What kind of material is used for RS type casing type retractor?

What kind of material is used for RS type casing type retractor?
Relying on the RS type casing type expander blade high speed rotation of centrifugal force generated by the transport medium to the high pressure end of the outlet, then in the inhalation port to form a vacuum, the medium is sucked in again, and so on cycle. If not water (should be exact medium), RS type casing type expander is no medium operation, can not work, not to mention, due to the RS type casing type expander and pipeline body of the mouth of the ring gap is very small, dry turn friction occurs after the adhesion, very easy to mechanical accidents, which led to the destruction of pipeline equipment.
 
In the RS type casing type expander manual will firstly indicate: it is forbidden to idle without liquid. To put it simply: the pipeline is the RS type casing type expansion device inside the air out, RS type casing type expansion device can work. RS type casing type expansion device in operation, if not filled with water, the pipeline is not filled with liquid or leakage of air in operation.
 
RS type casing type expander just drive the air inside the pipe rotation, due to the density of air is much smaller than the density of liquid, produce the centrifugal force is small, in the suction inlet at the formation of the vacuum is low, is not enough to suck the liquid into the pipeline, can not be all the air inside the pipeline and pipeline discharge, can not be again inside the pipeline to produce a vacuum.
 
Thus, the water can not be sucked up, then in order to prevent and eliminate the "air binding" phenomenon, usually in the pipeline before the start to fill the pipeline, so that the pipeline and the pipeline is full of liquid. Adding water and exhausting air, to RS type casing type expander pipe inside no air, in order to pump out the water.