Analysis on The Pressure-bearing Performance Differences between Trunnion Ball Valves And Gate Valves under API 6D And ASME B16.34 Standards

In industrial fields such as petroleum, natural gas, and chemical engineering, the pressure-bearing performance of valves is one of the key factors to ensure the safe operation of systems. API 6D and ASME B16.34 are two important standards widely applied in the design and manufacturing of valves. This article will conduct a comparative analysis on the pressure-bearing performance differences between TRUNNION BALL VALVES and GATE VALVES under these two standards, helping engineers and purchasers better select valves suitable for their application scenarios.

I. OVERVIEW OF API 6D AND ASME B16.34 STANDARDS

(1) API 6D Standard

The API 6D standard is formulated by the American Petroleum Institute (API) and specifically targets valves in petroleum and natural gas pipeline systems. It covers multiple types of valves, including TRUNNION BALL VALVES and GATE VALVES. The core of the API 6D standard lies in ensuring the safety and reliability of valves in long-distance transmission pipelines and process pipelines, especially under high pressure, high flow, and harsh environmental conditions. Its main features include:

· Full-bore design: Ensuring that pipeline cleaning and inspection equipment (such as pigs) can pass smoothly.

· Fire safety: Requiring valves to have a fireproof function. Even if the soft seal fails in a fire, the metal seat can still maintain the seal.

· Pressure relief: Valves must have an automatic cavity pressure relief function to prevent internal pressure build-up caused by temperature changes.

· Strict testing requirements: Including hydrostatic tests, sealing tests, and leakage tests.

(2) ASME B16.34 Standard

The ASME B16.34 standard is a more general valve standard formulated by the American Society of Mechanical Engineers (ASME), applicable to multiple industrial applications, including the petroleum, natural gas, chemical, and power industries. This standard mainly focuses on the pressure-temperature ratings, material selection, design requirements, and testing methods of valves. Its features include:

· Wide applicability: Covering multiple types of valves, such as flange-connected, threaded, and welded-end valves.

· Detailed pressure-temperature rating tables: Providing detailed ratings for valves of different materials and designs to ensure that valves can operate safely under specific working conditions.

· Material diversity: Supporting a variety of materials from common carbon steel to high-performance alloys to meet the corrosion resistance and high-temperature resistance requirements in different environments.

· Non-destructive testing: Requiring valves to undergo radiographic testing and ultrasonic testing to ensure the integrity of the internal structure.

II. COMPARISON OF THE PRESSURE-BEARING PERFORMANCE OF TRUNNION BALL VALVES AND GATE VALVES

(1) Trunnion Ball Valves

A TRUNNION BALL VALVE is a high-performance ball valve with its ball fixed inside the valve body. The opening and closing of the valve are controlled by rotating the valve stem. Under the API 6D and ASME B16.34 standards, the pressure-bearing performance of trunnion ball valves exhibits the following characteristics:

· High pressure rating: Trunnion ball valves are usually designed for high-pressure working conditions and can withstand relatively high working pressures, suitable for petroleum and natural gas pipeline systems.

· Bidirectional sealing: Trunnion ball valves have a bidirectional sealing function and can effectively prevent fluid leakage in both directions, which is crucial for preventing reverse flow and protecting pipeline systems.

· Fire performance: Under the API 6D standard, trunnion ball valves must have a fireproof function. Even if the soft seal fails in a fire, the metal seat can still maintain the seal to prevent the spread of the fire.

· Pressure relief: API 6D requires trunnion ball valves to have an automatic cavity pressure relief function to prevent internal pressure build-up caused by temperature changes, thus avoiding potential safety risks.

(2) Gate Valves

A GATE VALVE is a valve that controls fluid flow by the up-and-down movement of the gate. Under the API 6D and ASME B16.34 standards, the pressure-bearing performance of gate valves exhibits the following characteristics:

· Medium pressure rating: Gate valves are usually used in medium-pressure working conditions, and their pressure-bearing capacity is relatively lower than that of trunnion ball valves, but they can still meet the requirements in some application scenarios.

· Unidirectional sealing: Gate valves are mainly designed for unidirectional sealing, that is, they can effectively prevent fluid leakage in the normal working direction, but the sealing performance may be poor in reverse flow.

· Fire performance: Under the API 6D standard, gate valves also must have a fireproof function, but in practical applications, the testing and requirements for their fire performance may be different from those of trunnion ball valves.

· Pressure relief: Gate valves usually do not have an automatic cavity pressure relief function, but this requirement may be considered in some special designs.

III. DIFFERENCES IN PRESSURE-BEARING PERFORMANCE UNDER API 6D AND ASME B16.34 STANDARDS

The following is a comparison table of the pressure-bearing performance of trunnion ball valves and gate valves under API 6D and ASME B16.34 standards:

IV. SELECTION SUGGESTIONS

(1) Trunnion Ball Valves

· High-pressure working conditions: If the application scenario requires a high-pressure rating, the trunnion ball valve is a better choice. Especially under the API 6D standard, its design can meet the requirements of long-distance transmission pipelines and high-pressure working conditions.

· Bidirectional sealing requirement: In situations where bidirectional sealing is required, the trunnion ball valve can effectively prevent reverse fluid leakage and ensure the safety of the system.

· Fire safety requirement: In environments with a high fire risk, the fireproof performance of the trunnion ball valve can provide additional safety guarantees.

· Pressure relief function: In working conditions with large temperature changes, the pressure relief function of the trunnion ball valve can prevent internal pressure build-up and avoid potential safety risks.

(2) Gate Valves

· Medium-pressure working conditions: In medium-pressure application scenarios, gate valves can meet the requirements, and the cost is relatively low.

· Unidirectional sealing requirement: If the application scenario is mainly for unidirectional flow, the unidirectional sealing performance of the gate valve can effectively prevent fluid leakage.

· Fire safety requirement: In environments with a low fire risk, the fireproof performance of the gate valve can also meet the basic requirements.

· Pressure relief function: In working conditions where the pressure relief function is not required, the design of the gate valve is relatively simple and can meet the basic usage requirements.

V. SUMMARY

Under the API 6D and ASME B16.34 standards, there are obvious differences in the pressure-bearing performance between TRUNNION BALL VALVES and GATE VALVES. trunnion ball valves have higher pressure ratings, bidirectional sealing functions, fireproof performance, and pressure relief functions, and are suitable for petroleum and natural gas pipeline systems under high pressure, high flow, and harsh environmental conditions. While gate valves have medium pressure ratings, unidirectional sealing functions, and optional fireproof performance, and are suitable for medium-pressure working conditions and multiple industrial applications.

When selecting valves, it is necessary to comprehensively consider the differences in pressure-bearing performance under the API 6D and ASME B16.34 standards according to specific application scenarios, pressure requirements, sealing requirements, and fire safety requirements, and choose the most suitable valve type.