pipelines, gathering and transportation pipelines, and related equipment in the oil and gas industries. This standard imposes strict requirements on the design, manufacturing, testing, and quality control of floating ball valves, aiming to ensure the reliability and safety of the valves under high pressure, high flow, and harsh environments.

(A) Scope of Application
API 6D is applicable to floating ball valves with nominal pressure ratings ranging from Class 150 to Class 2500 and nominal sizes from NPS 1/2 to NPS 60. These valves are mainly used in long-distance pipelines, gathering and transportation pipelines, and related equipment in the oil and gas industries to control the on-off of fluids.

(B) Design Features
• Ball Support Method: API 6D floating ball valves adopt a floating ball structure. The ball is supported by the valve seats at both the inlet and outlet ends of the valve, and the valve stem is movably connected to the ball. When the valve is closed, the ball is pushed towards the valve seat at the outlet end under the action of the medium pressure to achieve sealing.
• Sealing Performance: The API 6D standard requires that floating ball valves must have good sealing performance and be able to withstand high pressure differences. When the valve is in the closed state, the sealing specific pressure between the ball and the valve seat should be high enough to ensure no leakage.
• Anti-static Measures: Due to the risks of flammability and explosiveness in the oil and gas industries, the API 6D standard requires that floating ball valves must be equipped with anti-static devices to prevent safety accidents caused by static electricity accumulation.
• Fire Resistance: The API 6D standard also requires that floating ball valves have fire resistance and can maintain their sealing performance in extreme situations such as fires to prevent the spread of fires.
• Operational Performance: API 6D floating ball valves have a small operating torque, open and close quickly, and are suitable for frequent operation.

(C) Testing Requirements
API 6D has very strict testing requirements for floating ball valves, including:
• Pressure Testing: Valves must pass pressure tests, including shell strength tests, sealing tests, etc., to ensure their reliability under the design pressure.
• Functional Testing: The functional testing of valves includes the testing of functions such as blowdown, venting, and overpressure relief to ensure their safety in practical applications.
• Durability Testing: Valves need to undergo durability testing to verify their reliability and stability during long-term use.

II. Overview of BS 5351 Standard

BS 5351 is a standard for ball valves formulated by the British Standards Institution (BSI). It is widely used in the industrial fields of the UK and other European countries. This standard also puts forward detailed requirements on the design, manufacturing, and testing of floating ball valves to ensure the reliability and safety of the valves under various working conditions.

(A) Scope of Application
BS 5351 is applicable to floating ball valves with nominal pressure ratings ranging from PN10 to PN40 and nominal sizes from DN15 to DN300. These valves are mainly used in industrial pipeline systems, such as in the chemical, oil, and gas industries, to control the on-off of fluids.

(B) Design Features
• Ball Support Method: BS 5351 floating ball valves also adopt a floating ball structure. The ball is supported by the valve seats at both the inlet and outlet ends of the valve, and the valve stem is movably connected to the ball. When the valve is closed, the ball is pushed towards the valve seat at the outlet end under the action of the medium pressure to achieve sealing.
• Sealing Performance: The BS 5351 standard requires that floating ball valves have good sealing performance and be able to withstand high pressure differences. When the valve is in the closed state, the sealing specific pressure between the ball and the valve seat should be high enough to ensure no leakage.
• Anti-static Measures: The BS 5351 standard also requires that floating ball valves be equipped with anti-static devices to prevent safety accidents caused by static electricity accumulation.
• Fire Resistance: The BS 5351 standard requires that floating ball valves have fire resistance and can maintain their sealing performance in extreme situations such as fires to prevent the spread of fires.
• Operational Performance: BS 5351 floating ball valves have a small operating torque, open and close quickly, and are suitable for frequent operation.

(C) Testing Requirements
The testing requirements of BS 5351 for floating ball valves include:
• Pressure Testing: Valves must pass pressure tests, including shell strength tests, sealing tests, etc., to ensure their reliability under the design pressure.
• Functional Testing: The functional testing of valves includes the testing of functions such as blowdown and venting to ensure their safety in practical applications.
• Durability Testing: Valves need to undergo durability testing to verify their reliability and stability during long-term use.

III. Comparative Analysis of API 6D and BS 5351

To compare the similarities and differences between the API 6D and BS 5351 standards more intuitively, we can make a detailed comparison through the following table:

(A) Scope of Application and Industries
• API 6D: Applicable to valves with higher pressure ratings and larger sizes, mainly used in long-distance pipelines and gathering and transportation pipelines in the oil and gas industries. These pipelines usually need to withstand the transportation of fluids under high pressure and high flow.
• BS 5351: Applicable to medium and low pressure working conditions, with a relatively narrow size range, widely used in industrial pipeline systems in the chemical, oil, and gas industries, and pays more attention to the universality and adaptability of valves.

(B) Design Features
• Ball Support Method: Both adopt a floating ball structure, with the ball supported by the valve seats at both the inlet and outlet ends. This structure is simple and reliable and suitable for frequent operation.
• Sealing Performance: Both API 6D and BS 5351 require that valves have high sealing specific pressure to ensure no leakage under high pressure differences. However, API 6D emphasizes more on the sealing performance of valves under extreme working conditions, such as overpressure relief and fire resistance.
• Anti-static and Fire Resistance: Both require that valves be equipped with anti-static and fire-resistant devices to ensure safety in flammable and explosive environments.

(C) Testing Requirements
• Pressure Testing: Both API 6D and BS 5351 require that valves pass strict shell strength tests and sealing tests to ensure their reliability under the design pressure.
• Functional Testing: API 6D pays more attention to the testing of functions such as blowdown, venting, and overpressure relief of valves to meet the special needs of long-distance pipelines. BS 5351 focuses more on the general functional testing of valves in industrial pipeline systems.
• Durability Testing: Both require that valves undergo durability testing to verify their reliability and stability during long-term use.

IV. Summary

API 6D and BS 5351 are two internationally widely recognized design standards for floating ball valves. They both put forward strict requirements on design, manufacturing, and testing to ensure the reliability and safety of valves under various working conditions. API 6D focuses more on the reliability and safety of valves in high-pressure, long-distance pipelines and is applicable to long-distance pipelines and gathering and transportation pipelines in the oil and gas industries. While BS 5351 focuses more on the universality and safety of valves in industrial pipeline systems and is applicable to industrial fields such as the chemical, oil, and gas industries.