sentences:  The cascade system allows small cylinders to be filled without a compressor.In addition, a cascade system is useful as a reservoir to allow a low-capacity compressor to meet the demand of filling several small cylinders in close succession, with longer intermediate periods during which the storage cylinders can be recharged.When gas contained in a cylinder at high pressure is allowed to flow to another cylinder containing gas at a lower pressure, the pressures will equalise to a value somewhere between the two initial pressures.