Congestion ignition sources

Two major hazards may occur from high pressure vessel failures. The vessel itself may rupture and the formation of vapor cloud as a result of the rupture is possible. If the vessel ruptures, it will produce flying projectiles and usually release large quantities of vapors, and in the case of most hydrocarbons are combustible.The projectiles could harm individuals or damage the process facility, possibly increasing the incident proportions. Secondly, the release of a combustible gas from a pressurized vessel may cause the formation of combustible vapor cloud, which if a suitable amount of congestion is present or some turbulence of the cloud occurs, an explosive blast may result once the cloud contacts an ignition source. 

Inadequate plant layout and spacing may lead to congested process and storage areas, lack of isolation for e.xtra liazardous operations mid areas, sources of ignition that are too close to liazm ds, and lack of proper emergency facilities. 

Turbulence is required for the acceleration of flame front to speeds required to produce the blast overpressure associated with a VCE. In the absence of turbulence, a flash fire will occur without any appreciable overpressure, with the hazard limited to the thermal radiation impacts associated with the burning of the cloud from the ignition point back to the release source, or within the flammable range of the cloud. Flame turbulence is typically formed by the interaction between the flame front and obstacles. The blast effects produced by VCEs vary greatly and are primarily dependent on flame speed therefore, areas of confinement and congestion near the release point can influence the likelihood of a VCE. Additionally the reactivity of the material is an important consideration highly reactive materials such as ethylene oxide are much more likely to lead to a VCE than lower reactive materials such as methane. 

Offshore facilities are congested, thus creating problems having to do with emergency escape and sources of ignition. 

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