CEMEX is a growing global building solutions company that provides products of consistently high quality and reliable service to customers and communities in more than 50 countries across five continents. It owns 67 cement plants worldwide with an annual production capacity of more than 96 million tons of cement (as of end of 2007). Being the only cement manufacturing plant of CEMEX in Egypt, Assiut Cement (Assiut), located in Assiyut (500km south of Cairo), is capable of producing up to 5 million tons of cement annually (as of end of 2007).
Assiut Cement’s Maintenance Challenge
In cement production, pyro-processing is a critical process clinkering (or burning) raw materials in the preheater system and the kiln. Induced draft (ID) fans are installed (near the cyclone preheater in this case) to pull hot air (flue gas) from the kiln operating at high temperatures up to 1,800°C to the preheater and then re-direct the flue gas to raw mill / electrostatic precipitator. Hot flue gas along with small amount of particulates and dust is constantly drawn through the ID fan As a result, the ID fan blades are exposed to intense abrasive wear and heat.
In this success case, due to the aforementioned possible causes of wear, all fan blades of one of Assiut Cement’s ID fans (specification shown below) needed to be repaired.
Specification of the ID Fans:
Media Stone Dust
No. of Blades 12
Inlet Blade Thickness 10 to 30 mm
Blade Material Alloy Steel
Magna’s Concrete Solution
Previously, Assiut Cement used a famous competing brand of electrodes to repair the blades. However, the job usually failed in three months and the maintenance department had to either replace the ID fan blades at a cost of USD18,000 or repair them. During their shutdown period in March 2008, Assiut Cement decided to repair the blades with another brand of electrode. They contacted Ometa Trading Co., Magna’s Egyptian distributor, who recommended Magna 401 (3.96mm) for the repair. On each worn blade, the area to be re-built was about 200mm x 800mm and 2 Kg of Magna 401 were required. In total, 12 Kg of Magna 401 were used to repair all worn fan blades (10% less than the amount of electrodes previously used to perform the same repair job).
Assiut Cement repaired the worn blades with the following important welding procedure:
1. Completely remove dust and particulates on the blades,
2. Use 150 – 200 amp (AC or DCSP) and start welding with the lowest possible current,
3. Maintain a short arc and travel slowly,
4. Take into consideration the Duty Cycle of the welding machine, and
5. Do not provide any buffer layer.
After the repair job, Assiut Cement’s maintenance personnel performed “Dynamic Balancing” of the ID fan and put it back into operation.
Assiut Cement applied Magna 401 to repair the ID Fan blades in April 2008. As of May 2009, i.e. more than one year after the repair job, the blades were in perfect condition (as mentioned in Assiut Cement’s Testimonial shown below). Not only did Assiut Cement save tens of thousands of US dollars of replacement cost, they also saved downtime in carrying out frequent repairs. Previously they needed to repair the blades every three months (As advised by the end-user, the downtime cost for shutting down the ID fan is equal to a production loss of 5,100 tons of cement).