EN 437 Test Gases - Test Pressures - Device Categories

The European standard "EN 437 Test gases - Test pressures - Appliance categories" describes test gases, test pressures, and appliance categories based on the use of gaseous fuels of the first, second, and third families. This standard serves as a reference standard for appliance-specific standards. It provides recommendations for the use of gases and pressures for testing appliances burning gaseous fuels.

Test procedures are outlined in the relevant instrument standards. The test gases and test pressures specified in this standard are designed for use with all types of instruments. However, some test gases and test pressures may not be suitable for use in the following situations:

• Devices with a nominal heat input greater than 300 kW
• Field-built devices
• Devices where the final design is influenced by the user
• Devices constructed for use with high supply pressures (especially direct use of saturated steam pressure)

In these cases, specific instrument standards may specify other test conditions to ensure compliance with their requirements.

Gases are divided into three families, each of which can be further subdivided into groups based on the Wobbe index, as given in the table titled "Classification of Gas Families and Groups by Wobbe Index, Dry Gas at 15°C and 1,013.25 mbar" provided in the standard. The classification given in the table is used to identify the gas types and corresponding supply pressures of gaseous fuels used in the territories of Member States.

The composition and basic properties of the different test gases corresponding to gas families or groups are given in the tables titled “Properties of test gases for the first and second families, gas dry at 15 degrees and 1 013,25 mbar” and “Properties of test gases for the third family, gas dry at 15 degrees and 1 013,25 mbar” given in the standard.

In special cases specified in individual instrument standards, G 24 gas, whose properties are given in the table, may be used, but only at normal test pressures. The calorific values ​​of third-family gases, expressed in megajoules per cubic meter in the table, can also be expressed in megajoules per kilogram of dry gas, as shown in the table.

The values ​​measured and expressed at 15°C in the tables are derived from EN ISO 6976. Conditions for the preparation of test gases are included in the standard's annex (Annex A). Properties of second-family gases at reference conditions other than 15°C for measurement and 15°C for combustion can be calculated using the coefficients given in the annex of EN ISO 13443 (Annex A).

The test pressure values, that is, the static pressure applied to the gas inlet connection while the device is operating, are included in the relevant tables. Test conditions are specified in individual device standards. However,

• For a still-air combustion test with G 21, the apparatus is first set at G 20 to provide a 5 percent increase in nominal heat input when a gas pressure regulator is present and a 7,5 percent increase when a regulator is absent. The G 21 gas is then replaced with G 20 without changing this setting.
• Ignition and cross-firing tests should be performed at an inlet pressure of 0,7 times normal pressure using reference gases for the first and second families.

The EN 437 standard is deemed necessary for the following important reasons:

• Standardized testing across Europe: This standard ensures that gas appliances are tested under consistent and comparable conditions across all European countries. This is crucial for safety, reliability, and marketability within the European Union.
• Safety assurance: By identifying specific test gases (such as G20 for natural gas, G30 for propane), devices are ensured to operate safely under real-world conditions, even if gas compositions vary slightly in different regions.
• Harmonization of appliance categories: This standard helps classify appliances according to the types of gases they can safely handle. This prevents misuse and reduces the risk of accidents.
• Regulatory compliance: Manufacturers must comply with the EN 437 standard to meet the EU gas appliance directive 2016/426. This is a legal requirement to place gas appliances on the European market.
• Inter-business compatibility and trade: A common standard encourages cross-border trade by allowing devices approved in one European Union country to be sold and installed in others without additional testing.

The gas categories or test gases defined in the EN 437 standard are:

• First group: Manufactured gas (G110). Rarely used today.
• Group 2: Natural gas (G20). Standard for pipelines. Its replacement, natural gas (G21), involves slight modifications.
• Third group: LPG (liquefied petroleum gas), butane (G30) or propane (G31). Generally used as bottled gas and in rural areas.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the EN 437 Test Gases - Test Pressures - Device Categories standard.