I talked with an engineer at GAST mfg. He said metals expanding differently is not the cause for vane shattering. He said all the metal and carbon vane expansion has been taken into account in the engineering and design of the rotary vane units. He said vane shatering is most likely due to foreign matter in the vane cavity (improper air filtration) or over pressurization. He said vane shattering often occurs soon after a rapair job or rebuilding which results in "dirt" in the rotar cavity to cause vane shatter.
I am not aware of the worm screw type units.
