Limiting Oxygen Index (HMI Model)

Critical limiting Oxygen Index apparatus is used for determining the minimum percentage of Oxygen required to just support flaming combustion of a material at room temperature in FTA mode or at Higher Temperature (up to 400oC) in HFTA mode.

Critical limiting Oxygen Index apparatus is used for determining the minimum percentage of Oxygen required to just support flaming combustion of a material at room temperature in FTA mode or at Higher Temperature (up to 400oC) in HFTA mode.

In the limiting Oxygen Index Test Apparatus the sample is burned in the mixture of nitrogen and oxygen, and the percentage of oxygen required just to support the flaming combustion is recorded through an imported Oxygen Analyzer, which gives direct oxygen readings.

The Limiting Oxygen Index Test apparatus also has a double walled test column of flame resistance glass of 75 mm dia. suitable for testing different size of samples in FTA or HFTA mode.

A digital temperature-indicating controller provided with the instrument controls the temperature for HFTA mode. The instrument is manufactured as per the ASTM specification and also conforms to various other international standards.

The instrument conforms to ASTM D- 2863, BS 2782 Pt 141, IS 13501, ISO 4589-2, ISO 4589-3, NES 714 and NES 715.

(Please note that the instruments conforms to these standards on broad terms. Please check all the specifications of the instrument against the required standard for further conformation) 

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The Critical Limiting Oxygen Index Test instrument comprises of –

      Paramagnetic Dumb Bell Oxygen Analyzer. (Permanent Sensor)

     Double walled glass test column with two heaters, for sample heating and gas heating

     Digital Temperature indicating controller.  

     Flow meters and valves

     Readout for Oxygen: 0 to 100% Oxygen, LC: 0.1%

     Readout for Temperature  up to 400oC , LC : 0.1oC

     Digital Total Gas Flow Indicator : 0 to 20 LPM, LC: 0.1 LPM

     ‘L’ Shaped LPG Burner to ignite the sample

     Sample Holder and hanger

     ‘U’ shaped RTD PT 100 Temperature Sensor  

     Control by PLC

     Display on touch screen HMI

The sample is ignited using the L shaped burner and oxygen % is adjusted till the sample starts to burn like a candle i.e. sustained burning without extinguishing or rapidly spreading the flame.  The Sample should burn in this condition for at least 3 mins. 

At higher temperature the requirement of Oxygen for combustion reduces. The environment around the sample is heated using double walled chimney with heaters for HFTA test. The procedure to determine the LOI remains the same as for ambient temperature.

The PLC plots the graph using various test points determined during the sample test. The PLC then extraplot the graph and determine the following results

a) LOI at ambient temperature

b) LOI at 400oC

c) Temperature if the LOI would be 20.9% oxygen.