What grade of flange is required for 12 kilograms of steam?
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Dear experts: Renovation of factory steam pipes. The steam pressure coming out of the steam cylinders is 12 kilograms, and the design institute requires us to use flanges with a pressure rating of 25 kilograms, as well as valves made of grade 20 steel. What is the basis for this?
At high steam temperatures, the allowable stress of the material decreases; 16 kilograms is not safe, while 25 kilograms is the correct choice
Generally, it is twice the medium pressure; this applies to the selection of pressure gauges. Of course, the value of the pressure gauge can also be lower, but it must not be less than 2/3
Is 12 bar the design pressure or the operating pressure? If it’s for design or pressure testing purposes, PN16 will suffice; if it’s for operational use, then choose PN25. Of course, choosing PN25 is definitely safer
For a 12-kilogram capacity, a 16-kilogram version is sufficient in terms of design, but are you sure this pipeline is designed to handle a pressure of 12 kilograms? What if its instantaneous pressure, even at 12 kilograms, exceeds 16 kilograms? That’s why a 25-kilogram class is safer
This post was last edited by At the foot of the hill on 2016-7-23 at 13:21. The temperature of saturated steam at 12 kilograms is around 190°C; at this temperature, the maximum allowable operating pressure for a flange made of 20-grade steel weighing 16 kilograms is 12.6 kilograms. If a 16-kilogram flange is used, the steam pressure will be close to the maximum allowable operating pressure; therefore, a 25-kilogram flange is chosen.
This post was last edited by Liu Jiajia on 2016-7-23 at 18:18. The main consideration is the temperature and pressure curve of the fluorine material; generally, it should be below that curve. Additionally, the superheat of the steam must be taken into account; to prevent a temperature drop during transportation, steam generally has a certain degree of superheat. Actually, for materials engineering, what matters to us is the design conditions; it’s sufficient to determine the process parameters. :lol
The steam cylinder is connected to the steam supply in the park, and the pressure is only 14–15 kilograms. The steam cylinder is equipped with a safety valve, whose setting pressure is 12 kilograms.
Additional question: The design pressure of the steam distribution cylinder is 12 kilograms, and the setting pressure of the safety valve on this cylinder is also 12 kilograms. Moreover, there is a control valve assembly in front of the steam distributor, which is automatically adjusted via a pressure transmitter on the steam distributor; this control pressure is also 12 kilograms.
The main consideration is the temperature-pressure curve of the fluorinated material; generally, it is sufficient to be below that curve. Additionally, the superheat of the steam must be taken into account; to prevent a temperature drop during transportation, steam generally has a certain degree of superheat. Actually, for materials engineering, what matters to us is the design conditions; it’s sufficient to determine the process parameters.
A 16-kilogram flange no longer has a pressure resistance of 16 kilograms as the design temperature increases. In this case, steel grade 20 is almost at its pressure tolerance limit, which is unsafe; it is better to use flanges rated for 25 kilograms of pressure – the design team’s choice was correct. Another option is to use 16Mn material; it can withstand a pressure of 15.6 kilograms at 200 degrees. It’s not clear what the price difference is compared to 20-stainless steel flanges that can handle 25 kilograms of pressure.