KUKA Robotics
A high-pressure diecasting cell, where lubricants under pressure are used to cool high-value equipment – and workers may be present.

Choosing a Fire-Resistant Hydraulic Fluid

Sept. 12, 2022
Deciding between water-based and synthetic, water-free formulations requires assessing the particular needs of every application, not just fire resistance but also environmental impact, thermal stability, fluid maintenance, system reliability, total cost

When lubricants operate under pressure there is a risk of small leaks and a fine spray of lubricant being atomized into the air. If such leaks occur with mineral oil-based lubricants in an area where there is an ignition source or near equipment running at high temperatures, a leak could lead to a catastrophic fire.

While both HFC (water glycol) and HFDu (synthetic, fire-resistant) hydraulic fluids reduce fire risk, improve operation safety, and enhance environmental performance, there are significant differences. Standing at 50-55% market adoption, HFC is a water-based fluid that can be used in all industries where there is a major risk of fire. HFDu is a water-free fluid that’s designed to replace anti-wear, mineral oil-based hydraulic fluids and has a market adoption of 20-25%.

Both fluids protect against fire and the consequential financial losses caused by application downtime, but choosing which to adopt primarily comes down to the specific needs of the application. For example, in applications where workers are present – for example, diecasting work cells – the uncompromising fire resistance of HFC often is favored. While in applications free of any human presence, such as a blast furnace, the enhanced system reliability offered by HFDu will generally drive decision-making.

While it is possible to convert applications from HFC to HFDu, the process is costly, requiring extensive flushing and testing. It’s therefore important to understand from the beginning which hydraulic fluid makes the most sense from safety, cost, and environmental perspectives, to optimize the associated benefits of increased productivity, reduced downtime, and enhanced work safety.

The case for water-glycol fluids. HFC are the most widely used fire-resistant hydraulic fluids because of their cost-effectiveness and their combination of excellent fire-resistant properties with good lubrication. Widely used in diecasting, steelmaking, pressure molding, and the automotive industry, HFC remains the market standard.

In addition to offering uncompromising fire resistance, other factors for choosing HFC include its OEM endorsements and comparable pricing with mineral oil. Unlike HFDu, HFC is also miscible with process water, a key environmental consideration. However, some compromises exist with HFC that need to be taken on board.

Ongoing maintenance of HFC is essential, with regular sampling and analysis required to protect against component damage. A properly maintained HFC-operated system can behave very reliably.

The impact of neglected maintenance often will be a period of unplanned downtime, which needs to be meticulously scheduled to minimize the associated inconvenience and revenue losses. However, with an effective maintenance plan in place the long-term cost efficiencies and safety benefits of HFC are beyond question.

While their fire-protection credentials are enviable, water-based fluids can result in a shorter service life for components due to corrosion and cavitation when maintenance is neglected. Hydraulic design limitations also exist in terms of pressure limitations, galvanized pipes, and paint inside tanks. In terms of limitations on flow and pressure, this can be resolved with the introduction of an HFDu, yet the associated costs may make HFDu are more viable long-term option.

The case synthetic water-free hydraulic fluids. Widely acknowledged as the best fire-resistant alternative to mineral oil despite being more expensive, HFDu fluids are designed to replace anti-wear, mineral oil-based hydraulic fluids used in applications where fire hazards exist. Additionally, they can be used in environmentally sensitive hydraulic applications without compromising the overall hydraulic system operations and design.

HFDu fluids are based on high-quality, synthetic, organic esters and carefully selected additives, and do not contain water, mineral oil, or phosphate ester. HFDu fluids deliver excellent and reliable hydraulic fluid performance. While initial fluid investments may be higher, HFDu fluids generally result in a total lower cost of ownership due to reduced downtime from maintenance and better lubrication resulting in less energy consumption. Additionally, HFDu products have a long fluid life, can perform at higher pressure, and enhance system reliability.

Some compromises exist however, as HFDu is two to three times more expensive than mineral oil. Its fire resistance meets international standards like Factory Mutual but is also not equal to its water-based alternatives — which is why HFDu fluids are often chosen for applications where there is less risk to human life, such as blast furnaces and where reliability of the system is prevailed.

Finally, HFDu is not miscible with water and as such does not mix with wastewater. It can be skimmed off, which can have an impact on chemical oxygen demand (COD) and more positive environmental and regulatory consequences. As ever, there needs to be a holistic view taken when weighing up the relevant benefits of water-free and water-based solutions.

It’s clear both HFC and HFDu hydraulic fluids offer benefits. Deciding which makes the most sense to use ultimately comes down to what’s best for any specific application. Therefore, fire resistance, environmental impact, thermal stability, fluid maintenance, system reliability, the total cost of ownership, and price all need to be given serious consideration.

Quaker Houghton’s expertise in fire-resistant hydraulic fluids can provide clarity and guidance. HOUGHTO-SAFE for HFC includes excellent corrosion inhibition, excellent lubrication and low heat release. HFDu QUINTOLUBRIC has properties that strongly limit the spread of fire, reduce environmental impact and lower the total cost of operation. By being able to offer both best-in-class HFC and HFDu products, Quaker Houghton can be completely objective in their recommendations, taking on the particular requirements and challenges of every application.

Ronald Knecht is the global OEM manager for hydraulics and lubricants with Quaker Houghton. Learn more at www.fireresistantfluids.com

About the Author

Ronald Knecht | Global OEM manager

Ronald Knecht is the global OEM manager for hydraulics and lubricants with Quaker Houghton.