High Pressure Vessels: Test Chamber Design
During my student years, doing research work at the MPA Stuttgart, I was fascinated when I was allowed to participate in container explosion tests at the army facility in Meppen. Containers with walls several centimeters thick would explode and become completely unrecognizable. The experiments were carried out with air and under the strictest safety conditions. The bursting pressures of containers several meters long were approximately 170 bar.
That was some 35 years ago.
The requirements for the pressure resistance of containers have increased since then. Peak pressures are now at a then unimaginable 25,000 bar, albeit only for very small diameters.
But even hydrogen tanks for vehicles are being tested at up to 1,200 bar. In these cases, the dimensions are within a range of about 1 m. In oil and gas drill pipes the range is up to 1,000 bar. Specimens here have lengths of up to 15 m. Because the dimensions here tend to be much larger, as for example in a high-pressure injection system, small pumps are not sufficient.
Since component failure is possible, and to ensure that these high pressures can be safely withstood, the burst pressure must be demonstrated in experiments. For this purpose, the test device is subjected in a test chamber with high-pressure water. According to what I was able to confirm during my first experiences with the tests conducted at Meppen, if air were used instead of water, the test would result in failure, since the stored energy due to the compressibility of air would be even higher.
But even water is no longer incompressible at these pressures. It compresses somewhat and is thus capable of storing large amounts of energy, which are of similar magnitude to the energy stored in the vessel itself. The total energy in typical applications are of the order of the energy of a small car at a speed of 120 km/h.
Therefore, it must be ensured that no persons are exposed during testing. In addition, the risk of causing any damage to adjacent installations, buildings or constructions must be avoided. Failure to heed these recommendations could result in personal injury, as the test chambers may be completely destroyed and it is sometimes impossible to find valves weighing more than 100 kg after the test. Even sandbags may sometimes not be of sufficient help.
Test chambers are designed and built so that after a test (be it a pump casing, tank, hose, pipe or bore) they remain operational or simply so that the damaged part can be replaced after the test. Which is undoubtedly an art. Determining the magnitude and direction of fragment energy is a challenge, which, without meaningful interpretation of the test chamber, would be practically impossible.
Merkle & Partner has a specialized department for the simulation and interpretation of pressure vessels and test chambers and is the world leader in this aspect, as well as in the simulation, dimensioning and development of various safety concepts. We can simulate the rupture behavior of a high-pressure pump weighing 25 tons under an internal pressure of 300 bar as well as the behavior of gas tanks. Regardless of whether water or gas is used during the test.
The following video shows a simulation of a rupture of a cylindrical vessel with water:
*** Translated with www.DeepL.com/Translator (free version) ***
The failure of the vessel, the behavior of the fragments, as well as the water jet on the vessel walls are detailed exactly. The tests are carried out safely on our computers, so there is no need for us to travel to Meppen either.
We can determine the dimensions of the test chamber and the process exactly, without having to dismantle the equipment - this saves costs and provides safety!
My experience with pressure chambers that were built by companies without the necessary practice is that the risks were probably underestimated.
Inquiries regarding containers and pressure chambers should be addressed to the Head of Structural Mechanics in Heidenheim, Dr. Maik Brehm. (m.brehm@merkle-partner.de).
I look forward to hearing from you!
Stefan Merkle
PS:
The design and verification of pressure vessels are performed according to standards (AD 2000, EN 13445, ASME Sec. 8 Div. 1 + 2, ASME Sec. 3, EN 1591, PD 5500, KTA, RCC-M), in which our Hamburg office is specialized. If you have any questions, please contact our Hamburg office manager, Alexander Haas.