MTS Series 505 SilentFlo Hydraulic Power Unit Model 505-180 - Manual (Page 19)

Options Available for the HPU
Model 505.60 - 505.180 SilentFlo™ HPU Introduction 19
The ROD option allows the HPU to turn individual pump motors on and off as
your system flow demand changes. A minimum flow reserve is maintained and
pump usage is equalized by sequentially turning on pumps starting with the
pump with the least amount of run time, and turning the pumps off in reverse
order. The cycling of these pumps is controlled by a PLC that takes into account
various system parameters such as system hydraulic fluid flow (both real time
and trends), the number of pumps currently running, and user configurable on/off
delay settings.