Industrial Safety with Secondary Refrigerants: Flammable vs Non-Flammable Heat Transfer Fluids
Abstract
This document examines safety hazards associated with secondary refrigerant selection in industrial cooling systems. Five real incident cases from 2025 are analyzed: methanol-based coolant with a flash point of 30°C, pressure excursion from 3 to 8 bar on system shutdown, reactor bulging from thermal expansion, coolant boiling from moisture contamination, and hydrofluoric/hydrochloric acid leakage into a cooling loop. The document provides engineering guidance on flammable versus non-flammable fluid selection, system pressure management, and chemical compatibility risk assessment.
1. Scope and Purpose
Secondary refrigerants circulate through occupied spaces, process areas, and heat exchange equipment. Unlike primary refrigerants, which are typically confined to mechanical rooms, secondary fluids travel through the building. A leak in a secondary loop is not a mechanical room problem. It's a workplace safety problem. It's an environmental release problem. And depending on the fluid, it's a fire problem.
This whitepaper focuses on the safety dimension of secondary refrigerant selection. It does not address thermal performance, cost, or material compatibility beyond their safety implications. The five incident cases presented here are drawn from Glacier Coolant's 2025 technical support database. Each case involved a real facility, a real hazard, and a real resolution. Names and locations are included because transparency matters in safety documentation.
2. The Flammability Question
Not all secondary refrigerants burn. But some do. And the ones that do are often the cheapest, the most widely available, and the ones that facility managers inherited from a previous installation that nobody has re-evaluated in twenty years.
The dividing line is straightforward. Water-based secondary refrigerants such as the Glacier Coolant LM-4 and LM-8 series are non-flammable. Water-free organic fluids such as the LM-10A, LM-11D, LM-11F, and LM-11C series have flash points well above ambient temperature—typically above 95°C closed cup for LM-10A—but they are combustible under the right conditions. Fluorinated fluids in the LM-14 series are non-flammable but carry their own safety considerations related to thermal decomposition products. Heat transfer oils in the LM-15 series are combustible at elevated temperatures.
The safety question is not binary. It's not "does it burn or not." It's "under what conditions could it burn, and are those conditions present in my facility?"
Flammable / Combustible Fluids
Methanol-based coolants (flash point ~12°C)
Ethanol-based coolants (flash point ~13°C)
Glycol-water mixtures (combustible at high temperature)
Heat transfer oils (LM-15 series, combustible above flash point)
Organic anhydrous fluids (LM-10/11 series, flash point ≥95°C)
Non-Flammable Fluids
Water-based with inhibitors (LM-4 series, -20~150°C)
Water-based low-temperature (LM-8 series, -50~120°C)
Fluorinated fluids (LM-14 series, ≤-100°C)
Low-conductivity water-based (LM-4D, LM-4D-YE)
PCM cold storage materials (LM-XL series, -70~30°C)
3. Incident Analysis
3.1 Beijing Zhong*** — Methanol/Glycol Flash Point 30°C
Incident GC-2025-004 — February 14, 2025
Heat Source Tower Coolant With Flash Point of 30°C
Location: Beijing • Product Involved: LM-8 (recommended replacement)
A heat source tower system was operating with a methanol/glycol mixture. The closed-cup flash point of the mixture was measured at 30°C. For context: a liquid with a flash point of 30°C is classified as a Class I flammable liquid under most fire codes. The system was in an occupied building. The pump was undersized for the application. Glacier Coolant recommended replacement with LM-8, a water-based non-flammable secondary refrigerant rated to -50°C. The pump sizing issue was a separate concern but the flammability hazard was the primary safety finding.
Safety Warning
Methanol-based secondary refrigerants with flash points below 37.8°C are classified as Class I flammable liquids. Their use in occupied buildings or near ignition sources requires explosion-proof equipment, gas detection systems, and ventilation in accordance with NFPA and local fire codes. Water-based non-flammable alternatives such as LM-8 eliminate this hazard entirely.
