Safety measures for tank cleaning

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I. Overview: The owner owns 1# to 5# vertical arch-top oil tanks, with a volume of V=10,000 M3; there are 2 such tanks, and 3 tanks with a volume of 3,000 M3 each. The medium in the oil tanks is all heavy oil; there are 3,000 M3 of it, as well as 2# light oil tanks. As required by the client, pre-renovation cleaning of oil tanks No. 2, No. 3, No. 4, and No. 5 is necessary to bring them up to safety standards, enabling them to operate under conditions where the online equipment installed on the tanks is in good condition. II. Basis for Compilation 1) \"Code for Construction and Acceptance of Vertical Cylindrical Welded Steel Oil Tanks\" (GBJ128-90). 2) “Quality Inspection and Evaluation Standards for Insulation Works of Industrial Equipment and Piping” (GB50185-93). 3) Standards for Quality Inspection and Evaluation of Petroleum Engineering Construction, Storage Projects (SY4026-93). 4) Compliance with the **Technical Quality Supervision Bureau’s “Rules for Chemical Cleaning”** standards. 5) Compiled based on materials provided by \"Chemical Cleaning Technology\" and the Ministry of Chemical Industry’s \"Practical Chemical Cleaning Technology\", as well as the results of \"Research and Development in Chemical Cleaning\". 6) Plan drawings of the oil tank provided by the owner. III. Scope and contents of cleaning inspection 1. Safety measures 1) Before starting work, all construction personnel shall receive safety and fire prevention training, being required to master basic knowledge of safety and fire prevention as well as the measures to take in case of a fire. All employees are required to comply with the owner’s safety regulations and keep records of safety checks at the site before beginning work. 2) All persons entering the construction area are strictly prohibited from smoking there. Any items that can produce flames, such as mobile phones and pagers, must be turned off when brought into the construction site. 3) Personnel entering the construction site must wear safety helmets, nail-free work shoes, and cotton work clothes. When working at heights, wear a safety belt, and it is strictly prohibited to throw materials downward. The owner and the construction contractor shall each assign a site safety officer who will be responsible solely for safety and fire prevention tasks. 4) The construction site is equipped with 6 4Kg1211 portable dry powder fire extinguishers and 1 mobile dry powder fire extinguisher, and is supervised by 3 full-time firefighters. 5) Before commencement of work, the safety officer of the construction party must submit an application to the owner and fill out a construction permit; work can only begin after it has been reviewed and approved by the owner’s safety officer. The construction permit must be kept with the on-site safety officer for easy reference at any time. (The electricity usage permit is attached.) 6) After the oil tank is taken out of service, all pipes connected to the tank as well as any static electricity discharge devices must be completely disconnected, except for the fire-fighting water pipes. 7) Before working inside the tank, open the manhole and install an axial flow fan to introduce air from the bottom of the manhole; also install a fan on the top of the tank to expel the gas from inside. Use a gas detector to monitor the conditions inside the tank, and remove any residual oil remaining in it. The gas must meet safety standards before work can proceed. 8) The owner shall assign a full-time staff member to use combustible gas detectors to monitor the concentration of combustible gases before and during each construction operation; if the concentration exceeds the permissible level, welding and other flammable work must be stopped immediately. 9) During the construction process, the owner and the construction contractor must maintain close communication to ensure that the construction site is under constant supervision. In case of special circumstances, such as during oil loading and unloading, electrical work must be stopped immediately. IV. Cleaning Measures: A thorough inspection will be conducted, and based on the original design of the oil tank, relevant specifications, the owner’s requirements, and the process flow of the oil tank area, appropriate cleaning measures will be established. The remaining oil in the tank will be transferred to a location designated by Party A. V. Quality Control: To ensure the quality of cleaning, including the removal of residual oil, dirt, hydrogen sulfide, etc., chemical treatment must be carried out under safe and stable conditions. Chemical monitoring of each step of the cleaning process is necessary, with the following specific requirements: 1) Dosage ratio: It must be determined in strict accordance with the required scale removal levels. It is strictly prohibited to allow inadequate descaling due to too low a dosage, as this will disrupt the continuity of all subsequent processes. 2) The owner’s quality inspection and technical departments supervise the quality as well as the quality of wastewater discharge on-site at any time. VI. High-pressure water jet procedure: To meet the cleaning requirements, the overall procedure involves: establishing a safety plan and signing a safety agreement as part of the approval process, signing a technical agreement → preparing for ventilation before stopping the equipment on site → using detectors to measure gas concentrations → cleaning with high-pressure water jets → applying partial chemical cleaning → intermediate inspection by the owner → final inspection. VII. Once the cleaning quality meets the requirements, proceed with the subsequent construction steps. VIII. Timeline: 1) 3 days of preparation before stopping the tank on-site. 2) Pour oil at the point designated by Party A within 3 days. 3) Add a ventilator to circulate the oil and gas in the inlet and outlet tanks for 2 days. 4) Clean the tank of low oil residues for 1 day (arranged by the owner). 5) Clean with high and low pressure water jets for 1 day. Note: The cleaning period is 10 days.