The safety risks of work with hydraulic oil are not only of high-pressure puncture accidents, but of fire, lacerations, severe burns, crushing and death. These risks apply not only to test-bed engineers, but to maintenance fitters, forklift and lorry fitters, millwrights, platers and welders… and ultimately, to anyone whose work involves hydraulics or who operates machines, whether they be milling machines or bulldozers, that use hydraulic pressure systems.

This photo was taken 7 days after a hydraulic oil puncture accident, involving  hydraulic oil in a pressure test rig. Three operations under general anaesthetic had been performed, and stitches had been undone in the ward to investigate. Two more operations followed. A leak had occurred and a fine jet of oil had been injected into the palm of a well-trained, skilled aircraft technician.

A jet of hydraulic oil from a burst hose can emerge at 3,000 psi and will penetrate the skin as easily as it would if it were delivered through a hypodermic syringe. External signs of injury may be slight, but the internal damage is not. Oil can penetrate muscles and organs, which usually means surgery. Oil is corrosive to body tissue and causes severe damage which may lead to amputation.

The purpose of this article is to bring to your attention the need for awareness of the hazards of working with hydraulics, and of the need for you to encourage discussion with management and in your safety committee about training that would prevent such accidents.  Aim for training in the hazards of hydraulic systems, and for competency in those who work with them.

Hydraulics is not a recognised safety hazard -- unless there is a lost time injury or death -- and as such, hydraulic "accidents" generally go unreported. The result is that there is no data on such accidents.  Of course, where there is no data, there is no recognised problem. The first step in preventing accidents of this sort, as with all types of accidents, is training. Poor training is the root cause of most accidents associated with hydraulics. No person should be permitted to work on or around hydraulic systems without proper training.

To do their work, hydraulic systems must store fluid under high pressure, typically 2,000 pounds or more per square inch. One hazard comes from removing or adjusting components without releasing the pressure. The fluid, under tremendous pressure, is also hot. The worker then is exposed to three kinds of hazards: burns from hot, high-pressure fluid; bruises, cuts or abrasions from flailing hydraulic lines; and injection of fluid into the skin.

This finger has been lanced in attempt to save the finger and the hand. The injury was caused by a high-pressure injection of hydraulic fluid.

Oil injection injuries and burn injuries are both very severe injuries, which can lead to death.  Pictured here is a
operator who was burned when a hydraulic hose, which had been neglected during maintenance, burst and spewed hydraulic oil, at normal operating temperature, over his entire body.

Hydraulic oil is a petroleum lubricating oil. It is a clear, light-yellow liquid with a mild, bland petroleum odour. When working with or near this material, avoid prolonged breathing of its vapour, mist, and fumes, and avoid prolonged or repeated skin contact.
     • Use chemical-resistant gloves, splash goggles, and a chemical-resistant apron or other impervious clothing to avoid prolonged or repeated skin or eye contact.
     • Elevated processing temperatures may cause release of toxic vapours which are harmful if inhaled.
     • Before working with hydraulic oil, know the location of the nearest emergency shower and eyewash station.
     • Wash off affected skin, eyes, and protective clothing immediately. Remove contaminated clothing, and launder or dry-clean it before reuse.
     • After contact with hydraulic oil (and especially before breaks and meals, and at the end of shifts), always cleanse skin with a waterless hand cleanser, and then wash with soap and water.

Fire and Explosion Risks
"Hydraulic oil becomes hot during operations. A heated petroleum-based hydraulic fluid presents a high fire hazard, particularly in those processes where ignition sources are usually present. A typical petroleum-based hydraulic fluid has a flash point that ranges from 149 to 315 degrees Centigrade (300 to 600 degrees F)) and an auto ignition temperature of 260 to 400 degrees C (500 to 750 degrees F). However, when hydraulic fluid is accidentally discharged under high pressure, it often results in an atomised spray or mist of oil droplets that may extend as far as 10 metres from the break.  The oil spray can be ignited readily by hot surfaces, such as heated or molten metal, electric heaters, open flames or welding arcs. The resulting fire usually is torch-like, with a very high heat release rate, and can cause loss of life and significant property damage.  If an oil mist is confined, a violent explosion can occur. The frequency of fires involving hydraulic fluids has prompted the introduction of fire-resistant fluids in hydraulic systems." - Thomas J. Shepich, Director of Technical Support, US Dept. of Labor, Occupational Safety & Health Admininstration, Washington, D.C.

Working with Hydraulic Oils and Systems
•  Never begin work on a hydraulic system until fully trained.
•  Carefully review the manuals on equipment before beginning work. Ask questions about anything you do not fully understand.
•  Maintain a clean work area free of slipping hazards and debris.
•  Use all required safety equipment.
•  Always use safety glasses.
•  Block, secure or lower to the ground components that may move, rotate or fall.
•  Relieve system pressures. (Note: Some systems use accumulators that store pressure. Identify the system before working on it.)
•  Use extreme caution when disconnecting hydraulic lines. Severe burns from hot fluid can result.
•  Use test equipment designed for higher pressures than the system being repaired. Use of gauges, lines, connectors, etc., designed for lower pressures can result in bursting or equipment damage. Start with high pressure gauges and work down. (Note: A good rule is to use equipment rated at twice what is expected. Example: For a 2500 psi system, use a 5000 psi gauge.)
•  DO NOT USE HANDS OR FINGERS to find leaks. Fluid under high pressure can be injected into skin causing extreme injury and serious infection.
•  Clean up spills immediately. Hydraulic fluid is an oily substance which can cause slipping, falling and resulting injuries.
•  Do not work under equipment/apparatus being supported by hydraulics. Stops, safety pins, etc. must be in place prior to beginning repairs.
•  Review the Material Safety Data Sheets (MSDSs) for all chemicals used.

Maintenance in Hydraulic Systems
All hydraulic hoses, tube lines and fittings should be periodically inspected. Any deterioration should be carefully examined to determine whether further use of the component would constitute a hazard. Conditions such as the following should be sufficient for consideration of replacement:
     a. Any evidence of hydraulic oil leakage at the surface of a flexible hose or its junction with the metal and couplings;
     b. Any blistering or abnormal deformation to the outer covering of a hydraulic hose;
     c. Hydraulic oil leakage at any threaded or clamped joint that cannot be eliminated by normal tightening or recommended procedures; and/or
     d. Evidence of excessive abrasion or scrubbing on the outer surface of a hose, rigid tube, or hydraulic fitting. Modification must be made to eliminate the interference of the elements in contact, or otherwise protect the components.

by Dennis Mac (IOSH accredited Unite Safety Rep, retired)
References: (1) Hazard Information Bulletin 19910711, US Dept. of Labor, Occupational Safety & Health Administration, 11 July, 1991; (2) Ryan, Kenneth E., Fire Hazards of Hydraulic Fluids, Professional Safety, June, 1984, pages 34 to 36;
(3) "Hydraulic  Fluids", Risk Logic Inc., September 1999, ©2002; (4) "Safety in Lubrication", Andy Donlon, Industrial Lubricants Advisor, ExxonMobil Lubricants  & Specialities; (5) Hydraulic System Repairs, North Carolina Dept. of Environment and Natural Resources, Workplace Safety Manual 26A