This case illustrates a common pattern: a legacy system designed years ago, using whatever coolant was cheap and available, operating in a building that has since been repurposed or upgraded. Nobody thinks about the coolant until something goes wrong. The flash point of 30°C means the vapor above the liquid surface can ignite at any ambient temperature above 30°C. In a heat source tower application, the fluid temperature routinely exceeds that threshold. The entire system was effectively a fuel distribution network.
The LM-8 recommendation was based on two factors: the -50°C temperature rating exceeded the system's requirements, and the non-flammable water-based formulation eliminated the fire risk. The undersized pump was a secondary issue that would need to be addressed regardless of which coolant was selected.
3.2 Hang*** — LM-8 Shutdown Pressure 3 → 8 Bar
Incident GC-2025-011 — March 30, 2025
System Pressure Spike From 3 Bar to 8 Bar on Shutdown
Location: Not specified • Product Involved: LM-8
An LM-8 secondary refrigerant system was experiencing pressure excursions from 3 bar to 8 bar during shutdown sequences. The cause was thermal expansion of the fluid in a closed section of piping with no pressure relief. The solution was to install a constant-pressure water makeup device to accommodate thermal expansion and contraction without allowing pressure to exceed the system's design rating.
Engineering Caution
All secondary refrigerant systems must include provisions for thermal expansion. A closed-loop system without an expansion tank, pressure relief valve, or constant-pressure makeup device is a pressure vessel waiting to fail. The pressure increase from 3 bar to 8 bar represents a 167% increase—well beyond the design margin of most piping and heat exchange equipment.
Pressure safety in secondary refrigerant loops is often overlooked because the operating pressures are typically low—3 to 5 bar is common. The assumption is that low pressure means low risk. This assumption is wrong. A pressure spike from 3 bar to 8 bar on a system designed for 6 bar is a rupture hazard. The energy stored in compressed liquid is substantial, and the release of that energy through a failed gasket, fitting, or pipe section can cause injury and equipment damage.
The constant-pressure water makeup device is a standard engineering solution. It maintains system pressure within a narrow band by adding or releasing small amounts of fluid as the system thermally cycles. The cost is modest. The alternative—a pressure relief valve that vents to atmosphere—is simpler but introduces oxygenation and contamination risks. The engineering trade-off depends on the specific application and the consequences of fluid release.
3.3 Da*** Pharma — LM-11C Reactor Bulging
Incident GC-2025-026 — September 29, 2025
Reactor Bulging Due to Thermal Expansion With Closed Outlet Valve
Location: Taizhou • Product Involved: LM-11C
A pharmaceutical reactor jacket filled with LM-11C water-free coolant experienced bulging deformation. The root cause was identified as thermal expansion of the coolant with the outlet valve closed. The coolant was trapped in the jacket, heated, expanded, and had nowhere to go. The reactor vessel deformed before any pressure relief activated. The corrective action was procedural: do not close the outlet valve on a reactor jacket when the vessel is heated. Ever.
Safety Warning
Thermal expansion of trapped liquids can generate pressures sufficient to rupture pressure vessels and piping. A temperature increase of 50°C in a completely filled, closed volume of organic coolant can generate pressure increases of 50-100 bar or more. No practical piping system is designed for these pressures. The procedural safeguard—never valve off a coolant-filled jacket while the vessel is heated—must be reinforced through operator training, written SOPs, and physical interlocks where feasible.
This incident is particularly instructive because it happened in a pharmaceutical facility, where safety systems are generally robust. The reactor bulging was not a failure of engineering. It was a failure of procedure. Someone closed a valve that should never have been closed under those conditions. The physical damage to the reactor was expensive. The production downtime was more expensive. The fact that nobody was injured is a matter of luck, not design.
The LM-11C fluid itself was not the cause. Any liquid, water included, will generate enormous pressure when heated in a confined volume. The difference is that water-based coolants are more forgiving in pharmaceutical applications because operators are more familiar with their behavior. Organic water-free coolants introduce a procedural learning curve that facilities must account for in their training programs.
