Hydraulic test bed

Hi, I am currently trying to assess a hydraulic hose and component test bed. I have 2 questions, I hope someone can help who has experience.
When a hydraulic hose under test 1.5xMOP, in this instance = 16 kpsi, Pump flow is extremely low at 1/3 gal/min or less at higher pressures.
1. I am getting all sorts of conflicting information. After the hose is pressurized and the end fitting rips off, I am told that the pressure will just go to zero. This makes sense, so if a fitting rips off, will it not become a projectile. The only thing to worry about is if the hose gets a pinhole. That needs to be protected against. It makes sense as well. BUT... On the other hand, I am reading from other sources that the fitting will be projected and high velocity impact will happen at the barrier. This makes sense in a gas, a compressible system.
2. If it is a projectile, what is the simplest way to model the impact, so that I can design the Lexan or high impact resistant plastic? Is it so complicated that no one knows? I can't believe it, yet everyone I talk to has a different approach,all of which will take days to solve. We have the projectile at the wall, just what is next.
Please Help in Florida. Diana
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Dear dhawkins:

Not "just".

Depends on your setup. You will have the hose which will get shorter and fatter under pressure, which will suddenly extend to full length. Next you will have a liquid that can dissolve a fair amount of gas (especially if it is being sheared across a relief valve) that can "fizz" just like mentos and diet soda.

Trust them. They probably still have all their fingers and eyes.

You can have that, if you don't degas the liquid, and control its temperature. It is really common to use manual foot-operated pumps, once the system is fully flooded and purged.

Test it under water (or oil).

It is a bullet. The amount of energy dependent on how you condition the liquid, and how much of it you have under pressure.

It would help if you descibed the exact setup.
I heard of a hydraulic setup that was put under pressure without purging the lines first. A hose let go, and struck and killed a man. It wasn't a big hose either.
I know of another installation where an 8 foot diameter, 6 inch thick metal cover was launched "30 feet" into the air, because the engineer drew the hydraulic control valve in the energized position... and the machine was not ready to take that.
David A. Smith
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...

Sigh...
The steel plate lifted far enough to clang back down. The dozen or so 1" dia studs and nuts shot up and hit the ceiling 30 feet up. Sorry.
David A. Smith
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wrote:

...
Disclaimer: no direct experience.
I'd suggest you model the available energy as a force provided by the 1.5 MOP acting on the fitting's cross section area, which tapers to zero over a travel distance of one tube diameter. This will give you a reasonably conservative estimate of the acceleration and hence the peak velocity for the fitting.     You can suppose that the initial flow rate is not limited by the pump's flow rate, but rather by the modest elastic expansion in the hose, 'deflating' when burst.
Brian Whatcott Altus OK
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Diana-
A hydraulic system pressurized to 16,000 psi & taken to component failure is a very dangerous situation. In spite of the fact that hydraulic fluid is rather incompressible......you have a compressible "system". There could be a significant amount of stored energy that will be released when the hose fails or the fitting rips free.
The amount of stored energy is dependent of the system geometry & the component material properties. How big is the hose? 1/2" 2" You need to calc the stored energy involved.
I would suggest you compare that value to the energy stored in a garage door tension spring. The comparison will give you a real world reference as to whether you are dealing with something 1x, 10x or 100x more stored energy. Even a failed garage door spring can do a fair amount of damage.
You need to design a system to direct the failed parts along a safe trajectory & into a safe catchment. Taking the impact of the projectile directly into some sort of barrier especially plastic doesn't sound like a great idea
The tone of your post is making me nervous about providing information for you to proceed.

not so fast............
You've got a dynamic failure situation..........I suggest you get some experience on "to failure" system with water, garden hose & garden hose fittings that will fail at a few 100 psi. I think you'll surprised at the behavior.
You've got potential danger from the hose, the fittings & the pressurized oil.
May I inquire as to your education & experience level?
Do you have a degree in mechanical engineering? If so where & when?
How much experience do you have with hydraulics >=3,000 psi?

In case you're wondering.... I'm a PE (mechanical) & I have 30+ years experience with hydraulics & have seen my share of scary failures, hydraulic & mechanical.
btw a 1/4" hydraulic hose (3000 psi) vented atmospheric pressure for <10 secs generates enough mist to fill a 100,000 ft^3 room with a nasty hydraulic oil cloud.
important safety tips.............. use a manual pump; hand or foot operated. minimize system stored energy when starting out, increase it as you gain experience.
cheers Bob
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As other engineers have stated here, it is not true that using an incompressible fluid for this pressure test will not launch the components at dangerously high speed. At 16,000 psi, a failure of even small parts can kill somebody. A pinhole would be a relatively minor failure compared to the injury that a launched fitting or whipping hose could cause. Using an incompressible test fluid and a low flow pump will greatly reduce the whipping, but still the hose must be properly secured so if it fails it won't smash up your test setup or beat somebody to death.
A fluid that is theoretically defined as incompressible is not absolutely incompressible.
Before I became an engineer, I performed high pressure burst, proof, and leak tests on small components, mostly valves about the size of your fist, but also some pumps and hoses. As an engineering intern, I performed burst tests on sample pipe welds. As an engineer, I performed pressure testing mostly on ASME pressure vessels.
I am now retired and no longer have access to test design references. I am sorry I can't help you design a Lexan window to view pressure tests, but I may have some suggestions that may help.
Your test procedure should first include a proof test where personnel are well protected. This is usually not witnessed; the test article is in a cell or behind a barrier. I conducted tests on the order of 10,000 psi behind a 1/4" steel plate barrier. The test article was pressurized with nitrogen while submerged in about 100 gallons of water in a tank, also constructed of 1/4" steel plate. After a proof test to verify the integrity of the test article, THE PRESSURE WAS REDUCED and the operator then entered the test cell to verify the leak tight integrity through about half a foot of safety glass (about 10 layers).
The pipe burst tests were conducted in a concrete block test cell. They were pressurized with water using a hand pump from a remote room.
I would guess that the impact calculation would be relatively complicated and would involve many assumptions. Factors would probably include the volume of fluid in the system; it's pressure; it's compressibility; and the weight of the assumed projectile.
I have never seen this calculation performed. I have seen pressure vessel blast energy related in terms of tons of TNT based on the pressure and volume of a particular fluid a couple of times but usually the test designs were based on the engineer's experience of failures and much, much extra precaution.
Your approach, contacting those who have designed these facilities, is wise. Good luck.
Mitch
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