Roger Willis details how a robust progressing cavity pump transports abrasive coal slurry from the coal face to the sump
At a coal mine in Eastern India, a mining company is using a progressing cavity pump for transporting coal slurry from the coal face to the sump. The unit is equipped with a gear motor that rotates at the right speed to keep the slurry suspended. At the same time, vibrations were minimised, which results in significantly less noise and wear. In addition, a stator made of nitrile rubber and a rotor made of chrome-plated tool steel were installed, ensuring a longer service life and reducing downtime caused by the difficult coal slurry medium.
In a mine in Eastern India, mining the coal in the bank produces a lot of dust that then mixes with the gravitational water directly in the mining area and accumulates near the continuous mining machine. To ensure that the machine can move forward in the underground mine to cut the coal, the resulting slurry has to be removed from the working face. There was not enough space to install the pump in the bank area or near the sump, which created a high risk of dry running. In addition, the pump had a long suction line which resulted in a poor NPSHa value. Due to the long distance between the coal face and the sump, the pumps had to handle negative suction. It also had to be capable of reliably transporting the abrasive medium with fluctuating concentration, size and texture of the solids content.
Pump Reliably Transports The Abrasive Medium
The company chose a Nemo pump from Netzsch that was adapted optimally to the application in the coal mine. The pump is equipped with a stator with a 1L geometry that is driven by a gear motor and features a optimally sealing point, optimally fit of rotor and stator and robust connection options. The materials chosen for the rotor and stator – nitrile rubber and chrome-plated tool steel – are particularly suitable for the abrasive medium. Furthermore, the pump is equipped with a gear motor that rotates at the right speed for keeping the slurry suspended, taking into account the speed in the pipe of more than 1.3m/sec. This results in fewer vibrations and less noise, which further increases the service life of the pump. This was also the reason why the medium flow and pressure range were adapted to pumping coal slurry.
The pump has been running in this mine since August 2018. The owner has found that the pump is very effective at transporting the slurry compared to the previous model. The increased service life of the components becomes evident from the fact that maintenance is now only required every eight to 10 months. This increased the service life by about 400%. After the first successful installation of a Netzsch pump for this application, the mining company decided to use additional pumps. The progressing cavity pumps from Bavaria are now in use at more than 20 other sites.
Roger Willis is with Netzsch