Embodiments of the invention efficiently conduct servo corrections for preventing error propagation during SSW. ULO is heated by mixing with superheated lubricant boiling range hydrocarbons recovered and recycled from the process. The up-count operation and the down-count operation of the updown counter is controlled to changeover by the output signal of the voltage comparator, and a voltage corresponding to the count value of the updown counter is output from the DA conversion circuit. The clamping member can be tightened and is shaped to contact the second surface of the housing and the second surface of the assembly such that when the clamping member is tightened the clamping member causes the housing and the assembly to compress the flexible member so that the flexible member provides a seal between the housing and the assembly.