Special High Grade (SHG) Zinc—99.995% (Physical Specification & Dimensions)
Advantages of Jumbo over Slab
The use of zinc jumbo (supplied as 1.0 metric tonne) instead of conventional 25kg small ingots provides galvaniz- ers with a number of benefits. These are:
Use of zinc jumbos simplifies storage, handling and loading of the zinc into the galvanizing bath. Jumbos Slabs are lowered easily and conveniently into the zinc bath using a chain sling attached to the crane hoist.
By comparison, using small ingots can have the following disadvantages:
Time and labour is required for removal of steel strapping
If unstrapped bundles are to be loaded into the bath, care needs to be taken to ensure bundle stability.
If small ingots are to be added piece by piece, the process is very time consuming and labour intensive.
Zinc is a valuable commodity. Ensuring secure storage at the galvanizing plant is therefore very important. Due to their large size, .zinc jumbos are much less vulnerable to the compared to small ingots. In fact, there has never been any reports of the the of zinc jumbos.
There is much less risk of operator injury using zinc jumbos, since loading into the bath primarily utilizes only the crane and operators can therefore re-main at a safe distance. Also, melting of zinc jumbos generally involves less ‘turbulence’ and therefore there is less risk of molten zinc splashing.
4.Better Bath Management
During the time the jumbo is submerged in the bath, it remains fully sup-ported by the crane. The situation with adding complete bundles of small ingots is different in that some of the ingots will separate during melting and fall to the bottom of the zinc bath. This is generally undesirable since it can result in some disturbance of the dross layer, causing dross to mix into the zinc bath and subsequently contaminate the galvanized coating. This is a con- cern also when adding small ingots piece by piece since these immediately sink to the bottom of the bath.
Zinc melting loss is lower if jumbos are used in preference to small ingots. This is due to lesser ash being generated on the galvanizing bath surface dur-ing melting of jumbos as a result of less ‘turbulence’ caused by splashingƒ bubbling. Turbulence created in the galvanizing bath when adding zinc is caused by its surface condition (such as the presence of minor oxidation, white rust, moisture condensation). This turbulence causes ash to form on the bath surface. The smaller surface area to weight ratio of zinc jumbos compared to small ingot means less turbu- lence and therefore less ash is pro-duced. Tests have shown that the use of jumbos instead of 25kg ingots re-sults in 15kgs less ash per tonne of zinc added to the bath. Even aGer allow-ing for the subsequent sale of zinc ash, the cost savings are estimated to be approximately $20ƒtonne of zinc added