Energy Sources

Hydraulic presses typically involve three primary energy sources that must be controlled during servicing and maintenance:

  • Electrical: Main power supply to the motor, control circuits, and any auxiliary systems (heating, cooling)
  • Hydraulic: Pressurized hydraulic fluid in the system, including accumulators that store energy even after the pump stops
  • Mechanical/Gravity: The ram itself, which can descend under gravity if not properly blocked

Typical Isolation Points

Each energy isolating device must be identified and locked out before work begins.

  1. Main electrical disconnect: Located on the power panel. Lockable disconnect switch rated for the press motor amperage.
  2. Hydraulic pump motor disconnect: If separate from the main disconnect, the hydraulic pump motor must be independently isolated.
  3. Hydraulic pressure relief: Bleed valves on the hydraulic manifold to relieve stored pressure. Verify pressure gauge reads zero.
  4. Accumulator isolation: If the system includes accumulators, isolate and bleed them separately.
  5. Ram block: Mechanical block or safety prop under the ram to prevent gravity descent.

Verification

After isolating all energy sources, the authorized employee must attempt to cycle the press using the normal operating controls. Verify the hydraulic pressure gauge reads zero. Confirm the ram is supported by the mechanical block and cannot descend.

Special Considerations

Hydraulic presses with heated platens require additional thermal energy isolation. Allow heated components to cool to a safe temperature or use appropriate PPE. Some presses have pneumatic counterbalance systems that require separate isolation.