1. Precautions for oxygen bomb: 
(1) Before testing every day, be sure to inflate enough oxygen to the empty oxygen bomb , and submerge it in water for a few minutes, to observe the oxygen bomb sealing.
(2)After the experiment, it is important to rinse the oxygen bomb parts with distilled water and clean it with special towel.
(3) If the oxygen bomb has leakage, replace the seal ring.
(4) If the oxygen bomb thread is stripped, it is forbidden to use it again.
(5)The  oxygen bomb shall be checked regularly, at least it shall be tested for water pressure once in a year. It can be sent to Sande company for testing).
(6) The crucible shall be cleaned after being used, it is better to put it for the high temperature electric furnace to heat for 3 ~ 5 min.
(7) It shall be very careful to take the oxygen bomb from the inner drum to prevent the collision or falling of oxygen bomb from damaging the inner drum.
2. The ignition wire shall not contact with the crucible and shall not be inserted in the coal sample, it shall be bent into a curved form and close to the surface of coal samples as possible.
3. when the oxygen bomb is filled with oxygen, the oxygen pressure indicated on the  high pressure gauge of the pressure relief valve of the oxygen cylinder shall be more than 5 Mpa, if the pressure is less than 5 Mpa, it shall be replaced with the new oxygen cylinder. If the pressure on the low pressure gauge is 2.6 ~ 2.8 Mpa, the oxygen filling time shall be 30 ~ 60 s. After enough oxygen is filled,  the valve core on the oxygen bomb protrudes upward. If the oxygen filling pressure of the oxygen bomb is more than 3 Mpa, the oxygen in the oxygen bomb shall be emptied and shall be filled with oxygen again.
4. Measurement procedures of calorific value:
(1) Precisely weigh the analysis sample from the burning utensil  (less than 0.2 mm) 1 ~ 1.1 g ( accuracy to 0.0002 g).
(2) Take a section of ignition wire with known mass and connect  both ends on the two electrodes column respectively. Add 10 ml  distilled water into oxygen bomb, be careful to tighten the oxygen bomb cover, in order to avoid the position of the burning utensil and ignition wire to be changed due to vibration, slowly fill oxygen into the oxygen bomb with oxygen  pressure of 2.6 ~ 2.8 Mpa. The oxygen filling time shall not be less than 30 s. When the oxygen pressure in the oxygen cylinder dropped below 5.0 Mpa,  the oxygen filling time should be extended.
(3) Add enough distilled water, into the inner drum and put the oxygen bomb into the inner cylinder, and start the test.
(4) After the test is finished, take out the oxygen bomb and exhaust the combustion waste gas. Open the oxygen bomb, if the samples are not completely burnt or the carbon black exists, the test shall be invalid.