Basis for setting high and low liquid level alarms, as well as high-high (low-low) liquid level alarms for the oil storage tanks in the oil tank area

\"Code for Fire Protection Design of Petrochemical Enterprises\" (2018 edition) (GB50160-2008) 6.3.11 Storage tanks for liquefied hydrocarbons shall be equipped with level gauges, thermometers, pressure gauges, safety valves, as well as high-level alarms and automatic interlock systems to shut off feed when the level reaches a critical value.

**Notice of the General Administration of Work Safety on Further Strengthening the Safety Management of Chemical Tank Areas (An Jian Zong Guan San [2014] No. 68) II. Further Strengthening the Safety Management of Chemical Tank Areas (1) Further improve the monitoring and control facilities in chemical tank areas. In accordance with regulatory requirements, high and low liquid level alarms are installed in the storage tank; automatic interlocks are employed to shut down the tank’s feed valve when the liquid level is too high, and to stop material transfer when the liquid level is too low. Ensure that the alarm systems for leaks of flammable, explosive, toxic, and harmful gases are in good working condition. Emergency shut-off valves must be installed on key storage tanks such as large-scale ones, those storing liquefied gases, and highly toxic chemicals.

According to the \"Design Code for Tank Areas in Petrochemical Storage and Transportation Systems\" (SH/T 3007-2014), storage tanks with a capacity of 10,000 cubic meters or more shall be equipped with high-level liquid level alarms, which should be interlocked with the control valves of the feed pipes; such valves should automatically close when the liquid level in the tank reaches the set value；

\"Safety Technical Code for Vertical Cylindrical Welded Steel Storage Tanks\" (AQ 3053-2015) 12.2.2 Level control accessories: For storage tanks holding flammable liquids, level gauges as well as high/low level alarm devices and high-high level alarm devices shall be installed in accordance with the requirements of the code and operational needs; the alarm signals and level information shall be transmitted to the control room. Storage tanks that are operated frequently should be equipped with automatic interlock emergency shut-off devices. Large tanks should be equipped with low and high liquid level alarms, high-high liquid level alarm devices, and emergency shut-off devices; in addition, interlocks should be established between the high-high liquid level alarm and the emergency shut-off devices. Interlock buttons for the emergency shut-off valves should be provided outside the fire dike as well as at the control room operation stations. In the event of a high level alarm or a fire in the storage tank, it is possible to remotely or manually close the feed cut-off valve; once the cut-off valve is closed, the feed pump should be automatically shut down via interlock.

This post was last edited by bfdlwolf on 2019-9-19 09:41. Notice on the Issuance of the \"Guidelines for the Campaign to Rectify Hazards in Tank Areas\" (Group Work Order Anfeng [2016] No. 39). Work Forms of the Safety Supervision Bureau of Sinopec Group. IV. Low-Low Level Interlocks and High-High Level Interlocks: 1. Storage tanks with a volume of more than 100 m3 should be equipped with continuous level measurement and transmission instruments for high level, high-high level, low level, and low-low level. However, whether interlocks should be installed to shut off the feed and discharge valves or to stop the pumps depends on the effects that such interlocks would have; the following regulations must be complied with: (1) Storage tanks that are classified as first-level or second-level major hazard sources should be equipped with high-high level interlocks to shut off the feed valve. It is also necessary to verify whether the design pressure of the inlet pipes and related pipelines meets the requirements of the most severe operating conditions (such as the head at the pump’s shut-off point), as well as whether the safety measures in place are adequate. (2) When the high liquid level interlock of a storage tank for a certain material closes the feed valve, in order not to affect the normal operation of the upstream units (facilities), an alarm should be triggered and the feed valve of another storage tank should be opened promptly. (3) For tanks in which automatic interlock shutdown of the pump is triggered when the low-low liquid level is reached, and which could cause significant disruptions such as shutdowns and restarts to downstream facilities or stations (such as feed tanks and intermediate feed tanks in processing units, as well as tanks at oil transfer stations), it is advisable to implement a secondary alarm system: the discharge valve should be closed via interlock when the liquid level reaches the low-low level, while the alarm should trigger the opening of the discharge valve of another tank. (4) For tanks in which automatic interlock shutdown of the pump is triggered when the low-low liquid level is reached, and which do not cause significant disruptions such as shutdowns and restarts to downstream operations (loading onto vehicles or ships) – such as finished product tanks in petrochemical plants or storage tanks in finished product depots – it is possible to use interlocks to close the discharge valve or to shut down the pump when the liquid level reaches the low-low level. 2. For storage tanks that are classified as major hazard sources of level 1 or 2, in addition to high and low liquid level alarms, corresponding alarms and interlock protection measures should also be installed for low-low and high-high liquid levels. For storage tanks that require a separate SIS system, the root valves (emergency shut-off valves) on their inlet and outlet pipelines must be equipped with fire protection measures; they should also have a manual operation function as well as fire protection features. In emergency situations such as high liquid levels in the tank or fires, the SIS system shall be used to interlock and shut off the feed supply ； For storage tanks that do not require a separate SIS system, the tank base valves on their inlet and outlet pipelines should be control valves equipped with manual operation capabilities; in emergency situations such as high liquid levels in the tank or fire incidents, feed can be shut off through interlocks in the basic process control system.

An expert who knows the regulations inside and out

Thank you for the compliment; I happened to do it well in that area