and the tank wall.


This arrangement


allows for the slurry in motion to be vectored from the outer annular zone, towards the mid annular zone, and for the slurry velocity at the outer zone to be dynamically modified. With the mixing arrangement selected, the key requirement was to engineer the bearing arrangement to provide the necessary life expectancy and minimal heat generation profile. For this decision, VA Tech paid particular attention to the largest sized slurry tanks in operation at the time of design of the LP units. VA Tech had previously installed many slurry tanks of 2M (6.5 ft) diameter and in some cases these had been operational non-stop for over 11 years. The decision was taken to base the


bearing


arrangement on this


proven


design and to utilize a spherical roller thrust bearing as the principal load carrying unit.


Bearing support, and


exacting precision were the key elements to engineer into the system, and the complete assembly was integrated into a large heavy duty machined housing. The housing had to protect and support the bearing system and provide the platform interface between the machine base structure and the rotating tank. Particular attention was paid to the selection


of suitable heavy pressure


lubricants and the routine charging arrangement. The seal arrangement was of key importance, and interestingly the ‘designed in’ service life is equivalent to 118,000 miles (180,000 km), or four


and a half times distance around the circumference of the Earth!


Based on previous experience, the


heat generation around the bearing assembly was the most likely to be minimal with the chosen design, an important feature for temperature critical slurry materials. Power transmission could now be determined and designed, and a heavy duty 20hp (15kw) motor gearbox was selected, operating through a multi strand precision roller chain and sprocket arrangement.


This choice


provided the necessary performance profile for continuous 24/7 operation, and life expectancy in excess of 10 years. The


transmission is enclosed


to prevent ingress of ceramic materials,


January 2018 ❘ 27 ®


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36