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Test procedure for the oxygen index tester surface combustion method

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Test procedure for the oxygen index tester surface combustion method

Author: Date :2023-02-21 Views: order

The oxygen index tester is an instrument for determining the combustion properties of substances. It is used for the evaluation of the fire performance of various types of fireproof materials, flame retardant materials, paints, etc., the classification of flammability classes of chemical products, and the exploration of the application areas of the combustion properties of certain special substances.

In the 60's, the oxygen index tester for solid materials was developed abroad, and the instrument was introduced into China in the early 80's. It has been widely used in fire protection research departments to determine the oxygen index, which is a parameter of the combustion characteristics of building materials and knotted materials.

UL94 Flame Chamber

The oxygen index is the minimum oxygen concentration required to maintain a smooth combustion of a specimen in a mixture of oxygen and nitrogen in a specified strip. It is expressed as a percentage of the volume of oxygen.

The oxygen index is an important physical and chemical parameter for determining the combustion characteristics and fire risk of a substance. Due to the needs of industry testing standards, Jensen has developed both an oxygen index value for testing the combustion properties of solids and an oxygen index value for determining the combustion of liquids.

Instrument construction.

A complete instrument for testing the combustion properties of insulating liquids - oxygen index - consists of a quartz glass combustion cylinder, test disc, test disc support, flow measurement and control device, ignition source, paramagnetic or chemical oxygen sensor, timer and smoke extraction system.

Test standard.

JB/T 8988-1999 Test method for determining the oxygen index of insulating liquids

GB/T 16581-1996 Test method for the burning performance of insulating liquids Oxygen index method

Test method.

(1) Wick method in the specimen immersed in an inert material (such as glass wire, asbestos wire, etc.) made of wick .

Only the wick is allowed to ignite.

(2) The surface burning method, also known as the wickless method, involves the ignition of the igniter against the entire surface of the liquid specimen, causing the entire surface to burn.

The test procedure for the surface burning method

1. Place the apparatus in a room at (23±2)°C

2、Remove the glass burning cylinder, ensure that the test disc support is on the central axis of the burning cylinder as shown in Figure 1, and install a clean test disc at the apex of the support.

Test procedure for surface burning method

3、Turn on the power, turn on the power switch

4、Use the pipette to inject the specimen into the test disc until the curved liquid surface of the liquid is 1mm below the mouth of the disc.

5、Select the appropriate starting oxygen concentration based on experience of testing similar liquids. If there is a lack of experience, ignite the specimen in air and observe the combustion. If the specimen burns, the starting oxygen concentration is about 18%: if the specimen does not burn, the starting oxygen concentration is about 25%

6. Adjust the oxygen and nitrogen controllers to obtain the required oxygen concentration. The total gas flow rate (cm3/s) divided by the cross-sectional area of the combustion brief (cm2) is calculated as the gas flow rate within the combustion brief should be (4±1) cm/s. Blow the test system with airflow for at least 30 s.

7, as shown in Figure 2, let the igniter flame all cover the surface of the liquid sample until the liquid ignites, and then remove the igniter.

Test procedure for surface burning method

If the flame is not burned for 60s, that is, the oxygen concentration is too small, the oxygen concentration should be increased, the liquid sample is replaced, and the test is repeated at a larger oxygen concentration

Note: If the liquid does not ignite, the liquid can be used again, do not need to be exchanged.

8, if a stable combustion and the continuation of more than 60s, that is, the oxygen concentration is too large, should be reduced. Use a clean test plate to reload new specimens, repeat the test at a smaller oxygen concentration. Until the minimum oxygen concentration that can just maintain the liquid burning 60S or a little more time, and when the oxygen index concentration value of 0.5% lower, the specimen burning less than 60s.

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