Chemical Technology April 2016

Chemical Technology • April 2016

The intention of this article is not to

produce a complete case study of the

pumping of gravel, but to interest the

reader in the sources of information and

give examples of the procedures to be

used when specifying pumping systems.

Are small operations

sustainable?

by Carl Schonborn Pr Eng

elevision viewing can be a relaxing pastime and

recommended for engineers and others who lead a

stressful existence in this technologically-driven era of

deadlines, professional responsibilities and tight budgets.

One is inclined to ask what kind of programme engineers

would prefer. Two great series on satellite TV [1] at the time

of writing are those about small mining operations, such

as ‘Gold Rush’ and ‘Diamond River Hunters’, the former

based in the Klondike in Alaska and the latter in the Lesotho

Highlands adjacent to South Africa. The stress and strain

of sustaining these operations is palpable; the individuals

who drive them can only be described as ‘men of steel’ for

whom one only wishes success. They live an almost ‘hand-

to-mouth’ existence with team-members who simply have to

be supportive, as the alternative would be a failed venture.

One could ask “What do these ventures have in common?”

The answer would incorporate the following points:

• Limited budgets and capital;

• A minimum of on-site spare parts for vehicles

and equipment;

• Skilled hands-on operators (an absolute essential);

• Utmost faith in the success of their venture;

• Limited or no professional or engineering assistance or

expertise; and

• Experienced entrepreneurs leading operations.

A case in point

For example, the diamond venture in the Lesotho Highlands

highlights the unit operations which consist of washing of the

river banks, divers manually moving the suction hoses which

dredge the gravel, centrifugal slurry pumps adjacent to the

muddy pools, the sluicing of the extracted gravel through a

‘trommel’, the recovery of bags of diamondiferous material

and lastly, hand sorting.

This may all sound straightforward and simple. The con-

cession is sound, as it is based in the rivers flowing from the

successful Letseng Diamond Mine (the highest diamond

mine in the world at 3 000mabove sea level) which produces

magnificent diamonds.

One of the problems, however, is the effect the mine’s