Purpose: To evaluate the strength of the tank car boiler during the transportation of liquid cargo. Methods: The Femap software package was used to determine the stress-strain state of the tank car boiler during the transportation of liquid cargo. The simulation of the behavior of virtual parts, components, and systems under loads and the assessment of their response to a given impact was facilitated by this. Results: A new method has been created to calculate a tank car boiler using the stress intensity factor. The stress intensity factor is directly dependent on the three components of the stress-strain state distribution and the reduction of pressure in the area of the boiler cantilever fixture (support on the sleepers) with maximum pressure. The stress tensor at the boiler attachment point has been identified. It depends not only on the specific features of the fixture but also on the displacement of the liquid cargo during movement that can lead to tank car instability. Practical significance: Calculations based on the proposed methodology will allow simulating the actual behavior of a tank car boiler during the transportation of liquid cargo and provide a clear picture of the distribution and concentration of stresses in any node or part, which is one of the main objectives in the design of tank cars.