As we move into Spring or Autumn, now is the best time for your dryer specialist to check and adjust your refrigerant dryers.
Compressed air systems generate a lot of condensate and in most cases this needs to be removed by some form of dryer. Today’s tip specifically covers refrigerant dryers that use cooling to condense the liquid out of the compressed air. Some systems may have desiccant or membrane dryers which work on different principals.
If we assume your refrigerant dryer has been sized, installed, and is functioning correctly, then most people never give it a second glance. As ambient conditions change between each season, so will the dryer’s performance. We recommend that your refrigerant dryer be checked and adjusted at least twice a year. Adjusting the refrigerant circuit for the coming ambient conditions can avoid freeze over issues in the winter months and moisture carry over in the summer months.
About Refrigerant Dryers
Refrigerant dryers typically have two internal heat exchangers:
- The first is the air to air pre cooler where incoming compressed air is cooled by the outgoing compressed air. This drops the incoming compressed air to slightly below ambient conditions and raises the outgoing compressed air to around +5 to +10°c (+41 to +50°F) below the incoming compressed air.
- The second is the refrigerant to air heat exchanger where the compressed is cooled to around +3°C (37°F). Some models use a thermal mass of glycol or similar liquid to cool the compressed air in conjunction with the refrigerant circuit, but the principal is the same.
When this cooling occurs, the moisture in the compressed air condenses into liquid which is primarily made up of water (Fun fact: when the ambient temperature drops below the dew point of the compressed air, the moisture will condense, no mater how ‘dry’ the air is). The water is then drained out of the heat exchanger through a condensate drain, but more on condensate drains in another tip.
The selection and performance of refrigerant dryers is affected by several factors (we’ve included an example table for reference (see below), but each dryer company has their own). These factors are:
- the desired dew point,
- compressed air flow rate,
- compressed air pressure,
- incoming compressed air temperature and
- ambient temperature.
It’s important to note that refrigerant dryers should not be selected for dew points close to or below freezing temperatures, this is because condensate is at risk of freezing and becoming a big block of ice.
Displays on Refrigerant Dryers might not show Dew Point
Many refrigerant dryers have a display on them indicating the temperature of the cooling circuit (see pictures), some refer to this as the dew point, but it is critical to understand this is not a dew point reading unless the dryer is fitted with a dew point sensor, the vast majority are not.
Measure your Dew Point
Moisture in compressed air can cause significant increases in maintenance costs by causing corrosion and component failure as well as directly affecting production performance. Measuring dew point and ambient temperature is the simplest way to monitor dryer performance and detect moisture issues before they can cause a problem.
Compressed Air Alliance can measure your dew point, as well as flow rate, system pressure, system efficiency, consumption and more. Learn more about our Measurement and Monitoring program.
We sell dew point sensors. Find out if our dew point sensors are right for your system.
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