Hydraulic pressure test. Pressurization speed 5 bar/s
Hydraulic pressure test. Pressurization speed 5 bar/s
(OP)
Hi there.
I am new here and this is my first post.
I have received a pressure test procedure and the pressurization and depressurization speed are 5 bar/s and 10 bar/s.
I am not sure if these values come from any standard or are the good engineering practices for pressure test speed.
Could you please help me?
Thank you very much
Jaime (Raton)
I am new here and this is my first post.
I have received a pressure test procedure and the pressurization and depressurization speed are 5 bar/s and 10 bar/s.
I am not sure if these values come from any standard or are the good engineering practices for pressure test speed.
Could you please help me?
Thank you very much
Jaime (Raton)





RE: Hydraulic pressure test. Pressurization speed 5 bar/s
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
My question is related to the pressurization speed in a pressure test @ 315 bar for a sea water valve.
The procedure says that the increase in pressure should be 5 bar per second so from 0 bar to 315 bar it will take 315/5= 63 seconds.
I would like to know if this speed to increase the pressure (5 bar/s) is a normalized value or if this is normal practice.
The same applies for depressurizing the valve from 315 bar to 0 bar.
Thank you very much and sorry again.
Jamie
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
If you threw a 60 kg mass at 9 m/s you would get the same momentum, but instead of penetrating the steel it would just dent the hell out it.
Same momentum, about the same total force, much longer duration. Duration really matters.
Same thing happens with pressurisation/depressurization. Going from 0 to 315 bar in 32 seconds is a really good way to turn a fabrication into scrap metal. If you give the elastic properties of the metal enough time to equilibrate, you'll get a test that means something. If you don't, then places of localized stresses will reach a peak stress and not be able to transfer the stresses to adjacent pipe and can just come apart.
Whoever wrote that you could go up at 10 bar/s and down at 5 bar/s is making a silly and very dangerous mistake. My guess is that he took a U.S. procedure that said you should go up at 10 psi/s (which is common, if not very conservative) and down at 5 psi/s and "converted" it to metric by replacing psi with bar. Just for reference, 10 psi/s would get you to 315 bar in about 8 minutes. That is REALLY fast. For a liquid test I usually use 50 psi/min (3.4 bar/min) with a 15 minute soak every 1,000 psi (69 bar). To get to 315 bar, I would take 90 minutes of active pressurization plus 15 minutes soak time every 69 bar (total 2.5 hours, not 32 seconds).
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
"It is always a poor idea to ask your Bridge Club for medical advice or a collection of geek engineers for legal advice"
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
Not a criticism as you're making lots of sense - but I think it would be useful to see another version of your last paragraph critiqueing a proposal that's "up at 5 and down at 10", instead of the other way round.
A.
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
Another shot at the last paragraph:
Not many changes.
David
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
Thank you very much for your useful answers.
The pressure test is for a valve installed in a submarine.
This submarine will see a depth of about 550 m and the valve will be placed in the pressure hull. This valve will be responsible for the inlet and outlet of sea water from the cooling services on board the ship. This ball valve will have double restriction in one body, which means two ball valves in one body.
I have a quick question for Ivymike.
What kind of valve are you testing? seems that from 190 bar in around 0.015 seconds is very quick!!!!
Thanks in advance.
Jamie
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
No worries, this depth is not a sensitive value... it is just an aproximate one.
Basically it is the normal depth for most of the submarines in the world.
Cheers
Jaime
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
I just pulled up an arbitrary set of cylinder pressure traces, averaged the measured cyl pres between two cylinders (to make it more "typical"), and found that for a particular engine and rating, the maximum rate of cylinder pressure rise over a firing event at full load at 900rpm was 700kPa/deg, which translates to 37800 bar/sec. Average over 40 deg period during firing was 350kPa/deg. Fastest on the down side was -407 kPa/deg, with a -300 kPa/deg average rate over 40 deg.
