high head slurry pump example

Centrifugal slurry pumps.

Centrifugal Slurry Pumps in the Modern Age

The pump can be said to be the heart of mineral processing operations. Yet, the pump stories that are heard in industry range from anecdotal to humorous and sometimes just outright scary. This begs the question, “Would anyone really treat a ‘heart’ that way?”.

Pump designs with increased efficiency and improved wear characteristics have made significant strides over recent decades. This is due to computer-aided fluid dynamics (refining features) and the functions of pump impellers and casings. However, slurry pumps offer the additional features of wear and durability, in the context of ownership costs.

Anything “built to last” must still be looked after, much like the human heart. With the advent of new technology simplifying equipment operation, maintenance and monitoring in various industries, the scope appears limitless. Yet, these are all aspects of symptomatic treatment, which will later be discussed.

When complaints are made about a Multotec pump not performing optimally, or not lasting as long as expected, the cause of issue often lies in the pump’s environment. General pump installations are deemed simple, yet process environments designed around pumps are the main cause for complaint, and the beleaguered pump bears the brunt of the criticism…

For example, installation guidelines are provided for the centrifugal slurry pump and, yet, installations and plant designs overcomplicate the process – with the attempt to create ‘favourable’ pump environments. These environments then cause harmful operating conditions for not only the pump, but the whole processing system (a case of “if the heart is not doing too well, the rest of the body suffers”).

Of all the critical features of any centrifugal pump system design, the suction line is the most important. Nevertheless, this is also the feature most neglected or taken for granted.

With the notable precautions taken and correct start-up procedures implemented, the pump would be well on its way to smooth operation, both inherently as well as for the plant process. _Fig. 1_ depicts a simple guide on optimal suction conditions for the pump.

The most important installation precautions are:

• Check that the impeller rotates freely, (although this is done at assembly, important to do prior to start-up to be sure
• If necessary, adjust the impeller
  • Normally towards the suction, close enough so that the impeller is not in contact with the throatbush/suction liner
• Check direction of rotation of pump (done with belts slackened off, by “bumping” the motor)
  • This is done to ensure that the impeller, which is screwed on to the threaded shaft, is rotated in the correct direction thereby avoiding the impeller unscrewing and causing serious damage
• Open inlet valve to flood/prime the pump
• If gland seal water is required, ensure supply is turned on
• Gradually crank open discharge valve as pump picks up load
  • Pumping into an empty pipeline, particularly with long distances yields no resistance and pump would tend “drop off” the curve with high flowrate, and high power draw
• Check gland leakage and adjust as necessary (when pump is not operating – for safety)

The monitoring & control side would now take effect.

_With the above measures implemented to ensure plain sailing:_

• Monitor pump: for any unusual noise
  • Casing: unusual noise (grinding, popping, knocking, etc.) & visible leaking
  • Undue vibration
• Bearings should be checked for temperature & noise
• Power draw
• Output(head and flowrate is as desired – with appropriate instrumentation
• Grease bearing seals, bearings & gland as necessary
• Adjustment of wearing components to extend wear life

_*Each sound would have a likely cause. If all necessary precautions have been taken, however, there would be no alarms raised here._

Previously, all these processes were all carried out manually. However, the Internet of Things is sophisticated enough to allow visualisation and implementation of the following scenarios:

• Sensors to monitor vibration, temperature, output flowrate & heat generated by pump
• Visual monitoring (camera)
• Automated lubricators to maintain adequate lubrication to applicable points
• Hydraulically-automated controlled adjustment of impeller(or liners) to extend wear life

These can all be harnessed to a single point of control. Similar to that of tracking devices, the pump can be monitored through its geographical location and the controls and condition monitoring implemented at the touch of a button. With ‘smart-tags’, this can all be fine-tuned and each pump can have its own ‘passport’ with service history.

Looking after your pump in the process is as essential as looking after your heart. Much like the heart ensures full-body functioning, the pump ensures the optimal operation of the whole mineral processing system.