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With the acceleration of urbanization and increasingly stringent environmental regulations, the sewage treatment and environmental protection industry is facing unprecedented challenges: how to ensure operational safety, reduce accident risks, and improve the reliability of equipment operation. In this context, trapped key interlocking, as an effective mechanical safety control technology, is playing an increasingly important role in the sewage treatment and environmental protection industry.
This article will discuss in detail the application scenarios, functional principles, and safety advantages of trapped key interlocking in the sewage treatment and environmental protection industry, and analyze it in combination with typical cases to provide a reference for enterprises in selection and system design.
1. What is trapped key interlocking?
Trapped key interlocking (TKI for short) is a safety interlocking system based on mechanical key sequence control. The core idea is that only after completing a certain operation (such as power off, closing the valve) can a specific key be released, and this key is the prerequisite for the next operation step.
This system mainly consists of three parts:
Key: has a unique code and can only be inserted into a matching lock.
Interlocking device (Interlock): installed on power switches, doors, valves and other equipment to control their open and closed states.
Key exchange box: used for the management and conversion of multiple keys in complex processes.
Because it does not rely on power supply and has a sturdy structure, the TKI system is particularly suitable for use in environments with moisture, corrosive gases, high temperatures, and explosives, which meets the on-site needs of sewage treatment plants and environmental protection facilities.
2. Key safety risks in the sewage treatment and environmental protection industries
There are many safety hazards in the operation of sewage treatment and environmental protection equipment:
Equipment maintenance without shutdown: For example, sludge dewatering machines and electric agitators are not powered off, and workers mistakenly enter and cause casualties.
Misoperation of pipes or valves: Repairs are carried out without completing exhaust and isolating the water inlet valve, resulting in liquid splashing and chemical damage.
Dangerous gas release: Leakage of biogas, hydrogen sulfide, etc. is extremely dangerous for maintenance personnel to enter confined spaces.
Misopening of access control: Misopening of electric control cabinets and high-voltage equipment rooms without permission approval or without completing the previous operation.
The above scenarios show that sewage treatment sites are highly dependent on the correctness and sequence of operating procedures, which is exactly the advantage of trapped key interlocking technology.
3. Application scenarios of trapped key interlocking in the sewage treatment industry
Interlocking of dewatering machine and conveying equipment
Scenario problem: When the sludge dewatering machine or screw conveying equipment is not powered off, maintenance personnel enter the maintenance area, which is very likely to cause strangulation or extrusion accidents.
TKI solution:
Electrical interlocking device is installed on the power switch.
The mechanical key can be released after power failure.
The key can be used to open the interlock on the safety door or equipment maintenance door.
The key can be returned to restore power only after the door is closed and relocked.
This process ensures that the equipment is completely powered off during the maintenance process, and power is allowed only after the personnel are evacuated, effectively preventing power-on accidents caused by misoperation.
Interlocking of pipeline system and valve operation
Scenario problem: When maintenance personnel need to replace or clean the water inlet/drainage pipeline, if the relevant valves are not closed or the pressure is not vented by mistake, liquid splashing, personal injury or equipment damage may occur.
TKI solution:
Valve interlocking devices are installed on both the water inlet valve and the drainage valve.
The key can be pulled out only after the valve is closed.
The key is used to open the inspection valve, blind plate or access door for the next stage.
This method ensures that the isolation, venting and pressure reduction of the pipeline have been completed before maintenance.
Access interlocking of confined space operation area
Scenario problem: Anaerobic tanks, reaction tanks, sedimentation tanks and other areas are closed or semi-closed spaces, and there may be hypoxic and toxic gases. They must be entered after gas detection and ventilation are completed.
TKI solution:
The gas detection system releases the key after the detection is completed.
The key is used to open the inspection door or personnel entrance door.
If the detection exceeds the standard, the key cannot be removed and personnel cannot enter.
This type of control process is physically blocked by TKI, avoiding the problem of regulation enforcement relying on human judgment, greatly improving the safety of confined space operations.
Interlocking of chemical dosing system
Scenario problem: Acids, alkalis, coagulants, flocculants and other chemicals are often used in environmental protection treatment processes. The maintenance of dosing pumps, storage tanks and pipelines requires strict control steps.
TKI solution:
The key can only be pulled out after the dosing pump stops running.
The key can be used to open the manhole of the tank or the valve of the pipeline.
After the inspection is completed and the closure is confirmed, the key can be returned in reverse to restart the system.
This "stop before inspection" interlocking mechanism effectively prevents chemical damage accidents caused by leakage and splashing of reagents.
4. Typical case: Application practice of TKI system in a sewage treatment plant in a certain city
Project background: In order to meet the requirements of the new "Safety Production Law", a large sewage treatment plant in a certain city needs to add safety interlock devices to its sludge treatment system, reaction tank area, confined space and other key areas.
Solution:
A total of 50 sets of TKI devices were deployed, including power interlocks, door locks, valve interlocks and key conversion boxes.
Develop an inspection flow chart and a key transfer table.
Cooperate with employees for training, and register the key usage status in conjunction with the dispatching system.
Application results:
The number of safety accidents has decreased by 90%.
The inspection process is more standardized to avoid unlicensed operations.
It has received praise from the special inspection of the Environmental Protection Bureau and has become an industry demonstration project.
With the deepening of the concepts of "safe production" and "intrinsic safety", trapped key interlocking is becoming an important part of equipment safety control in the sewage treatment and environmental protection industries. It implements "operating specifications" from paper to the site in a simple, reliable and mandatory way.
In the future, with the integration and development of intelligent manufacturing and digital operation and maintenance, TKI will also be combined with sensors, industrial Internet of Things, and data acquisition systems to develop into a hybrid interlocking system of "mechanical + electronic", further improving the intrinsic safety level of the industry.
If you are planning a safety interlocking system for sewage treatment plants and environmental protection equipment, trapped key interlocking is a low-maintenance, highly reliable solution that deserves priority consideration.
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