Hot work|knowledge summary

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Summary of hot work knowledge

First, the definition

1. Hot work: refers to the temporary work of welding, cutting, heating, grinding, and using electric drills, grinding wheels, etc. in the flammable and explosive places, which may produce flames, sparks, sparks and red hot surfaces.

2. Flammable and explosive places: mainly refers to the company's painting and sandblasting yards, oil depots, gas stations, dangerous goods warehouses, material warehouses, oil products and paint thinners, pretreatment agents and other chemical storage and use places, liquefied gas cylinders Storage areas, power distribution rooms, areas where mutual contraindications may cause fires.

Second, classification

Class A hot work The hot work carried out in a flammable and explosive place, the flammable and explosive place refers to the area specified in Article 2 of the second paragraph of this regulation.

Class B hot work In addition to inflammable and explosive places, the company or the contractor performs temporary maintenance, renovation, construction and other hot work.

Class C hot work refers to fixed long-term hot work performed in the company's welding line area. In the case of holidays, weekends or special circumstances, in addition to the C-class hot work, other hot work carried out in the company will be upgraded and managed according to the A-class hot work.

Third, the six bans on hot work

1. The fire certificate is not approved and fire is prohibited.

2. Not reliably isolated from the production system, prohibiting hot fire.

3. Do not clean, replace unqualified, and prohibit moving fire.

4. Do not remove the surrounding flammable materials, and prohibit the fire.

5. Do not do the fire analysis on time, prohibiting the fire.

6. No fire fighting measures, no fire.

Fourth, the fire safety measures

Maintenance of hot work includes electric welding, gas welding, cutting, soldering iron brazing, blowtorch, boring asphalt, baking and incineration residue waste liquid. In addition, there is another type of operation. Although it does not use fire itself, it can generate impact sparks, friction sparks, electrical sparks and static sparks during construction. If the work place is arranged in the fire-proof area, it should also be listed. Enter the fire range. Generally, in the chemical maintenance fire, there are the following safety measures. In practice, corresponding safety measures can be taken for different situations.

1. Demolition method

The demolition method is to remove the equipment, pipelines and accessories that need to be fired in the fire-fighting area from the main body, move them to the safe area, and then put them back in place. This method is the safest, as long as the workpiece can be removed, it should be used as much as possible.

2, isolation method

One is to effectively isolate the hot-fire equipment from the operating equipment, such as blinding the pipe, adding a plug to the head, and removing a pipe. The other is to trap sparks, isolate the slag, and isolate the hot point from nearby combustibles. For example, use incombustible materials such as wet cloth, sacks, asbestos blankets, cover the flammable materials and their pipe joints, or use iron sheets to surround the welders and isolate them to prevent Mars from flying out. If the fire is on the upper level of a building or equipment, it is necessary to block the loopholes and isolate them from the upper and lower levels. In the outdoor high place, the spark direction is controlled by a fire-resistant non-combustible baffle or a water tray.

3. Remove combustibles

Wherever welding sparks can be reached, all combustible materials should be removed, including bamboo frame boards and waste cotton yarns. Separation measures must be taken for cumbersome or unremovable combustibles.

4, cleaning and replacement

These two measures are measures to eliminate hazardous substances in the equipment and should be carried out before any maintenance work. After cleaning and replacing the equipment in the tank, the following requirements must be met:

(1) The aqueous rinse solution is substantially neutral.

(2) The oxygen content is 18-21%

(3) The concentration of toxic gases complies with national health standards.

If a hot work is required in the tank, the concentration of flammable gas must meet the requirements of the hot fire.

5, dynamic analysis

Equipment and pipelines that have been cleaned or replaced should be inspected and analyzed before they are fired. Generally, it should be determined by chemical and instrumental analysis. The standard is: if the lower explosion limit is greater than 4% (volume), the concentration of flammable gas or steam should be less than 0.5%. If the lower explosion limit is less than 4%, the concentration should be less than 0.2%. The sampling analysis time should not be earlier than half an hour before the start of the hot work, and attention should be paid to the representativeness of the sampling so that the analytical data is accurate and reliable. It should be analyzed again after two hours of continuous operation.

6, open and ventilated

Equipment that requires hot fire, all the pot lids, manholes, material holes, etc. that have conditions to open must be fully opened. When indoors are hot, natural ventilation must be strengthened. In winter, doors and windows should be opened, and local exhaust should be used if necessary. Ventilation is more important if there is a fire inside the equipment.

7. Prepare fire equipment and monitoring

In the dangerous fire scene, there must be someone to supervise and prepare enough fire extinguishing equipment to extinguish the initial fire, and sometimes send a fire truck to the scene.

(Source: Binzhou Safety Supervision Office)

[Editor: Chen Guofang]

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