How are external level measuring instruments applied in storage areas for hazardous chemicals such as those in the petrochemical industry

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Must emergency shut-off devices be installed in key storage tanks such as liquefied gases and highly toxic liquids that constitute major hazard sources? Must all storage tanks be equipped with high and low liquid level alarms and interlocks? 01. GB50074-2014 “Code for Design of Oil Depots” (1) Installation requirements: 15.1 Automatic control systems and instruments 15.1.1 Storage tanks with a capacity greater than 100 m3 shall be equipped with remote liquid level measurement instruments, and the following requirements shall be met: 1 The continuous liquid level measurement signals shall be transmitted to the automatic control system in either analog form or via communication; 2 High and low liquid level alarms shall be installed within the automatic control system; 3 The set height for the high liquid level alarm shall comply with the relevant provisions of the current industry standard “Code for Design of Tank Areas in Petrochemical Storage and Transportation Systems” SH/T 3007; 4 The set height for the low liquid level alarm shall ensure that cavitation does not occur in the pumps. For external floating roof tanks and internal floating roof tanks, the set height of the low liquid level alarm (measured from the bottom of the tank) should be at least 0.2 m higher than the height at which the floating roof touches the bottom of the tank. 15.1.4 The level measurement instruments used for high and low high/low level alarm signals in storage tanks shall be separate continuous level measuring instruments or level switches, and alarms and interlocks shall be provided in the automatic control system. 02. GB 50737-2011 “Code for Design of Oil Reserve Tanks”: (1) Requirements for installation: 11.1 Automatic control systems and instruments. 11.1.2 Each oil tank shall be equipped with continuous level measurement instruments as well as high-level and low-level switches, and the following requirements shall be met: 1 The accuracy of the level gauges shall be better than ±1 mm; 2 The continuous level gauges shall have the functions of issuing alarms for high levels, low levels, and automatically shutting off the tank’s inlet valve when the level reaches an extremely high value. The setting height for the low-level alarm (measured from the bottom of the tank) should not be less than 2 m; 3 The high-level switches shall have the function of automatically shutting off the tank’s inlet valve when the level reaches an extremely high value; 4 The low-level switches shall have the function of stopping the oil pump and shutting off its outlet valve when the level drops to an extremely low value. The setting height for the low-level switches (measured from the bottom of the tank) can be no less than 1.85 m. 03. GB 50160-2018 “Code for Fire Protection Design of Petrochemical Enterprises”: (1) Requirements for installation: 6.2.23 Tanks storing flammable liquids shall be equipped with level gauges and high-level alarms. If necessary, automatic interlocks that can shut off the feeding system should also be installed; in addition, automatic dehydrators are recommended. (2) Interlock requirements: 6.3 Above-ground storage tanks for liquefied hydrocarbons, combustible gases, and oxidizing gases; 6.3.11 Liquefied hydrocarbon storage tanks shall be equipped with level gauges, thermometers, pressure gauges, safety valves, as well as high-level alarms and automatic interlocks to cut off feed at extremely high levels. 04. GB 17681-1999 \"Technical Requirements for the Acceptance of Safety Monitoring and Early Warning Systems for Flammable and Explosive Tank Areas\" (1) Installation requirements: 5.5 Liquid storage tanks must be equipped with level detection instruments, and at least two different types of such instruments shall be installed in each tank. Storage tanks holding flammable and explosive materials should be equipped with high and low liquid level alarm circuits; where necessary, they should also have an interlock system linking the liquid level to relevant process parameters. 05、AQ 3036-2010 \"Code for the Installation of On-site Safety Monitoring Equipment in Tank Areas for Major Hazardous Sources of Hazardous Chemicals\" (1) Installation requirements: 6.3.1 Storage tanks shall be equipped with level monitors that have the capability to issue alarms when the liquid level is too high or too low. Interlock requirements: 6.3.7 Large combustible liquid storage tanks (over 5000 m3) and pressure storage tanks for hazardous chemicals (over 400 m3) shall be equipped with separate high-high liquid level monitoring, alarm, and interlock control systems. 06、SH/T 3007-2014 \"Code for Design of Tank Areas in Petrochemical Storage and Transportation Systems\" (1) Requirements for installation: 5.4 Selection and installation of instruments 5.4.1 Storage tanks with a capacity greater than 100 m3 shall be equipped with remote transmission instruments for continuous level measurement. 5.4.2 High- and low-level alarms shall be installed in the automatic control system, and shall comply with the following provisions: a) The set level for the high-level alarm of the storage tank shall not exceed the designed maximum storage level of the tank; b) The set level for the low-level alarm of the storage tank shall not be lower than the designed minimum storage level of the tank. 5.4.5 The high-high and low-low level alarm signals for storage tanks, as well as the level measuring instruments, shall utilize separate continuous level measuring instruments or level switches. The alarm signals shall be transmitted to the automatic control system. 6 Pressure Tank Area 6.3 Selection and Installation of Tank Instruments 6.3.3 Level measurement remote transmitters shall be equipped with high and low level alarms. The set level for the high liquid level alarm should be the designed maximum liquid level of the storage tank; the set level for the low liquid level alarm should ensure that the pump will not experience cavitation within 10 to 15 minutes after the alarm is triggered. In accordance with the above specifications, Dinghua Electronics continuously improves the functions of its instruments. The external level gauges and ultrasonic external level switches have obtained the functional safety integrity SIL3 certification, ensuring the safety required for use in tank farms. Secondly, external level gauges are installed outside the tank; no drilling or welding is required, and the gauge does not come into contact with the medium inside the tank. They can be easily installed online, representing an isolated, contactless level measurement technique that is very safe. Utilizing micro-vibration analysis technology, the instrument boasts extremely high stability and a small blind zone.