Both DRG and DP are forms of constant pressure control, but they are designed for different applications:
• DRG (Remote Pressure Control): Allows the pressure setpoint for the pump to be adjusted remotely via an external pressure control valve.
• DP (Multi-Pump Parallel Pressure Control): Specifically designed for systems where multiple pumps work in parallel. It contains an additional element (a variable orifice, valve 5) that mechanically links to the swangle. This design automatically compensates for differences between pumps, ensuring they share the load equally and operate at the same swashplate angle when working together at the set pressure. The DP control has a larger control deviation (~6.5 bar) compared to DRG (~3 bar).

When multiple pumps with standard DR controls are set to the same pressure and run in parallel, slight inherent differences in their response characteristics and pressure settings can cause them to not reduce displacement (cut off) at exactly the same time and rate. This lack of synchronization can lead to interactions between the pumps, resulting in pressure fluctuations and potentially causing severe pipeline vibration.