Safety in mining and at construction sites where explosives are used was a problem for a long time, because the storage and transport of “volatile” explosives always constitute an enormous risk. In order to reduce the danger and achieve a better explosive performance, there has for some time been greater use of pumpable emulsion explosives.
A global explosives manufacturer had used a progressing cavity pump to fill the storage silos with the ready-to-use ammonium nitrate emulsion. However, the pump did not provide the required level of performance and delayed the supplying of the mines and customers due to regular breakdowns. The pin joint could not withstand the torque nor the deflection on the coupling rod and therefore often failed. The shortness of the coupling rod increased the angle which the joint had to compensate. That not only increased the stress on the joint itself, but also the dynamic load on its seal system. The lubricating effect of the lubricant used for the pin joint was not sufficient either. As a result, the pump was constantly breaking down. Since the pump had a crucial role to play in the process chain, every breakdown led to costly delivery delays.
In order to increase the service life for the application and the throughput rate of the whole system, the emulsion manufacturer searched for a more reliable pump with a larger capacity and found NETZSCH. Mining specialist Tyron Adam proposed a NEMO® progressing cavity pump for the job. It is ideally suited for ammonium nitrate emulsion, because consistency and viscosity of the medium are insignificant in terms of the product flow. At this application the NEMO® progressing cavity pump was also fitted with the NEMO® V-pin joint, that is filled with oil in order to achieve a long service life. To increase the lifetime of the pin joint even in the toughest operating conditions, it also has hardened bushes. These are pressed into the boreholes of the coupling rod and the rotor head or drive shaft head and can be particularly easily replaced during maintenance work. For reasons of safety, the pump was not fitted with a single mechanical seal with pressure-free quenching: To further increase process reliability and minimise risk of product crystalizing between seal faces, a double-acting ASSEAL mechanical seal with thermosiphon vessels was used. In addition, the installation of a variable speed control enables the manufacturer to implement a control concept which provides for adjusting the conveying speed of the pump to the specific quantity of emulsion which is available for filling the storage tanks. This process optimization allows a considerable reduction of the number of pump starts during a shift, which significantly increases the service life of the pump. Since March 2013 the NEMO® pump has been running trouble-free.