Panametrics DewPro MMR30, Installation & Operation Manual

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Chapter 2. Installation Guidelines
6 DewPro® MMR30 Installation & Operation Manual
2.2 Method I - Orifice at Outlet
Figure 5: DewPro Installation with Orifice at the Outlet
2.2.1 Pressure Dewpoint
Refrigeration air dryers producing general instrument air are typically specified with a pressure dewpoint rating. The
majority of dryers operate in a dewpoint range b2°C to +10°C (+35°F to +50°F). A pressure of 7 to 8 bar

(= 100 psig) is very common.
2.2.2 Air Flow
The DewPro is designed to measure the pressure dew point. By restricting the flow at the outlet of the integral bypass
with an orifice, the sensor monitors the dewpoint at process pressure. The bleed off air to the atmosphere at 7 to 8
bar (100 psig), is approximately 70 cc/min. (=4 l/h or =0.14 cfh). For smaller sized dryers of 3m
3
/min.(=100 cfm) the air
loss is only 0.002% of the air production and is negligible.
Despite the very low flow rate through the bypass as shown in Figure 2-1 on the previous page, the air sample in the
DewPro bypass chamber is refreshed every second due to the small volume design. As a result, the sensor sees
changes in moisture instantaneously.
Due to the low flow rate, the flow velocity is also very low at <0.01 m/sec. (=34m/h).The low flow velocity prevents the
inlet filter from clogging, since there is not enough kinetic energy to push dust particles into the filter.