Donaldson HLP PN 25 / PN 40 High-Pressure Adsorption Dryer

A heatless adsorption dryer for high-pressure compressed air

The Donaldson HLP is a heatless regenerating high-pressure adsorption dryer supplied as a complete purification package with pre-filter and after-filter. It is offered in two pressure classes: HLP PN 25 (sizes 0040 to 1130) for 17 to 25 bar g and HLP PN 40 (sizes 0050 to 1200) for 26 to 40 bar g. Donaldson specifies compressed air or nitrogen as the medium and a pressure dew point of -40 °C at 100 % load.

Incoming air passes the pre-filter, which removes particles and condensate, then flows into one of two adsorber vessels where the desiccant dries it to the required dew point. The dried air leaves through a non-return valve and an after-filter that retains any desiccant abrasion. While one vessel is in operation the other regenerates: a partial stream of already dried air is expanded through a nozzle to atmospheric pressure, passes over the desiccant bed and is released through a pneumatically operated valve and silencer. Operating status (adsorption, regeneration, pressurising, service, alarm) is shown by LEDs, intermittent operation is standard and the valves are pneumatically controlled seat valves.

Technical specifications

Sizes and flow ratings

Flow is stated at 1 bar abs and 20 °C, for 7 bar system pressure at the compressor intake and 35 °C inlet temperature into the dryer. Correction factors for other pressures and inlet temperatures from 30 to 55 °C are printed in the datasheet.

Connections on the smaller sizes are G 1/4 (HLP PN 25 0040 and PN 40 0050), G 1/2 (PN 25 0080 and 0125, PN 40 0095 and 0155) and G 3/4 on the 0260 and 0310 units. Larger sizes are listed in the datasheet dimension tables.

Selection and documents

Choose the dryer from the corrected volume flow: divide the required flow by the correction factor for your operating pressure and inlet temperature, then pick the first size at or above the result. Donaldson’s worked example for 200 m3/h at 40 °C and 20 bar g selects an HLP 0500 PN 25. Send the flow, operating pressure, inlet temperature and dew point requirement and the size can be confirmed. The attached Donaldson datasheet F119088 carries the full tables. See also the compressor and air treatment category.

How the Donaldson HLP PN 25-40 works

The HLP PN 25-40 dryer has two adsorber vessels filled with desiccant. Wet compressed air first passes the pre-filter, which removes particles and condensate. It then flows through one vessel, where the desiccant takes up moisture and the air leaves at a pressure dew point of minus 40 degrees C. The dry air passes a non-return valve and an after-filter. While one vessel dries, the other regenerates: a small stream of dried air is expanded to atmospheric pressure and carried over the bed, then released through a valve and silencer. The two vessels swap roles on a timer.

Where the Donaldson HLP PN 25-40 is used

• High-pressure compressed air systems
• PET bottle blowing air
• Nitrogen drying
• Instrument and process air
• Pneumatic test and control air

Selection checklist for the Donaldson HLP PN 25-40

• Pressure class: PN 25 (17 to 25 bar g) or PN 40 (26 to 40 bar g)
• Dryer size from the flow rating
• Inlet temperature from 30 to 55 degrees C
• Ambient temperature from 4 to 50 degrees C
• Power supply of 230 V, 50 to 60 Hz
• Condensate drain: hand-operated or electronic
• Dew point-dependent capacity control
• Control air supply and starting valve

Installation, commissioning and maintenance notes for the HLP PN 25-40

Place the dryer on a level floor in a frost-free room. Connect the compressed air to the pre-filter inlet and the dried air from the after-filter outlet. Wire the 230 V supply, which draws about 40 W. Open the air slowly to pressurise the vessels. Check the condensate drain and change the filter elements and desiccant on the interval in the manual.

Requesting a quotation for the Donaldson HLP PN 25-40

Please send the flow, the working pressure, the inlet temperature, the dew point needed and the quantity. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

HLP PN 25-40 sizes

The PN 25 range runs from size 0040 to 1130. The PN 40 range runs from size 0050 to 1200.

HLP PN 25-40 flow rating basis

Flow is stated at 1 bar abs and 20 degrees C, for a 7 bar compressor intake and 35 degrees C inlet. Correction factors for other conditions are in the data sheet.

HLP PN 25-40 pressure equipment

The adsorbers and filters are designed, made and tested to directive 2014/68/EU.

HLP PN 25-40 status display

LEDs show adsorption, regeneration, pressurising, service and alarm. Intermittent operation is standard.

Dryer records for the HLP PN 25-40

Keep the dew point readings, the filter change dates and the desiccant change in the dryer file.

Choosing the right HLP PN 25-40 class

Choose PN 25 or PN 40 from the compressor discharge pressure, and the size from the corrected flow.