Donaldson HRS+ 0375-2750 Zero-Purge Adsorption Dryer

A heat-regenerated dryer that uses no compressed air for regeneration

The Donaldson Ultradryer HRS+ 0375-2750 dries compressed air and nitrogen up to 10 bar(g) with a pressure dew point of -40 C at 7 bar(g) or lower. Its regeneration is zero-purge: the saturated desiccant is heated with ambient air that a side-channel blower draws through an electric heater, and cooled by sucking ambient air through the bed at partial vacuum, so no compressed air is lost to regeneration.

Ten flanged steel dryers cover 375 to 2,750 m3/h. The Ultraconomy dew point control keeps the desiccant in service until it is used up, and the Siemens S7-1215C controller with a KTP700 touch panel runs the six-hour cycle and shows dew point, alarms and service messages.

Technical specifications

Sizes, connections and power

• 0375: Rated flow m3/h 375; Port DN 50; Power kW 7.8; Pressure loss mbar 110
• 0650: Rated flow m3/h 650; Port DN 50; Power kW 11.5; Pressure loss mbar 120
• 1000: Rated flow m3/h 1,000; Port DN 80; Power kW 14.5; Pressure loss mbar 110
• 1650: Rated flow m3/h 1,650; Port DN 80; Power kW 24.0; Pressure loss mbar 170
• 2250: Rated flow m3/h 2,250; Port DN 100; Power kW 32.5; Pressure loss mbar 140
• 2750: Rated flow m3/h 2,750; Port DN 100; Power kW 38.0; Pressure loss mbar 180

Sizes 0375 to 0850 have the connections on the front, sizes 1000 to 2750 on the back of the dryer.

Options for energy and data

Standard equipment includes 230 V AC supply for up to four condensate drains, four drain alarm inputs plus four free alarm inputs, valve position control and a thermostat-controlled fan for the control box. The sheet lists options such as the ENERSAVE desiccant concept (10 to 14 percent lower average power), vessel and pipework insulation, a Weekend STOP mode, differential pressure and flow monitoring, energy monitoring, Modbus TCP/IP, Modbus RTU or Profibus communication, an MMC backup card and seaworthy packing.

Choose HRS+ when plant air is available at 40 C or less and the standard -40 C dew point is enough. Where ambient conditions are hot and humid, or a -70 C dew point is needed, the HRS-L+ and HRE+ dryers use other cooling concepts.

Why zero-purge regeneration matters for compressed air costs

Compressed air is one of the most expensive utilities in an industrial plant, because a large share of the electrical energy used by a compressor is lost as heat. In a conventional heatless adsorption dryer, part of the dried air is continuously released to regenerate the desiccant, which means the compressor must produce more air than the plant actually uses. The HRS+ avoids this by heating and cooling the desiccant with ambient air moved by its own blower, so all the air the compressor produces is available to the process. For plants that run compressors for long hours, this difference in delivered air is often the main reason to consider a heat-regenerated design, alongside the Ultraconomy dew point control that extends each adsorption phase while the desiccant still has capacity.

Applications for a -40 C pressure dew point

A pressure dew point at this level keeps moisture from condensing in distribution piping and at points of use, even when lines run through cooler areas of a building. Typical users include instrument air systems in process plants, pneumatic control and actuation, painting and coating lines, food and beverage packaging, pharmaceutical utilities and nitrogen systems where dry gas is needed to protect products or equipment. Dry air reduces corrosion inside steel pipework and limits the risk of moisture affecting valves, cylinders and instruments downstream.

Sizing and integration with the compressor station

Selecting a size starts with the actual flow the dryer must handle and the conditions at its inlet, not only the compressor nameplate. The nominal flows in the table apply at the stated reference pressure and inlet temperature, so a dryer operating at a lower pressure or a higher inlet temperature needs to be reviewed with the real operating conditions in mind before a size is fixed. Allowing some margin for future growth in air demand is also sensible, since replacing a dryer later is more disruptive than selecting a suitable size at the start. The electrical supply for the heater and blower must be planned with the compressor house power distribution, and the location of the connections, front or rear depending on size, affects the piping layout. The PLC and touch panel can pass status and alarms to a plant control system through the communication options listed, and the drain alarm inputs allow condensate drains around the compressor station to be monitored from one point.

Operating in Oman and GCC conditions

The HRS+ is designed for indoor installation with ambient and inlet air at or below the stated maximum, and its regeneration uses ambient air. In Oman and much of the GCC, compressor rooms can become very hot and coastal sites can be humid for long periods, which affects both inlet temperature and the moisture in the regeneration air. For these sites the compressor room ventilation and the expected summer inlet temperature should be reviewed before choosing between the HRS+ and the HRS-L+ or HRE+ dryers mentioned above. Vessel and pipework insulation from the option list can also be considered where heat losses or surface temperatures are a concern.

Documents and quotation

For a written offer on HRS+ 0375-2750, use the form. the flow, inlet temperature, ambient conditions and power supply must be confirmed against the attached Donaldson Ultradryer HRS+ 0375-2750 data sheet (F119011, 11/2025) beforehand. Explore Compressors.