Selection of plates for liquid ammonia spherical tanks

Liquid ammonia (NH3) does not corrode steel, but it does corrode when in contact with water. The difference can be understood by looking at its properties. Physical and chemical properties: it is a colorless gas with a pungent odor; it is readily soluble in water, ethanol, and ether, and its aqueous solution is alkaline. Melting point: -77.7°C, boiling point: -33.5°C, autoignition temperature: 651°C, explosion limit: 15.7%-27.4%, saturated vapor pressure: 506.62 kPa (4.7°C). It can be easily pressurized to liquefy into liquid ammonia, and a large amount of heat is released during this liquefaction process. When the pressure is reduced, liquid ammonia vaporizes while absorbing a large amount of heat from its surroundings; therefore, it is commonly used as a circulating refrigerant in refrigerators and ice makers. It is also used to manufacture ammonium salts and nitrogen fertilizers. Hazardous characteristic: The pressure inside the bottle increases when heated, posing an explosion risk. When the concentration of ammonia vapor in the air reaches 15.7%-27.4%, it can cause combustion and explosion upon contact with a spark; the presence of oils further increases the risk of fire. Toxic; the maximum allowable concentration in workshop air is 30 mg/m3. Gas leakage irritates the mucosa, and high concentrations can cause tissue dissolution and necrosis. Liquid ammonia is corrosive and can burn the skin. Extinguishing agents: fog water, alcohol-resistant foam, carbon dioxide, sand. Firefighters must wear gas masks and protective clothing. Extinguish the fire from upwind. Storage and transportation notes: It can be stored in a cool, well-ventilated warehouse, away from sources of fire and heat, and protected from direct sunlight. It should be stored separately from fluorine, chlorine, bromine, iodine, and acidic substances. Handle with care during transportation to prevent damage to the gas cylinder and its valve. When transported in tank trucks, an appropriate amount should be filled; transportation under pressure or in excess quantities is not allowed. Drive along the designated route without stopping en route.

This post was last edited by yakui on 2009-8-19 at 17:13. Liquid ammonia is subject to the risk of stress corrosion; please refer to clauses 6.7 and 6.7.4 of HGJ20580. For storage tanks, materials such as Q245R or Q345R can be used.

I’m just saying that the original 16MnR is now Q345R, right?

Q345R GB713 replaces 16MnR GB6654, Q370R GB713 replaces 15MnNbR GB6654

Q345R is the same as 16MnR. Liquid nitrogen can cause stress corrosion in low-alloy steel; pay attention to the heat treatment process.

There are differences: one is the level of stress, and the other is that Q370, which is equivalent to 15MnNbR, contains the element Nb, which gives it resistance to H2S corrosion. Q345 is less effective in this regard; however, it does have an advantage in terms of weldability, as its weldability is better than that of Q370. When using forgings for flange connections, there is no need for welding different types of materials – 16MD forgings can be used directly.

The steel plates, pipes, bars, and forgings used to manufacture the pressure-bearing components of tanks shall, in addition to complying with the provisions of Chapter 2 of the \"Design Code for Steel Pressure Vessels in the Petrochemical Industry\" (hereinafter referred to as the \"Vessel Design Code\"), also meet the following requirements: 1. The steel plates used for manufacturing tanks shall conform to Grade II of JB1150 \"Ultrasonic Testing of Steel Plates for Pressure Vessels\". 　　When pressure vessel steel plates with a specified yield strength of 400 MPa (40 kgf/square millimeter) or higher are used, in addition to meeting the aforementioned requirements, the condition in which the steel plates are supplied, as well as aspects related to their design, selection, manufacturing, testing, and inspection, must all strictly comply with the relevant current standards. 　　2. The forgings shall meet the requirements of Grade II as specified in JB755 \"Technical Requirements for Forgings of Pressure Vessels\". 　　3. When foreign materials are used, the tank material shall be steel suitable for pressure vessels, and must meet the standards of the country where the material is produced as well as the requirements of these regulations. 　　4. The tank material shall meet the requirements of the Charpy V-notch impact test at –20°C, with Akv ≥ 2IJ (joules, i.e., 2.1 kgf·m).