0

ICQCC 2011-Yokohama

1. “TO REDUCE COBBLE OCCURRENCE IN BETWEEN STAND#10 – STAND#11”2. PATHFINDER 522

3. AMITAVA CHOUDHURY (LEADER), SANJIB DUTTA (DY.LEADER)NILANJAN BANERJEE, SUBIR GHOSH, ANGSHUMAN GHOSH,

SATYA RANJAN KAR (FACILITATOR)4. QUALITY CIRCLE FORUM OF INDIA (QCFI)

5. “INSTALLATION OF ROLLERS IN REPEATER#2”

6. DURGAPUR STEEL PLANT/STEEL AUTHORITY OF INDIA (SAIL)7. INDIA

8. ABSTRACT

PROBLEMIn Merchant Mill the rolling process involves 13 nos. Roll Housings, four nos.Repeaters, several cassette guides, troughs and 5 nos. Shears. During rolling each of theseHousings & equipments should be perfectly aligned for smooth rolling. Any misalignmentor obstruction in these equipments interrupts the flow of the rolling material and as aresult rolling materials turns into a huge hot metal mess called “cobble”. Extensive dataanalysis reveals that maximum no. of cobble occurs in between stand #10 to #11 due toexcessive “sticker “formation in Repeater #2. Sticker is a thin layer of steel materialgenerated due to friction between rolling material and Repeater inner arch and sticks toother equipments. During rolling these stickers flow to the cassette guides & troughs withthe rolling materials and obstructs the flow due to jamming in narrow rolling passages andas a result cobble occurs. In Merchant mill one cobble costs Rs. 9000 and it leads tovarious negative impacts like delay, damages of equipment, fatigue, accidents etc.

To minimize negative impacts, our team members came up with an idea to install six nos.Roller blocks along the inner arch of Repeater #2. The Roller Block which was designedby the members consists of one cylindrical roller ,two nos. of taper roller bearings alongwith a shaft inside, two no’s of retainers, one base block and a holder plate to hold theroller in a particular position. To minimize friction, rollers were installed tangential to therolling material and perpendicular to the Repeater #2 floor at equal intervals whichconverted sliding friction into rolling friction between steel & steel. Rolling friction isabout 100 times less than sliding friction. As a result sticker formation reduced and hencethe problem of jamming in cassette guide at stand#10 to stand#11 has been reduceddrastically and therefore cobble occurrence also reduced. Thus minimization of frequentcobble occurrence between stand#10 and 11 established some positive impacts likeincreased productivity, minimum damage of material and equipment, reduced workpressure and accidents, moreover huge delay has been reduced. This indigenous, lesscostly & minimum maintenance device has become the essential equipment of Repeater#2.The drawing of this device was incorporated in ISO document & Drawing department.The successful installation of the “Roller blocks” has been appreciated by everyone; italso enabled Merchant Mill to benefit to the magnitude of Rs. 1,51, 38,000/- in the year(2009-10) moreover our success improved mutual relationship and motivated others togenerate fresh idea through QC activity.

SOLUTIONINSTALLATION OF THE “ROLLER BLOCKS IN REPEATER #2”