I want guidelines for heaters dry out.How much temperature should be in firebox ?we can do dry out with media (steam,nitrogen and oil) or with out and why?
The refractory linning constructor shall fournish to you a dry out procedure and the dry out heat curve. the dry out of a refractory linning is normaly done with burners, the temperature in the fire box is dependent on the proprieties of the linning.
General guidelines for dry-out conventional refractory is to use 3 or 4 heating schedule. Heating rate is 30 -40°C/hr to avoid thermal stress and refr spalling and cracking . Rather use fuel gas than oil and avoid direct flame impingement. No flow in the tubes during dry-out. During dry-out measure the temperature with inserted few TIs with tip to 1/2 inch from refr surface.
After 24 hrs curring of fresh refractory at ambient temp rise temperature to 120°C (250°F). Hold period is 1/2 hr/per inch refr.
Next levels are 500°F, 700°F ,and 1000°F if needed, also with heating period 1/2hr /inch refractory. If refr steaming observed maintain until steaming subsides.
If Thermoband type of refractory is used more relaxed procedure is used. Best to contact manufacturer.
