Software solutions
Software solutions
(OP)
My problem involves a fuel transfer pump. Each time my client first turns it on (1-2 times a week) to pump fuel from the holding tank to his truck loading rack, the pump creates a pressure surge which is breaking piping mounts. The pipe is visibly moving 6-12 inches depending on the location. Once it has been started, subsequent restarts cause no problems.
Luckily I did not design the pipeline, however, I am interested in what other engineers would suggest in the way of modeling software to root out the real problem. I am not looking for anything free, but really just ease of use and say less than 20K a seat.
The specs are 6"-8" pipeline, about 1,143 feet long. The pump is a Goulds Pump 3196 4x6, 1200 GPM. I walked the pipeline today and there are a couple of things that don't look right, but I would really like to model the thing and see what I can come up with.
thanks for your reply's in advance
-dave
Luckily I did not design the pipeline, however, I am interested in what other engineers would suggest in the way of modeling software to root out the real problem. I am not looking for anything free, but really just ease of use and say less than 20K a seat.
The specs are 6"-8" pipeline, about 1,143 feet long. The pump is a Goulds Pump 3196 4x6, 1200 GPM. I walked the pipeline today and there are a couple of things that don't look right, but I would really like to model the thing and see what I can come up with.
thanks for your reply's in advance
-dave





RE: Software solutions
So, based on what your describing I suspect the line isn't full of fuel when the pump starts. The slug of fuel races down the line, compressing the air untill the air won't compress any more, and the line jumps as the fluid is brough to a stop.
Your client may be pruging the line between uses. (which is a bad idea for several reasons.) Or there could be a leak somewhere which lets air in and allows product to drain back to the tank. Solutions would be to find the leak (look near high points) and / or to install a check valve at the pump outlet.
Now that I think about it this did happen to me once. On startup i shattered a meter blade because i didn't purge all the air out of the line before starting the pump.
RE: Software solutions
I use Stoner Pipeline Simulator by Advantica, but don't know the current cost. Applied Flow Technologies has a series of programs that you might want to investigate. I think "AFT Arrow" is their basic transient analysis package.
You have to sort through the options you want to add to arrive at the pricetag.
http://www.aft.com/products/fathom/
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Software solutions
Another thing that struck me as very strange was that about 900 feet away from the pump, the pipeline the line size goes from a 8" to 6" line size. There are no branches it just necks down before going back up to a pipe bridge and over to the truck rack itself.
As for the size of the motor I agree it likly too large, it is a 75 hp motor. Strangely enough after the tech bumped the pump (and the pipe made a horrible noise) he let it sit a moment then restarted the pump and there was no problem. The pump had not been ran in about 7 days.
All in all an interesting problem, you should see the pipe support that our client tried to clamp the pipe down to. The concrete was basically torn from the ground.
RE: Software solutions
John
RE: Software solutions
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Software solutions
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Software solutions
This is me just talking out loud and may not be an effictive solution.
Zuccus
RE: Software solutions
and
"Strangely enough after the tech bumped the pump (and the pipe made a horrible noise) he let it sit a moment then restarted the pump and there was no problem. The pump had not been ran in about 7 days."
Biginch, if the motor were too powerful, why would the problem dissapear after a subsequent restart? I assume the restarts are a few minutes apart shuch that the fluid has stopped.
RE: Software solutions
And at the truck rack no fuel was moving at all. As far as I could tell all we were really doing was pressurizing the pipeline.
RE: Software solutions
khardy,
Transients are the result of either converting static head to velocity head = v^2/2/g, or converting that velocity head into a pressure head. Any change in momentum of the fluid must go somewhere. After the first start the line is packed full as product enters the pipeline and the pipeline reaches pump discharge pressure. The second start does not add enough additional fluid volume to the pipeline's already packed and compressed contents to create another velocity with enough momentum to kick the pipe around again. If he depressurized the pipeline than restarted, I'm pretty sure he would get the same results.
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Software solutions
I agree with the suggestion of John Breen; the installation of a pulsation damper should go a long way toward solving your problem.
