Breathers & Dryers: Transformer Breathers

The first line of defense against lubricant contamination and dielectric loss

The failure or malfunction of many transformers or similar equipment can be directly attributed to the lack of proper control of the level of moisture entering the equipment. It is essential, therefore, that a very low level of humidity is maintained in the air space in the top of the conservator tank to avoid deterioration of the insulating properties of the cooling medium.

Transformer breathers provide an economic and efficient means of controling the level of moisture entering the conservator tank during the change in volume of the cooling medium and/or airspace caused by temperature changes. However, with a new moisture content specification of oil being kept at less than 35 ppm moisture (ASTM D-1533 test method), higher performance desiccant than silica gel is needed. ZEOZORB transformer breathers exceed the ASTM D-1533 testing specifications and out perform silica gel breathers by over 75% at average operating temperatures 77°F.

In addition, testing shows that if the free air volume above the conservator tank oil is kept very dry, below 100 PPM it will actually liberate and pull moisture from within the transforming insulating lubricant, maximizing performance and life. This dynamic is crucial to optimize operations and maintenance procedures.

High Voltage Enclosures – High voltage motor protection desiccators provide protection against corrosion, dampness, and contamination in electrical, high voltage motors and switch gear. These desiccators incorporate a humidity which monitors saturation and indicates when desiccant change or cartridge replacement is required. They are blue when the desiccant is dry and turn pink when the maximum amount of moisture has been adsorbed. For our full range of desiccators, please visit our Breather Desiccators page.

Switchgear SF6 – Drytech Inc. offer a range of desiccant solutions to combat the problems of moisture within SF6 filled high voltage switchgear enclosures. Sulphur hexafluoride (SF6) is used as an insulating gas in transmission and distribution equipment such as switchgear and circuit breakers.

In order to maintain SF6 insulation properties and to reduce the formation of unwanted secondary decomposition products the amount of water vapor in the gas insulated system (GIS) should be kept to a minimum.

If moisture levels are not kept to a minimum then the formation of acidic by-products, such as Hydrogen fluoride, Sulphur dioxide, Sulphur fluoride and thionyl fluoride can be generated. This reaction may yield hydrofluoric acid, which is extremely corrosive and will react with electrical equipment components.

In order to maintain these low levels of moisture, a passive desiccant solution must be included within the cabinet.

Drytech suggests that a large pore molecular sieve (13x) be used as this has the ability to co-adsorb both moisture and arcing by-products. See our range of Desiccant Bags for a solution.

Drytech Transformer breathers reduce the relative humidity levels in a consevator tank to less than 5% RH.

ZEOZORB R Series Transformer Breathers

Model Desiccant Capacity Connection Transformer mVA Transformer Oil Quantity Height
R 1.32 lbs ¾” FNPT < 1.25 mVa 400 gallons/1500 liters 6.2"
R1 2.64 lbs ¾” FNPT 3  mVa 800 gallons/3000 liters 10.2"
R2 4.2 lbs ¾” FNPT 6 mVa 1250 gallons/4750 liters 14.2"

ZEOZORB Small Power Transformer Breathers

Model V W X Y Z
Dim. "B" 14.76” (375mm) 21.85” (555mm) 28.94” (735mm) 19.09” (485mm) 25.39” (645mm)
Dia. "A" 10.03” (255mm) diameter 13.97” (355mm) diameter
Dim. "C" ‘V,W, & X’ uses 3/4” FNPT, ‘Y&Z’ uses 1” FNPT
Transformer Rating 9 mVA 30 mVA 60 mVA 100 mVA 180 mVA
Max Transformer Oil Quantity 11,350 liters 22,700 liters 34,050 liters 45,450 liters 68,150 liters
Desiccant weight 7.2 (10kg) 10.5 (4.75kg) 13.2 (6kg) 17.6 (8kg) 22 (10kg)
Unfilled weight 13.3 (6kg) 17.6 (8kg) 24.25 (11kg) 30.8 (14kg) 39.7 (18kg)



  • Extend the life cycle of your lube oil
  • Minimize component wear, down time and repairs
  • Protects against high humidity, water condensation, pressure variations
  • Maintain ISO cleanliness codes
  • Protects against dielectric loss, mold growth
  • Extend MTBF and reduce O&M costs

Features & Performance

1. Bi-directional Air Flow
  • Air entering the breather is filtered and dried. Air expelled through the breather is filter through an activated carbon filter, prolonging the life of the breather.
2. Rugged construction
  • ZEOZORB transformer breathers are made of robust cast aluminum and UV resistant polycarbonate tube.
3. ZEOLITE adsorbent
  • ZEOLITE adsorbent provides up to 28% by weight adsorption and provides clean dry air less than 100 PPM. ZEOLITE also maintains performance in high temperature environments, unlike Silica Gel.
4. Easy to use and ergonomically friendly
  • All ZEOZORB transformer breathers use a visual sight window to indicate when replacement is necessary. To replace, simply empty the spent breather contents and refill with new desiccant.
5. Protective housings
  • Optional protective stainless steel and expanded metal housings are available for additional protection.
6. Application flexibility
  • Transformer breathers are offered in a variety of NPT/BSP and flanged connections.
7. Color Indication
  • When maximum adsorption is reached, the blue indicating ZEOLITE beads will turn from blue to beige, to indicate that a replacement is required.

How do they work?

Drytech Transformer Breathers operate as your first means of protection againt moisture contamination. Transformer breathers take the approach of filtering atmospheric air BEFORE it enters your equipment, rather than trying to take moisture out AFTER it has been introduced into a system.

Inhale Cycle

  1. Air will enter the base of the breather
  2. As the air is drawn into the breather, the moisture is adsorbed
  3. This dry air will then flow upward and into the tank or reservoir being protected
  4. The very dry air will blanket the free air volume inside the tank and will liberate moisture from within the tank Exhale Cycle
  5. Air will be pushed down through the top of the breather
  6. The air will flow back down through the desiccant and out of the bottom of the breather


Technical & Dimentional

Series ZEOZORB Transformer Breathers
Model ZZ-T-1045 ZZ-T-1320 ZZ-T-1760 ZZ-T-2200
Dim.  “A” 15.75” (400mm) 17.32” (440mm) 22” (560mm) 26.77” (680mm)
Dia.  “B” 8.46” (215mm) diameter
Dim. “C” 4.5” (115mm) 4 hole flange
Transformer Rating 10,000 kVA 15,000 kVA 20,000 kVA 25,000 kVA
Max Transformer Oil Quantity 10,782 liters 13,620 liters 18,159 liters 22,698 liters
Desiccant weight 10.5 (4.75kg) 13.2 (6kg) 17.6 (8kg) 22 (10kg)
Unfilled weight 17.6 (8kg) 24.25 (11kg) 30.8 (14kg) 39.7 (18kg)