· Reduced Downtime
· Improved Product Quality
· Lower Gobweight Variation
Johnson Matthey and Parkinson Spencer Refractories have produced a spout-bowl system that allows longer intervals between spout changes, an increase in product quality and more consistent gob weights.
The new system is a two-part design incorporating an ACT™ platinum coated ceramic insert mated to the main body of the bowl.
This spout-bowl system is completely compatible with standard Emhart design feeder systems so no modification of the feeder system is required.
The new design maximises service life by eliminating the two major failure mechanisms that occur in standard spout bowls, tube seat wear and thermal shock cracking.
· Tube Seat Wear
Corrosive wear of the tube seat will eventually prevent the tube from sealing. Leakage of glass during o-ring changes will necessitate replacement of the spout bowl.
The wear also results in uneven flow during operation, which may lead to significant problems with gob weight control.
A further side effect of this corrosion, so close to the forming stage, is that un-dissolved corrosion products may result in stoning or cord.
In the new system, the ACT™ platinum coating on the insert completely eliminates any wear in the region of the tube seat and inside the bore.
This not only extends the operational lifetime of the spout but also reduces the defects in the product and provides better gob weight control.
· Thermal Shock Cracking
Thermal cracks almost invariably initiate from the spout exit region close to the o-ring, typically during o-ring changes. Once a crack has initiated it can propagate quickly in the ceramic and normally results in failure and replacement of the spoutbowl.
Ceramics with good thermal shock resistance suffer from poor corrosion resistance; those with good glass corrosion resistance have low shock resistance. The choice of ceramic normally involves a compromise between the two.
Because the ACT™ platinum coating provides complete glass corrosion resistance, a ceramic with high thermal shock resistance can be used for the insert. Therefore the likelihood of crack initiation is drastically reduced. The two-part design ensures that any that do form are contained within the insert and prevented from propagating into the body of the bowl.
The elimination of tube seat wear and the crack prevention system mean that the minimum lifetime expectations for these spoutbowls are at least 2 years.
The picture above shows an ACT™ coated insert after a full year in service (removed due to factory closure). The near pristine condition of the part can clearly be seen. Other bowls have been running for longer and are already providing operational benefits.