governor overspeed trip elevator

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Elevator Overspeed Incidents Expert Article

Elevator overspeed incidents are among the elevator malfunctions that appear in our forensic casework. The sudden and unexpected acceleration of an elevator beyond the accepted contract speed, followed by an abrupt stop, can result in serious injuries for passengers.

In this article, Elevator & Escalator Expert, Dennis Olson explains the purpose and function of an overspeed governor and the maintenance policies and procedures which should be followed to ensure safety.

Elevator Overspeed Incidents – Expert Article

Overspeed incidents are often caused by the failure of the elevator controls system to accurately regulate the acceleration of the elevator creating what the industry identifies as an “overspeed” condition.

ASME A17.1 Safety Code for Elevators provides the definition of a Governor:

“A continuously operating speed monitoring and detection device which, at predetermined speeds, provides signals to the controller and imparts a retarding force to activate the car or counterweight safety.”

The purpose of the governor is to measure and regulate speed in a manner that prevents the elevator from exceeding a predetermined upper speed limit.

In the event the governor detects an overspeed condition, it is designed to respond by bringing the system to a halt. This can be achieved with or without activation of the mechanical safeties, depending on the elevator settings and specific conditions. After the governor initiates the stopping procedure, the elevator remains immobilized until it is re-set.

Should an elevator exceed 115% of the rated contract speed, an emergency stopping of the elevator will occur by activation of the governor overspeed switch. Activation of the governor switch will remove electrical power to the elevator hoist machine. The resulting loss of power will cause the elevator brake to set, resulting in an immediate hard and abrupt stopping of the elevator.

Should the elevator exceed 120% of the rated contract speed, an emergency stopping of the elevator will occur by activation of the safety devices mounted under the elevator car platform. The safety device shall be capable of stopping and sustaining the entire car with its rated load. Activation of the safeties will also result in an immediate hard and abrupt stopping of the elevator.

Elevator Maintenance Standard of Care

The ASME A17.1 Safety Code for Elevators and Escalators is a standard for elevator design, maintenance and operation which is widely accepted throughout the elevator industry and the building management industry. To meet the intent of the Code, the most widely recognized industry practice is for the elevator company to maintain a logbook containing the required information in the elevator machine room. The purpose of the maintenance log is to provide a written record of work performed on the elevator that mechanics and inspectors can reference when performing maintenance or responding to service calls.

Elevators require regular and systematic maintenance at predetermined periodic timeframes, in addition to unplanned/as-needed adjustment and/or repair when a specific issue is reported. Factors considered when developing a maintenance plan for elevators / escalators and other forms of vertical transportation equipment are identified in ASME A17.1.

The maintenance procedures and intervals shall be based on:

• equipment age, condition, and accumulated wear
• design and inherent quality
• environmental conditions
• improved technology
• the manufacturer’s recommendations for any SIL rated devices or circuits

In a forensic investigation, review and understanding of the information provided in the maintenance log and maintenance records may provide critical information about the condition of the elevator and the maintenance that was performed leading up to the incident.

Elevator Safety Investigations

The Elevator and Escalator experts at Robson Forensic have the necessary training, education and experience to investigate a broad range of mishaps involving elevators, escalators and other forms of vertical transportation equipment encompassed under the A17.1 and associated Safety Codes. Our elevator and escalator experts are industry veterans who have worked for companies involved in the design, manufacture, installation, modernization, service/repair and maintenance of elevators, escalators and various other forms of vertical transportation equipment. They understand how this specialized equipment is designed to function and can reliably identify the factors related to the failure of system components that may or may not have contributed to the injury or loss in your case.

For more information, submit an inquiry or contact the author of this article.

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WITTUR OVERSPEED GOVERNOR OL35-NA, OL35E-NA

600.00 €

As for material, labor, transportation cost and exchange rate are changing,  the price for this is just for reference only, please contact us beforehand if you are interested.

Description.

• Reviews (0)
• Engagement of the safety gear in down direction
• Overspeed contact operated in up and down direction
• Outline dimensions do not change over whole speed range
• Tripping possible at any point along perimeter of governor pulley
• Guaranteed minimum rope pull through force 500N
• Pull through force created by inbuilt friction brake exerting brake torque to governor pulley
• Suitable for conventional elevators with machine room but also for MRL-elevators
• Wide range of options available as remote control, base plates, tension weights, providing maximum flexibility
• Meets code requirements of ASME A17.1

Technical features

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Tripped overspeed governor electrical switch initates emergency stop; entraps elevator passenger

Incident investigation, may 20, 2018, reference number:.

II-692976-2018 (ID: 7308)

Incident Overview

The elevator overspeed governor electrical switch tripped during travel and caused an emergency stop of the elevator resulting in an entrapment of 1 person in the car. The lifting arm attached to the elevator safeties engaged the safeties during the emergency stop. Service personnel manually controlled car and removed person in the elevator.

