Overspeed Protection Systems

Electronic Overspeed Protection System

There are several reasons to upgrade to an Electronic Overspeed Protection system:

  • Most new turbines today are equipped with Electronic Overspeed Protection as a standard.
  • Electronic Overspeed Protection systems provide safe, simple, and reliable testing.
  • Electronic Overspeed systems are very reliable, and come with modern features such as a testable set point and speed rate of change detection.
  • An Electronic Overspeed Protection system fulfills international safety specifications.
Woodward’s ProTech™TPS (Total Protection System) is a safety system that provides specialized overspeed protection functions plus additional programmable logic to address other safety-critical functions.

Mechanical Overspeed Mechanism Replacement


A number of concerns come to mind related to your operation, but overspeeding a turbine usually ranks near the top of the list. Overspeed protection is the most important aspect of control on all types of rotating equipment.  If this protection fails, human lives are endangered and substantial damages followed by long-term forced outages can occur.

Mechanical Overspeed Protection

While ‘state of the art’ in their time, if still in service Mechanical Overspeed Devices have many drawbacks compared to today’s modern systems.

  • Industry data shows one principal cause of failure of turbine components is testing the mechanical (bolt) overspeed protection system; ‘one must create an overspeed condition to test the protection’. This method of testing also causes additional turbine and driven load life consumption.
  • The overspeed “bolt” does not operate (or trip) at the same speed all of the time. The cause of this unreliable performance can be traced to vibration. Depending on the phase angle, this vibration can cause the trip speed to vary approximately ±2.5% from the typical RPM set point.
  • Mechanical overspeed “bolts” can hang up and fail to operate.

The use of mechanical overspeed trip devices was the original OEM design, but today you have options that increase reliability and safety for your operation.

Electronic Overspeed Protection

Today you can have electro-hydraulic systems with redundant or triple modular redundant (TMR) micro-processor based protection circuits. Electronic Overspeed Protection provides peace-of-mind for your most critical rotating machinery control safety systems.

There are a number of benefits to your operation in upgrading to an Electronic Overspeed Protection system:

  • Most new turbines today are equipped with Electronic Overspeed Protection as a standard. Very few are supplied with a mechanical bolt.
  • It is not necessary to test the overspeed system by running the turbine up to the set point trip speed (typically 110% speed). Testing at lower ‘test trip speeds’ results in no additional life consumption; critical for older turbines.
  • Today electronic systems are more reliable then the Mechanical Overspeed Bolt because the systems can operate on both specific “set point speeds” and “rate of change” derivative.
  • A Electronic Overspeed Protection system fulfills international safety specifications, and based on product selection be can be SIL2 or SIL3 rated.