Hydac BDE Breather Dryer with Two-Stage Desiccant

Dry, clean air for oil tanks and gearboxes

The Hydac BDE is a breather dryer. Humid air entering a reservoir leaves water in the oil, where it speeds up additive depletion and oxidation and can cause corrosion and hydrogen embrittlement of components. The BDE removes both particles and moisture from the incoming air.

It has two separate chambers filled with two different desiccants for two-stage drying, and an air filter element for particles above 2 µm. As the desiccant saturates, its colour changes from dark red to light orange, which shows when the cartridge is due for replacement. Two sizes are listed: BDE 400 and BDE 1000.

Technical specifications

Valves, sizing and the order code

An option with four valves in the base keeps the desiccant from absorbing moisture while the system is shut down, because the bypass valves stop air from moving in and out when the tank is idle. Without them, mist or humid air can drain the desiccant’s capacity when the plant is not running. The model code is BDE 400 G 2 W 1 .X /-RV0.003, which means size 400, G thread, 2 µm absolute, no indicator port (W), and a bypass or protection valve with a 0.003 bar rated pressure. A vacuum indicator (UBM) can be specified instead of W, and the flange version can include a filler strainer (ELF).

The replacement cartridge is coded as BDE 400 X 2 W 0 .X, and the whole cartridge is replaced, since the filter element is built into it.

Sizing guidance from the datasheet

Incorrectly sized tank breather filters can put extra strain on a system and reduce the life of the hydraulic filter elements. For gearbox lubrication in wind turbines the datasheet suggests BDE 400 for installations up to 3 MW and BDE 1000 above 3 MW under standard conditions, with larger or doubled arrangements for longer service intervals or very humid climates.

Dryers for hydraulic tanks are matched to maximum suction rate and tank volume as shown in the table above. Tell us the tank volume, the highest suction flow and the climate when you ask for a quotation, so the size can be checked against those values.

For gearbox lubrication in wind turbines, the datasheet gives this sizing table:

How the Hydac BDE breather dryer works

When the oil level in a tank or gearbox falls, or the oil warms and cools, the tank breathes. Air flows in through the breather, and it brings moisture and dust with it. The BDE forces this incoming air through an air filter element and then through two chambers of desiccant. The dust stays in the filter, and the desiccant takes up the water vapour. Only dry, clean air reaches the oil. On the way out the air passes back through the desiccant, which can release some moisture.

Where the BDE is used

• Hydraulic oil tanks
• Gearbox housings
• Lubrication oil reservoirs
• Tanks of mineral oil, bio oil or diesel
• Static venting of larger gear sumps

Selection checklist for the BDE

• Size, BDE 400 or BDE 1000
• Tank size and suction rate
• Hydraulic tank or static venting
• Connection type and thread
• Humidity level on site
• Need for the bypass valve option
• Fluid in the tank
• Ambient temperature range

Installation, commissioning and maintenance notes for the BDE

Fit the breather to the tank connection with a suitable seal, and keep the air inlet clear of splashes and dirt. Never use it on tanks that hold highly flammable liquids such as fuel or solvents. Check the colour of the desiccant at regular intervals. When it turns from dark red to light orange, replace the unit or cartridge. Also change it after a long shutdown if the colour has changed.

Requesting a quotation for the Hydac BDE

Please send the size, the thread, the tank volume and the quantity. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

BDE sizes

Two sizes are listed: the BDE 400 and the BDE 1000.

BDE filter element

A pleated element of resin-impregnated paper holds particles above 2 micrometres. Its dirt retention is 26 g.

BDE drying capacity

At average humidity the BDE 400 dries 25 cubic metres of air and the BDE 1000 dries 42. At high humidity the figures are 15 and 25.

BDE tank size limits

For hydraulic tanks the BDE 400 suits up to 600 litres and the BDE 1000 up to 1000 litres.

BDE housing and seals

The housing is plastic (PA, PC and POM) and the seals are NBR.

BDE temperature range

Operating temperature runs from minus 30 to plus 100 degrees C.

BDE connections

The list includes DIN 24557 flange, G thread, NPT thread and M42 by 2 metric thread.

Breather records for the BDE

Record the fitting date, the desiccant colour at each check and the date of replacement.

Choosing the right BDE size

Choose by tank volume and by the air flow the tank draws in. Use the larger size for bigger tanks or for wet sites.

Documents and quotation

The datasheet (EN 7.407.1.4/06.22) is attached. Related: filter housings and the Hydac RFM return line filter.