Compressed Air Dew Point & Pressure Dew Point: Measurement, Sensors, & Nitrogen Applications
Compressed air systems are frequently used across industrial manufacturing processes for cooling, heat generation, equipment maintenance, and power tool operation. During the production of compressed air, an unavoidable by-product is water vapor which condenses onto the air compressor system or attached process components.
While a little moisture within a compressed air system is to be expected, the accumulation of significant condensation can damage sensitive equipment and deteriorate the quality of finished products. In this regard, monitoring the compressed air dew point and pressure dew point is vital to ensuring the working life of your machinery is preserved and your product quality is standardized.
ISO 8573.1 addresses three critical impurities in compressed air: excess moisture, particulates, and oil. This compressed air standard sets forth testing parameters designed to maintain proper purity levels in compressed air.
What is Compressed Air Dew Point (Air Compressor Dew Point)?
The dew point of an air compressor system refers to the temperature at which vaporized water is condensed into its liquid state at the same rate at which it is evaporating. At this temperature, the compressed air is fully saturated and can no longer hold water vapor.
For industrial operators who use compressed air systems for manufacturing, constant dew point monitoring is necessary to prevent instrument damage and minimize process contamination. The dew point in compressed air directly impacts corrosion risk, freeze potential, and overall system reliability.
Is Dew Point Measured in Degrees?
The dew point temperature of compressed air is measured in degrees Fahrenheit or Celsius using a dew point sensor or compressed air dew point meter. For most systems, the dew point temperature of the air is maintained within a controlled range depending on the application. At higher dew point temperatures, the water suspended in air will precipitate and start to collect on compressor components.
If accurately read, dew point sensors and compressed air dew point meters allow operators to implement different methods of water removal and preserve the integrity of their machinery.
Why is Dew Point Important in Compressed Air Applications? (Significance of Dew Point)
Maintaining moisture within certain levels is critical to preserving the function of sensitive industrial equipment. If left unchecked, Moisture precipitated from compressed air at its dew point can trigger corrosion of metallic machinery leading to costly system failures and downtime for maintenance.
Also, unwanted moisture within the compressed air supplied to industrial processes can have undesirable impacts on product quality. Accumulated water vapor can pass impurities including dust and bacteria to sensitive food and drug manufacturing processes rendering their output unsafe for consumption.
The financial implications of moisture damage to air compressor systems make the case for why all operators must strictly monitor water saturation in their air systems. In practical terms, this is the primary reason dew point measurement is required in regulated industrial environments.
Dew Point vs Pressure: Understanding Pressure Dew Point
There is a clear link between the dew point at which compressed air becomes saturated and the pressure at which it is being conducted. For any gas, an increase in pressure is followed by a corresponding increase in its dew point.
Pressure dew point is the temperature at which moisture condenses in compressed or pressurized air at operating pressure. This differs from atmospheric dew point because compressed air holds more moisture at higher pressures.
A series of calculations and conversions are done manually or using software that can accurately predict the dew point of air and help operators put appropriate moisture elimination protocols in place.
How Does Dew Point Differ from Pressure Dew Point?
In practice, the terms “dew point” and “pressure dew point” are frequently used interchangeably. However, this substitute is not accurate.
While the dew point refers to the temperature at which air becomes saturated under atmospheric pressure conditions, the pressure dew point refers to the dew point of gas measured at pressures above normal atmospheric level. Understanding dew point vs pressure is essential when specifying air dryer performance and instrument air requirements.
Dew Point Measurement in Compressed Air: Sensors, Meters & Monitoring
The dew point of compressed air can be accurately measured using a dew point sensor or dew point monitor for compressed air systems. Similar principles of operation apply to most dew point measurement tools regardless of manufacturer.
Outlined below are key factors to consider when attempting to measure the dew point of compressed air.
Instrument Selection
The first step in assessing the dew point is the selection of the right dew point instrument or compressed air dew point meter. Some manufacturers make devices that measure very high dew points while other manufacturers craft sensors optimal for measuring very low pressure dew point levels.
To avoid errors in measurement, operators must purchase the device most suited to their air compression unit and required dew point range.
Understanding Variations in Instrument Pressure Characteristics
Some dew point sensors are suited to measuring moisture saturation at atmospheric pressure, while others more accurately relay pressure dew point readings at higher operating pressures. Again, you must select the right measuring device based on the pressure characteristics of your compressed air system to ensure the most error-free results.
Correct Sensor Installation
Dew point sensor installation kits come with specific instructions on proper installation. Adhering to manufacturer guidelines while fitting a dew point sensor for compressed air will help ensure its optimal functioning and long-term stability.
Dew Point Sensor Working Principle
Most compressed air dew point sensors operate using one of three primary technologies:
- Capacitive polymer sensors, which measure changes in capacitance as moisture content changes.
- Aluminum oxide sensors, commonly used for low dew point measurement in dry air systems.
- Chilled mirror sensors, which determine dew point by cooling a mirror surface until condensation forms.
Dew Point of Compressed Air Chart (Typical Industrial Ranges)
The required dew point for compressed air varies by industry and application. Below is a simplified reference chart of common pressure dew point targets.
| Application | Typical Pressure Dew Point |
| General plant air | +38°F (3°C) |
| Instrument air dew point | -40°F (-40°C) |
| Critical process air | -70°F (-57°C) |
| Ultra-dry systems | -100°F (-73°C) |
Air dryer dew point performance is often specified based on these target ranges. Refrigerated air dryers typically achieve higher dew point temperatures, while desiccant air dryers are used when very low dew point of compressed air levels are required.
Dew Point Meter for Compressed Air: Purchase vs Rental
In some cases, operators may require temporary dew point verification for audits, commissioning, or troubleshooting. A compressed air dew point meter rental can be a cost-effective option for short-term dew point measurement.
For continuous monitoring, installing a permanent dew point monitor for compressed air systems is typically recommended to ensure ongoing compliance and system reliability.
Nitrogen Dew Point vs. Compressed Air Dew Point
Due to its inert nature, nitrogen gas can be used in several industrial processes including equipment flushing procedures. Gaseous nitrogen passed through a system or process will effectively eliminate moisture and oxygen without altering any critical chemical reactions.
The dew point of nitrogen is typically much lower than standard compressed air. The dew point of dry nitrogen gas often reaches approximately -94°F or lower, depending on the nitrogen generation method and purity level.
Understanding nitrogen dew point performance is important when comparing instrument air dew point requirements with nitrogen drying applications.
For cost-efficient nitrogen gas production in the field, consider using an on-site nitrogen generator from NiGen.
What is Dew Point Used for in Industrial Systems?
Dew point is used to determine how much moisture is present in compressed air, instrument air, or nitrogen systems. It helps operators:
- Prevent corrosion and freezing
- Protect pneumatic equipment
- Maintain product quality
- Ensure compliance with ISO standards
- Verify air dryer performance
NiGen is Your One-Stop Shop for Industrial Air Solutions
At NiGen we are committed to providing you with the highest-quality compressed air-drying solutions for use in various industrial applications. If you are looking for effective compressed air generation, industrial air dryer systems, or nitrogen equipment, NiGen is for you.
Contact us online today for more information about industrial air compressor rentals and other products and services we offer.