How trapped key interlocks work?

In industrial safety control, equipment maintenance and special operation processes, the trapped key interlocking (TKI) system is a widely used safety mechanism. It is used to ensure the correct execution of the operation sequence, prevent misoperation, and thus reduce the risk of accidents. The trapped key interlocking system was first used in the railway industry, and later gradually extended to manufacturing, energy, chemical industry, ports and other fields, especially in scenarios involving high-risk equipment, such as high-voltage switchgear, conveyor belts, valves, dangerous machinery, etc.

This article will provide an in-depth analysis of how the trapped key interlock works to help readers better understand the role and application of the system.

1. Basic composition of the trapped key interlocking system

The trapped key interlocking system is mainly composed of the following core components:

Interlocking Key (Trapped Key): The interlocking key is the core component of the entire system. It can be a mechanical key or an electronic key, and usually uses a specific code and shape to ensure uniqueness. The insertion and removal of the key controls the status of different devices or components.

Locks: Interlocking devices contain multiple locks, which can be installed in key locations such as doors, control panels, switches, valves, etc. of equipment. When a key is inserted into a lock, the corresponding equipment will remain locked or unlocked.

Key exchange box: A device for storing and exchanging keys, usually designed so that keys can be removed or inserted only under certain conditions.

Control system: Used to monitor and manage the status of keys and locks to ensure the normal operation of the system.

2. Working principle of trapped key interlock

The working principle of the key interlock system can be simply summarized as "key exchange" and "sequential control". Specifically, the system forces operators to perform operations in a predetermined order through the exchange and locking of keys. For example, in high-voltage equipment, operators must turn off the power before they can open the equipment for maintenance. The key interlock system ensures that the key to open the equipment can only be taken out after the power is turned off through the exchange of keys.

The working mechanism of the trapped key interlock system can be divided into the following steps:

Key insertion: The operator inserts the key into the lock, and the lock will verify the key according to the shape and coding to ensure the correctness of the key.

Key lock: After the key is inserted, the lock locks the key so that it cannot be removed. This step ensures that the operator must complete the current operation before proceeding to the next step.

Conditions met: The system monitors the status of the current operation and releases the key only when all conditions are met. For example, in high-voltage equipment, the system monitors whether the power is turned off, and only when the power is turned off will the key to open the equipment be released.

Key release: When all conditions are met, the lock releases the key and the operator can remove the key for the next operation.

A comprehensive understanding of the working principle of the trapped key interlock is essential for industrial safety. Due to its significant advantages in controlling the operation sequence of equipment, improving safety, and reducing accidents, it is particularly important to ensure the correct use of the trapped key interlock.

In industrial production, operational errors are often the root cause of accidents. Many equipment and systems have high risks during operation, such as high-voltage equipment, mechanical equipment, electrical systems, etc. Once an operation error occurs, it may cause equipment damage, personal injury, or even major safety accidents. The role of the trapped key interlock is to avoid accidents caused by errors or out-of-sequence operations by forcing the operation sequence and restricting improper operations.

In an efficient industrial environment, equipment failure not only affects production progress, but may also cause equipment damage, production line stagnation, and even cause significant economic losses. Trapped key interlocks avoid equipment damage caused by improper operation by ensuring that equipment operations are performed in the correct order, and improve the equipment's operating reliability and production efficiency.

By correctly using trapped key interlocks, operators can form clear operating procedures and specifications, and reduce safety issues caused by irregular or unauthorized operations. This mandatory mechanism not only improves operators' safety awareness of equipment operation, but also encourages employees to consciously abide by operating specifications, reducing human factors from interfering with the production process.

As an important safety protection measure, trapped key interlocks play a vital role in modern industrial environments. It ensures the safe operation of equipment, the safety of operators, and the smooth progress of the production process by enforcing the equipment operation sequence, restricting improper operation, and improving operational safety. Therefore, the correct use of trapped key interlocks plays an important role in ensuring industrial safety, improving production efficiency, and avoiding accidents.

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Shanghai Nudango Safety Equipment Co., Ltd.