Additively manufactured pressure vessel exceeds expectations in testing
May 30, 2024
Dimecc Ltd, Helsinki, Finland, has reported that a pressure vessel, produced in cooperation with Andritz Savonlinna Works Oy and the Finnish Additive Manufacturing Ecosystem (FAME), withstood the non-destructive and destructive tests carried out by Lappeenranta-Lahti University of Technology (LUT). In the tests, the pressure was increased until the vessel started to break, happening at a pressure of 111 bar, exceeding expectations.
“The test results have been published in an article for the benefit of the entire AM community. We are proud to have made such a significant effort publicly available,” stated Eetu Holstein, FAME Ecosystem Lead at DIMECC.
The vessel is manufactured with Andritz Savonlinna Works Oy’s Wire Arc Additive Manufacturing (WAAM) equipment. Made of acid-resistant stainless steel (316L), the approximately 300 kg pressure vessel has a diameter of 900 mm and a height of 1600 mm.
“This vessel was designed for an operating pressure of 10 bar, which includes the safety factors. The preliminary calculation showed that the rupture would occur at around 90 bar, i.e. the actual durability far exceeded expectations. It must be noted that in real production pieces, the test pressure of the pressure vessel is usually only done at around 1.5X the operating pressure, i.e. in this case the test pressure would have been only 15 bars,” added Santeri Varis, Additive Manufacturing Manager at Andritz Savonlinna Works Oy.
In the pressure test, water was pumped into the vessel, and it was monitored what changes it causes in the diameter of the widest part of the vessel. The pressure was gradually increased until it reached its maximum.
During the pressure test, water was pumped into the vessel, which was monitored to observe changes to its diameter at its widest point. The pressure was progressively increased until it reached its maximum.
“Under 66 bars, there were still no noticeable changes in the vessel. The shape started to give way after 80 bars. We continued the test so long that some water leaked out of the vessel at 111 bars. At that point, a small crack appeared next to the legs of the vessel. The diameter had expanded by seven percent. The result is very good for a piece like this, which is designed to withstand much lower pressure,” said Doctoral Researcher Kalle Lipiäinen from LUT University.
The crack was welded, but, in the next test, there was a fracture right at the leg again. This indicated that the leg area was a structural weak point, and the first breakdown was not due to, for example, a manufacturing error.
“Manufacturing and mechanical performance of a large-scale stainless steel vessel fabricated by wire-arc direct energy deposition”, was published in Materials & Design and is available here.
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