Alarm system operating upon predetermined excess or lack of water in steam boilers

摘要

923,505. Controlling fuel supply. SOC. TECHNIQUE POUR L'EQUIPMENT GENERAL DES USINES S.A. Sept. 23, 1959 [Sept. 30, 1958], No. 32369/59. Class 51 (1). [Also in Groups XVIII and XXIX] A high and low-level alarm for a steam boiler comprises a container 1 connected by pipes 2 to the water and steam spaces of the boiler and housing a float 3 to which is attached a rod 7. The rod is slotted at 6 to engage a pivot-pin on which hinge two arms 5 the arms being pivotally secured to respective links 9 carried on fixed pivots 10. Pivoted links 12 connect the links 9 to bell-cranks 14 which engage a pin 16 carried by a pusher rod 17 extending upwardly through a steam exhaust pipe 18 and into the lower end of a guide tube 20 held within a tube 23 threaded on to the pipe 18. The upper end of the guide tube is formed as a seating for a conical valve 21 which is normally held closed by a spring 22. The tube 23 extends above the valve and contains a throttling orifice 30 gauged to pass just sufficient steam to sound an alarm whistle 26 which is connected to the upper end of the tube 23 by a pipe 25. In operation, with the float at either the lowest or highest permissible level, respectively shown in full and dotted line on the drawing, the links 9 are drawn inwardly by the arms 5 and the pusher rod 17 is forced upwards to open the valve 21 so that the alarm is given. At normal level, however, the arms 5 open, forcing the links 9 apart to retract the pusher rod and allow the spring 22 to close the valve. To prevent crushing of the float by the boiler pressure a predetermined amount of distilled water 31 is introduced into the float, the water evaporating under working conditions to generate an internal pressure which substantially balances the external pressure on the float. In a modification a second steamfeeding pipe is provided through which steam flows when the " low " level is reached to actuate a valve to cut-off the feed of fuel to the boiler fire-box.