InsulMax® Extends Critical Transformer Life by 3x

This case study documents 10 years of field data across four mission-critical power transformers, validating InsulMax® as a proven strategy for moisture control, oxidation management, and long-term asset life extension.

Challenge: Aging Assets Need More Than Acceptable

The owners of four large, mission-critical power transformers — two generator step-up units (GSUs) and two auxiliary transformers — were managing assets that ranged from 30 to 50 years old at the start of the study period. All four units were part of a prominent power-generating site, and all four met the liquid quality thresholds set out in IEEE C57.106, the industry standard guide for acceptance and maintenance of insulating mineral oil. By conventional measures, the oil quality was acceptable.

Acceptable, however, was not the objective. GSUs are known to operate at elevated temperatures, making them especially susceptible to oxidation, moisture generation, and combustible gas production over time. For assets of this criticality and age, the owners recognized that meeting minimum thresholds offered no margin — and no visibility into how those metrics would trend over the remaining service life of the units. The goal was not compliance with a standard. It was the best achievable protection for the full remaining life of assets that could not be easily or quickly replaced. Most large power transformer manufacturers are currently quoting delivery times of one to two years, making unplanned failure of a critical unit an operationally untenable outcome.

The core challenge in long-term transformer asset management is that the two primary drivers of insulation aging — moisture and oxidation — are progressive and compounding. Industry standards confirm that when moisture content in the insulation doubles, service life is cut in half. Oxidation byproducts accumulate in the cellulose insulation paper over time, accelerating degradation in ways that cannot be reversed without a costly and disruptive rewind. Oil can be reclaimed; paper insulation cannot be restored. The owners needed a continuous, always-on intervention — not a periodic service — to keep these aging mechanisms in check across the full remaining operating life of each unit.

Solution: InsulMax Permanently Installed on Four Units

SDMyers recommended and installed InsulMax permanently on each of the four units. Unlike periodic oil sampling or scheduled service intervals, InsulMax is an online passive system that operates continuously — 24 hours a day, 365 days a year — addressing the conditions that drive insulation aging as they occur rather than after the fact. Annual site inspections were conducted throughout the study period to generate a longitudinal dataset against which the system’s performance could be objectively evaluated.

What InsulMax Controls and Why It Matters

InsulMax performs four distinct functions, each targeting a specific mechanism of transformer aging or failure:

• Moisture control — Maintains moisture at the lowest measurable levels, well under IEEE limits in both parts per million and percent relative saturation, keeping insulation below the 0.5% moisture-by-dry-weight threshold prescribed by industry standards. When moisture doubles in the insulation, service life is cut in half — continuous moisture suppression is the single highest-leverage intervention available for life extension.
• Acid and oxidation byproduct removal — Filters acidic oxidation byproducts as they form in the mineral oil, preventing their accumulation in the insulation paper where they drive irreversible degradation. Even in sealed or conservator-type preservation systems where oxygen ingress is minimized, heat and trace moisture are sufficient to sustain low-level oxidation over time.
• Particle filtration — Removes particles down to the 2–5 micron level, maintaining very high dielectric strength in the oil in conjunction with low moisture levels.
• Hydrogen gas monitoring — Continuously monitors hydrogen as a primary indicator gas for developing faults, providing early detection capability between annual dissolved gas analysis sampling intervals.

The technology is rooted in SDMyers’ field experience with nearly 1,000 DryMax® installations — an online passive dryer supported by IEEE C57.140 and IEEE C57.162 — in which oil quality metrics beyond moisture also showed measurable improvement following installation. InsulMax extended that foundation into a permanently installed, multi-function system with a U.S. patent and remote cellular monitoring capability.

Annual Testing Protocol and Parameters Monitored

Each unit was assessed annually using a standardized oil testing regimen measuring the following parameters in accordance with ASTM standards:

• Acid Number — ASTM D974; primary indicator of oxidative degradation and acid accumulation in the oil
• Interfacial Tension (IFT) — ASTM D971; sensitive to the presence of polar oxidation contaminants and aging byproducts in the oil
• Liquid Power Factor — ASTM D924; measures dielectric losses in the oil; increases with contamination, moisture, and oxidation
• Dielectric Strength — ASTM D1816; measures the oil’s ability to withstand electrical stress without breakdown; degrades with moisture and particle contamination
• Hydrogen Content — ASTM D3612C; monitors for developing faults between DGA sampling events; hydrogen is the earliest and most sensitive indicator gas for a range of internal fault conditions

This five-parameter annual regimen provided a consistent, standards-based record of oil condition across all four units over the full 10-year study period.

Results: Every Aging Metric Held or Improved Over 10 Years

After a decade of continuous operation, the field data produced a clear and consistent finding: every aging-related oil quality metric across all four units either held steady or decreased from its already-acceptable starting point. No unit showed deterioration in any of the five monitored parameters over the study period.

Hydrogen levels — the most sensitive early-warning indicator for developing internal faults — remained in single digits across all units throughout the 10 years of monitoring, with no evidence of a hydrogen-generating fault in any of the four transformers. For GSUs operating at elevated temperatures, where oxidation risk and thermal stress are highest, maintaining single-digit hydrogen readings over a full decade is a meaningful performance benchmark.

