Identification of patterns of the stress-strain state of a standard plastic tank for liquid mineral fertilizers

In this study, using the method of probabilistic deterministic planning (PDP), the optimum design parameters of a standard polyethylene tank used worldwide for transporting liquid mineral fertilizers (LMF) were determined. By the finite element method, the effect of the density of liquid mineral fertilizer, tank wall thickness and four motion modes (braking, acceleration, jump and landing) on the strength of standard polyethylene tanks was studied. According to the results of the study, the five most informative areas in the tank design were identified, for which the values of maximum stresses (σmax) were obtained: filler neck, pockets, walls, tap-in points and wall transition to the tank roof. As the LMF density increases, σmax in the tank increases linearly. Increasing the tank wall thickness by 1.5 times reduces the maximum stresses by 30 to 50 %. It was found that motion mode has a significant effect on the stress-strain state of a standard tank. The “heaviest” mode for a standard tank is “braking”. The “acceleration” motion mode causes σmax of no more than 60 % of the “braking” mode values. The “lightest” mode is “landing”, in which σmax is no more than 28 % relative to “braking”. Based on the PDP method, equations were derived for calculating maximum stresses depending on LMF density, wall thickness and motion mode of the tank. Nomograms were built that make it possible to quickly determine the wall thickness of a standard tank without calculations, depending on external factors. The results of the study can be used in practice when designing safe and durable tanks for transporting liquid mineral fertilizers.