Hydraulic Power Unit

A Hydraulic Power Unit, commonly abbreviated as HPU, is a self-contained system that generates, controls, and supplies the high-pressure hydraulic fluid required to actuate industrial brakes. It is the heart and brain of a hydraulic braking system, converting electrical energy from a motor into hydraulic power.

The primary function of an HPU in a braking application is to provide the necessary flow and pressure of hydraulic fluid (oil) to either apply or release the brake, depending on the system’s design.

A typical HPU consists of several key components:

1. Electric Motor: The prime mover that drives the hydraulic pump.
2. Hydraulic Pump: The core component that draws hydraulic fluid from a reservoir and pressurizes it, creating flow.
3. Reservoir (Tank): A container that holds the supply of hydraulic fluid. It also helps to cool the fluid and allow contaminants to settle.
4. Valves: These are the control center of the HPU.
   • Directional Control Valves: Direct the flow of fluid to the correct ports on the brake caliper to either extend or retract the pistons.
   • Pressure Relief Valves: A critical safety component that prevents the system from becoming over-pressurized, protecting the brake, hoses, and the HPU itself.
5. Filtration: A filter system that cleans the hydraulic fluid, removing contaminants that could damage the pump, valves, or brake seals.
6. Instrumentation: Gauges for monitoring system pressure, level indicators for the reservoir, and sometimes temperature sensors.

The HPU’s role is fundamentally tied to the brake’s actuation principle:

• In hydraulic-applied (active) braking systems, the HPU is idle until a stop is commanded. It then rapidly builds pressure to engage the brake for a dynamic stop.
• In hydraulic-released (fail-safe) systems, the HPU’s role is reversed and even more critical. It must maintain a constant “brake-off” pressure to hold the powerful brake springs in the released position during machine operation. Any loss of power to the HPU or a drop in hydraulic pressure will cause the brake to safely and automatically engage.

In essence, the HPU provides the controlled, high-force power necessary to operate large-scale industrial brakes, enabling their use in the most demanding high-torque applications where electromagnetic or pneumatic forces would be insufficient.