Posted By Mark Bishop
Is there a cut off for determining what is high pressure and what is low pressure?
For example, would a pressure of 140 bars be classed as low or high?
Could 140 bars cause a high pressure injection of oil into the skin if released from hydraulic equipment?
Is there any guidance in this area?

Posted By Sean Fraser
Mark,

I'm not a qualified engineer / technician, but I work in such industries and have experience in oil & gas processes accordingly.

Don't get too hung up on the definitions of low and high - especially as "low" pressures in high volumes can be just as dangerous should there be a catastrophic loss of containment, with potentially greater loss as a consequence. It all depends on what you are referring to? 1 bar = 14psi, so the example of 140 bar put into contect would be 2030 psi (pounds per square inch). When you consider that atmospheric (1 bar) is 14.7psi, that is significant.

A good training video frequently cited in the industry is "Teasing the Tiger", which deals with the dangers of pressure and pressure systems. Not sure who the source is however as I haven't a copy here, sorry.

When considering the pressure you need to consider the forces involved. The danger is mutliplied when dealing with gas (pneumatic) as opposed to liquid (hydraulic). For example, damage to a hydraulic line may take some time to expand as the pressure forces any fault wider, starting with a slow drip and over time becoming a rapid flow (e.g. a leaking joint). In contrast, any damage to pneumatic pressure containment (a pressure line or vessel) will result in rapid expansion (in terms of milliseconds e.g. with a burst) as the remaining gas seeks to equalise to atmospheric, causing additional damage to the system as it escapes with force and possibly creating debris as a result - not to mention the danger of the rapidly expanding gas itself! Anything gets in the way of that it can be very nasty. So horsing about with a high pressure water hose is not the same as a high pressure air hose - but although the dangers are different the important thing is to tackle the inappropriate behaviour through education on relative risk. A well maintained system under the Written Scheme of Examination should be reasonably safe for use - it would only be in abnormal conditions that it creates a danger.

The HSE publication INDG261 - Pressure Systems - Safety and You is a good reference source:-

http://www.hse.gov.uk/pubns/indg261.pdf

However, I would emphasise that the requirements on competency - if you are simply interested in the dangers of hydraulic pressure, consult your maintenance engineers for advice. It is not a subject you would want to tackle on your own without the right qualifications and background.

Posted By allan wood
from what i have read hydraulic pressure release of 100 p.s.i. is enough to inject the fluid through the skin. the danger of this happening is that most hydraulic fluids, paints etc are corrosive to body tissue. high pressure water is also dangerous due to the fact that the water may be contaminated (check the water jetting association web site for more details) so it is not only the fluid you have to contend with here. just over 2 years ago i suffered a high pressure injection injury, water jetting equipment failed without warning and at 22,000 p.s.i i suffered a compartment syndrome. 3 operations later, 8 days in hospital, 2 years down the line nerve damage in my right arm & had to ghange jobs. and i was lucky the water wasnt contaminated! people have had to have fingers and even limbs amputated due to high pressure injuries. dont take any chances. look up high pressure injection injuries on google for examples. nasty stuff mate take care.