Pump expertise turns mine dewatering problem around

In 2018, a magnetite mine in Australia – a customer of Metso Outotec – reported that excessive manhours were being expended on the maintenance and repair of the filter feed pump glands in its Metso Outotec HM250 slurry pumps. The pumps were used in the mine’s dewatering process, in which excess water is removed from the magnetite concentrate after beneficiation.

The HM series slurry pumps have been specifically developed to provide trouble-free operation and minimal downtime with long wear life, and have a reputation as reliable ‘workhorses’ in mineral processing applications. Metso Outotec sent representatives to the site for a full investigation to help diagnose and correct the problem.

Finding the root cause

The plant had undergone some changes since original installation, and as such pump duty conditions had also changed to align with updated plant requirements. Additionally, piping upstream of the pumps had been replaced.

During a week-long consulting engagement, Metso Outotec’s experts discovered that the upstream pipework had been replaced with a different third-party product from that which had originally been installed. With the newer pipes, the inner polyurethane lining of the pipes had been delaminating, and particles of the lining were mixing with the slurry and getting trapped beneath the back liners of the pumps’ impellers, wearing out the seals. This was found to be the chief cause of the need for excessive maintenance, as the debris needed to be constantly removed from the pumps, and damaged seals replaced. Damaged seals also often resulted in excessive water leakage.

The customer had already come to a similar conclusion and had installed trash screens upstream of the pumps to trap the debris, however they had only just been placed in service at the time of the site visit.

Optimizing pump performance

The Metso Outotec experts also examined how changes in the pump duty conditions had affected the performance of the pumps. They noted that across the site the settings for gland water flow and pressure were inconsistent, and not at the optimal level for best performance. If these parameters are not correct, they can lead to not only sub-optimal performance, but also premature wear on the pumps’ components.

An examination of the gland water being utilized for flushing the slurry pumps found that it was from nearby water ponds and from desalinated process water, and it was recommended that steps be taken to improve the water quality for best performance.

The customer also enquired whether using an alternative type of seal, such as a centrifugal seal, would offer an improvement in reliability, so Metso Outotec performed a review of alternative seal options. The advantages and limitations of each alternative options were provided for client’s consideration.

It was also recommended that adequate polyurethane coating or suitable rubber lining for the upstream pipework is used, but if this was not feasible, then the trash filters may be adequate to protect the pumps from the debris.

Pumps expertise delivers results

In the end the pump parameters were re-set. The very same HM250 pumps, installed over 10 years ago and the ‘workhorse’ at site, now continue to deliver on their reputation for reliability and performance. The issue of excessive maintenance has been resolved since the Metso Outotec team helped identify the root cause of the problem and optimised the pump performance. The mine is now experiencing many benefits, including reduced labour usage on pump maintenance, improved pump seal life, and an increased opportunity for better labour utilization for other critical assets on plant.

From the financial side, the mine has reduced its spending on pump spare parts by nearly 50%. The dewatering section of the plant is also now safer and is far more water efficient, as water leakage from pump seals has been significantly reduced.

Metso Outotec’s partnership approach to customer engagement meant that while the cause of the problem was not related to the Metso Outotec pumps themselves, their expert advice and in-depth process know-how provided the necessary solution to the mine’s dewatering pump maintenance issues. The mine is in discussions on taking further advantage of Metso Outotec products and services in the future.