Standardised hydraulic power units have been to holy grail of hydraulic systems manufacturers since I have been in the industry. Recently Bosch Rexroth released the CytroPac and this intrigued me, an HPU in a can!
For many years the standard hydraulic power unit for industrial applications consisted of a standard range of tank sizes, coupled with a range of electric motors and pumps. Generally they all looked to be the same with the motor mounted vertically and the pump in the tank.
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In the 1990’s when working in the Steel Industry, Vickers (now part of Danfoss) offered a compact standard HPU in a horizontal configuration. From my memory the electric motor and tank were packaged together so you had difficulty identifying either. I don’t think the product took off.
Recently Bosch Rexroth released the CytroPac as part of their ctrlX product range. I needed to know more so I downloaded the data and installation sheets. Basically it is a small range of HPU’s with a maximum power rating of 4kW, which translates to a maximum flow of 35 l/min at pressure up to 240 bar. There are lower power options available but the maximum pressure reduces accordingly. The flow is controlled by varying the speed of the motor, which I assume is in closed loop control with the outlet pressure transmitter so as not to overload the motor. Strangely I don’t see a relief valve in the schematic, so I presumed the pressure sensor prevented over pressurisation. However in the installation instructions it advises you to install an external pressure relief valve. This is unusual, I don’t think I have seen a system where a relief valve is not fitted. The schematic shows a 10 micron return filter with 75% and 100% blocked switches. Also there are tank level and temperature switches. For a modern HPU I would have expected sensors not switches.
The top cover slides open to reveal connections for the switches, the breather and also the inputs/ outputs. According to the information from Bosch Rexroth the HPU can be controlled by the machine tool it is fitted to. One innovation is the heatpipe, which cools the motor, frequency converter and hydraulics, and a cooling water supply is required for this. The tank is smaller than the standard for an HPU, and Bosch Rexroth say it because of their innovative degassing technology.
The oil level is shown on the side with a green LED strip behind it for ease of visualisation.
Overall I think this is a very interesting development and it looks good. Certainly vastly different and looks better than most standard HPU’s. As with anything it depends on the price and return on investment.
