The machine, a basin type ironer, uses pressurized steam (10 bar) to iron and reduce the thickness of the fabric entering the machine, to the desired value. The steam, supplied by the user company network, is filtered and distributed along steel pipes to the process components (cylinders, vaporizers, basin). The process logic is implemented through actuated valves, pressure and temperature sensors. The condensate produced is drained and collected and then returned to the steam circuit.
STEM’s consultancy was focused to the CE marking of the equipment and the pressure assembly, according to the PED Directive.
Due to its internal volume and the maximum allowable pressure PS, one of the pressure equipment was assigned to risk category III and therefore the involvement of a Notified Body was necessary (mandatory involvement for categories II, III and IV).
STEM initially performed a structural calculation (design by analysis) with finite elements (FEM) to verify the state of stress of the material (spheroidal cast iron) deriving from the constraints and the loads applied. The applied standard, EN 13445-3 Unfired pressure vessel part 3: Design, required to consider both the load condition relative to the machine operation (therefore with steam at the TS design temperature equal to 200 ° C), and the condition load relative to the final PED test, which consists of hydrostatic pressing at 20 °C, but at a pressure value significantly higher (18 bar) than that which occurs during operation.
The design also considered the phenomenon of fatigue, considering that the equipment undergoes pressure cycles due to the daily start and stop of the machine.
As regards the documentation, STEM has prepared the technical file to be submitted for validation by the Notified Body, with documents such as the risk assessment, the checklist of the essential safety requirements applicable, the use and maintenance manuals, the control plan of the equipment, the SEP Sound engineering practice for the elements referred to in article 4.3 (uncategorized), the collection of material certificates, the P&I of the whole, the 3D model of the piping (pipes, valves, …), the management of the laboratories who have performed the tests and in general STEM has provided assistance to its Customer by placing itself as a technical interface towards the laboratories and the Notified Body.
The technical legislation also prescribed the performance of some tests both on the cast iron material (tensile test, chemical analysis, microscopic analysis, resilience) and on the equipment (magnetoscopic control, ultrasound control, verification of wall thicknesses).
Finally, STEM gave assistance to the customer for the organization and execution of two final checks, in the presence of an inspector of the notified body: verification of the equipment (hydrostatic pressing test at a pressure of 18 bar for about 60 minutes) and a leakage test on the pressure assembly.
