Is Hydraulic Fluid Flammable?

Hydraulic fluid or oil is usually used to transmit power in hydraulic systems. The fluid serves various purposes and possesses many different characteristics. Most hydraulic fluids consist of 99% base stock which is usually mineral oil with about 1% additives.

Apart from transmitting power, hydraulic fluid can also serve as a lubricant – it reduces friction on metal surfaces that can reduce wear and tear.

But is hydraulic fluid flammable? Generally, hydraulic fluids are considered to be flammable, especially petroleum-based hydraulic fluids. Water-based hydraulic fluids have high water content and thus are inflammable in most circumstances.

In other words, petroleum-based hydraulic fluids can result in fire safety hazards in situations where high-pressure leaks can result in aerosol formation.

Let’s talk more about some of the critical properties of hydraulic fluid and it’s relationship with fire.

Is Hydraulic Fluid Flammable?

Mineral oils, fire-resistant fluids, water/oil emulsions, water-glycol, and phosphate are all classified under the different categories of hydraulic fluids. Naturally, petroleum-based hydraulic fluids like mineral oils have flashpoints.

The water-based hydraulic liquids are flammable. However, decay and deterioration can result while using water-based hydraulic fluids. The flammability analysis of hydraulic fluids is usually dependent on its ISO 12922 specification.

Note that the manner, type, and way hydraulic fluid is used will affect its flammability level.

In cases where petroleum-based hydraulic fluid is used in contact with ignition sources and hot surfaces such as furnace chargers and dischargers, hot metal shears, coke furnace door openers, and die-casting machines, there is a high chance of fire hazards.

What is Hydraulic Fluid Made from?

Hydraulic fluid is made of 99% base stock with about 1% additives. The base stock is mostly mineral oil (belongs to group 1 base oil) and, in some rare cases, propylene glycol or silicone oils. The new biodegradable hydraulic fluids now have a natural base such as canola oil.

The 1% additives added to hydraulic fluid give its unique properties. Commonly, additives include corrosion inhibitors, anti-erosion additives, friction reducers, and anti-formant.

Apart from providing hydraulic fluid its unique characteristic, additives are also used to change the color of the hydraulic fluid.

How is Hydraulic Fluid Used?

Is Hydraulic Fluid Flammable

As mentioned earlier, hydraulic fluids serve different purposes. Below are some of the uses of hydraulic fluid:

  • Hydraulic fluid transmits the power in hydraulic systems: it is practically impossible for a hydraulic system to function without the presence of hydraulic fluids. The fluid is used in various applications ranging from toys to larger applications like aircraft and robotics
  • Hydraulic Fluids acts as a lubricant: As a lubricant, it reduces friction and protects metal surfaces from wear and tear, rusting, and deterioration
  • Hydraulic fluid helps keep components cool by conducting heat away
  • Hydraulic fluid also protects metal surfaces from corrosion
  • It provides a viscous seal and resists water
  • Hydraulic fluid also has a low tendency to cavitate, be thermally and chemically stable, and have a near-constant viscosity

Is Aircraft Hydraulic Fluid Flammable?

Remember that hydraulic fluid’s level of flammability depends on the type of hydraulic fluid (petroleum-based hydraulic liquids are more flammable than water-based ones) and how the liquid is used or applied (when used in high ignition points, they are highly flammable).

Most hydraulic fluids used in aircraft are thin and fire-resistant, thus not flammable. This is, however, a new innovation.

Before now, the hydraulic fluids used in military and commercial aircraft like the MIL-H-5606 are highly flammable and may have been responsible for the loss of military aircraft in the past.

The MIL-H-83282 and MIL-H-87257 hydraulic fluid used by the Air Force since 1982 is much less flammable, especially when compared to the MIL-H-5606.

Skydrol and Hyjet are regarded as the first fire-resistant hydraulic fluid in the aviation industry, respectively.

The Mobil HyJet V is approved for all commercial aircraft, which means that it is almost impossible for fire hazards due to hydraulic fluid ignition to occur in all commercial planes.

Is Elevator Hydraulic Fluid Flammable?

The NFPA 13 (an installation standard for most industrial projects) specifies that the hydraulic fluid used in all elevators must be a Class III-B hydraulic fluid with a Hydro-Safe.

Hydro-Safe hydraulic fluids have fire-resistant qualities and are less hazardous, which means that the chances of a fire hazard occurring in an elevator are almost close to none.

The hydraulic fluid used in elevators is less flammable than other oils, although not non-combustible.

Conclusion

The importance of hydraulic fluid in hydraulic systems cannot be over-emphasized; in fact, it is the lifeblood of your hydraulic system.

When it comes to the question, is hydraulic fluid flammable? We should have it in mind that the type of hydraulic fluid used and the temperature determine its flammability level.

For most industrial public projects like aircraft and elevators, fire-resistant hydraulic fluid is used, ultimately reducing the chance of a fire accident. We hope this post has answered all the essential questions you have pertaining to hydraulic fluids!

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