Figure 1. Hurricane Alex path towards Monterrey area
The recovery of a glass plant of two float lines after hurricane Alex that hit on July 1st, 2010 is presented, furnaces damages are described and how the problems were addressed and eventually overcome the situation to get back to “normal” operation. Bubble glass quality issues presented during and after the recovery of the glass plant are presented.
On July 1st, 2010, Alex, a category 2 hurricane with wind speed of 165 miles/hr, entered the coast of Gulf of Mexico containing lots of rain, as shown in Figure 1. Alex is considered the largest hurricane that has reached Monterrey area ever, with more rain that hurricane Gilberto in 1988. On July 2nd, the normally “Dry” Santa Catarina River (Figure 2) carried out water all the way across its 500 m width.
Figure 1. Hurricane Alex path towards Monterrey area
Figure 2. Santa Catarina river
VF-1 & VF-2 are two float lines located side by side in Vitro float glass plant at García, NL, Mexico, dedicated to both automotive and architectural glasses.
When constantly raining during the arrival of Hurricane Alex to Monterrey surroundings, the river next to the plant road became dammed-up when floating debris clogged the river’s entrance to a bridge, The accumulating water then flooded the streets and flow down the ramp into the basements of both glass furnaces trough the ramps. The ground was already saturated water.
5 meters of water and mud entered into the basement in less than 30 minutes (as shown in Figure 3) creating a great amount of steam that went into the melter through the regenerators and suddenly increasing the furnace internal pressure from 0.25 mm of water column to more than 10 mm.
Figure 3. Water path from river to furnaces basement
Combustion air fans, diesel motors, electric boost transformer and regulator, and other equipment were in the basement. They were covered with water and mud with no possibility to operate. Water at the basement entered the regenerators and tunnel, and blocked the exit of the flue gasses to the chimney. Several days afterwards the water level (Figure 4) was still too high to resume operations.
Figure 4. Water level at basement
With the lack of natural gas, both furnaces started to cool down and the main task at that time was to maintain them hot enough to prevent any refractory failure.
VF1 & VF2 Back wall silica toes fell down on the glass and froze in place due to lack of enough natural gas. At VF2, due to the cooling down of the waist area, two previously cracked pieces of the waist entrance arch slipped down and fell into the glass.
10 days were required to pump out all the water and clean up the mud from the basement, bottom regenerators and tunnels.
Regenerators and rider arches during cleaning of mud inside after the water level receded. Water literally “washed out” all the sulfates from raider arches
VF1 suspended wall (shown in Figure 5) was the most damaged part. Even after steel structure reinforcement, the refractory was too damaged to continue operating. The decision was to stop the furnace for a cold repair. A Merkle suspended wall steel structure was bought from a float furnace stopped in the USA. Merkle supplied the refractory material within a couple of weeks. Some adjustments had to be done to the length of doghouse to allow the charger to operate properly. Hotwork was the first supplier to arrive at the plant, and the last to leave few months later. VF1 started operation on Sep 11, 2010, after almost two and a half months since the flood. By Sep 20th, it was already producing automotive quality glass.
Figure 5. VF1 suspended wall
VF2 suspended wall was less damage than VF1. Air cooling was re-established in 3–4 days after the flood and steel structure was also reinforced with an additional dead beam on top of the existing one. Silica toes fell down in the same way as happened at VF. The wall was bent in the middle and, in order to stop radiation towards the steel structure, the toes had to be installed again. 27 silica toes installed at the right hand side of the wall. All silica toes were installed and missing silica blocks located in position. Silica ceramic welding was applied to all the wall joints to prevent air from leaking into the melter. VF2 Furnace started up on July 23rd.
By this time a significant amount of bubble defects were present in the glass ribbon. With the waist stirrers off, bubbles were present mostly in the right half of the ribbon.
During an inspection at furnace waist: Foam was accumulated on the RHS waist pipe. When removed, the pipes presented signs of accumulated bubbles in a very specific position. A very defined line of foam was seen at the working- end on the RHS. Bubble tracking by mathematical modeling was performed to identify the possible location of the source. Everything pointed out to the missing blocks of the waist arch (shown in Figure 6), the bubble gas analysis was consistent with a contamination of Silicon and Aluminum, coming from the unreacted ceramic weld material previously applied to this arch.
Figure 6. Two Pieces of refractory blocks missing from furnace waist arch
In order to try to take the pieces out, the glass was drained to the lowest possible level. Once reached the minimum level, it was possible to see the two ~90 kg blocks sitting on the bottom of the furnace waist.
Several tools and devices were manufactured and tested to take out the pieces from the furnace. Finally on Saturday, August 14th, it was possible to take the blocks out from the waist, after several days of failed trials. Temperature at this area was around 1200°C.
When the block was inspected, it was found that ceramic weld material was attached to the block as thick as 4 to 5 inches. A large amount of bubbles were frozen off when the glass cooled down. It was possible to see the bubble generation coming out from this material, as shown in Figure 7.
Figure 7. Bubbles generation from ceramic weld material
VF2 Operation re-started on Aug 22nd, a month later from the previous start up, and almost two months after the flood. Bubble defects levels went down; however, the level was still high for some glass qualities. Chemical gas bubble analysis showed that there must be some remaining contamination material still located in the right side of the waist area.
In order to inhibit the mechanism of bubble generation of the remaining ceramic weld material, a waist cooler was proposed to reduce glass temperature and increase the viscosity. After the coolers installation the fault index went down from values of 4.0 – 5.0 to 1.0 – 1.2 Defects/10m2. By October, VF2 furnace was producing close to the usual 95% yield, as demonstrated in Figure 8.
Figure 8. Bubble defects recovery after water cooler installation
It took several months for the Vitro team to sort out the total condition of the plant. Many extra hours per day and weekend work time were required but we continued producing glass to serve our customers, which is the very bottom line.