The significance of this outcome extends beyond the individual data points. These were not new units operating well within comfortable margins. They were 30- to 50-year-old assets, already approaching or past the typical design life expectations for their class, operating under real-world load and thermal conditions. The fact that aging metrics did not simply plateau — but in several cases continued to show slight improvement from already-acceptable baselines — validates the core premise of the InsulMax® program: that continuous, active management of moisture and oxidation can arrest and partially reverse the aging trajectory of insulation oil in operating transformers.

The performance record across 950+ DryMax and InsulMax installations, involving more than 5 billion gallons of processed mineral oil, is consistent with the findings from these four case study units. The 10-year longitudinal dataset presented here provides the most rigorous field validation available for the technology under sustained, mission-critical operating conditions.

Economics: Low Cost of Ownership, High Asset Protection

The economic case for InsulMax is grounded in the same 10-year field dataset. Across all four units over more than 40 combined operating years, the InsulMax filtering columns required just six total exchanges — approximately one exchange per unit per decade. Over that same period, the system processed more than 32 million gallons of mineral oil. Each column exchange uses patented green filtration technology; the media is recycled and reused, producing zero waste.

When total cost of ownership — purchase, installation, and maintenance — is amortized across a 50-year asset life, the per-unit cost can run as low as $300 per month. For context:

• Asset value protected — Large critical power transformers can carry valuations of $2 million or more; at $300 per month, InsulMax represents less than 0.2% of asset value annually.
• Replacement lead times — With most large power transformer manufacturers currently quoting one- to two-year delivery windows, the cost of an unplanned failure is not limited to the asset replacement cost; it includes the full operational, contractual, and reputational consequences of extended unplanned outage on a critical unit.
• Failure cost comparison — A single transformer failure event — including emergency response, oil containment, short-term load management, expedited procurement, and installation — routinely exceeds the total lifetime cost of an InsulMax® installation by a substantial margin.

The filtering column exchange cadence documented in this study — six exchanges across four units over 40+ years — also confirms that InsulMax’s mechanical reliability matches its oil quality performance. The system’s sealless, magnetically coupled pump has a single moving part, is built to outdoor substation-grade construction standards, and operates on a low-amperage 110V single-phase service. Maintenance demand is minimal, and remote cellular monitoring of operating data — including moisture in and out, temperature, percent relative saturation, hydrogen level, pump pressure, and run hours — allows SDMyers engineers to track performance and anticipate column exchange needs without requiring additional site visits.

Deployment Scenarios: Three Ways to Apply InsulMax

InsulMax is designed for flexibility across the transformer lifecycle. Three deployment scenarios cover the full range of asset conditions in which the system delivers value:

• Remediated unit — For transformers that have progressed along the oxidation curve, a general service rendering — including regasketing, electrical testing, oil reclamation, and corrective maintenance — is completed first to restore acceptable oil quality. InsulMax is then permanently installed to maintain those restored conditions going forward and prevent re-accumulation of aging byproducts.
• Aging unit in acceptable condition — This is the scenario documented in this case study. Older units meeting acceptable oil quality standards, but without significant margin, have InsulMax permanently installed to stabilize existing metrics and maintain those qualities throughout the remaining asset life. The 10-year data confirms this approach produces measurable, sustained results.
• New unit at commissioning — Installing InsulMax at commissioning is the highest-leverage deployment scenario. Preventing moisture and oxidation from establishing a foothold from day one maximizes the compounding benefit of continuous protection and produces the best-case life extension trajectory over the full asset life.

For any of the three scenarios, InsulMax operates alongside — not in place of — a comprehensive maintenance program. Electrical testing per NFPA 70B guidance (recommended every five years), tap changer inspection and maintenance, gasket assessment for aging units, and periodic DGA remain important complementary practices. InsulMax addresses the oil and insulation aging mechanisms continuously; these additional practices address the broader range of fault modes and mechanical conditions that fall outside the scope of oil quality management.

Summary: A Validated Path to Transformer Life Extension

• The core aging problem is moisture and oxidation — when moisture in the insulation doubles, service life is cut in half; oxidation byproducts accumulate irreversibly in the cellulose paper; both are controllable with the right continuous intervention.
• InsulMax performs four functions simultaneously — moisture control, acid and oxidation byproduct removal, particle filtration to the 2–5 micron level, and continuous hydrogen monitoring for early fault detection.
• 10 years of field data across four critical units confirm the technology works — every aging-related oil quality metric held steady or improved from already-acceptable baselines across 30- to 50-year-old GSUs and auxiliary transformers operating under real-world conditions.
• Hydrogen levels remained in single digits throughout the study — no hydrogen-generating fault was detected in any unit across the full monitoring period, including units operating at elevated temperatures where oxidation risk is highest.
• Total cost of ownership can run as low as $300 per month per unit — less than 0.2% of asset value annually for a transformer valued at $2 million or more.
• Six filter column exchanges across four units over 40+ operating years — confirms mechanical reliability consistent with the oil quality performance record; 32 million gallons of mineral oil processed with minimal maintenance demand.
• Three deployment scenarios accommodate the full range of asset conditions — remediated units, aging units in acceptable condition, and new units at commissioning; installing at commissioning delivers the maximum compounding life extension benefit.
• InsulMax complements but does not replace a full maintenance program — electrical testing, tap changer maintenance, gasket inspection, and periodic DGA remain important practices alongside continuous oil quality management.