Are there any issues with the safety valve design process? The design process is as follows
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Operating temperature: 240°C; Operating pressure: 10 MPa. The design pressure for the equipment is set at 1.1 times the maximum pressure that the equipment can reach, which is 11 MPa, resulting in 12.1 MPa. The design temperature is taken as the highest operating temperature plus 30°C. Basis for determining the design pressure: The design temperature is determined based on… Basis for determining the allowable overpressure range of the safety valve: Since this equipment allows the safety valve to be designed for fire conditions, the allowable overpressure is calculated at 121%. Design standard for reseating pressure: The reseating pressure is set at 93%-97%, with 95% selected here. The set pressure of the safety valve is designed as follows: it is set to be higher than the maximum operating pressure, at 1.1 times the normal operating pressure – that is, 10*1.1 = 11.1. The value falls within the range of 11.1 and 12.1. To prevent the safety valve from activating frequently, the set pressure is slightly higher than the maximum operating pressure, namely 11; therefore, the set pressure is designed to be 11.5 MPa. The design of the safety valve is as follows: The temperature of the equipment here is 240°C and the pressure is 10 MPa; therefore, it is designed in accordance with criterion 6.0.4, and a safety valve equipped with radiators is selected. The discharge pressure = starting pressure/setting pressure * allowable overpressure range = 11.5 * 121% = 13.915 MPa. The return pressure = 0.95 times the setting pressure = 11.5 * 0.95 = 10.925 MPa. The discharge temperature is calculated using the ideal gas law: PV = NRT. Since V and NR remain constant for the equipment, P1/P2 = T1/T2. P1, the discharge pressure, = 13.915 MPa; P2, the operating pressure, = 10 MPa. T1, the discharge temperature, and T2, the operating temperature, = 240°C. K = °C + 273.15 = 240 + 273.15 = 513.15. Thus, the discharge temperature can be calculated as P1/P2 * T2 = 13.915/10 * 513.15 = 714.05 K. T1, the discharge temperature, = 714.05 K – 275.15 = 439.90°C. Is there anything wrong with this design process?
For selecting safety valves, some software or websites offer options for making such choices; in most cases, the decision is based on determining the appropriate size. As for temperature, it’s not a crucial factor after all; what matters is pressure (whether it’s during operation or recovery, etc.). I’ve previously helped other teams with evaluations as well, and calculating temperature isn’t the key point; it probably shouldn’t be estimated using the ideal gas law either...
I’ve never been able to figure out exactly how to calculate the discharge temperature; could you give me some guidance?
The discharge temperature… I’ve discussed this with the manufacturer before, and you have the same confusion. Basically, they suggest using the design/operating temperature of this pipeline to determine the specifications for ordering the product. As for calculations… as I mentioned in my previous reply, temperature isn’t a critical parameter; what’s important are pressure and flow rate. So if you look up information online, you’ll find that temperature isn’t that important. Below are a few websites I found online; you might want to give them a try if you can access them: http://www.enground.com/ https://www.checalc.com/instrument.html From an API perspective as well, discharge temperature isn’t considered an important factor. That’s all I have to share with you
Thank you very much. I’ll get back to you once I’ve made a decision