Variable Frequency Drives (VFDs) are often used in wastewater stations that transport sewage. They are used to control the flow of sewage through the pumps and help wastewater treatment plants achieve the required flow. Like any piece of equipment, it must work with the whole system to be truly effective.
This article, from Horst Sturm of KSB, discusses important considerations for VFDs in wastewater applications. Some of what is discussed in this document includes:
- Check velocities – compare the velocity of the minimum required flow with the recommended minimum velocity to get a good indication of whether or not the system is working properly.
- Implement a short ramp for the start of the pumps and perform some smart programming, which makes it possible to flush the system during operation and helps to minimize risk.
- De-ragging – some VFD manufacturers have designed the VFD converter with a “de-ragging” function, which is a feature that changes pump speed and/or operates the pump “backwards”. This de-ragging feature works to help pumps avoid getting clogged by fibrous rags. This can be a very helpful function, but has some limits.
Download the document for the full details.