Also, your 1200 gpm of liquid going through a section of 6" NPS piping gives a fluid velocity of ~ 13+ feet per second, which seems a little high.
Any chance that a high-range pressure gauge (or two) could be installed on the line to get an idea of the magnitude of the surge ?
Actual pressure measurements could come in handy if you do decide to verify computer analysis done on the system
-MJC
RE: Software solutions
a high-range pressure guage would be great, but like most clients they would only like to know real answer to the problem if it does not cost them additional $.
I am guessing that I will probably be installing a VFD or control valve to eliminate the symptoms and changing out to a smaller impeller.
RE: Software solutions
I'm assuming like most loading racks, the pump starts, pressurizes the line, and a moment later a valve at the loading station is opened either automatically via a controller or manually. Is this the case? Also, is this a centrifugal pump or PD? Is there a pressure relief valve in the line?
RE: Software solutions
Your assumtion is correct.
Centrifugal pump. There is a pressure relief in the line, it is near the pump/tank and is connected downstream of the check valve and connects back to the Pump outlet.
I downloaded a free demo of AFT Arrow and AFT Fathom to see how they actually work. As soon as I get a chance at least.
thanks,
dave
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RE: Software solutions
The demo only works on their included example problems. You can't set it up to run your's. But you can see how it works.
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Software solutions
I agree that transients are the results of a change in fluid velocity. But just pressurizing the line won't do it; there has to be a change in velocity. In "subsequent restarts," the line is packed and starting the pump causes no change in velocity, thus so pressure wave. When you say, "After the first start the line is packed full as product enters the pipeline and the pipeline reaches pump discharge pressure. The second start does not add enough additional fluid volume to the pipeline's already packed and compressed contents to create another velocity with enough momentum to kick the pipe around again." you are baisically restating my theory. What I don't understand is how the line is getting "unpacked" when they secure from loading for a few days.
Kepharda,
After they are done loading for the day, do they close one or more of the pump isolation valves? If so, here is a theory: After securing from the day's loading the staff closes the pump's isolation valve(s). During the following days, sun heats the discharge line, expands the product, which in turn is vented through the pressure relief line back to the tank. When the line cools at night the product contracts and pulls air in through a very small leak in a valve or flange at the rack. When they start the pump a few days later for the first time, the fluid rushes down the line, compressing the air trapped in side, until the air won't compress anymore. The product stops suddenly and the resulting pressure wave causes the pipe to jump.
I know you said the line is packed, but this is the only thing I can think of.
RE: Software solutions
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Software solutions
The relief is connected back to the piping just downstream of the pump's outlet....I don't exactly know what you are asking for sure, there is only one fluid outlet on a pump,....let me know if this is unclear.
Khardy,
The pipeline isn't operated in that manner, it is only run sporadically lets say 3 times a month. Yes, the "sunshine pressure" is created because the pipeline isn't operated continuously. So transmix does sit and depressurize thru the relief back to the tank.
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RE: Software solutions
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Software solutions
I am calculating the pipeline head as I write. I am just estimating there is approximately 2.5 times as much head as is required.
I was out on site looking at the pipe supports today trying to figure out how we can fix them and while we pressurized the line just the other day, today the Bi-metal pressure gauges all read zero PSI.
Although with the transients they (Press Gauges) have seen, I doubt they are too accurate anymore.
Even for US Government work :)
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RE: Software solutions
[pump]-[check or valve]-[relief back across check or other valve]-[pipeline]
I don't understand how the relief valve is supposed to work. I don't see how you can relieve anything into the pump discharge when the pump is running. What is it doing? Just providing thermal relief when the pump is off?
Ya, 2.5 times the head and no telling how much torque you've got coming on at startup will knock the socks off that line.
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Software solutions
And yes again there is a check valve between the pump and the pipeline.
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RE: Software solutions
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: Software solutions
Even with a conservative estimate I am only finding about 109 total head due to line losses and elevation change.
The pump installed is rated at 300 ft of head at 1200 GPM.
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