SISTEM Tank Pressure Test

The SISTEM 13-liter tank was designed to sustain a maximum pressure of 60 bar, accounting for the maximum design pressure of 48 bar and proof factor of 1.25. 

The tank pressure test plan was defined in several steps, as recommended in ECSS standards for pressurized hardware and fracture control. The prototype tank passed visual inspection and initial leak test, but a rupture occurred in the bladder at an area that was identified as having a manufacturing defect, preventing further pressurization. Several attempts were made to repair the bladder and finally an alternative non representative rubber balloon was used to pressurize the tank past 10 bar pressure.

Whilst this is below the target maximum pressure of 60 bar, there was sufficient data to check the pressure and displacement of the tank against the predicted stiffness profile from the Finite Element Model. The results available from the test were within the predicted limits of strain and displacement for given pressure levels, showing the simulation was conservative and tank elongation (in the radius and along the length) were within expected values, at least for the pressure level achieved.