Is there a table for when a leakage becomes a "spray" instead of a flow incl. pressure ?

[RedSnake]

Is there any table for the correlation between pressure, pipe/hose thickness and leakage opening when a leakage becomes a spray and not a flow?
I got this mission from my boss's, boss, boss to describe the electrical functionality between our machine parts and which pumps can be turned of without great consequences to avoid a "imaginary" spray of hydraulic oil at the same time as when there is a fire.
And how much work it will be to do this.
I ain't supposed to do a risk analyzes of the hydraulic system for this scenario but just a general one for what can be turned off and in which order to avoid other consequences.
I thought that I would at least try to see which pump systems have this risk.

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[hydtools]

Not aware of 'pin hole = spray' or 'x size hole or burst = flow'.
Some nozzle performance may apply relating deltaP to exit velocity and flow characteristics.

Ted

 

[1503-44]

I dont think it would be worth the time in finding out what parameters of pressure, hole size and shapes of "nozzle", distances, room temperatures, etc. would result in a flow or spray. As Murphy says, the conditions will always eventually result in the worse case possible. If you are investigating explosive atmospheres, assume atomization and vaporisation resulting in an explosive atmosphere. If you are investigating maximum flow to feed a fire, assume you will have maximum flow anywhere within a vertical height of H, or radius of a leak (or complete line break?) with a 45° trajectory. Convert your pressure to head and initial velocity V= (H*2g)^0.5

 

[RedSnake]

Well I think this is a far fetched Murphy at work at best.
This thing with turning off the pumps are just a secondary "system".
If the fire alarm goes off, the high fog system sets in.
And when this has happened in the past the fire has been put out long befor the fire brigade is in place.
There is very few things if almost none that actually can burn and keep feeding a fire.
And it would take a great amount of heat and fire to damage the pipes or hoses so a leak could arise.
So this two things need to happen simultaneous and separate for this to happen.

It is not that I am against turning the pumps off, it is just that this line is so old so doing it in a electrically secure and reliabel way would render a total rebuild of the entire electrical system in all parts of the machine and there is several separat parts that needs to communicate with each other for this to work.
I am not sure it would be wort the money especially since it want prevent or put out a fire.
Then it would be better to put the money in a better fire extinguishing system.

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[LittleInch]

No table but I think anything over 0.5 barg would likely result in a spray rather than a drop.

Can't understand why you want any pumps running if you have a fire??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[hydtools]

Perhaps an emergency pressure dump valve to remove pressure from the hydraulics followed by a more orderly pump shutdown as fire is being doused.

Ted

 

[RedSnake]

LittleInch it's not that I "want" them running.
What they asked for was that we prevented oil spray if there was a fire alarm, but in my mind it is already prevented since the hydraulic system is built with high mechanical security margins to prevent leakage in the first place since it is a personal security risk if it starts to leak.

Anyone knows at which temperature hydraulic oil starts burning?

I have 6 different pump systems running in each machine.
One is the main pumps 1100 liter/min max pressure 325 bar and there is 4 of them in one machine.
Saying it like this, of course there would be great consequences if there would be a fire and a pipe would start leaking with spraying.

But we have a super sensitiv fire alarm system so when the fire alarm goes off.
The people running the line puts the line in cykel stopp and then goes outside if they don't do this they will have a whole bunch of material on the floor when they get back in.

What happens then is that the pumps are standing in there zero position no flow no pressure.
The motor is running but the only pressure is in the pipes on the minus side of the cylinders and that pressure is the weight of the ram but this weight is also out balanced with a pneumatic cylinder.
If the ram falls down under a certain position the pumps will angel out and pull it up again with very low flow and pressure during a couple of seconds.
This pipes has the dimension 76,1x12,5 and the visible part is maybe 50 cm the rest is inside the hydraulic tank.
And then maybe a total of 3 meters on top from the pumps to the high pressure block only pressurized under the pulling up part.

If a leakage of this pipes would arise during production then the machine would not be allowed to run until it is fixed since it is a personal safety issue since the ram can fall down uncontrollably.

So I am just trying to figure out if this "not fulling the fire with hydraulic oil spray" is achieved by just having the pumps in "idle" mode.




