Patent GB-600906-A (GB)
Title: Process and apparatus for regulation of steam generators
IPC: F22D11/00
Filed: 1943-07-13
Abstract: 600,906. Automatic control systems for steam generators. LOUMIET, J. P. July 13, 1943, No. 11391. Convention date, July 3, 1942. [Class 38 (iv)] [Also in Group X11I] Fluid pressure ; fluid level.-The fuel, water and air supply means of a drumless forced flow boiler are driven in common and controls operating automatically in response to steam pressure variations and to waterlevel variations in a separator between vaporizer and superheater are applied, one to govern the motor, e.g. a steam turbine, driving the supply means and the other to govern further one or more of the feeding rates, a proportion of combustion gases being directly supplied to the superheater before they have traversed half the heating surface of the vaporizer and being regulated automatically in accordance with the temperature of thesuperheated steam to maintain that temperature constant. The proportion of combustion gases similarly supplied to an economizer may also be regulated in accordance with the temperature at the outlet thereof. These diversions of combustion gases may be additionally regulated in accordance with steam pressure, and by the same means as control the aforesaid motor. Fig. 1 showsa system in which the water content of the separator H is maintained proportional to steam consumption by withdrawing water at a rate proportional to the basic water feed rate by means of a pump BR driven in common with the feed pump BW, fuel pump BP and fan VA. A turbine T coupled to these is driven from the superheated steam and is regulated by a valve v in accordance with the steam pressure in the separator. The water supply is additionally regulated in accordance with the water level in the separator by means of a byepass valve w. Combustion gases are withdrawn from the combustion space and sent direct to the superheater R through a valve C which is adjusted automatically in response to outlet temperature of the superheated steam. Combustion gases are similarly directed and controlled through a valve C1 to the economizer E. All these controls may be electrical, fluid or mechanical. In a modification, Fig. 5 (not shown) the separator steam pressure controls valve v and also valves controlling fuel and air supplies and supplements also the temperature controls of valves C, C1 ; the water level in the separator operates supplementary controls of the air and fuel supplies instead of controlling the water supply. A particular arrangement of the valve C is shown in Fig. 4 in which the superheater is in four separate flue sections controlled by separate valves Cl ... C4 operated in turn from a rack actuated by the control electric motor. Control by water level : Water level variations are amplified (1) by an inclined capillary tube N, Fig. 2, and (2) by apparatus generating a pressure varying with the level, which pressure is applied to a U-tube arrangement controlling a, valve actuating motor. The tube N is conducting and contains mercury from a tube U so that the combined electrical resistance varies according to water level. A current passing through this tube N heats a resistance r in a tube containing a quantity of methyl chloride (which circulates through a condenser E) whereby a pressure varying according to water level is generated and applied at G to a U-tube containing mercury and incorporating an upward conducting loop K containing an insulating liquid. The limbs of the loop K communicate with side chambers each containing an insulated electrode Pa, Pb and communicating through relief valves Q, Q<SP>1</SP> with the mercury in the opposite limb. When the mercury is moved by change of pressure at G contact is made with electrode Pa or Pb whereby a relay Sa or Sb is energized to produce motion of a valve operating motor in a direction to correct the rate of supply of water or combustion material. Control by steam pressure.-The steam pressure is applied to a body of mercury in a tube containing electrodes Pa, Pb, Fig. 3, arranged in a similar manner to the electrodes Pa, Pb of Fig. 2. The mercury tube terminates in a space O<SP>1</SP> containing compressed air. To ensure that the control does not operate under transient variations in steam pressure additional electrodes Va, Vb are arranged to control relay contacts I<SP>1</SP>a, I<SP>1</SP>b in series with each of the control motor circuits. Specifications 541,840, 552,364, 554,130, [Group XXXVI], and 563,928 are referred to.