What’s Fr3 Fluid?

March 6, 2015

FR3 is a natural ester fluid that’s a derivative of vegetable oils. The eco-friendly fluid, designated as ultimately biodegradable by the EPA, maintains dielectric strength at low temperatures. Developed as a non-toxic alternative with 98.5% biodegradable content, it’s free of petroleum, halogens, sulfurs and silicones.

Reason for Development

Transformers positioned indoors, underground and in close proximity to other buildings and equipment have the potential of a high flash point of 360°C and 330°C, respectively. FR3 fluid is FM Global Approved and classified by Underwriters Laboratories as a less-flammable dielectric liquid.

FR3 versus Mineral Oil

This derivative of vegetable oils can draw moisture of the insulating paper and keep it continuously dry throughout aging. Because the acids formed in the oil are non-corrosive, proper breakdown voltage in the water content is maintained up to 430 ppm.

Additionally, paper quality is increased and load-ability is enhanced up to 20%. Other benefits include slowed asset replacement time, reduced routine maintenance, and extended life of Kraft Paper by 5.3x because of the ability to handle higher temperatures, and an increase in the allowable Hottest Spot Temp by 15°C. Lower environmental cost of spills and a reduction in fire risk mitigation allow simplified containment.

Retrofitting with FR3 is compatible with conventional mineral oil and high temperature hydrocarbon fluids (R – Temp fluid). This is not recommended for units previously filled with silicone. For a retrofit, it’s critical to limit the air and moisture exposure as much as possible. While most moisture removal methods are acceptable, hot air drying is not recommended. All units must be sealed with a nitrogen blanket to prevent fresh air contact and to ensure long-term stability of the natural ester fluid.

Positive Properties of FR3

  • High fire/Flash points
  • Keeps insulating paper dry
  • Doesn’t create corrosive byproducts when exposed to water
  • Low carbon generation as compared to mineral oil
  • Allows smaller transformer designs with lower material costs
  • Increases insulation life and overall life of transformer


FR3 and Transformers

FR3 Transformers, also known as PEAK transformers, can overload transformers by 10% during peak loading conditions. Because PEAK transformers have the capacity to load continuously at higher temperature and varying loads without causing damage to the transformation, there is better overall system reliability. In addition, PEAK transformers are typically smaller and lighter.

FR3 at Solomon Corp.

At Solomon, FR3 is sold in a variety of sizes from 55 gallon drum, 300 gallon totes and in bulk tanker loads. Because of our volume, Solomon purchases FR3 per job in totes. This method reduces the need to construct and maintain a separate oil tank and plumbing system and it also elements any storage issues, such as temperature.




S900-20-2FR3fluidretrofillguide-Sept2006CPS_001 (PDF)

Alan Sbravati Cargill Adopting Natural Esters (PDF)