## 3 State of the Art of Burst Containments
### Commercially Available Test Rigs  
Some companies offer industrialized spin rigs / spin pits for sale, or they offer spin services for rent. Table 2 gives an overview of some well-established companies in this field.  
Apart from the companies listed in Table 2, some turbo machinery manufacturers (i.e., MAN Turbo, Rolls-Royce, MTU, etc.) and several research institutions, such as Ohio State University [30], Naval Postgraduate School [31] or NASA [32] own spin pits, which they use for their own internal  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Organization** & **Year** & **Description** & **Speed** & **Energy** & **Ref.** \\ \hline \multirow{6}{*}{\begin{tabular}{c} Lockheed \\ Martin \\ \end{tabular} } & \multirow{3}{*}{1972} & Steel ring with a & & & \\  & & diameter of 515 mm and & 22,820 & & \\  & & a wall thickness of 75 & rpm & & \\  & & mm; solid steel flywheel & & & \\ \hline \multirow{6}{*}{\begin{tabular}{c} Steel Flywheels \\ \end{tabular} } & \multirow{3}{*}{1972} & Steel ring with 12.7 mm & & & \\  & & wall thickness and & 16,750 & & \\  & & rotating liner made of & rpm & & \\  & & GRP (178 mm thick) & & & \\ \hline \multirow{6}{*}{\begin{tabular}{c} EHT Zürich \\ \end{tabular} } & \multirow{3}{*}{1996} & Steel tube in concrete & & & \\  & & pit; solid steel rotor & & & \\ \cline{1-1}  & & & Rectangular steel & & \\  & & housing with 10 mm & & & \\  & & wall thickness and & & & \\  & & wooden lining; ceramic & & & \\  & & flywheel & & & \\ \hline \multirow{6}{*}{\begin{tabular}{c} Schenck \\ Rotec/TU \\ Graz \\ \end{tabular} } & \multirow{3}{*}{2008} & Laminated steel rotor & & & & \\  & & and steel housing & 45,000 & & \\  & & consisting of 2 & rpm & & \\  & & concentric rings with 8 & & \\  & & mm wall thickness & & & \\ \hline \multirow{6}{*}{\
\begin{tabular}{c} Fiber-Composite \\ Flywheels \\ \end{tabular} } & Lockheed & \multirow{3}{*}{1972} & Steel ring with a & & & \\  & & diameter of 515 mm a & rpm & & \\  & & wall thickness of 75 mm & & & \\ \cline{1-1}  & & Oak Ridge & & & \\ \cline{1-1}  & National Laboratory & 1980 & Flywheel made of fiber & & \\ \cline{1-1}  & & composite in steel & - & - & [19] \\ \cline{1-1}  & & & housing & & \\ \cline{1-1}  & ETH Zürich & 1996 & Wound rotor made of & & \\ \cline{1-1}  & & & glass fiber rovings and & - & - & [17] \\ \cline{1-1}  & & & epoxy matrix & & \\ \cline{1-1}  & & CEM, & Carbon fiber flywheel & & \\ \cline{1-1}  & University of & Texas & 2002 & in burst containment & 35,200 & \\ \cline{1-1}  & & Texas & & made of aramid fibers & rpm & \\ \cline{1-1}  & & Ricardo UK & 2016 & & \\ \cline{1-1}  & Ltd. & 2016 & &
\begin{tabular}{c} Woven rotor made of \\ aramid fibres for \\ reproducible burst tests \\ \end{tabular} & 90,000 & - & [21] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Over-speed tests of steel and fiber-composite flywheels.  
other hand, a statistically significant number of tests would be ideal to validate numerical models and fully exploit the energy storage potential of the rotor material. This is why a low-cost test rig for spin testing was designed at the Energy Aware Systems Group at the Institute of Electrical Measurement and Measurement Signal Processing (Graz University of Technology).