GB737936A - Steam trap - Google Patents

Abstract

737,936. Thermally actuated valves. VELAN, A. K. Feb. 18, 1953, No. 4497/53. Class 135. [Also in Group XIII] A bimetal assembly 45, 46, 47 responsive to fluid pressure and temperature is mounted in a chamber 12 of a steam trap between inlet and discharge passages 14, 16 to engage and actuate a valve having, for closing on a seat 24, a bulbous head 32 on a stem 30 pivotally connected to the bimetal assembly with a loose fit, so as to be capable of radial movement relative to the valve seat axis and also capable of longitudinal movement and of rotation about its own axis. The bimetal elements 45-47 are spaced by shims 90 and secured by nuts 49 to a base 44. The inner end of the valve stem 30 carries an adjusting nut and an adjacent locking nut 33 next to an enlarged portion 31 which is a sliding fit in a hole 53 through a chamfered rocker 52 pivoted in a yoke 50 secured to the first bimetal 45. The adjusting nut provides means for setting the valve but, for running adjustment, a bifurcated wedge 70 can be raised or lowered between the nut and the rocker 52 by screwing an external cap 71 up or down so that, owing to the loose mounting of the valve stem 30, 31, the distance of the valve 32 from its seat 24 can be altered. The stem 30 passes freely through notches in the tops of the bimetals. In operation, upon heating, the tops of the bimetals 45-47 bend towards the inlet 14 to tend to close the valve 32 on to its seat, the bimetal 45 having first effect at low pressures and temperatures since it is secured to the mounting of the valve stem. As the pressure and temperature of the steam rise, the remaining bimetals 46, 47 bow successively a sufficient amount to contact their neighbour and add their power to hold the valve 32 against steam pressure. Accumulation of condensate cools and straightens the bimetals, so that fluid pressure on the valve 32 moves it to the open position and the condensate flows into the return line. The bimetal assembly is arranged so that its deflection characteristic follows that of the saturated steam curve. In practice, the bimetals 46-47 each comprise a number of bimetallic plates. Since the valve stem 30 is free to move axially until either the valve 32 is seated or the adjusting nut contacts the wedge 70, back pressure from the return line, in an outlet chamber 20, will move the valve 32 to closure so that it acts as a check valve, or, when starting from cold, air will be vented by its pressure moving the valve to an open position. A bimetal element thermometer 112 is screwed into the chamber 20. An observation glass 102 and a cylindrical strainer 124 are included in the casing.