Structural Loads Due to Detonations in Hydrogen Emergency Vent Systems

Abstract

Hydrogen emergency vent systems are safety equipment to release hydrogen from storage in terms of pressure rise. Sometimes, the safety vent systems become a risk when it fails, and several explosions happened due to this failure. In this study, hydrogen explosions at different concentrations were conducted in a 4 m single obstructed closed pipe to observe the maximum pressure and strain response. PicoSope and NI instruments were used to measure the pressure and strain respectively and it was found that NI recorded a lot of noise. No detonation or DDT was observed at 0.6, but DDT was observed after the obstacle at 1.0 and 1.2. The run-up distance was minimum in stoichiometric and rich mixtures. Maximum overpressure was observed as 1.85 MPa at 1.5 m distance at 1.2. DDT was observed in end pipe at 0.8 with a maximum reflected overpressure of 2.56 MPa. A DDT in the end pipe is dangerous and can develop a pressure of 5 MPa or even more. A dynamic amplification factor of 1.67 was found between the hoop strain recorded from strain gauge and strain calculated from internal pressure at 2.0 m distance for 1.0. A random choice numerical simulation was conducted and compared with experimental results which was in good agreement. From the simulation it was found that a pressure of 5.7 MPa can be developed if detonation occurred in the end pipe. The simulation can predict the pressure response both in an open and closed pipe.

For industrial application the material of the vent systems should be low electric conductive, high convection heat transfer coefficient, low roughness, leaked tight and unobstructed. The initial conditions and flow rate of the hydrogen should take into account before implement the vent systems.