Non-condensable gas tolerant condensing chamber

A liquid level instrumentation measurement system for measuring the level of liquid under high pressure in a pressure vessel containing liquid and vapor with non-condensable gases and having a lower tap connected to the pressure vessel at a point below the lowest liquid level to be measured;

• an upper tap connected to the pressure vessel at a point above the highest liquid level to be measured;
• a reference leg outside the pressure vessel extending substantially from the level of the lower tap to a point above the upper tap;
• a condensing chamber at the upper end of the reference leg defining a vapor space in which vapor condenses to keep the reference leg filled with liquid;
• a vapor inlet extending between the upper tap and a vapor entrance in the condensing chamber through which vapor passes from the pressure vessel to the condensing chamber;
• a variable leg connected to the lower tap on one end;
• and a differential pressure detector connected to the variable leg on its end opposite the lower tap and to the lower end of the reference leg for generating a signal proportional to the level of liquid in the pressure vessel;
• the improvement comprising:
• a vent outlet disposed in the condensing chamber opposite the vapor entrance;
• and
• a vent leg disposed between said vent outlet in the condensing chamber and the variable leg, said vent leg removing the non-condensable gases from the vapor space of the condensing chamber and having:
• (a) a sloping portion slanting continuously downward and away from said vent outlet, and
• (b) a vertical portion extending between said sloping portion and said variable leg.