Is hydraulic fluid flammable? (hydraulic fluid flash point)

Do you know some of those most demanding things required in the present world and field of technology?

I can tell that the roles of modern machinery are worth mentioning one!

Advanced and hydraulic machines are now an everyday affair in every sector, whether industry, mills or anything else. Hydraulic fluids are great amongst such inventions, whose job is to supply power to the hydraulic machines!

For the parts of the machine where a higher ignition point sustains, is hydraulic fluid flammable?

The answer varies a lot! The petroleum-based hydraulic fluids are on the side of catching fire, whereas the water-based liquids are non-flammable. This is because petroleum fluids have relatively higher flashpoints, and the water hydraulic fluids have high water content.

Let’s march on!

Also Read: Check out our other article about Does Crude Oil Burn Easily?

Hydraulic fluid is a lubricant used in hydraulic machineries such as motors, pumps, valves, and cylinders. It also has many other uses, including steering systems on boats and cars.

What is Hydraulic Fluid?

Is Hydraulic Fluid Flammable

There are two types of hydraulic fluids:

  1. Oil-based Hydraulic Fluid : A thin oil-based liquid with water consistency made from crude oil.
  2. Synthetic Hydraulic Fluid: A thick liquid made from petroleum products that do not need to be mixed with a thinner base oil for use in some applications.

is hydraulic fluid combustible or flammable?

Yes and no at the same time! Hydraulic fluids are relatively flammable due to their raw material and flashpoint. But they are also non-flammable depending on the variant. There are two types of hydraulic fluids which are petroleum-based and water-based.

The flammability of the hydraulic fluids depending on the variants are as follows:

    Petroleum-based      Water-based
Hydraulic fluids containing petroleum are more flammable than water-based oils.Water-based hydraulic fluids are almost non-flammable due to their nature.
The petroleum-based hydraulic fluid contains high levels of mineral oils. This results in more flammability of the substance.The water-based ones have higher water content. The more the water level, the higher is the non-flammability.
They have a reachable flashpoint which results in their ignition.The flashpoint of these fluids cannot be reached easily, resulting in incombustibility.

Why is hydraulic liquid flammable?

Hydraulic fuel is not a highly flammable substance. But, it is relatively volatile and can catch on fire non-occasionally. They are not fire-hazardous due to their higher ignition point. But, they still cause flammability for several reasons, some of which are mentioned below:

  • Hydraulic fluid is made out of the base element, which remains 99% of its total volume. That element is the mineral oil which reacts with the fire very well. As a result, they are also flammable.
  • The flammability also depends on the flashpoint of any substance. The lower the flashpoint, the easier the importance is to burn in the fire. Due to a moderate flashpoint, hydraulic fluids can be burn on fire and create flames.
  • The ignition temperature is relatively more accessible for the hydraulic fluid to reach and causing a fire.

What are the hazards of hydraulic fluid?

Every action has opposite reactions. There are enormous advantages of hydraulic fluids. Amongst them, some of the drawbacks are also expectable. These drawbacks bring many hazards in the environment and our day-to-day life, some of which are mentioned below:

  1. Hydraulic fluids are so much harmful to the environment and climate. They cause environmental pollution by polluting the air, water bodies, and the soil. These can result in changing the climate of the world and cause global warming.
  2. They are flammable because of which they release harmful toxic smoke. These fumes are so much harmful to the human body and damages the lungs when inhaled. As a result, various heart diseases arise.
  3. Besides bronchitis, asthma, and many more, they also cause fluid injection injuries, slipping, falling and tripping hazards, etc.

What are the benefits of using hydraulic fluid?

  1. It has very low friction properties that make it ideal for use in areas with a lot of movement or heavy loads.
  • It can reduce noise compared with other oils due to its low viscosity (thickness).
  • It does not contain any harmful chemicals like most other oils do, so it’s more environmentally friendly than those alternatives.
  • It can be mixed with other oils for various motor oil and transformer oil applications to form a one-fluid system called Hydraulic System Fluid (HHF).
  • The property of hydraulic fluid allows it to overcome the effects friction will have on moving parts. Thus hydraulic fluid is often used to lubricate heavy machinery such as generators in power plants and stationary motors.
  • Also considered to be a high-performance product, it has superior service life at higher temperatures than other oils do but lacks its counterparts over a long time of storage (Shelf Life)
  • Because of its ability to dramatically reduce friction, hydraulic fluid can help increase productivity and profitability in certain processes like manufacturing and transportation systems through reduced cost per unit value.

