Petrochemical storage tank breather valves

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I. Which storage tanks require breather valves? 1. Article 6.2.19 of the \"Code for Fire Protection Design of Petrochemical Enterprises\" GB 50160-2008 (2018 edition): Fixed-roof tanks storing Class A B and Class B liquids shall be equipped with flame arresters and vent valves ； Storage tanks for Class A B and Class C liquids that use nitrogen or other gases as a gas seal should also be equipped with emergency pressure relief devices. 2. Article 5.4.15 of the “Code for Fire Protection Design of Buildings” GB 50016—2014 (2018 edition): For boilers and diesel generators installed within buildings, their fuel supply pipelines shall comply with the following requirements: 1 Automatic and manual shut-off valves shall be installed on the pipelines both before they enter the building and inside the equipment room ； 2 The tanks in the oil storage area must be sealed, and ventilation pipes leading to the outside should be installed. These ventilation pipes should be equipped with pressure relief valves that include flame arresters. Facilities to prevent the spillage of oil should be placed at the bottom of the tanks ； 3 The installation of gas supply pipelines shall comply with the provisions of the current **standard, the ‘Code for Design of Urban Gas Systems’ GB 50028. 3. Article 6.4.4 of the «Code for Design of Oil Storage Tanks» (GB 50074-2014): Breather valves shall be installed at the vents leading to the atmosphere of the following storage tanks: 1. Fixed-roof storage tanks and above-ground horizontal storage tanks used for storing Class A and B liquids ； 2. Earth-covered horizontal oil tanks for storing Class B liquids ； 3. Tanks equipped with a nitrogen sealing protection system. Section 6.4.5 The exhaust pressure of the breathing valve shall be less than the design positive pressure of the storage tank, and the intake pressure of the breathing valve shall be greater than the design negative pressure of the storage tank. When the ambient temperature around the breathing valve may be less than or equal to 0°C, an all-weather breathing valve should be selected. 4. Article 6.4.4 of the “Code for Fire Protection Design of Petroleum and Natural Gas Engineering” (GB 50183-2004): Breathing valves, flame arresters, and hydraulic safety valves shall be installed on the tops of oil sludge tanks and sewage sedimentation tanks. The purpose of requiring that breather valves, hydraulic safety valves, and flame arresters be installed on the tops of oil sludge tanks and sewage settling tanks is to prevent the tanks from rupturing due to overpressure or complete vacuum formation, which could lead to leakage of the contents inside the tanks. It also prevents external sources of fire from igniting the medium inside the tank. Each vent valve and hydraulic safety valve shall be equipped with a flame arrester, and their performance shall meet the requirements of \"Vent Valves for Oil Storage Tanks\" SY/T 0511, \"Hydraulic Safety Valves for Oil Storage Tanks\" SY/T 0525.1, and \"Flame Arresters for Oil Storage Tanks\" SY/T 0512, respectively. II. Requirements for the inspection and maintenance of breather valves: 1. \"Integrity Management of Atmospheric Storage Tanks\" (GB/T37327-2019) 8.6.1 Breather valves used in atmospheric storage tanks shall be inspected at least once a year. 8.6.2 Before inspection, the following documents shall be reviewed: a) Product model and operating pressure rating of the relief valve; b) Date of manufacture, product certificate, date of installation, and completion acceptance documents; c) Records of on-line inspections during the operating period; d) Previous periodic inspection reports. 8.6.3 Before the inspection, the inspection items and acceptance criteria shall be clarified and approved by the user unit, which shall then carry out the necessary preparatory work as required. 8.6.4 The inspection items for breather valves include visual inspection, opening pressure test, air flow rate test, and leakage test. 8.6.5 The appearance of the breather valve shall show no abnormal rust, leakage, or blockage by foreign matter. 8.6.6 Opening of the breather valve: The pressure, ventilation volume, and leakage rate shall meet the design requirements. 2. “Guidelines for the Investigation, Management, and Rectification of Safety Hazards in Enterprises Dealing with Hazardous Chemicals”, Emergency Management [2019] No. 78. (IV) Management of static equipment: Enterprises shall install safety accessories such as tank breather valves (hydraulic safety valves), flame arresters, foam generators, level gauges, and vent pipes in accordance with relevant standards; they must also conduct regular inspections or tests and keep records of such inspections and maintenance. 3. “Notice on Carrying Out Safety Risk Assessments for Large Oil and Gas Storage Facilities” – Enterprises shall install safety accessories such as tank vent valves (hydraulic safety valves), flame arresters, foam generators, level gauges, and vent pipes in accordance with relevant standards, and conduct regular inspections or tests while keeping records of these inspections and maintenance activities. 