How to improve the efficiency of slurry pump?

You know? When the slurry pump is in operation, the working point of the pump in the pump efficiency of the appropriate region. At this time, we need a change of slurry pump flow to adjust the pump efficiency. Here are some ways to change the slurry pump efficiency, I hope for your help
1, change the pump speed
2, in the centrifugal pump outlet pipe is provided with a regulating valve, changing the valve opening
3, change the turning impeller diameter
So, the characteristic curve of the pump will not change, but the pipeline characteristic curve is changed, when the pump operating point provided by the new flow can not meet the need of the flow conditions, should immediately try to change the location of pump operating point to improve pump efficiency!