“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[1503-44]

I agree that you should not consider a leak plus fire, but you should possibly consider the piping system's response to a fire. If the pipe is so old to make you question its integrity during normal operation, or during a fire, it should be hydrotested and replaced, if found to be deficient. Otherwise do not combine what should remain two separate issues.

You should examine the pressure increase due to temperature expansion from a fire heating the pipe and contents, which should remain below pipe system design pressure. If that is not the case, such overpressures are usually limited by using a "thermal event" pressure relief valve discharging to a safe drain location. It is actually a pressure relief valve set to pipe design pressure + 10% or so.

 

[mk3223]

Q: Anyone knows at which temperature hydraulic oil starts burning?

Typical petroleum based hydraulic fluid has flash point that range from 300 to 600 Deg-F, and an auto ignition temperature of 500 to 750 Deg-F.

The material MSDS (or SDS) has the detail information of the specific hydraulic oil, including chemical properties, health/safety/fire/environmental hazards, etc.

https://whyps.com/is-hydraulic-fluid-flammable

 

[Latexman]

The flammability of “hydraulic fluid” varies a lot. Which hydraulic fluid is used?

Good Luck,
Latexman

 

[RedSnake]

Only 99% sure it's DTE 25..

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[3DDave]

I recall a fluid power safety article that talked about a case where hydraulic fluid spray reached the overhead infrared-heaters, triggering a fire. The bad news was the spray also reached the ceiling material that was above the sprinkler system, burning through through the roof and then burning down the building.

 

[Latexman]

SDS says FP > 200 C, so somewhere between 201-315 C. AIT, not determined. Great, limited data.

Unfortunatly, the mist of a fluid is much more flammable than the fluid. My company considers "lube oil systems where an oil leak/spray could be ignited by a hot surface" to be a fire hazard.

With limited data, I'd say plan for the worst, and hope for the best.

Good Luck,
Latexman

 

[1503-44]

IMO evaluating a scenario that is already a "double jeopardy" situation which, for some reason, does not burn or explode, is kind of like relying on a good miracle to counteract a bad miracle. I generally allow for a maximum of only one miracle to happen in any given scenario. I never look for 3.

 

[Latexman]

I’m not familiar with the area/room/building, but the way it might happen is:

Oil spray/leak reaches hot surface/finds arc/flame and a fire or worse occurs.

I count that as a single failure, but it depends on what’s in the area. The OP will have to weigh in. This may not be credible. It sure would be good to know the AIT of DTE 25 mist.


Good Luck,
Latexman

 

[1503-44]

Leaked oil hitting a hot surface, or ignition source, yes. That's not double jeopardy.

 

[RedSnake]

Oil spray/leak reaches hot surface/finds arc/flame and a fire or worse occurs.

There is no hot spots or heat sources around or in the vicinity, normal surface temperature can reach maximal around +55 C.
The area and the building is concrete and steel.
The only burnable material except the oil is cables, electrical equipment inside cabinets, and sometimes wood crates and packing material but that is always at the end of line where people work with packing.
The fire detectors also detects oil mist, they think it's smoke.

On the old line which I am looking at there have been more "false" fire alarms for oil mist then actual fires.
The only open flame fires there has been two (not counting electrical short circuits inside cabinets) has always been during commissioning no hydraulic systems running, it's more then 30 years since the last time that happened.
A mechanic using a plasma cutter and hadn't cleaned up the area as required before starting even the inspector hadn't done his jobb properly, some cotton rags with oil on court fire but it was soon put out, no big fire.

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[1503-44]

Oil mist can easily create an explosive atmosphere incompatible with cables, ignition sources and other "non-explosion proof" equipment. Definitely want to guard against that condition and take immediate action if it occurs.

 

[Latexman]

Response to fire/oil mist detectors should handle that.

With OP's description and hottest surface 55 C, I really don't see any fire issue.

Good Luck,
Latexman

 

[1503-44]

I think she said smoke detectors, which might not work if the oil mist evaporated, right.
And there still might be a problem with high pipe pressure due to thermal expansion from just any fire that might occur for any reason.