Elevator Overload Protection Devices: A Comprehensive Guide

What Are Elevator Overload Protection Devices?

Elevator overload protection devices function to monitor cabin weight and stop operation when the load surpasses the rated capacity by around 10% or hits a minimum threshold of 75 kg as specified in EN 81-20. Elevator overload protection devices use sensors, relays, or load cells to detect when weight exceeds limits and send signals to the control system to stop operation or provide warnings. Modern elevators must incorporate these devices to adhere to safety requirements while ensuring passenger and cargo safety along with machinery protection.

Key components include:

• Load Cells/Sensors: The load cells or sensors for weight measurement are positioned beneath the cabin or attached to suspension ropes.
• Control Interface: Relays and electronic circuits analyze sensor inputs to activate appropriate actions.
• Indicators: LED displays and alarm systems work as visual and audible alerts to inform users about overload situations.

How Overload Protection Devices Work

Overload protection devices maintain safety through continuous load monitoring of the elevator and implementation of corresponding safety measures.

Weight Measurement:

• Load cells placed under the cabin floor or integrated into cable springs measure the total weight including cabin structure and payload. Zemic’s round load cells compensate for non-axial forces to produce accurate readings.
• The elevator’s sensors trigger an alert when the load surpasses 90–110% of its rated capacity following ASME A17.1 standards.

Signal Processing:

• The sensor transmits data to the programmable logic controller (PLC) of the elevator. Upon reaching the load limit, the PLC engages a relay which stops the elevator from moving and typically turns off the “door close” feature or halts the motor.
• For example, ADCO Controls’ devices offer two relay outputs: The system features two relay outputs with one dedicated to full load detection and another for overload situations along with a seven-segment display which shows weight readings.

Safety Response:

• The elevator stops moving while an alarm or display message (such as “Overload”) instructs passengers to reduce the weight inside. Zemic systems stop operation when weight falls beneath 15 kg to protect children.
• During emergency situations devices activate to halt the elevator while safeguarding its mechanical parts.

Calibration and Maintenance:

• Devices operate within the elevator’s specified weight capacity range which Elevator World notes as 560 to 1500 kg. Regular checks prevent sensor drift, ensuring accuracy.

Types of Overload Protection Devices

• Mechanical Devices: Simple mechanical switches activated by excessive force on ropes or springs serve as overload protection but lack precision. Common in older systems.
• Electrical Devices: Measure motor current draw and activate hoist disengagement when overload conditions appear. Widely used for reliability.
• Electromechanical Devices: Electromechanical systems integrate mechanical switches with sensors to fine-tune voltage according to load deflection for accurate measurements.
• Load Cell-Based Systems: Advanced sensors such as Zemic’s which are placed under the cabin or ropes deliver both high accuracy and robust durability making them perfect for contemporary elevators.

Benefits for Safety and Efficiency

Enhanced Passenger Safety:

• This safety feature stops elevator operation when loads are unsafe to prevent cable strain and free falls. Local reports indicate Singapore’s elevator systems equipped with overload sensors experienced a 10% reduction in operational incidents.
• The child protection feature prevents elevators from operating when they carry insufficient weight to protect young passengers.

Equipment Protection:

• The system protects motors and cables from excessive stress which extends elevator life by 10–15% according to industry estimates.
• The system lowers maintenance expenses by blocking damage that occurs due to overload conditions.

Improved Efficiency:

• Full-load contacts in elevators stop unnecessary stops when fully loaded to improve traffic flow in high-density buildings such as Dubai’s skyscrapers.
• The energy-efficient motor management system adjusts power levels according to load requirements to reduce consumption by 5–8% as reported by Zemic.

Regulatory Compliance:

• The product complies with EN 81-20 and ASME A17.1 standards which guarantees certification while preventing penalties.

Applications

• Commercial Buildings: Load cells enable high-traffic offices to detect overloads with precision.
• Residential Elevators: Child protection features in apartment complexes provide essential safety for residents.
• Freight Elevators: The system can support heavy loads that reach up to 5 tons according to ADCO Controls through its durable sensors.
• Hospitals: Accurate load monitoring ensures safety for both patients and sensitive medical equipment.

Challenges and Solutions

• Sensor Sensitivity: Load cells can be damaged by shock. Solution: Zemic’s rubber shock absorbers protect sensors.
• Cost: Advanced systems cost $500–$2,000. Solution: Mechanical devices offer affordability for older elevators.
• Maintenance: Sensors require regular calibration. Solution: Diagnostic tools, like ADCO’s, simplify upkeep.

Why Overload Protection Matters Now

As urban areas are expected to house 68% of the world population by 2050 according to the UN, elevator safety becomes essential. Sustainable and dependable vertical transportation solutions that fulfill 2025 needs include overload protection devices which X platform recognized. By optimizing energy use elevator overload protection devices support green building goals while preventing accidents and reducing operational costs.

Tips for Building Managers

1. Choose Robust Systems: Load cell-based devices like Zemic’s deliver accurate performance and should be your choice for reliable systems.
2. Schedule Maintenance: According to MAS Industries standards, elevator sensors require inspection every six to twelve months.
3. Integrate Smart Monitoring: Implement TRUCONNECT systems to obtain real-time alerts about overload conditions.