This was posted on the Garage Journal forum and I thought it'd be good to get the word spread. I did not write this. Hydraulics always give me heebi-jeebis.
I work in hydraulic hose direct with the worlds largest hose manufacturer as a field engineer. I do a lot of training, including safety training. We commonly train about safety around charged hydraulic systems, to help people avoid the potentials for dangerous fluid injection into the flesh.
If a failed hose or connection creates a small jet of fluid it only takes 100 psi to pierce the skin. 300 psi of fluid pressure can create a fluid jet to go through the hand flesh. Common hydraulic system pressure can cause fluid to travel DEEP up in the flesh. An employee got fluid injected at his wrist and the pressurized fluid traveled up to his elbow. 1st part of the cure was to cut a 1/2" of flesh off his arm, wrist to elbow, in order to drain the oil from the flesh. If not treated as a DEEP FLESH WOUND within 24 hours the flesh goes gangrenous and dies. Nerves and capillaries die quickly causing permanent damage. If an injection happens, get to a deep flesh wound specialist within 24 hours. DO NOT let an emergency room nurse, or doctor, apply topical cleaning and antiseptics as a cure. If not treated within 24 hours, flesh amputation is the process applied 50% of the time to stop further damage.
Used to be that only persons in industries were susceptible to these issues. But nowadays, hydrostatic drive systems at 3,000, to 6,000 psi are not uncommon on a home lawn tractor or ZTR. Many people may have a compact tractor with hydraulic features or attachments. These days it is common to have pressurized hydraulic systems in your garage. Pressurized oil, grease or paint can all cause a deep flesh wound injury.
One thing about any grease gun, do NOT use the cheapest grease gun hose you find at most stores. When I worked in engineering for Dayco, one of our highest liability claims was for failed grease gun hoses that resulted in grease injection into the skin of the operator. Think about it, you hold the grease hose nozzle onto the zerk, and apply pressure by the handle, or power switch. Grease guns have no relief, the "relief" is when the grease projects from the item being greased. I was involved in testing development for a grease whip hose for Lincoln. The hose Lincoln was using would easily burst at FAR less than a 4:1 safety factor. A hand held grease gun, or electric grease gun, can easily exceed WELL over 3,000 psi. The hose we developed at Dayco wouldn't burst until 18,000 psi and you could not kink it. The hose Lincoln was using could easily kink and fail.
Again, IF you ever get grease, oil or paint injected into your skin, get to a DEEP FLESH WOUND specialist immediately. Don't go after your project is done, don't go after your shift is done, don't go after you get all cleaned up, go immediately. If grease, oil, or paint gets injected into the flesh, the flesh dies and get gangrenous within 24 hours. Amputation is the most common treatment at that point. Tell the flesh wound specialist the following: tell the pressure of the system, tell the type of fluid injected (bring MSDS data), tell them the amount of fluid injected, tell the amount of time from when the fluid was injected. It all matters if you loose only some flesh, or feeling, or if you loose half of your hand and capabilities. I've heard stories and seen pictures of a person's hand ballooned up like a rubber glove blown up, saying the pain is SO intense to just cut it off to relieve the pain. I have a video of a hand after being flayed open to drain the fluid, and still moving , because the wound must heal from deep in the flesh out to the surface. Just be careful with ANY pressurized hose assembly.