The operating pressure is 30 MPa, and the set pressure is 33 MPa. Can a regular flare be connected to the outlet of the safety valve?
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Currently, the gas flow rate is 2500 cubic feet per hour, with an operating pressure of 30 MPa and a set pressure for the safety valve of 33 MPa. The safety valve selected has dimensions of 1.5’×3’, and its pressure rating is class2500×class300. Can the outlet with this class300 rating be connected to the existing venting system? There is an existing venting system with a venting capacity of over 5,000 cubic meters per hour; simultaneous venting is not taken into account. The design pressure of the pipelines is only 1.0 MPa (with corresponding pipe fittings of Class 150), and the back pressure is 0.2 MPa; therefore, the maximum operating pressure of this system is currently 5 MPa. How should I deal with this?
It seems like an outlet of class 300 should be connected to something of class 150, but this doesn’t make sense from a design perspective – there’s not even a place where such classification can be applied
Hello! The outlet of this safety valve is rated at 300BL, while the design pressure for the flare is only 1.0; the flange grade used is 150BL. From a design perspective, this makes no sense – a 300BL component and a 150BL component are combined together, with no separation point between the two pressure grades
No action is needed; just control the back pressure of the safety valve. It’s sufficient to calculate it based on the rated discharge volume.
Thank you. I also have a question: there is a pressure of 30 MPa before the safety valve, and 2 kg of backpressure after it. With such conditions, the temperature drop is quite significant – according to HYSYS simulations, the temperature drops from 40°C to -50°C. How should the material for the safety valve be chosen? Since throttling occurs right after the valve core, such low temperatures will definitely be transmitted to the side with a pressure of 30 MPa. The material used for the pipelines downstream of the safety valve can be low-temperature steel, which can undergo low-temperature impact tests; but choosing a suitable material for the safety valve itself is quite challenging. I don’t know what material to choose. How should this be handled here, including the pipelines near the safety valve?
Stainless steel can be considered for low-temperature operating conditions