Over-/ under-pressure valve ÜU TT

The valve features an immersion cups and two sealing fluid chambers, one for over pressure and one for under pressure. The response pressures for over-pressure and under-pressure can be set independently of each other. The response pressures are determined via the weight of the respective immersion cup. 

The maximum filling level of the sealing fluid is determined by the height of the internal chamber standpipe. Additional water which has accumulated from condensation or rainwater runs off outside automatically. 

For the gas, escaping at over pressure a flange is provided, to which a discharge pipe (optional) is connected.

Upon actuation of the underpressure valve, external air flows through air intake opening into the gas line. 

The filling level of the overpressure cup (above) can be controlled via an immersion pipe. Filling level of the underpressure cup (below) can be controlled at the inspection glass. 

At the upper gas inlet, a ½ "connection is to be found e.g. for cleaning (rinsing), topping up, for sampling or to connect a pressure gauge.

Response to over-pressure 

With increasing pressure on the gas side, the pressure cup is raised (above) and after emersion from the sealing liquid, the gas can flow through and escape through the blow-off pipe. The vacuum cup remains closed.

Response to under-pressure 

Conversely at under-pressure, the vacuum cup is raised (below) and after emersion from the barrier fluid, air can flow into the control valve and into the gas line. The pressure cup remains closed.

Heat insulation

The over-,under-pressure valve is thermally insulated with a rubber flex insulation. The insulation is resistant to moisture, closed and flame retardant. The thermal insulation is covered with a protective cover made of stainless steel sheet.


We offer three different sizes for the over-, under-pressure OP TT. These depend on the respective flow amounts:

  • ÜU TT 150 for gas amounts up to 150 m3/h at 3 mbar pressure response

  • ÜU TT 200 for gas amounts up to 220 m3/h at 3 mbar pressure response

  • ÜU TT 273 and OP TT 300 for gas amounts up to 600 m3/h at 3 mbar pressure response