24 March 2023

Refractory Dry Out | RDO

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Refractory Dry Out


Dry out is required to remove excess water in the refractories and to ensure that there is no spalling & to ensure optimum performance.

Dry out required for Insulyte refractory and not for hot face refractory or ceramic fiber board / Hysil block because insulyte refractory having moisture up to 25% which is compulsory for remove, while dense phase (hot face) refractory having 7-8% moisture compare to less moisture so RDO cycle hours can be reduced. Ceramic fiber board / Hysil block having 0% Moisture.

If, we will replace Insulyte refractory by ceramic fiber board/Hysil block then only we will be able to save dry out.

If We will take Combination of refractory – 220 MM                                                       Ceramic Board 50 MM + Insulation refractory 100 MM + Dense phase 70 MM                          Than RDO cycle will be taken 72 hrs just because of remove water content from refractory.

But, If We will take Combination of refractory -170 MM                                                          Ceramic Board 100 MM + Dense phase 70 MM                                                                          Than RDO Can be clubbed with Kiln gases temp. for 16-20 hrs.

Solution for Eliminate RDO:-

Change of dense phase refractory is not the solution but elimination of insulyte refractory replacment by hysil or ceramic fiber is the solution

To reduce  dry out time,  replace insulyte layer castable with CF board or we may increase thickness of plastic castable layer.

Followig Points are:-

1.) Three layer system currently followed (70mm dense castable+100mm Insulating castable+50mm ceramic fibre Board) is the optimum lining design and is our normal recommendation.

2.)To reduce the dry out schedule. For achieving reduced dry out schedule, changing only hot face layer will not help. Insulating castable layer also contains excess water and the same also to be removed through the dry out process.

3.) So to achieve the reduced dry out schedule, we need to change both hot face layer as well as insulating castable layer.

4.) With the above change, it is recommended that we increase the hot face layer to get higher safety margin in case of erosion. So we can go for 90mm of hotface layer+125mm of Ceramic fibre board+5mm ceramic fibre paper.

Important Points for RDO:-

1. Should excessive steaming develop at any time the drying & firing procedure, hold temperature until the excessive steaming subsides.
2. Temperature holds are not required or recommended during the heating period where excessive steaming is not present.
3. Temperatures listed are refractory surface temperatures unless otherwise noted.
4. Temperatures should be monitored at several locations in the unit.
5. Always control the schedule according to the hottest part of the unit. Any gun mix may be heated at a slower rate than recommended.
6. As with all Vesuvius drying and firing schedules, once begun, the schedule should be followed without interruption.
7. Good airflow is essential during all stages of the drying and firing schedule. The unit should be vented during the schedule to allow venting of steam. Weep holes are suggested to allow venting of steam from the cold face.
8. Flame impingement must be avoided at all times (May not be applicable in this case).

Equipment’s Used for RDO

  1. Burner
  2. Flame Failure detector
  3. Blower
  4. Recorder
  5. Pump Set
  6. Oil Tank
  7. All Piping for Fuel Transfer

Vendor for RDO:-

  1. BARODA HEAT-UP CONTROLS PVT. LTD.                                                                              Contact Name:- Mr. Samir N Shah                                                                                         09327223488                                                                                                     bhcl@bhclbaroda.com
  2. HEAT TECHNOLOGIES PVT. LTD.                                                                                        Mr. S.K.Dube                                                                                                                09824011380                                                                                                        skd274@yahoo.com


RDO Cycle for various thickness:-

Refractory Dry Out (RDO) Cycle for thickness having 220 mm

Insulite 100 mm having 25% water


Different option for RDO Cycle Calculations:-



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