3.4 Chongqing***Electromechanical — LM-15B Boiling Overflow
Incident GC-2025-014 — April 27, 2025
Heat Transfer Oil Boiling and Overflow at 106°C
Location: Chongqing • Product Involved: LM-15B
An LM-15B heat transfer oil system was boiling and overflowing at 106°C. The LM-15B is rated for operation from -15°C to +160°C. Boiling at 106°C is well below the expected boiling point and indicated contamination. The root cause was identified as high moisture content in the system. Water in the oil was boiling, creating steam that caused the overflow. The corrective action was to separate the water from the oil before resuming normal operation.
Engineering Caution
Moisture in heat transfer oil systems reduces the effective boiling point dramatically. Water boils at 100°C at atmospheric pressure. Steam formation in a hot oil system creates pressure surges, pump cavitation, and overflow hazards. Any heat transfer oil system that shows signs of boiling below the rated temperature should be immediately checked for moisture contamination. The water must be separated before the system is returned to service.
The boiling overflow hazard is both a safety issue and an operational issue. Hot oil overflowing from an expansion tank creates a burn hazard for anyone in the vicinity. It also creates a slip hazard, a fire hazard if the oil contacts hot surfaces, and an environmental release if the overflow reaches drains or soil. The LM-15B product itself was not defective. The system was contaminated. The distinction matters for root cause analysis but not for the operator standing next to a tank of boiling oil.
Moisture ingress into heat transfer oil systems typically occurs through open expansion tanks, leaking heat exchangers, or condensation in systems that cycle below the dew point. Prevention requires sealed expansion tanks with nitrogen blanketing where appropriate, regular moisture testing, and an understanding that "oil and water don't mix" is true but "oil and water in a hot system create a hazard" is more important.
3.5 Ling*** Pharma — HF/HCl Leak Into LM-8
Incident GC-2025-007 — February 20, 2025
Hydrofluoric and Hydrochloric Acid Leak Into Secondary Refrigerant Loop
Location: Shandong • Product Involved: LM-8
A pharmaceutical facility in Shandong experienced a leak of hydrofluoric acid and hydrochloric acid from the process side into the secondary refrigerant loop. The coolant was LM-8, a water-based non-flammable fluid. Because LM-8 is water-soluble, the acids dissolved into the coolant rather than forming a separate phase. This made the hazard relatively safer than if the coolant had been an organic fluid—the acids were diluted and contained rather than concentrated and separated. The corrosion protection of the LM-8 was compromised by the acid ingress, and the anti-corrosion effect was reduced. The system required neutralization and replenishment of the inhibitor package.
Safety Warning
Hydrofluoric acid is one of the most hazardous chemicals in industrial use. It penetrates skin, attacks bone, and can cause fatal systemic toxicity from apparently minor exposure. Any process that uses HF must have double-contained cooling systems, continuous pH monitoring on the coolant loop, and emergency response procedures that account for the possibility of a coolant loop contaminated with HF. The fact that LM-8 is water-soluble and diluted the acid is a mitigating factor, not a safety strategy.
This incident raises the most serious safety concerns of any case in the 2025 database. HF and HCl leaking into a cooling loop that circulates through a facility is a worst-case scenario for chemical cross-contamination. The water-soluble nature of LM-8 meant the acids formed a homogeneous solution rather than a separate corrosive phase. This is better than the alternative—an organic coolant with concentrated acid sitting at the bottom of a low point—but "better" is a relative term when HF is involved.
The corrosion protection compromise was the least of the concerns. The primary concern was that the coolant loop was now carrying a toxic chemical mixture through the facility. Any leak, any maintenance activity, any sample drawn from the system was a potential exposure event. The facility's response included neutralization of the coolant, replacement of the fluid, inspection of all piping and heat exchange surfaces for corrosion damage, and a root cause analysis of how the process-side leak occurred.
Technical Note
Water-based secondary refrigerants provide a safety advantage in chemical cross-contamination scenarios: they dilute water-soluble contaminants rather than allowing them to concentrate as a separate phase. This does not eliminate the hazard, but it does reduce the risk of a concentrated chemical release from a low point in the system. For facilities handling highly hazardous chemicals, double-walled heat exchangers or intermediate loops are strongly recommended.
