The challenge
Preheater ducts carry hot, dust-laden gases at high temperature under negative pressure. Where the refractory lining fails, hot gas erodes the steel shell until it perforates.
Every hole draws false air into the system: the kiln loses heat efficiency and the ID fan works harder. The ducts hang high inside a congested tower beside hot vessels, with no room for scaffolding while the kiln is running.
Scope of works
- Dual-rope rope access with heat-resistant rope protection around hot ducts
- Visual testing (VT, EN ISO 17637) of shells, stiffening rings, supports and expansion joints
- Ultrasonic thickness mapping of shells and elbows, and dye penetrant testing (PT, EN ISO 3452-1) of critical welds
- Flange bolt audit and re-torquing to EN 1090-2, replacing corroded fasteners
- Crack arrest, seal welding and welding of external doubler plates and stiffeners over thinned areas
Outcome
Perforations and split seams were sealed and the duct shell reinforced, stopping false-air ingress and restoring stable kiln draft, all without stopping the kiln and with zero LTI. See our NDT services and the related preheater tower inspection.
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