What temp does hydraulic oil ignite?

All flammable substances have specific points of ignition. That is to say; the burning senses start to burn at certain levels of temperature. This is called the flashpoint. Like other substances, hydraulic oil also contains specific flashpoints at which it begins to ignite.

The temperature of that ignition point of the oil is mentioned below:

Hydraulic fluids are flammable once they exceed a flashpoint. The temperature at which they start to hit their flashpoint is above 300° Fahrenheit. They generally burn at a temperature range of 300°-600° Fahrenheit Celsius. The auto-ignition point of the oil is around 475° Fahrenheit.

Also Read: Which Fuel Is Most Flammable?

What is the Flashpoint of Hydraulic fluid?

The Flashpoint of hydraulic fluid is the lowest temperature at which a liquid will ignite. The Flashpoint of hydraulic fluid is the lowest temperature at which a liquid will ignite.

In case of an accidental fire, it is important to know the Flashpoint of hydraulic fluid, as it can be hazardous to human life. The Flashpoint of hydraulic fluids is 214 degrees Celsius (°C).

What class fire is hydraulic oil?

The flammability is divided into many classes according to the list of the items, characteristics, and combustibility rate. Those classes are divided into class A, class B, class C, and class D, respectively. The type of hydraulic oil is mentioned below:

  • Hydraulic oil is from class B of the fire. All the mineral oils, including petroleum, hydraulic oil, petroleum, alcohol, and many more, are included in this class.
  • This class B is generally comprised of flammable liquids which have combustibility and reactions with fire.
  • Besides class B, there are many other classes in the fire. This represents elements from style C, which are all metals and great combustions of fire. Class D represent the cooking oils which also have lower flashpoint and catches on fire.
  • The flammability of all the classes follows a definite order. The highest rate of flammability of the elements is in class B, compared to type C. Again, the combustibility of class D elements is even lower than class C.

What is fire-resistant hydraulic fluid?

Fire-resistant hydraulic fluids are water-based hydraulic fluids used as alternatives to petroleum ones. Water-based hydraulic fluids are used where there is a potential risk of ignition point, and petroleum should be avoided. These hydraulic fluids fulfill the demand for the hydraulic energy needed to run the task.

Fire-resistant hydraulic fluids are those which are non-flammable and don’t have the risk of catching fire. This is only possible by the water hydraulic fluids, which have significantly higher contents of water. The presence of water in the fluids makes them unable to burn.

Synthetic fuels, glycols of water, oil emulsion water, and more items fall under water-based hydraulic fluids.

What is fire-resistant hydraulic fluid

How to prevent hydraulic oil fires?

Prevention is always better than cure. But, to prevent this, one first needs to identify the source of obstacles. For example, a fire can be the most significant obstacle in the path of hydraulic oils in performing their job. And, for this fire, the main thing responsible for is the mineral oil itself which comprises the whole fluid.

The things needed to be done in the prevention of the hydraulic oil fires are mentioned:

  • Mineral oils are the main responsible for the catching of hydraulic oil fires. The mineral oils should be replaced with non-combustible fluids.
  • One such non-combustible fluid includes the water, one of the most effective extinguishers of all time.
  • Hydraulic oil fires can also be prevented by using the alternatives of petroleum which is water-based oil.

What are the risks of using hydraulic fluid in an aircraft?

The risks of using hydraulic fluid in an aircraft include:

  • Failure to use proper fluid or not to change the fluid often enough can cause leaks and fires.
  • Hydraulic fluids are toxic and should be disposed of properly, including following all safety precautions.
  • The fumes from a leaking hydraulic system may be hazardous to passengers and crew members.


Hydraulic fluids are customized forms of flammability, which can be adjusted according to the need. When there is no risk of fire hazards, general petroleum hydraulic fluids are used, which are on the go catching on fire. But, at the time of usage in sensitive ignition points, the particular non-flammable water variant is used!



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