4. Risk Assessment Framework
The five incidents described above span the range of safety hazards in secondary refrigerant systems. Drawing on these cases and the broader 2025 technical support database, the following risk assessment framework is proposed for facility engineers evaluating their secondary refrigerant safety profile.
4.1 Flammability Risk
Question: What is the flash point of the current secondary refrigerant, and is it below the maximum operating temperature of the system?
If the flash point is below the maximum operating temperature, the system is operating with a flammable liquid above its flash point. This requires explosion-proof equipment, gas detection, and ventilation per applicable fire codes. The Beijing Zhongran Senchuang case is the reference: methanol/glycol with a flash point of 30°C in a system that routinely exceeded that temperature.
Mitigation: Replace with a non-flammable fluid such as LM-4 (water-based, up to 150°C) or LM-8 (water-based, up to 120°C, non-flammable). If a water-free fluid is required for low-temperature operation, the LM-10A (flash point ≥95°C closed cup) provides a higher safety margin than methanol- or ethanol-based alternatives.
4.2 Pressure Risk
Question: Does the system have adequate provisions for thermal expansion, including during shutdown and startup transients?
The Hangtian Yisenlin case (3 to 8 bar spike) and the Dachen Pharma case (reactor bulging) are both pressure-related. The mechanisms are different—one is system-level thermal expansion, the other is localized trapped-fluid expansion—but the root cause is the same: uncontrolled pressure from thermal expansion of a liquid.
Mitigation: Expansion tanks sized for the full thermal range of the system. Pressure relief valves set below the system design pressure. Constant-pressure makeup devices for systems with wide temperature swings. Procedural controls that prevent valve closure on coolant-filled equipment during heating. Physical interlocks where the consequence of failure justifies the cost.
4.3 Chemical Cross-Contamination Risk
Question: If the process-side fluid leaks into the coolant loop, what happens?
The Lingkai Pharma case is the reference. HF and HCl leaked into an LM-8 loop. The water-soluble nature of LM-8 provided some dilution benefit, but the fundamental hazard remained. The question is not whether the coolant can handle the contamination. The question is whether the facility can handle the contaminated coolant.
Mitigation: Identify all process-side chemicals that could leak into the coolant loop. For each chemical, determine the reaction products with the coolant. For high-hazard chemicals (HF, HCl, nitric acid, ammonia), consider double-walled heat exchangers, intermediate loops, or continuous coolant chemistry monitoring with automatic shutdown on contamination detection.
4.4 Moisture Contamination Risk
Question: Can water enter the system, and what happens if it does?
The Chongqing Changyu case (LM-15B boiling at 106°C) and the broader pattern of ice blockage cases in water-free systems both trace to moisture contamination. In heat transfer oil systems, water causes boiling and overflow. In water-free low-temperature systems, water causes ice blockage.
Mitigation: Sealed expansion tanks with nitrogen blanketing. Regular moisture testing. Moisture removal procedures (separation, molecular sieve, vacuum dehydration). For water-free systems, a moisture sensor with alarm is a minimal investment with a high return.
5. Product Safety Profiles
The following profiles summarize the key safety characteristics of the Glacier Coolant product families. These are not complete safety data sheets. They are reference summaries for engineering hazard assessment.
LM-4 Series (Water-Based Anti-Corrosion)
Temperature: -20 ~ 150°C • Flammability: Non-flammable
Water-based with corrosion inhibitor package. Six variants: LM-4 (general), LM-4D (low conductivity, copper-friendly), LM-4D-YE (ultra-low conductivity <800μS/cm), LM-430 (economic, -15°C freeze point), LM-445 (low-temp), LM-495 (high reserve alkalinity >12mL, pH 7.5-9.5). Non-flammable. Water-soluble contaminants are diluted rather than separated. Primary safety consideration: pressure management at high temperatures. The 150°C upper limit requires pressurized system design to prevent boiling.
