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OFAF Transformer Coolers

OFAF transformer coolers for extreme conditions

Our oil forced/air forced (OFAF) coolers help control the temperature of insulating oil. They are used in large transformers and other large, high voltage equipment across the power generation, transmission and distribution industries. We typically supply to transformer manufacturers and maintenance companies. Our OFAF coolers are customised to meet specific operating and environmental requirements.

Key benefits of OFAF coolers

  • Improved performance – Effective cooling helps transformers operate at peak efficiency. While ensuring long life and reliability, they also require less maintenance. Our highly efficient fin block and fan design ensures low sound levels and energy consumption.OFAF Transformer cooler manufactured by Sterling Thermal Technology for JST Transformateurs
  • Rugged and robust – We design our OFAF transformer coolers to withstand vibration shock, seismic forces and thermal movement. Aluminium alloys are used as the standard for the tube, fin and tubeplate to minimise corrosion. We provide custom options as required. Components supporting the fans and cooler elements are protected to C3 as standard, increased to C5-M(H) when conditions dictate.
  • Flexible – The modular construction of our OFAF cooler range means the products fit all oil filled transformers. The highly configurable design can also meet all thermal requirements. Different materials, finishes and coatings are used to suit the most stringent operating conditions and to offer long service life.

For this challenging project (Ghazlan II, Saudi Arabia), the biggest transformer we have ever developed, we needed to partner with a reliable manufacturer that could supply truly robust transformer oil coolers. Sterling understood our challenges and delivered everything we asked for – transformer oil coolers that fully satisfied our specifications.”

Jean-Claude Brantis, Sourcing and Supply Chain Leader, JST transformateurs

What is OFAF?

OFAF stands for oil forced/air forced. It describes how an oil type transformer is cooled by forced movement of both air and oil to aid in heat dissipation.

It’s a compact, highly effective cooling method for a range of equipment.

How oil forced/air forced coolers work

Our OFAF transformer coolers operate in ambient temperatures, from -40°C to +50°C. Optional -45°C and +60°C limits are available to order.transformer oil coolers manufactured by Sterling Thermal Technology to keep a colossal power plant cool in desert conditions

The cooling element is made from materials suitable for the local environment and designed to ensure high levels of heat transfer. It is housed within a robust, long-lasting frame for protection against vibration and thermal shock. We work with you to design an OFAF transformer cooler that suits your requirements.

The coolers can be custom designed and manufactured in lengths of 1 to 4 fan bays. Typical configurations include 1, 3 or 5 pass arrangements, in a depth of 4 to 8 rows. A wide range of fans and motors are available to meet local electrical requirements, specified noise levels and ingress protection.

Fan construction is an external motor rotor with die-cast aluminium low noise blades, balanced to G6.3 standards or better as required. The fan housing is a robust composite and the discharge grill is electrostatically powder coated. All fan mountings are stainless steel. The ingress protection is IP54, with optional IP55, and the bearing life is expected to be more than 30,000 hours.

The standard OFAF cooler is produced without cabling

Electrical options include:

  • Wiring of fan motors and pump to suit equipment layout
  • Electrical safety switches/isolators for easy isolation of fan motors during maintenance and replacement
  • Speed and sequence controls

Additional options and accessories include: 

  • Angled fans for efficient evacuation of hot air in confined spaces
  • Hinged/lift-off fans for easy coil cleaning and replacement
  • An inlet grid to prevent large particulates such as vegetation choking the element inlet face
  • Oil circulation pumps
  • Enhanced paint finishes
  • Mating flanges and gaskets
  • Customised packing for shipment

Transformer Oil Cooler with 2 x fan assemblies & oil circulation pump, manufactured by Sterling Thermal TechnologyWe design compact and low weight OFAF transformer coolers to ensure fast, easy implementation. We provide fully factory-assembled units with a wide range of mounting choices. All coolers are thoroughly tested to check vibration levels, electrical continuity and pressure. They are designed and manufactured as per our quality management system BS EN ISO 9001:2015.

OFAF transformer case study

Screen shot of the case study with JST Transformateurs about the OFAF designed and manufactured by Sterling Thermal TechnologyWe helped JST transformateurs to keep a colossal power plant cool in desert conditions using our OFAF transformer coolers. Read the full case study.

If you need another type of heat exchanger, visit our products and services page or contact us. Our range includes air to air coolers, CACW, lube oil coolers, hydrogen coolers and more.


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