4. Guidelines for Safety Risk Assessment of Oil and Gas Storage Enterprises (Trial) 4.3 Equipment Safety Risk Assessment 4.3.1 Key assessment items 1) Assess whether the selection of storage tanks meets the requirements related to the hazards of the stored materials. 2) Has effective safety and reliability assessment been conducted for the tank type adopted for the first time in the country? 3) Evaluate the compliance, effectiveness, and operating conditions of safety accessories related to storage tanks (such as safety valves, rupture discs, breather valves, flame arresters, nitrogen padding, etc.). 5. “Notice of the State Administration of Work Safety on Further Strengthening the Safety Management of Chemical Tank Farms” (Document No. Anjian Zongguan San [2014] No. 68). (IV) Strengthen the management of equipment and facilities in chemical tank farms. Equipment and facilities in chemical tank farms must be regularly inspected and tested to ensure that storage tanks, pipelines, valves, pumps, and other equipment remain in good condition. Strengthen corrosion monitoring of chemical storage tanks; conduct regular tank cleaning and inspections; and promptly address any corrosion-induced thinning. Ensure that the safety accessories of the storage tank, as well as the lightning protection, anti-static measures, flood control facilities, and fire suppression systems are in good condition ； For storage tanks equipped with nitrogen protection systems, it is necessary to ensure that the nitrogen sealing system is in good working condition. 6. Article 7.4.1.1 of \"SY 5225-2005 _ Technical Regulations for Safe Production in Fire and Explosion Prevention during Oil and Gas Drilling, Development, Storage, and Transportation\": The installation of breather valves, flame arresters, and hydraulic safety valves in oil storage tanks shall be carried out in accordance with SY/T 0511, SY/T 0512, and SY/T 0525.1 respectively. The safety valve should be inspected and calibrated at least once a year by a qualified testing institution. Clause 7.4.1.2: Flame arresters shall be installed at the bases of breather valves and hydraulic safety valves. Breather valves and hydraulic safety valves shall be inspected at least twice a month during winter, and calibrated once a year. The flame arrester should be inspected at least once per quarter. The breather valve is flexible and easy to use. The oil level of the hydraulic safety valve is within the specified range, and the oil quality is satisfactory. The flame arrestor’s flame suppression layer is in good condition, with no sludge blockage. III. Recommendations for the maintenance of breather valves: 1. The common faults of breather valves include air leakage, jamming, sticking, blockage, freezing, as well as the valves remaining open under pressure or vacuum conditions. (1) Air leakage: It is generally caused by rust, hard objects scratching the contact surface between the valve and the valve disc, deformation of the valve disc or seat, and tilting of the valve disc guide rod. (2) Jamming: This usually occurs when the breathing valve is not installed correctly or when the oil tank deforms, causing the valve disc’s guide rod to become misaligned or the rod to rust; as a result, the valve seat cannot move up and down along the guide rod properly, and the valve disc gets jammed at a certain point on the guide rod. (3) Adhesion: This occurs as oil vapors, moisture, and dust and other contaminants deposited on the valve disc, valve seat, and guide rods undergo chemical and physical changes; over time, this leads to the adhesion of the valve disc to the valve seat or the guide rods. (4) Blockage: This is mainly caused by the long-term lack of maintenance of mechanical breathing valves, which leads to the accumulation of dust, rust, and other debris inside the valve or the breathing tube. It can also be caused by bees or birds building nests at the opening of the breathing valve, resulting in blockage. (5) Freeze of the breathing valve: This occurs due to temperature changes, causing moisture in the air to condense on parts such as the valve body, valve disc, valve seat, and guide rod of the breathing valve, eventually leading to freezing and making it difficult to open the valve. 2. Contents of regular inspections: (1) Check for phenomena such as constant opening, air leakage, jamming, sticking, blockage, freezing, and rusting ； (2) Check whether the sealing gasket is leaking; if so, it should be replaced ； (3) Check whether the valve disc can rotate freely and whether there is any sticking issue ； (4) Check whether the sealing mesh of the valve body is frozen or blocked, and whether there is dust or dirt attached to the mesh ； (5) To check whether metal components such as the valve disc, valve seat, guide rod, and air guide spring are rusted or contaminated, kerosene can be used for cleaning. (6) When loading and unloading materials from the storage tank, check whether the breathing valve is operating properly. 3. The breathing valve should be calibrated regularly once a year, and the calibration method shall follow SY/T 0511.1-2010 \"Attachments for Oil Storage Tanks – Part 1: Breathing Valves\".