Why is there water in the main pipe, with an instrument air dew point of -36.6 and a pressure of 0.7 MPa?

There shouldn’t be any water at the atmospheric pressure dew point either; it must have accumulated in the pipes earlier. Or the analysis was incorrect

The atmospheric pressure dew point of -36.6, when converted to 0.7 MPa, should be around -10°C

How did you get your dew point of -36.6°C? Measure by using a handheld dew point meter at a certain discharge point? That is extremely inaccurate; the most accurate way to determine the dew point is through online measurement. The dew point values claimed by dryer manufacturers are generally unattainable. Firstly, they never take into account the possibility that the dryer might be operated beyond its capacity, as if all the inlet and outlet pipes are opened, the flow rate will definitely be much higher than the rated value. Generally, no flow meter is installed at the outlet, and if one is used, it is usually a glass rotor flow meter, which does not provide any compensation and thus gives inaccurate readings. In any case, water contamination in the instrument air is usually caused by the dryer operating at too high a capacity. Additionally, over time, the alumina components can become defective, for example due to oil contamination

At 0.7 MPa and a dew point of -36.6°C, the dew point at normal pressure is -17.6°C. As for normal pressure versus pressurized conditions, it is sufficient to consider the ambient temperature at that time; of course, the heat transfer efficiency of the material also needs to be taken into account. If the factor of external temperatures being below the dew point is excluded, it is very likely that there was already water accumulation inside the pipe prior to operation. From a monitoring perspective, single sampling-based dew point measurements have little significance; long-term continuous monitoring is necessary, with portable measurements serving only as an auxiliary measure. Fault monitoring is similar to seeking medical treatment in a hospital – could it be that there are issues with the tests themselves? What instruments are you using, and could you provide more detailed information? If possible, you can send more detailed information to this email address of mine: yh@tyrande-sc.com

It’s normal to have water in the car right after driving; it’s impossible for there to be absolutely no water. Also, if water appears suddenly during normal operation, measure it at the dryer outlet or the main air separation pipeline outlet to determine whether it is water introduced by the user or resulting from inadequate water removal by the machine itself.