| 摘要 |
<p>The invention involves a closed loop control method and apparatus for starting up a steam-heated heat exchanger by controlling the heating-steam pressure. According to the invention a correcting variable is established by a controller from an actual pressure value, measured by an actual value transmitter, and from a reference value, generated by a reference value generating device, the heating-steam pressure being modified by at least one control valve on the basis of said correcting variable. The pressure reference value S is selected from three pressure set values, ST, SP1 and SP2, the lesser value of ST and SP1 being established as an intermediate pressure set value S' (that is, S' = Min (ST, SP1)), and the pressure reference value S is selected as being the greater value of S' and SP2 (that is, S = Max (S', SP2)), where ST represents that permissible maximum desired pressure value which is a function of the momentary metal temperature Th of an endangered component of the heat exchanger, SP1 represents that permissible maximum pressure set value which is a function of the momentary existing quantity of working medium and thus of the momentary existing power, and SP2 represents the permissible minimum pressure set value as a function of the same momentary factor.</p> |
