Interpretation of Differences in Explosion-proof Certification: Comparison of Fire Testing Requirements for Ball Valves And Gate Valves under The ATEX Standard

In industrial environments involving flammable and explosive media, the fire resistance performance of valves is of crucial importance. The ATEX standard is an authoritative standard used in Europe to evaluate the safety of equipment in potentially explosive environments and is widely applied in industries such as petroleum, natural gas, and chemical engineering. BALL VALVES and GATE VALVES, as common types of industrial valves, have significant differences in their fire testing requirements under the ATEX standard. This article will interpret the different requirements of these two types of valves in terms of fire testing through detailed comparison, helping users better choose suitable valve products.

I. THE ATEX STANDARD AND FIRE TESTING REQUIREMENTS

The ATEX standard (Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres) aims to ensure the safety of equipment in potentially explosive environments. According to the ATEX directive, all equipment used in potentially explosive environments must pass the corresponding explosion-proof certification. Fire testing is an important part of explosion-proof certification, especially for valves that may be exposed to fire environments.

The core objective of fire testing is to verify the sealing performance and operational performance of valves under fire conditions. Valves must maintain the integrity of their seals in a high-temperature flame environment to prevent medium leakage and still be able to operate normally after a fire.

II. COMPARISON OF FIRE TESTING REQUIREMENTS FOR BALL VALVES AND GATE VALVES

(1) Testing Standards

• Ball Valves: Fire testing is usually carried out in accordance with the API 607 standard. API 607 is applicable to quarter-turn valves (such as BALL VALVES) and valves with non-metallic seals.

• Gate Valves: Fire testing is usually carried out in accordance with the API 6FA standard. API 6FA is applicable to valves compliant with API 6A and API 6D standards, mainly metal-sealed valves.

(2) Testing Conditions

• Ball Valves:

• Combustion Temperature: 750 °C to 1000 °C.

• Combustion Time: 30 minutes.

• Test Pressure: The rated working pressure of the valve.

• Test Position: The valve stem and flow passage are kept in a horizontal position.

• Gate Valves:

• Combustion Temperature: 750 °C to 1000 °C.

• Combustion Time: 30 minutes.

• Test Pressure: The rated working pressure of the valve.

• Test Position: Testing is carried out according to the actual working position of the valve.

(3) Testing Contents

• Ball Valves:

• Internal Leakage: Measure the leakage amount of the valve seat during and after combustion. The leakage amount must not exceed the maximum allowable value specified by the standard.

• External Leakage: Check the leakage situation outside the valve (including the connection between the valve stem and the valve body).

• Operational Performance: After combustion, the valve should be able to operate normally under the rated pressure without the need for additional tools.

• Gate Valves:

• Internal Leakage: Measure the leakage amount of the valve seat during and after combustion. The leakage requirement for gate valves is more stringent because they are usually used in high-pressure and large-flow working conditions.

• External Leakage: Check the leakage situation outside the valve, especially at the connection between the valve stem and the valve body.

• Operational Performance: After combustion, the valve should be able to operate normally under the rated pressure, but the operating torque of the gate valve may be larger.

(4) Evaluation of Test Results

• Ball Valves:

• Internal Leakage: A small amount of leakage is allowed, but it must not exceed the maximum leakage amount specified by API 607.

• External Leakage: Obvious leakage is not allowed.

• Operational Performance: The valve should be able to operate normally after combustion.

• Gate Valves:

• Internal Leakage: A very small amount of leakage is allowed, but it must not exceed the strict standard specified by API 6FA.

• External Leakage: No leakage is allowed at all.

• Operational Performance: The valve should be able to operate normally after combustion, but a larger operating torque may be required.

III. COMPARISON TABLE OF FIRE TESTING REQUIREMENTS

IV. SELECTION SUGGESTIONS IN PRACTICAL APPLICATIONS

(1) Selecting Valve Types According to Working Conditions

• Ball Valves:

• Suitable for working conditions that require quick opening and closing, such as emergency shut-off and frequent operations.

• Suitable for pipeline systems with medium and low pressure and small and medium diameters.

• The fire resistance performance is certified by API 607, which is suitable for occasions with a relatively high fire risk.

• Gate Valves:

• Suitable for working conditions with large flow and high pressure, such as main steam pipelines and boiler feedwater systems.

• Suitable for large-diameter pipeline systems.

• The fire resistance performance is certified by API 6FA, which is suitable for high-temperature and high-pressure environments.

(2) Selecting Testing Standards According to Fire Protection Requirements

• API 607:

• Applicable to ball valves and other quarter-turn valves.

• The testing requirements are relatively lenient and suitable for medium and low-pressure working conditions.

• API 6FA:

• Applicable to gate valves and other metal-sealed valves.

• The testing requirements are strict and suitable for high-temperature and high-pressure working conditions.

(3) Selecting the Explosion-proof Level According to the ATEX Standard

• ATEX Standard:

• Ensure that the valves meet the requirements of the ATEX directive, especially when used in potentially explosive environments.

• The explosion-proof level should be selected according to the actual working conditions, such as Zone 1, Zone 2, etc.

V. SUMMARY

Under the ATEX standard, there are significant differences in the fire testing requirements for BALL VALVES and GATE VALVES. Ball valves usually follow the API 607 standard, with relatively lenient testing requirements and are suitable for medium and low-pressure working conditions. Gate valves usually follow the API 6FA standard, with strict testing requirements and are suitable for high-temperature and high-pressure working conditions. When selecting valves, users should comprehensively consider and choose appropriate valve types and testing standards according to the actual working conditions (such as pressure, temperature, operation frequency, etc.) as well as fire protection and explosion-proof requirements.