Regulated industry sector

Elevating Devices - Elevator

Coquitlam, BC

Investigation conclusions

Site, system and components.

The overspeed governor electrical switch is designed to trip when the speed of the car exceeds the normal rated speed of the elevator. If the elevator car exceeds its rated speed (overspeed), the electrical switch will trip and open the safety circuit and stop the movement of the car by applying an emergency brake on the main drive (motor). The car safeties are triggered mechanically by the overspeed governor at a speed that is higher than the speed at which the overspeed governor electrical switch will trip. When the overspeed governor is tripped mechanically, jaws will grab the governor rope and pull the lifting arm connected to the car safeties. The car safeties will engage and stop the motion of the car. When the safeties engage, the safety plank switch will open and remove power to the drive(motor).

Failure scenario(s)

Failure Scenario 1 The overspeed governor electrical switch was adjusted to trip at a speed only 16fpm faster than the rated speed of the elevator. A larger margin between the actual speed (354 fpm) and the electrical tripping switch speed (370 fpm) would be needed to prevent accidental contact with the governor flywheel and the electrical switch if the speed of the car fluctuates. There was insufficient tension on the governor rope and the lifting arm that is connected to the car safeties, allowing excessive movement (bounce) of the lifting arm. When the overspeed governor electrical switch tripped, the safety circuit was opened and the emergency brake on the main drive (motor) applied and stopped the car abruptly. The hard stop would cause the elevator car to bounce and the excessive play in the lifting arm allowed the car safeties to apply and open the safety plank switch.

Failure Scenario 2 The car door operator clutch may have contacted the roller assembly of a landing door while travelling, causing an abrupt stop when the safety circuit opens and causing the lifting arm connected to the car safeties to bounce.

Facts and evidence

On-site Investigation observations:

• Service personnel confirmed the overspeed governor electrical switch was tripped.
• Service personnel confirmed that the car safeties were engaged and safety plank switch was tripped, but the overspeed governor was not mechanically tripped and did not contribute to the safeties being engaged. The mechanical tripping speed of the overspeed governor was confirmed to be 450 fpm.
• Performed test to confirm actual tripping speed of the overspeed governor electrical switch. 370 fpm (16 fpm above normal run speed – 354 fpm).
• Observed insufficient tension in the governor rope and lifting arm connected to the car safeties allowing excessive movement (bounce) enabling car safeties to engage and trip the safety plank switch.
• Phase I fire service was initiated by the Firemen responding in an attempt to recall the car to the designated landing. Fire service was not related to the incident.
• Service personnel noted that a landing door counterweight for the door close tensioner was detached from its cable connected to the landing door – Landing door had no close tension.

Causes and contributing factors

It is possible that a door lock roller misalignment with the car door power operator clutch may have caused the door lock circuit to open while the car is in motion, resulting in a sudden de-acceleration of the elevator car. The sudden de-acceleration would cause the car to bounce and trip the electric switch on the overspeed governor. The excessive movement of the lifting arm connected to the car safeties would allow the car safeties to engage.

• Qty injuries: None
• Injury description: None
• Injury rating: None
• Damage description: Loss of operation. Overspeed governor electrical switch tripped. No tension on the lifting arm connected to the car safeties.
• Damage rating: Insignificant
• Incident rating : Insignificant

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Medium speed and rise governor

Ol35 / e / m.

The OL35 detects overspeed by its flyweight mechanism and engages the safety gear on the entire circumference of brake mechanism. This brake mechanism is pre-adjusted and limits the brake-force to protect the synchronization of the safety gear from excessive stress to the linkage.

Technical sheet

• Fields of application

• Unidirectional (mechanical)
• Bidirectional (electrical)
• Optional: external encoder, remote control, noiseless
• New installation and modernization
• Upside down applicable
• Speed monitoring by flyweight mechanism
• Internal clutch prevents the pulley from blocking

Available documents  14 files

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Self Resetting Overspeed Governor: NEW

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Self Resetting Overspeed Elevator Governor Description

• Built to meet ASME A17.1 and EN81-1
• CSA approved limit switch
• Remote set and reset capabilities
• Tested, preset and sealed at factory
• Comes with overspeed switch
• Comes with full rope guard
• Comes with selenoid
• Live shaft for encoder available (diameters: .25″ / .472″ / .75″ & 1″)
• Sheave diameter: 305mm/12″
• Rope type: 9.5mm or 10 mm, 3/8 inch or 10 mm  
• Max. pull through: up to 660 lbs
• Pre-set pull through: 400lbs
• Shipping weight: 35kg/77lbs

Self-Resetting Overspeed Elevator Governor Tripping Speed Chart

We welcome your questions

Elevator governors are an important elevator component. The correct speed and model must be selected for your elevator modernization. Please ask Delco's knowledgeable customer service for assistance.

In stock in the United States and in Canada

All models are in stock and available for quick shipping, with 24-hour order fulfillment and shipping from either Vancouver, BC or Ferndale, WA.

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