Elevator Overspeed Governor: All You Need to Know


What is an Elevator Overspeed Governor?

An overspeed governor in elevator is a safety protection device to prevent the elevator from exceeding its speed limit. It monitors and controls the speed of the elevator every time. If the elevator exceeds its rated speed, the overspeed governor will be triggered to ensure the safety of the passengers.

How Does an Overspeed Governor Works

The governor sheave detects speed changes as it rotates due to the movement of the governor rope. When the elevator exceeds its rated speed, the flyweights move outwardly due to centrifugal force, or the weight shift in position due to inertia, depending on the type of speed governor. This movement of the flyweights is the action of the speed-sensing mechanism.
When this occurs, it activates the safety mechanism, which pulls the actuating rod. The actuating mechanism engages with the safety jaws to stop the elevator. At the same time, an electrical switch is activated, cutting off the power circuit to prevent further movement.

Types of Overspeed Governor Elevator

Generally, there are two types of overspeed governor elevator. The centrifugal overspeed governor and the inertia overspeed governor. Both types of governors can either be monodirectional or bidirectional.

They work almost similarly to activate the safety mechanism. The difference is that while the centrifugal governor uses centrifugal force, the inertia governor uses the principle of inertia to activate the tripping mechanism that stop the elevator.

Monodirectional speed governor is a speed governor designed to detect over speeding in a single direction, typically in a downward direction. Bidirectional speed governor on the other hand detects and respond to unsafe speed in both directions- downward and upward.
The bidirectional speed governor is constructed differently with more components than the single direction speed governor. This enables it detect the tripping speed in both directions effectively.

Centrifugal Overspeed Governor

This type of overspeed governor uses centrifugal force to trigger the safety mechanism when the elevator is moving at a speed above its preset limit. As the speed increases, the flyweights or fly balls swing outward due to the centrifugal force. This outward movement causes the elevator to stop. If the speed decreases, the flyweights move inward, resetting the system for normal operation.

Inertia Overspeed Governor

This type of overspeed governor uses the inertia of weight, typically an assembly of flyballs or flyweights instead of a centrifugal force. As the speed increases, the inertia of the flyweight assembly causes it to shift position to slow down the elevator or stop it.

Components of An Overspeed Governor System

These components coordinate together to make sure the elevator operates within safe speed limits.

Governor Rope: The governor rope is connected to the governor sheave. It fits into the groove of the sheave. As the elevator ascends and descends, the rope moves along with it. This causes the governor sheave to rotate.

Governor sheave: The governor sheave is a wheel or pulley that has a groove around its edge. The groove is designed to hold and guide the governor rope. As the governor rope runs over the governor sheave, the governors sheave turns. The rotation of the governor sheave allows the speed-sensing mechanism to keep track of the speed of the elevator.

Speed sensing mechanism: The speed sensing mechanism consists of flyweight or flyballs. As the governor sheave rotates faster, the centrifugal force acting on the flyweights causes them to move outwardly. However, for the inertia governor, instead of using the centrifugal force, it uses the inertial of a flyweight assembly. So, as the governor sheave rotates faster, the inertia of the weight causes it to shift position.

Triggering the safety mechanism: The movement of the weight triggers a tripping or safety mechanism, which activates the actuating rod. This safety device is attached to the elevator car with a flexible arm or spring. This allows it to move as necessary.

Actuating rod: The actuating rods then activate the safety jaws onto the elevator guide rails. This brings the elevator to a controlled stop.

Electrical switch: the electrical switch cuts off power to the elevator motor when the governor detects an overspeed condition. This ensures that the elevator does not continue to ascend or descend, thereby enhancing the overall safety of the system.

Elevator Overspeed Governor FAQs

What Causes an Elevator to Overspeed?
There are many reasons for the overspeed of the elevator, such as damage to the traction machine parts, failure of the electrical control system, brake failure, etc. Therefore, please make sure to check the elevator regularly and replace parts when it fails.

What Speed Does The Speed Governor Trip at?
When the elevator’s operating speed exceeds 115% of the rated speed, the mechanical action of the speed governor will be activated, and the car will be stopped by pulling the safety clamp to clamp the guide rail.

Can Overspeed Governors Be Upgraded to Newer Technology or Modernized?
Yes, overspeed governors can be upgraded to new technology to enhance the safety and performance of the elevator system. Modernizing your overspeed governors offers advanced features and improved reliability.

How Long Before A Speed Governor is Replaced?
Overspeed governors in elevators can last for 10 to 15 years depending on the manufacturer, usage, and maintenance. However, we recommend regular, and careful inspection to ensure the operational safety of the elevator. This involves periodic maintenance checks and thorough overspeed tests to ensure the speed governor is functioning properly and meets safety standards. The overspeed test involves running the elevator at high speed to check if the governor will activate both the electrical and mechanical safety mechanisms. If the governor does not activate the safety mechanisms as it ought to, that means the governor is not functioning properly. In this condition, the governor needs to be replaced immediately. Also, replace instantly if it is worn, to ensure the safety of the elevator.


The elevator overspeed governor is the tool that prevents an elevator from breaking its speed limit when ascending or descending. When the elevator is moving at a high speed, the speed governor will activate the safety mechanism, turn off the power circuit, and stop the elevator car. It is worth noting that a faulty or malfunctioning overspeed governor can cause the elevator to overspeed and put the passengers at risk.

The elevator speed governor ensures the safety of the passengers in a lift system, and it must be regularly checked and replaced when necessary. It is installed on the load bearing beam or floor of the machine room.

At Dazen, we offer different types of speed governors to meet your specific needs, including single direction and double direction speed governors. We also have speed governors for machine room and machine roomless elevators. Contact us today for more information.

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