Is it necessary to install cofferdams around the reactors in petrochemical plants? Under what circumstances should cofferdams, fire dikes, etc. be installed?

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This post was last edited by 328104062 on 2017-3-13 at 13:51. As the title suggests: GB50160 \"Code for Fire Protection Design of Petrochemical Industries\" – 5.2.28: In areas around equipment where there is a risk of leakage or spillage of flammable liquids during startup, shutdown, or maintenance operations, dikes and liquid diversion facilities with a height of not less than 150 mm should be installed. This standard specifies that dikes are only required in areas where there is a liquid leak; dikes are not necessary in the case of gas or solid leaks. According to the relevant regulations, fire dikes serve to prevent the leakage of liquids and the spread of fires, and they are installed in tank storage areas ； The cofferdam serves solely to prevent the leakage of liquids. According to GB50160-2008, the Code for Fire Protection Design of Petrochemical Enterprises, section 6.3.5, the installation of fire dikes and partitions shall comply with the following requirements: 1. For liquefied hydrocarbon storage tanks using full-pressure or semi-frozen systems, a fire dike no higher than 0.6m should be installed. The distance from the base of the dike to the tanks should be at least 3m. The floor inside the dike should be made of cast concrete, and it should slope outward. The partitions inside the fire dike should not be higher than 0.3m ； 6 The requirements for fire dikes and separation dikes for fully pressurized and semi-frozen liquid ammonia storage tanks are the same as those for liquefied hydrocarbon storage tanks. 6.3.6 Liquid hydrocarbon fully refrigerated single-containment tank assemblies shall be equipped with fire dikes, and shall comply with the following requirements: 1 The effective volume within the fire dike shall not be less than the volume of the largest storage tank ； 6.3.8 Fully refrigerated liquid ammonia storage tanks shall be equipped with fire dikes, the effective volume within which shall be not less than 60% of the capacity of the largest tank. 6.3.9 The storage coefficient for tanks storing liquefied hydrocarbons, liquid ammonia, etc., shall not be greater than 0.9. HG/T 20546.2-2009 Specifications for the Layout Design of Chemical Plant Equipment 5.5.4 If it is necessary to collect spilled materials, the thickness of the bund constructed shall be at least 150 mm; its volume must be sufficient to hold the capacity of the largest storage tank under normal pressure, and the minimum height of the bund shall be 450 mm. GB50074-2002 Code for Fire Protection Design of Oil Depots, 6.0.6: Above-ground oil tank groups shall be equipped with fire dikes, and the installation of such dikes shall comply with the following requirements: 1 The fire dikes shall be constructed from non-combustible materials, and they shall be able to withstand the static pressure of the oil stored within them without leaking. 2 The calculated height of the fire dike for vertical oil tanks should meet the requirements of the effective volume inside the dike. The actual height of the fire dike should be 0.2m higher than the calculated height. The actual height of the fire dike should not be less than 1 m (measured from the designed floor level on the inside of the fire dike), and should not exceed 2.2 m (measured from the road surface on the outside of the fire dike). The actual height of the fire dike for horizontal oil tanks should not be less than 0.5 m (measured from the designed floor level on the inside of the fire dike). If a soil fire dike is used, the width of the dike crest should not be less than 0.5m. 3 It is strictly prohibited to make holes in the fire dike. The areas where pipes pass through fire dikes should be tightly filled with non-combustible materials. At the points where rainwater drains pass through firewalls, oil-blocking drainage measures should be taken. 4 The walkways on the fire dike of the oil tank cluster should be provided in no fewer than two locations, and they should be in different directions. 6.0.9 The effective capacity within the fire dike shall comply with the following requirements: 1 For fixed-roof oil tanks, it shall not be less than the capacity of the largest oil tank in the tank group. 2 For floating roof tanks or internal floating roof tanks, it shall not be less than half of the capacity of the largest tank in the tank farm. 3 When fixed-roof oil tanks and floating-roof or internal floating-roof oil tanks are arranged in the same tank farm, the larger value specified in the above two clauses shall be adopted. 4 The specified effective capacity within the fire dike for covered oil tanks is the same as above, but the tank capacity shall be calculated based on the volume of its part that is above the ground level. 6.0.10 Diaphragms shall be installed within vertical oil tank groups in accordance with the following provisions: 1 When the capacity of a single tank is less than 5000 m3, the number of tanks within the diaphragm area shall not exceed 6. 2 When the capacity of a single tank is equal to or greater than 5000 m3 and less than 20000 m3, the number of oil tanks within the dike should not exceed 4. 3 When the tank capacity is equal to or greater than 20,000 m3, the number of oil tanks within the dike should not exceed 2. 4 The number of boiling oil storage tanks within the dike shall not exceed 2. 5 For non-boiling-over Class B oil storage tanks, a dike is not required. 6 The elevation of the top surface of the dike should be 0.2～0.3 m lower than that of the top surface of the fire dike. 7 The dike shall be constructed of non-combustible materials, and shall be able to withstand the static pressure of the oil it contains without leaking. Specifications for the layout design of chemical plant equipment HG/T 20546-2009. Part 2 of this standard, in clause 5.5.4, specifies that when it is necessary to collect spilled material, the thickness of the dike used must be at least 150 mm; its volume must be sufficient to hold the capacity of the largest storage tank under normal pressure, and the minimum height of the dike must be 450 mm. Part 5, Chapter 14 of it deals with the layout of tank areas. Section 14.2.3 stipulates that dikes should be installed around storage tanks containing toxic, corrosive, or valuable materials to prevent the spread of such materials (see Article 5.5.4 of Part 2 of these regulations), as well as sump pits to facilitate centralized collection. The “GB50016-2006 Code for Fire Protection Design of Buildings” only covers provisions related to fire dikes and partitions (without the concept of cofferdams); relevant provisions are also included in the “GB50160-2008 Code for Fire Protection Design of Petrochemical Enterprises”, the “GB50351-2005 Code for Design of Fire Dikes in Tank Farm Areas”, and the “GB50074-2002 Code for Fire Protection Design of Oil Depots”.