Sava has extensive experience in the optimisation of fire protection of pressurised equipment with flammable inventories and structures affected by fire.
Sava has conducted more than eighty multi-physics thermodynamics and mechanical analyses for the fire protection of pressurised equipment to determine the optimum fire protection to prevent the boiling liquid expanding vapour explosion (BLEVE) of pressure vessels for piled platforms, floating production and storage units (FPSOs), and onshore process plants.
Figure 1 illustrates in axial view into a horizontal pressure vessel typical temperatures of vessel wall resulting from the heating-up of vessel inventory. The heating-up of the vessel inventory of 50% oil and 50% gas is caused by the effects of fire on the outside surface of the vessel. The fire attacks the vessel during the vessel depressurisation. The top left figure shows relatively cold vessel at the start of the fire. Top middle and right: The top part of vessel containing gas becoming hot whilst the bottom part is cooled by the liquid in the vessel. Bottom left and right: Note the reducing level of stratification between oil and gas as the oil boils and evaporates with gas remaining. All these processes are time-dependent.
Figure 2 shows typical stress and inventory mass results varying with time resulting from the analyses. The time to vessel burst is approximately 40 minutes after the start of fire impinging on the vessel.
Sava carried out this work using the computer program VESSFIRE. VESSFIRE is the only computer program which has been verified against full scale tests.
Figure 3 illustrates the thermal and structural behaviour of a structure affected by fire impinging on the KT joint in the structure upper deck.
The structure is a pre-assembled unit (PAU), where the KT joint does not have any fire protection. The joint is progressively heated-up and heat is conducted into the structural members joined-up in the joint. The temperature of the steel members rises and their load bearing capacity reduces. This happens progressively with time. The top picture shows the temperature distribution (red hottest, blue coldest) in the structural steel at 16 minutes after the start of the fire. The bottom picture shows the structure deformation (progressive collapse) and stresses (red highest stress, blue lowest stress) at the same point in time. The time to collapse depends on fire scenario, layout of the structure, sizes of structural members, stress distribution before the fire, etc.
The fire loads for this analytical work were determined by probabilistic analysis. The combined transient thermal and structural collapse analysis was carried out using the computer program USFOS.
Figure 4 shows a local deformation of a structural column affected by fire. Such deformation may be acceptable providing that the structure functionality during and after the fire is acceptable.
Sava has carried out the fire protection optimisation work of structures and equipment for more than thirty facilities, including piled platforms, floating production and storage units, refineries and terminals. His work has resulted in improved fire protection and big cost savings.
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