So anyway, it's interesting to me that the non-engine components are so sensitive to rate of pressure rise. The components I'm used to are, but in a completely different rate regime and the main effects are due to inter-body behavior rather than intra-body behavior.
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
I've never thought about the hellish environment that engine valves see continiously. One possible difference is that static tests are done at ambient temperature and engine valves operate at significantly elevated temperature. Cooler steel is far less elastic than warmer steel and normalizes stresse much slower. Whatever the reason, I've seen static tests fail from pressurizing the line too fast when I was sure the system would have passed with a much slower rate of pressurization.
David
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
perhaps a difference between slow vs. fast pressurization is in the momentum of the fluid used to pressurize the line (it has to stop @ the valve, which may increase pressure at that end considerably)?
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
I thought your original explanation was very well presented, even though someone wanted you to change a few numbers a little bit. And, I thought your bullet vs. 60kg mass was relevant and educational as related to your explanation and situation. Then, ivymike had to stick his nose in the discussion, and get things all complicated again.
As long as the materials we use act properly within the range of their operating temps.; that is, maintain their yield and ultimate strengths and toughness and their modulus of elasticity and other mechanical properties; and we pay some considerable attention in our design and shaping and sizing of them so as to minimize stress raisers and stress concentrations; and then treat them as best the design will allow as regards fatigue and shock loading, we seem to come up with some pretty nifty machines. Don't we? My questions are: can you actuate a ball valve fast enough so the OP'ers. test makes any sense; it may have to resist this pressure but the sub can't dive fast enough to cause the pressurization rate; zdas is talking about an incompressible fluid test, and ivymike is talking about a highly compressible fluid problem, how does this enter the discussion; zdas assumed a fairly large complex fabrication or casting, while ivymike is talking about smaller, generally symmetrical, well refined parts, of special materials, how does this enter the discussion? You guys are a good deal more versed on fluid mechanics than I am after all these years. So, let's you and him fight, I'll watch and hold the bets.
My, my, what complicated things we engineers are asked to design and explain to someone who just wants to turn the valve on and not have it explode, or someone who just wants to get in his truck and drive away without warming it up.
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
It's possible that the pressurisation rate for the hull valve is being driven by the valve being opened to admit pressurised water while the boat is already dived.
A.
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
David
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
To be honest, it had never occured to me before this thread that testing quickly was more likely to break the parts than testing slowly (for a given load range and number of cycles).
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
thank you very much again for your valuable posts.
Basically the question is answered, however I would like to support the final discussion with some standard or code regarding the speed to increase and decrease the pressure during the pressure test.
From the top of your heads, is there any standard that deals with this kind of topic?
Thank you very much in advance
Jaime
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
I'm having the same issues... and despite your guidelines are the right ones, as Jaime says, I am not able to find a code that give us a justification
Thanks again in advance
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
This type equipment when used for testing small volume valves will have a very steep pressure rise when using an air powered pump or intensifier.
We tested one of our valves to 6750 psig and as I recall two strokes of the pump put us above 5000 psig. The approach to 6750 psig required a little finesse by the operator as the compressibility of water started to play a role. We were reasonably safe as these valves were designed for a little over 10,000 psig for H2, NH3, and an organic service.
You might give Calder a call to ask about testing your valves and see what they say. Calder is one of several manufacturers of test equipment.
http://www.caldertesters.com/testing_services.php
We had positive displacement pumps to achieve the 6750 psig pressure that used ball check valves. The inlet valve went fro 450 psig to 6750 at 33 times per minute.
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
Non-sense. What to you think presses do? Pressures will increase that amount if low fractions of a second.
10 bar/second is slow.
I bet this guy can can make a test system for you.
h
He just got his test system running and the first graph show 7 bar/s. I bet he can increase the pressure faster if asked.
I know have customers that change pressures in their test system must faster than 10 bar/s.
Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
RE: Hydraulic pressure test. Pressurization speed 5 bar/s
I have asked for that at my office, friends, here... but it seems that there is no code that can give you a way to justify calculations.
Thanks again!!