Scientific Analytical Calorimeter Solutions

Solving or Preventing a Misfire using the CAL3K Bomb Calorimeter

A ‘Misfire’ is indicated by the calorimeter when the temperature has not risen above the ‘MISFIRE TEMPERATURE RISE’ limit 30 seconds after firing.

This can have several reasons which are explained below:

  1. Open the vessel and check:
  2. If the cotton is fully intact: Go to Electrical Firing Problem
  3. If the cotton lays on top of the sample or has wire burn mark then there was no (or too little) oxygen. Go to Oxygen Leak
  4. If the cotton is burned but the sample is not then go to Sample Ignition
  5. If the unit reports a ‘FIRING MISFIRE’ then go to Firing Charger Problem


  • This means that an electrical firing has taken place but the firing current did NOT go through the wire. It was shorted in the vessel lid. Replace the top O-ring on the center electrode and try again.


  • When the wire glows at firing it burns the cotton (and the cotton falls of the wire). But it doesn’t ignite if the oxygen pressure is too low.
  • Put the vessel in to the filling station and fill it to the recommended pressure. Then remove it and check for leaks with ‘bubble’ water (dishwashing liquid and water). Replace the large lid O-ring and the top O-ring on the center electrode.


    Here are some reasons why a sample is NOT igniting:

    • Too wet! Reduce moisture or spike the sample with Benzoic Acid
    • Too difficult to ignite. The calorific value is too low. Use BA to spike the sample
    • Cotton string does not touch the sample. Tie the cotton with un-equal length to the wire and try again.
    • Cotton burn temperature too low. Use BA or other to spike the sample.

    Benzoic Acid Tablets - Close Up Image


    This is reported by the calorimeter when the firing voltage has not declined after firing: the firing charge was not depleted. This points to a bad contact in:

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