LM-8 Series (Water-Based Non-Flammable Low-Temperature)
Temperature: -50 ~ 120°C • Flammability: Non-flammable
Water-based with freeze point depression for low-temperature operation. Non-flammable. Appears in 8 of 34 support cases, including the Lingkai Pharma acid leak and the Hangtian Yisenlin pressure excursion. Primary safety considerations: pressure management at high temperature, corrosion protection if process contaminants are present (LM-8 has less aggressive corrosion inhibition than LM-4), and icing risk if the system is pushed below the rated temperature.
LM-10A / LM-11D / LM-11F / LM-11C (Water-Free Organic)
Temperature: -25 ~ -85°C range • Flammability: Combustible (flash point ≥95°C for LM-10A)
Water-free organic fluids for low-temperature applications. Combustible at elevated temperatures but with flash points well above typical ambient conditions. LM-11D is the most widely used product in this family (10 of 34 cases). Primary safety considerations: flammability risk assessment, thermal expansion pressure in closed systems (Dachen Pharma case), moisture ingress causing ice blockage, and the procedural learning curve for operators accustomed to water-based fluids.
LM-14 Series (Fluorinated Fluid)
Temperature: ≤ -100°C • Flammability: Non-flammable
Fluorinated fluids for extreme low-temperature applications. Non-flammable. Chemically inert. Ultra-low viscosity at low temperature. Primary safety considerations: thermal decomposition products at elevated temperatures (relevant if the fluid is used near hot surfaces or in fire conditions), environmental regulations (F-gas rules in applicable jurisdictions), and high cost that makes leaks more financially significant.
LM-15 Series (Heat Transfer Oil)
Temperature: -15 ~ +160°C • Flammability: Combustible
Heat transfer oil for wide-range temperature cycling. Combustible. Appears in 2 of 34 cases, including the Chongqing Changyu boiling overflow. Primary safety considerations: moisture contamination causing boiling and overflow, oxidation at elevated temperatures, thermal degradation products, and fire risk if the oil contacts surfaces above its autoignition temperature.
6. Recommendations for Facility Engineers
Based on the 2025 incident data and the safety analysis presented above, the following recommendations are offered for facility engineers responsible for secondary refrigerant systems:
One: conduct a flammability audit of every secondary refrigerant loop in the facility. Document the fluid type, flash point, maximum operating temperature, and proximity to ignition sources. If the flash point is below the maximum operating temperature, flag the system for fluid replacement with a non-flammable or higher-flash-point alternative.
Two: verify that every coolant loop has adequate thermal expansion provisions. This includes expansion tanks, pressure relief, and for systems with wide temperature swings, constant-pressure makeup devices. The absence of these provisions is not a cost-saving measure. It is a deferred pressure vessel failure.
Three: for any facility handling hazardous process chemicals, conduct a cross-contamination risk assessment. What happens if the process chemical leaks into the coolant? What happens if the contaminated coolant leaks into the facility? The answers should inform heat exchanger design, coolant chemistry monitoring, and emergency response procedures.
Four: for water-free coolant systems, implement moisture monitoring and moisture exclusion protocols. The 2025 case data shows that moisture ingress is the dominant failure mode for water-free systems. A sealed system with nitrogen blanketing and a moisture sensor costs less than a single emergency coolant replacement.
Five: train operators on the specific hazards of the coolant in use. Water-based coolant operators need to understand pressure management. Water-free coolant operators need to understand moisture exclusion and thermal expansion. Heat transfer oil operators need to understand moisture contamination and fire risk. The training should be specific to the fluid, not generic "chemical safety" training.
7. Closing Statement
The five incidents analyzed in this document are not hypothetical. They happened. Facilities were damaged. Production was lost. In one case, a reactor vessel deformed. In another, a coolant loop carried hydrofluoric acid through a pharmaceutical facility. Nobody was seriously injured in any of the 2025 cases—a fact that should be attributed to luck as much as to safety systems.
Secondary refrigerant safety is not a product selection problem. It is a system design and operational discipline problem. The safest coolant in the wrong system is a hazard. A moderately hazardous coolant in a well-designed, well-operated system is manageable. The goal is not to eliminate all risk—that is not possible in industrial cooling. The goal is to understand the risks, design for them, and operate accordingly.