Retrofill with FR3® Natural Ester Fluid
- Knowledge Center
- Guides
- Retrofill with FR3® Natural Ester Fluid
Retrofill with FR3® Natural Ester Fluid: Better for Your Facility, the Community, and the Planet
An overview of retrofilling distribution and power transformers with Cargill’s FR3® natural ester fluid — the safety, reliability, load capacity, and environmental benefits, plus what transformer owners should evaluate before they retrofill.
Topic: FR3 Natural Ester | Transformer Retrofill | Asset Life Extension
Provider: SDMyers, Authorized Service Partner of FR3 from Cargill
Download the Guide
Overview: Why More Owners Are Switching to Natural Ester Fluid
Mineral oil has long been the standard transformer oil, but it isn’t the optimal dielectric fluid. Choosing FR3 natural ester fluid for distribution and power transformers offers long-term safety, reliability, and environmental benefits.
As an Authorized Service Partner of FR3 fluids from Cargill, SDMyers is equipped to help owners see up to 10 years of additional life from their transformers through a retrofill process.
This guide gives transformer owners and maintenance teams a clear picture of what FR3 offers, how testing and analytics change (and don’t), which industry standards apply, what to consider before retrofilling, and how the SDMyers retrofill process works from pre-testing to post-testing.
Immediate and Long-Term Benefits of FR3
| Benefit Area | Key Figures |
| Superior fire safety | 0 reported fires in 25+ years |
| 2x mineral oil’s flash and fire points | |
| Improved reliability | 10x higher moisture content by comparison |
| Asset life extension | Up to 50% maximum anticipated asset life extension |
| +10 years of life added to the transformer | |
| Better for the environment | Biodegradation in as few as 10 days |
| Carbon neutral | |
| Increased load capacity | 15% additional loading or load capacity |
Source: Cargill, cargill.com/bioindustrial/dielectric-fluids/fr3-fluid
Key Findings: What Maintenance Technicians Need to Know
Testing and Analytics for FR3
- Testing natural esters is very similar to testing mineral oil. Only a few parameters in laboratory test methods differ — for example, DGA and furan testing — so existing sampling programs and diagnostic habits largely carry over.
- Annual testing is recommended. Just as with mineral oil, regular sampling and analytics reveal critical information about transformer health, identify potential problems early, and help maximize reliable life.
- SDMyers tests more than 22,000 transformers filled with FR3 on a regular basis, and that number rises every year as more owners switch to natural esters.
Equipment Compatibility
- Bushings and Load Tap Changers (LTCs) can operate normally in FR3. Consult the unit manufacturer for safety standards and any specific requirements.
- FR3 is recommended for non-free-breathing transformers. Free-breathing units can be filled with synthetic esters.
- FR3 can be used in transformers of most voltage classes, including high voltage.
The SDMyers Retrofill Process
- Perform electrical pre-testing
- Drain the original mineral oil
- Allow drip after draining
- Perform optional regasketing
- Flush the active part with hot FR3
- Allow drip after flushing
- Remove dregs from the bottom of the transformer
- Fill the transformer with or without a vacuum
- Perform electrical post-testing
Key Findings: What Transformer Owners Need to Know
- Retrofilling can add up to 10 years of life to a transformer, with a maximum anticipated asset life extension of up to 50%, according to Cargill.
- FR3 delivers a stronger safety profile: twice the flash and fire points of mineral oil, with zero reported fires in more than 25 years.
- Additional load capacity of up to 15% is possible with FR3.
- Environmental benefits are built in: FR3 is carbon neutral and biodegrades in as few as 10 days.
- Assess before you retrofill. To ensure return on investment, evaluate every transformer’s existing condition and any technical issues before retrofilling with FR3. Retrofilling is not the right answer for every unit.
- Proven experience matters. SDMyers has retrofilled 100 transformers and used 150,000 gallons of fluid over the past three years, backed by 60+ years of experience in testing, diagnostics, and maintenance.
Retrofills by the Numbers with SDMyers
transformers tested regularly with FR3
gallons used in retrofills, past three years
transformers retrofilled, past three years
years of testing, diagnostics, and maintenance
Standards for Natural Esters
| Topic | IEEE | IEC |
| New unused fluid | ASTM D6871 | IEC 62770 |
| Maintenance limits | IEEE C57.147 | IEC 62975 |
| DGA interpretation | IEEE C57.155 | In process |
| High temperature insulation | IEEE C57.154 | IEC 60076-14 |
| High temperature loading guide | IEEE Std. 1276 | IEC 60076-14 |
| Transportation and commissioning | IEEE C57.93 | WG A2.58 |
| Fire safety | FM LPDS 5-4 / IEEE Std 979 | IEC 61936-1 |
EXPERT INSIGHT
“Although mineral oil has long been the standard transformer oil, it simply isn’t the optimal dielectric fluid.”
SDMyers, Retrofill with FR3®
Bottom Line for Transformer Programs
FR3 natural ester fluid gives owners a practical way to improve fire safety, add load capacity, reduce environmental impact, and extend the life of transformers already in service — without changing the fundamentals of how those transformers are tested and monitored.
The key is fit. Vacuum rating, voltage class, age and condition, and bushing and LTC requirements all shape whether a retrofill makes sense for a given unit. A pre-retrofill condition assessment protects your return on investment, and a structured, standards-supported retrofill process protects the transformer.
Topics covered in the full guide
- Immediate and long-term benefits of FR3 natural ester fluid
- Testing and analytics for natural esters (including DGA and furan differences)
- IEEE and IEC standards for natural esters
- SDMyers retrofill experience by the numbers
- Considerations for owners: vacuum rating, voltage class, age and condition, bushings and LTCs
- The nine-step SDMyers retrofill process
