Thanks to Mr. Beshan Singh of Auto and industrial bearings (AIBS)…..
Thanks to Mr. Beshan Singh of Auto and Industrial Bearings (AIBS), our authorized Magna distributor in South Africa and our Senior Marketing Consultant, Mr. Prashant Fanse, we are delighted to release this success story about the excellent performance of Magna 770 on repairing a cast iron refiner door fractured due to high stress, at Mondi Paper’s paper mill in Merebank, South Africa.
Publicly listed in London & Johannesburg, Mondi Paper is a renowned international packaging and business paper producer with over one hundred plants across 31 countries worldwide. One of Mondi Paper’s key operations is in South Africa where Mondi Paper is the market leader in office paper and “Uncoated Fine Paper (UFP)”. Mondi Paper’s Merebank mill (Modi Merebank) in Durban produced more than 500,000 tons of these two types of papers in 2009.
The MRO Challenge
Prior to making paper, “refining” is an important process to improve the fiber bonding property of pulp. In this process, pulp is fed into refiner/s in which strong mechanical and hydraulic forces are employed to cut, open up and de-cluster the fibers and increase the surface areas of the fibers. As a result, many parts or components of the refiners are exposed to high stress. In this case, the cast iron door of one of Mondi Merebank’s Swiss refiners cracked into 2 pieces (see pictures on the right) due to the stress caused by frequent pounding. After checking with numerous welding services providers and the Swiss manufacturer of the refiner who stated that the broken door was irreparable, and considering the long lead time of 3 to 4 months to deliver a new door, Mr. Les Winkworth (Mondi Merebank’s welding foreman) contacted Mr. Beshan Singh of AIBS for solution. Mr. Singh, after inspection of the broken door, recommended Magna 770 (3.96mm).
The Benefits of Magna 770
As per usual practice, detailed welding procedure specification (WPS) was prepared by Mondi Merebank (based on the information indicated in the PIM of Magna 770) for the repair job. The WPS (approved by an inspection company) is summarized below:
1/ Joint design used for welding: 60° single V-groove,
2/ thoroughly clean the V-groove with wire brush to prevent any graphite from entering the weld surface during welding,
3/ in this case, pre-heating is required at 200°C minimum,
4/ apply string bead technique with multi-pass,
5/ inter-pass temperatures: at 280°C to 350°C, and
6/ after welding the weldment must be covered with asbestos sheet to ensure successful result.
Following the above WPS, Mr. Winkworth executed the repair job using Magna 770. The result was superb, as in many other repair jobs applying Magna Welding Alloys. The end-user was amazed by the physical strength and the bonding ability of Magna 770. A pressure test was conducted and it was found that the repaired refiner door could withstand pressure up to 29 bars (whereas new door is built to handle 27 bars). After discounting the money for the Magna 770 consumed, the end-user saved about USD64,000 (US Dollars Sixty-Four Thousand) of replacement cost. Moreover, the end-user saved at least eight weeks of lead time or potentially downtime in replacing the broken refiner door.