Work procedures and steps for tank cleaning

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Reasonable and well-defined work procedures and steps are a prerequisite for carrying out tank cleaning tasks efficiently. Based on the actual conditions of on-site work, environmental factors, and past experience, it is necessary to strictly follow the established procedures and steps for cleaning crude oil tanks. (1) Select a team. Tank cleaning is a highly specialized task that involves many aspects; therefore, the selection of the construction team must first meet the following requirements: a) market access permit; b) safety production license; c) waste discharge permit; d) safety management personnel’s ‘Safety Qualification Certificate’ ； e) Operator’s “Safety Education Certification”. (2) On-site verification. Once the team responsible for tank cleaning is determined, the production unit and the construction unit must first conduct an on-site inspection. The production unit is required to inform about any changes in the manufacturing process, provide detailed information regarding all aspects of the tank cleaning, maintenance, and repair work, and analyze issues such as safety measures, fire protection systems, the surrounding environment, and operations that may take place within the area where personnel carry out their daily tasks. This provides comprehensive and sufficient information for the construction unit to prepare operation guidelines. The construction unit shall, based on the relevant information provided by the production unit and taking into account the actual site conditions as well as weather conditions, prepare a practical and feasible guide for tank cleaning operations, that is, the construction plan. (3) Develop a plan. After inspecting the tank cleaning site, the construction team began to prepare a construction plan, namely the tank cleaning operation manual, through technical discussions with the production unit. The main contents of the work instruction include: project overview, basic information on the construction unit, HSE policies and objectives, HSE management organization and responsibilities, technical measures, risk identification and control, emergency response measures, HSE management systems and document control, information exchange, audit, monitoring, and corrective actions. If necessary, attach diagrams of the workplace and process flowcharts, etc. (4) Construction work. Once the preliminary preparations meet the requirements for commencement, the responsible supervisor issues the start-order, and the tank cleaning operation officially enters the construction phase. First, open the manhole for ventilation; if necessary, install an axial flow fan for ventilation ； Secondly, based on the location of the storage tanks and the fire access routes, dig oil storage ponds and implement measures to prevent leaks; provide sand bags for sealing leaks, and also prepare homemade oil storage ponds to avoid contamination caused by the spillage of dirty oil. While installing the sludge pump, fill the tank truck with oil, and carry out all necessary grounding checks and monitoring. Third, it is necessary to conduct regular monitoring of hazardous factors such as oxygen levels and flammable gases inside the tank during the tank cleaning process, as well as to ensure the protection of personnel who enter the tank to remove contaminated oil and keep proper records of them. After the cleaning of the oily waste and sludge is completed, sandblasting for rust removal begins. The key aspects of safety protection during this process are the use of protective face masks and strict control of the time spent working inside the tank. Subsequent seal replacements should pay attention to the quality of seal installation and the quality of the materials. During inspection, maintenance, and repair operations, the replacement of components such as coils requires the use of fire. When performing fire-related tasks in confined spaces, a flame test must be conducted to ensure absolute safety. Pressure tests must be conducted at all stages of coil replacement to ensure construction quality. (5) Inspection and acceptance. After the tank cleaning, inspection, and maintenance work are completed, it is necessary to organize relevant parties such as the user, the contractor, and the supervising authority to conduct inspections and acceptance checks. Special attention should be paid to the quality of the on-site work and the related documentation, with all parties signing off on them. Once everything meets the requirements, the manhole should be sealed up for future use. (6) Confirm commissioning. Once it is confirmed that the storage tank is ready for use, the production unit submits an application to remove the blind flanges and restore the tank’s operational process. During the initial period of use, inspection frequency is increased to ensure normal operation of the tank, after which it returns to its regular operating status. Identification of hazard factors in crude oil tank cleaning operations: Hazard factors refer to both risk sources and environmental factors. Those factors that affect the physical, mental, and behavioral aspects of all personnel in the work area, as well as those that may cause injury or illness to people, lead to property loss, damage to the working environment, or harmful environmental impacts during the tank cleaning process, are all included in the scope of identification. By identifying and controlling these factors in a comprehensive manner throughout the tank cleaning process, preventive management can be achieved. Human behavioral factors: 1. Safety awareness – Safety officers ask questions to the workers during inspections, but the accuracy of their answers is low, and safety is neglected. 2. Management of workers – The personnel in the construction team are not fixed; there are instances of staff changes. During tank cleaning, the division of tasks is not clear, and the work is not organized in a structured manner. External supervisors do not pay sufficient attention to key aspects of supervision. 3. Habitual behavior – Workers have been engaged in oil cleaning tasks for a long time; their daily speech and actions are casual, and they do not pay enough attention to the requirements specified in the operation manuals and work orders. They are reluctant to use static discharge devices and protective equipment when entering tanks, and ignore warnings. 4. Lack of knowledge about oil properties – When questioned on site, workers give incomplete answers regarding their understanding of crude oil and emergency prevention measures. 5. Protective measures for working in confined spaces – Personal protective equipment is generally worn properly, but some workers do not wear gas masks when cleaning tanks. Poor safety awareness. 