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Organisationseinheit der BAM
How can the risk of a BLEVE be reduced? That is the main question based on different research projects. In various large scale fire tests fire protection coating systems were used of different manufacturers. The degree of the coating as well as the layer thickness and the processing were varied. These experimental configurations were partly tested with and without pressure relief valve. The pressure relief valves were not protected again the thermal Load from the test fire. The ambition is to find a minimum of the thickness from the fire protection coating witch delay a BLEVE up to 90 minutes. Here are given the most interested configurations of tanks in fire and a description of the test-rigs.
A new tank design for Hazmat
(2016)
Initial studies have shown pre-deformed honeycomb structure
pressure vessels to have comparable burst pressure to straight steel vessels.
It was shown that honeycomp structured tanks have a higher energy absorption than straight steel tanks.
Future studies will investigate optimization of the deformed plate, to determine if increased payloads or a reduced wall thickness can be achieved.
Liquefied propane gas (LPG) tanks in a fully engulfing accidental fire experience a fast increase in internal pressure. The result is often a Boiling Liquid Expanding Vapor Explosion (BLEVE) that can result in a large fireball and flying debris over a radius of more than 100 meters.
In the last 30 years BAM has carried out more than 30 real scale fire tests on propane storage vessels across three test sites. The primary research goal was to identify systems that can delay or prevent a BLEVE. Early studies started with water deluge systems, and have since moved on to consider alternative protection systems.
It has been shown that an unprotected vessel fails within 10 minutes or less. Tests with different oil and propane fueled fires have given an overview on possible real accidents involving full-engulfing scenarios. LPG tanks of various sizes (2.7 m³, 3.6 m³, 4.8 m³, 6.7 m³) were used with different filling levels. Numerous protection systems, ranging from active systems like water systems to passive thick- and thin-film layers. Also, the degree of thickness of these layers was variated. Pressure relief valves (PRV) have also been investigated, both alone and in combination with protection systems.
This paper gives an overview of the work performed by BAM in the field of BLEVE prevention of protecting system since the last 30 years. It has been shown that e.g. with a full applied coating degree on the tank with and without PRV can be reached an exposition in a test fire scenario a duration of more than 60min. For partly coated tanks with and without PRV the duration time is like an unprotected vessel. Furthermore, it could be shown that the active water system also protects with technically correct design.
Several geometrical analytical tools can be used for assessing the potential benefits of any alternative tank shape. The quasistatic evaluation of the cargo-vehicle behavior represents a fast way to objectively determine the roll stability benefits of any potentially new tank shape. In this paper, the geometrical, quasistatic rollover performance of a convex bottom tank shape is compared with that of standard tank shapes, finding that in spite of the lower position of the cargo´s center of gravity in such a tank shape for the un-perturbed condition, it has the same performance as the elliptical tank shape when subjected to Steady lateral acceleration. That as a result of the large cargo´s lateral displacement. Consequently, the combination of a lower center of gravity for the cargo when it is not perturbed, and a Minimum lateral shift due to lateral accelerations inputs, define the conditions for an ideal tank shape.
A simplified methodology is proposed to estimate the dynamic pressures developed within partially filled cylindrical vertical tanks when subjected to earthquake-related horizontal accelerations. The total pressure at the bottom of the tank is calculated as the superposition of vertical and horizontal pressures. While the magnitude of the vertical pressure depends on the free surface height of the liquid, the horizontal pressure depends on the magnitude of the horizontal acceleration and on the diameter of the tank. The liquid free surface oscillation angle is simulated based upon the principles of the simple pendulum analogy for sloshing. The length of the pendulum, however, is set on the basis of a methodology to calculate the free sloshing frequency of partially filled containers. Such a methodology is experimentally verified in this work. The outputs of the model for full scale situations, suggest that the lateral perturbation - sloshing phenomenon (earthquake effect) can generate an increase in the total pressure of 56% above the no lateral perturbation situation, further suggesting that such an overpressure should be taken into account when designing tanks that could be potentially subjected to earthquake-related perturbations.