Heatless Twin Tower Desiccant Dryers

A desiccant dryer is a type of compressed air dryer that removes moisture from compressed air using a desiccant material—typically silica gel, activated alumina, or molecular sieves. These materials attract and hold water vapor from the air, ensuring the output is extremely dry. You need a desiccant dryer when moisture in compressed air could cause problems or damage, such as: precision manufacturing, pneumatic tools and valves, food processing, pharmaceutical, paint spraying, cold environments. In cold climates, a desiccant dryer is required to prevent moisture in compressed air lines from freezing. They are essential when ultra-dry air is required, typically reaching dew points as low as -40°F to -94°F. 

Dew point is the temperature at which air becomes saturated with moisture, meaning it can no longer hold all the water vapor it contains. When air is cooled to its dew point, water vapor starts to condense into liquid water. On a humid day, the dew point might be 65°F. If the temperature drops to that level overnight, dew forms on surfaces.

In compressed air systems, if the dew point is higher than pipe or ambient temperatures, condensation will form inside the system, leading to corrosion or contamination.

In compressed air systems, moisture is your enemy — it causes:

•  Corrosion in pipes and tools
• Malfunction of pneumatic equipment
• Product contamination (especially in food, pharma, electronics)

The HL range utilizes a two-tower system, where one tower dries the compressed air, and the other undergoes regeneration using a portion of the dried air. This heatless regeneration process ensures continuous operation without the need for external heat sources. The system employs strategically positioned valves to switch between drying and regeneration cycles.

The HL dryers provide a standard pressure dew point (PDP) of -40°F, which corresponds to approximately 0.1% relative humidity at room temperature—suitable for most industrial applications. For more demanding environments, an optional -94°F PDP is available, delivering ultra-dry air that is virtually free of moisture. This lower dew point is crucial for critical applications where even minute traces of moisture can lead to problems such as corrosion, bacterial growth, or product contamination. Typical industries requiring a -94°F PDP include pharmaceutical manufacturing, semiconductor manufacturing, aerospace, and cleanroom laboratories. However, unless your application demands explicitly ultra-low humidity, a -40°F dew point is a more cost-effective and energy-efficient choice.

Moisture is adsorbed by the desiccant (activated alumina) as compressed air flows through the drying tower. The regeneration tower then uses a small amount of the dry air to remove moisture from the saturated desiccant.

1.    Determine required air flow (measured in standard cubic feet per minute, scfm)

2.    Know your inlet conditions, as your dryer performance depends on the actual conditions of the air entering the dryer.

• Inlet Temperature (°F)
• Inlet Pressure (psig)
• Ambient Temperature (°F) – where the dryer is located

3.     Select the required pressure dew point (PDP).

• -40°F: general industrial use (standard)
• -94°F: critical applications (pharma, electronics)

Typically, 15–20% of the dried air is used for regeneration. This is a trade-off for not using heat during the regeneration phase.

• Low dew point option (-94°F).
• Various bypass options
• Electrical protection upgrades (NEMA 7, Z-purge).
• Dew point monitors (integral or portable).
•  Stainless steel control tubing.
• Low ambient temperature protection
• Visual moisture indicators.
•  Run time hour meters.
• Additional pressure and temperature gauges

HL series desiccant dryers are equipped with corrosion-resistant NEMA 4X electrical enclosures as standard, making them suitable for outdoor and harsh environments. However, additional modifications—such as a low ambient package and stainless steel control lines—are often recommended to ensure optimal performance and durability in extreme conditions.

Yes, all HL desiccant dryers undergo comprehensive quality assurance procedures, including complete functional testing, pressure and leak testing, and verification of the control system before shipment. This ensures each unit meets performance specifications and is ready for reliable operation upon installation.

• Desiccant replacement (every 3–5 years, depending on use)
• Filter (control air, inlet and outlet) & Muffler annual replacement
• Valve inspection
• Checking for desiccant dusting or channeling

The cost varies depending on the flow rate and pressure dew point (PDP) required for your compressed air system.

Period: 18 months from date of shipment from the factory or 12 months from date of installation/start up, whichever occurs first • Coverage: 100% parts and labor per defined service time allowances • Extended coverage: Inlet & purge exhaust valves: 5 years from date of shipment (parts only)