Before the operation, all relevant personnel shall understand and be familiar with the safety work plan, ensure that all relevant personnel grasp the relevant HSE requirements, and conduct special training when necessary.
(1) The pipeline or equipment to be opened must be isolated from the system, and the materials shall be removed by means of draining, flushing, replacement and purging. Qualified cleaning shall meet the following requirements:
1. The system temperature is between -10℃ and 60℃;
2. Atmospheric pressure has been reached;
3. The risks associated with the toxicity, corrosiveness and flammability of gases, vapors, fogs and dust have been reduced to an acceptable level.
(II) If the pipeline/equipment cannot be completely confirmed to be safe before opening, the following preparations shall be made before opening the pipeline/equipment:
1. Confirm that pipeline/equipment cleaning is qualified. When using the method of solidification (solidification) to isolate the medium, the possibility of re-flow of the medium should be fully considered;
2. If the pipeline/equipment cannot be cleaned up to the standard, such as the residual pressure or medium is blocked at a dead corner, the source of all the pressure or medium is not isolated, and the low point and high point are not drained, etc., the work shall be stopped, the work plan shall be reformulated, the control measures shall be defined, and the risk shall be eliminated or controlled.
(I) Isolation shall meet the following requirements:
1. The territorial unit shall provide diagrams showing the status of the valve switch, the position of the blind plate and the blind flange, such as the list of locking points, the blind plate drawing, the field diagram, the process flow chart and the instrument control diagram, etc.;
2. All blind plates and flanges shall be listed;
3. All valves in the isolation system must be kept open, and the pipeline must be cleaned to prevent the retained media in the pipeline/equipment;
4. For pipelines/equipment with secondary energy sources, the sequence and steps of isolation shall be taken into account when isolating them. It should be considered that the solidification (solidification) process is used for isolation and that the medium may evaporate after heating.
(II) The choice of isolation method depends on the danger of the isolation material, the structure of the pipeline system, the frequency of opening the pipeline, and the risk of possible leakage due to isolation (such as purging, cleaning, etc.).
(iii) If double isolation is not feasible and single globe valve is used for isolation, a safety work plan shall be formulated, effective protective measures shall be taken, and an emergency plan shall be formulated when necessary;
(4) Manual valves, which can be gate, plug or ball valves, should be considered for isolation. The control valve cannot be used as a material isolation device alone.
(v) All isolation points shall be effectively separated and marked.