Chemical production process is relatively complex, chemical equipment towers, kettles, tanks, tanks, boilers, pressure vessels and pipelines most of the special equipment, and these chemical equipment operating in contact with the media, most of them are toxic, harmful, flammable, explosive, strong alkali strong acidic substances, in the chemical process operation process and in the high temperature, high pressure environment. Therefore, there are many unsafe factors in the process of overhauling restricted spaces in chemical equipment. To ensure the safety of workers in chemical equipment, it is necessary to strictly implement the relevant safety regulations and seriously implement safety measures for restricted space operations.
The person in charge of site safety at the base unit and construction unit should provide the necessary safety education to site guardians and operators. This should include at least the relevant safety rules and regulations; the possible dangers and hazards and the safety measures to be taken; the use of personal protective equipment and precautions; knowledge of accident prevention and self-rescue; and the experience and lessons learned from relevant accidents.
Safety emergency plans or safety measures should be formulated, including escape routes and rescue methods in case of emergencies, contact signals agreed between the guardian and the operator, life-saving facilities and fire-fighting equipment to be equipped on site, etc. Site personnel should be familiar with the contents of the emergency plan and be equipped with a certain number of emergency rescue appliances (including air breathing apparatus, air-supplied protective masks, lifelines, etc.) and fire-fighting equipment in accordance with the regulations at the site outside the confined space. There should be no obstructions inside or outside the entrances and exits to ensure that they are unobstructed, allowing easy access and rescue evacuation.
When the condition of the restricted space changes, the operator should immediately withdraw from the site and a warning sign should be set up at the entrance to prohibit entry and take measures to prevent mis-entry. A new permit is required for entry after processing.
Before entering the restricted space operation, the process should be done effectively, the restricted space will be purged, steamed and replaced with qualified; all the pipelines and valves connected to it and there may be combustible, explosive, toxic and hazardous materials are isolated by adding blind plates, and the valves should not be closed instead of installing blind plates. Signage should be hung at the blind.
To ensure air circulation in restricted spaces and the breathing needs of personnel, natural ventilation may be used, and forced ventilation may be taken if necessary, and the wind source should be analysed and confirmed before the ducts are fed. The working time of the personnel entering the restricted space should not be too long at a time and should be rotated or rested.
For equipment with rotating parts such as agitators, the power supply should be cut off after shutdown, the insurance removed or the grounding wire hung, and a warning sign hung on the switch "someone is working, strictly forbidden to close the switch", with special supervision if necessary.
Safe voltage and safe running lights should be used when entering restricted spaces. When working in metal containers (furnaces, towers, kettles, tanks, etc.) and non-metallic containers that are particularly humid and have a narrow working area, the lighting voltage should not be greater than 12 V. When working in humid environments, the operator should stand on an insulated board and ensure that the metal container is grounded reliably. When using electric tools or lighting voltage greater than 12 V, the installation of leakage protectors should be in accordance with the regulations, and their terminal boxes (boards) are strictly prohibited to be brought into the container for use. If the working environment is originally filled with explosive liquids, gases and other media, an explosion-proof torch or explosion-proof safety lamp with a voltage of not more than 12 V should be used, and the transformer of the lamp should not be placed inside the container or on the container; workers should wear anti-static clothing and use explosion-proof tools.
Within 30 min before operation, the restricted space should be analysed for toxic and hazardous, combustible gases and oxygen content according to the process conditions of the restricted space equipment, and the analysis should be qualified before entry. The samples should be retained for at least 4 hours after the analysis results have been reported. If the operation is interrupted for more than 60 min, the analysis should be repeated. Analytical instruments should be within the validity period of calibration and should be in proper working order before use. Monitoring personnel should take effective personal protective measures when monitoring confined spaces.
Sampling and analysis should be representative and comprehensive. When the volume of the restricted space is large, the upper, middle and lower parts should be sampled and analysed to ensure that the concentration of combustible gases and oxygen content in any part of the restricted space are qualified (when the lower explosive limit of combustible gases is greater than 4%, the measured concentration is not greater than 0.5% as qualified; when the lower explosive limit is less than 4%, the measured concentration is not greater than 0.2% as qualified; oxygen content 19.5% to 23.5% as qualified) and toxic Harmful substances shall not exceed the national regulations of the "maximum permissible concentration of toxic substances in the air of the workshop" indicator; the temperature in the restricted space should be around room temperature. If one of the monitoring results does not pass, the work should be stopped immediately.
The operator should wear a portable gas alarm when entering the restricted space and should monitor regularly during operation, at least once every 2 h. If the monitoring and analysis results change significantly, the frequency of monitoring should be increased. Restricted spaces where hazardous substances may be released should be continuously monitored and, in the event of abnormalities, operations should be stopped immediately, personnel evacuated, the site treated and the analysis qualified before resuming operations.
For equipment containers that have been filled with self-polymerising substances, process treatment should be carried out before operation, taking methods such as steaming and replacement, and making tests such as polymer heating.
The tools and materials brought by the workers shall be registered, and it is forbidden to enter the restricted space with people and tools not related to the work.
General repair methods in case of damage to the
Reactor In special cases, workers may wear air supply masks, air breathing apparatus and, if necessary, lifelines. When using air supply masks, a person must be assigned to supervise the air supply equipment.
During work in restricted spaces, it is strictly forbidden to carry out at the same time all kinds of test runs, pressure tests or tests related to the restricted space.
In the event of poisoning or asphyxiation, rescue personnel must enter the confined space wearing isolated protective masks, unprotected rescue is strictly forbidden and at least one person should be responsible for liaison work outside the confined space.
During work stoppages, warning signs should be placed at the entrances, entry is strictly forbidden and measures should be taken to prevent people from entering by mistake. At the end of the operation, the restricted space should be fully inspected, the number of people and tools counted and confirmed correct, the construction unit and the grassroots unit both sign for acceptance and the manhole is immediately closed.
All open manhole analysis before passing and non-operating period must be closed with manhole closers and hanging warning signs strictly prohibited to enter, strictly forbidden to enter private.
Abnormal changes occur during the operation, should immediately stop the operation, after processing and achieve safe working conditions, need to re-apply for the operating permit, before continuing the operation.
Source: Reprint
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