Hydraulic oil fires – what to look for?

The most simple and reliable way to prevent a hydraulic oil fire is to replace mineral oil with non-combustible fluid. Naturally, using electric or pneumatic drives instead of hydraulic drives will also prevent hydraulic oil fires. Although there are some fire risks related to these technologies, they are not as fierce and difficult to control as oil fires.

Industrial building on fire due to a hydraulic oil.

Non-combustible or combustible?

Fluids considered to be non-combustible consist of water-based solutions, featuring less than 20% oil. Control of fluid leakages is important for several reasons: fire safety, the functionality of the machines and soil protection. With water-based solutions, however, it is important to understand that the residues are combustible, when water has evaporated.

However, the transition to water-based solutions has been slow. As this requires component changes, including valves for example, there are costs involved and thus water-based solutions are seen as unattractive. After the replacement of hydraulic oil, the manufacturer of the respective machine may cancel the warranty.

From a fire safety perspective, this would be an important upgrade to help reduce the risk of hydraulic oil fires.

Where are the potential risks?

How can clients understand where the potential risks are? In some situations, conditions that can cause a hydraulic oil fire will include the presence of hot surface or momentary high temperatures such as a flame or electric arc, which come in contact with pressurized oil. In most cases, such conditions can be identified at the hydraulic cylinders and motors, as well as at the hydraulic hoses and pipes at the processing line, rather than at the hydraulic pack, which can be in a segregated room or further away from process equipment. 

Understandably a hydraulic aggregate in a separate hydraulic room can catch fire although such fire losses are rare. Common causes of such fires are pump breakdowns and burning rubbish at a hydraulic aggregate.

Another loss scenario, although rare, is a pin hole leak, which creates an oil mist cloud. If this cloud is met by an ignition source which appears on the scene, the oil cloud will easily catch fire, resulting in a flash-over.

Oftentimes, insurers may simply state that if a single hydraulic system contains less than 100 gallons of hydraulic oil the consequences of an oil fire are considered low. In these cases, the priority is in the fire protection at the hydraulic unit, rather than the fire safety of the process equipment, where hydraulic oil is utilized.

Determining factors

There is no direct dependency between the volume of the oil tank and the severity of potential loss in case of an oil fire. More determining factors are the vulnerability and criticality of the items, which are exposed. Almost in all oil mist fires in industrial facilities some power cables, data cables and electrical components will be destroyed. If the destroyed electrical components belong to an obsolete electric control system, the restoration of the system can be difficult. In the worst case, the old control system needs to be replaced with a fully new process control system.

Assessment of the consequences

To assess the consequences of an oil fire within a separate hydraulic room with no reliable extinguishing system is rather simple. If the hydraulic pack consists of standard pumps and valves with no special components, the hydraulic pack can be restored within 4 to 6 weeks. Should the hydraulic pack have tailor made servo valves and similar components, the restoration could take 3 to 5 months.    

There is no simple formula, even less than 100 gallons of hydraulic oil will burn fiercely and cause damage to the unit, as well as the immediate environment in which it is situated.

Points to consider

Other points to consider, include:

  1. The hydraulic unit itself; how expensive will it be to repair, what are the delivery times for key components, are there any tailor-made components in the unit?
  2. Discharging high-pressure oil poses risk to people. Hydraulic hoses should therefore be introduced in fire protection hoses, also known as fire jackets, which must be fixed with wire rope and clamps to steel pipes to keep them in place. In the event of a hose burst fire jackets will restrain oil discharge and let it run on the floor.
  3. Slowly progressing contamination of floor and soil must also be considered. Control of oil leaks is important not only from fire prevention standpoint, but also from environmental standpoint. When an old hydraulic system will be removed, contaminated concrete and soil may also be necessary to be removed and treated. The treatment of oily soil and concrete is expensive.

The use of hydraulic oil with a higher ignition temperature will not much reduce the risk of a hydraulic oil fire. Practically in all cases, the ignition source is well over 300 degrees thus overriding the fire protection properties of such hydraulic fluids. Exposed power cables and mechanical components will be damaged although the energy of the flames can be lower than in mineral oil fire.

pneumatic system operating.
There are clear differences between electric, pneumatic and hydraulic systems. For example, pneumatic systems (shown here) operate at 8 bar pressure, while hydraulic systems operate at 200 bar.

Eero Kankare

Risk Engineer, If