6. Regarding the operation instructions: the equipment listed in the instructions does not match what is actually present on site; the responsibilities in emergency situations are not clearly defined; the workers have not studied the instructions properly and are unaware of the components involved. 7. Supervision: The supervisors at the work site focus more on progress and less on supervision, giving more attention to the operation of the equipment than to the safety of the workers. 8. The monitoring by the production unit did not cover the entire process. Supervision and inspection: Supervisors failed to use safety check sheets during on-site inspections. 9. The supervisors were not familiar with the requirements of monitoring; when questioned about these requirements, their answers were incomplete, and they did not read carefully the rules regarding the issuance of work orders, resulting in inadequate implementation of these rules. 10. Emergency response: Supervisors were not well-versed in emergency response procedures. Status of equipment: 1. Explosion-proof rating of mud pumps: Intrinsically safe type (I) or positive pressure type (P); IP54 protection. The pumps are connected to the tank’s grounding electrodes, and they have protective covers. 2. Explosion-proof rating of axial flow fans: Flameproof type (D). They are connected to the tank’s grounding electrodes, and rubber isolators are used at the fixing points to prevent metal contact. 3. Explosion-proof tools: All tools used on site are made of copper or wood. 4. Protective facilities: Gas masks, safety ropes, first-aid kits, warning tapes, positive pressure respirators, and explosion-proof emergency lights. 5. Personal protective equipment: Anti-static work clothes, shoes, gloves, corrosion-resistant boots, and safety helmets. 6. Testing instruments: (1) No 4-in-1 testing instruments were available during the preliminary preparation phase; however, such instruments were provided for both parties involved in tank cleaning operations. (2) Clamp-type resistance meters were available. 7. Condition of vehicles: Safety signs, color strips, grounding systems, fire extinguishers, and flame arrestors are all in place. 8. Equipment grounding and testing: Mud pumps, axial flow fans, oil pipelines, and vehicles all have proper grounding systems, with corresponding test records. 9. Condition of oil pipelines and cables: Armored pipelines and 4-core cables are used, with no signs of aging. 10. Temporary power usage: “In use” signs are placed at the power connection points, and cables are properly covered. An explosion-proof power distribution box is available outside the fire barrier, allowing separate control of electrical circuits, with designated personnel responsible for it and appropriate safety signs in place. Qualification verification: 1. The safety production license is valid. 2. The waste discharge permit is valid. 3. Safety qualification certificates: Project managers or site supervisors must hold safety qualification certificates issued by local safety authorities. 4. Market access permits: Required to operate in oil fields. 5. Safety contracts: Agreements between parties to ensure construction safety, outlining their rights, obligations, and responsibilities during construction. Document management: 1. HSE guidelines for tank cleaning operations provide clear instructions regarding the procedures and methods to be followed. There are instructions available on site, but the workers and supervisors have not organized a study of their contents. *2 Permit for working in confined spaces: No approval was obtained for entering the storage tank using such a permit; the supervisors and workers are not clear about the requirements specified in the permit. 3 Permit for temporary electrical use: The supervisors and workers are not aware of the requirements outlined in the permit regarding electrical connections. 4 Permit for hot work: No approval was granted for using grinders or welders during maintenance tasks; the supervisors and workers are not familiar with the requirements specified in the permit. 5 Permit for installing/removing blind flanges: A change was made to the procedure before emptying the tank, which involved installing blind flanges on the inlet and outlet valves, as well as on valves related to steam and waste water, with those flanges being labeled. 6 Register for external personnel: The workers who enter the site (i.e., the oil depot) are registered on a daily basis. 7. Records of supervision for work in confined spaces: The supervisors involved register the personnel entering the storage tank for tank cleaning, in order to determine the number of people inside the tank.
8. Records of static electricity grounding checks: Grounding of pumps, fans, vehicles, and oil pipelines is checked and recorded.
9. Records of oil and gas concentration as well as oxygen level measurements: When working inside the storage tank, oxygen levels, hydrogen sulfide, carbon monoxide, and flammable gases are measured every 30 meters.
10. Supervision confirmation form for the oil depot construction site: The supervisors on site check this form before starting work each day to determine whether work can proceed.
11. Start-up order: Once all preparations for the tank cleaning project are complete and work can begin, the responsible supervisor issues a start-up permit. Once work is approved, it continues until the task is fully completed and approved.
12. Safety inspection form for tank cleaning operations: The safety department uses this form to conduct inspections on site.
13. Sign-in sheet for safety inspections: Inspectors sign in after arriving at the site, providing their suggestions and comments, which helps with safety management and improving safety measures.

Environmental conditions:
1. Safety passages and fire roads should have clear signage, and these roads must remain unobstructed.
2. The area designated for construction is determined based on the construction conditions and environmental requirements; access is restricted to other people to minimize hazards. Safety distances are typically marked using the fire dike surrounding each storage tank.
3. Tools should be arranged in categories and sizes, ensuring that the site remains tidy, easy to use, and clearly organized.
4. Fire-fighting equipment should be kept in ready condition and placed near potential danger areas.
5. Safety signs should be displayed in prominent locations, including prohibitory, warning, instructional, and directional signs related to the work being carried out.
6. Special weather conditions such as high temperatures, low temperatures, wind direction, and sandstorms require advance data collection and appropriate warnings. Wind vane-like markers should be used on site as references.
7. The work area should have sufficient lighting, proper ventilation, and a smooth surface—these are all important factors to consider at the site