1. Ensure motor power availability
A well-designed plant has enough power allocated to mill pumps. Pumps typically operate on variable speed drives, meaning that there are many process variables affecting speed and, finally, the power draw. It is a good idea to look at SCADA data on historical power drawn to better estimate the amount of power that would be available for tonnage increases. Rather than using engineering data sheets that are somewhat oversimplified, it is beneficial to use a point cloud type plot showing flow and pump pressure as a function of time. This information makes it possible to determine the optimal size of all the pumps and cyclones for the plant.
2. Minimize impeller wear when reducing inlet velocity
High inlet velocities combined with large, sharp objects is a significant cause of impeller wear. As a guideline, 4.5–5 m/s (meters per second) is considered the maximum limit for abrasive duties, but it is useful to check the inlet velocity with the supplier before increasing the pump flow. Typically, pump suppliers offer a variety of impellers and inlet liners for the same casing that can help reduce inlet velocity without sacrificing efficiency or requiring an expensive pump upgrade.
3. Consider gearbox cooling at higher power
As pump duty is increased, it usually also increases the power transmitted through the gearbox. This means that the amount of heat increases as well: a gearbox that is sized marginally for air to air cooling may overheat with higher continuous duty. Consideration must be given to the cooling capacity of the lubrication system, particularly at higher ambient temperatures and altitudes.
4. Gland seal water pressure at higher heads
The pump gland seal water system should be sized so as to be able to deliver a constant flow of gland water under all operational conditions. This applies to the pump duty, including any increase in head due to tonnage increases. It should also be checked that the gland seal water system is adequate when other demands are placed on it, such as hose downs or flushing.
5. Consider larger pipes with friction and wear in bends
If you double the speed, the rate of material loss increases 16-fold and the rate of abrasive wear on the surface is approximately proportional to the fourth power of velocity. If there is a significant increase in input, it is necessary to consider whether the pipe sizing is optimal. The right size allows friction losses and wear to be minimized. Of course, if there is a large variation in flow, then minimum velocity to prevent settling should be examined.