Fuel going thru Air Eliminators 2

[caluna]

Fuel leaking thru Air Eliminators at tank farm dispenser bldgs.
In several of our installations we have had problems with fuel leaking thru air eliminators. These are small scale dispensing facilities for diesel. We do not have this propblem in every facility, nor can we figure out why it occurs in some and not in others. We have Neptune compact meters with air eliminators located in the piping. We have looked at the PRVs in bypasses around all the valves on the lines and checked them for direction of flow and setting. Even when these are all OK we are still having troubles in one location with fuel blowing thru. Any thoughts?
thanks.

 

[BigInch]

786392 There should be no air in the pipeline. Theses are refined products. Where is the air supposed to be coming from? Presumedly, a thermal relief valve would only open if its temperature set point were exceeded, thus any air passing by at lower temperatures would not exit through a thermal relief valve.

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
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http://virtualpipeline.spaces.live.com/

 

[786392]

Dear BigInch,
I do have highest degree of respects for your good self& an admirer, as I have been going through your posts in the past, made me learn a lot.
However here I will like to differ that if the system is completely "Closed" without any possibilities (normally) for air entry, then why the air eliminators provision existed?
Not clear to me. Please elaborate.
Moreover in case of long pipeline systems (if not properly designed and/or subsequently modified without adequate hazops) such problems may be faced and get aggravated as referred in my previous post.
We faced a similar problem on re-locating the Jet fuel Filter/Water separator and modifying the pipeline leading to this equipment; may had been an outcome of our poor designing/lay-out work.


Best Regards
Qalander(Chem)

 

[BigInch]

OK. Any significant amount of air like that shouldn't be there and would indicate other things need to be fixed before messing with the air valves.

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************

http://virtualpipeline.spaces.live.com/

 

[786392]

Dear caluna,
I would suggest you to further explore on JMW's post, with specific reference that; if there is Batch/ parcel pigging taking place?
Normally for multi product pipeline’s economical usage separator pigs are employed in many situations.
If so, then subject to the system involved at Pig Launcher/ Retriever air introduction possibility into the pipeline system can not be ruled-out especially if pigging was not initially practiced and to minimize contamination/ downgrading recently employed.
Please appreciate we have to look for a 'change' for problem identification/resolution.
Please review/confirm.


Best Regards
Qalander(Chem)

 

[Daianto]

Caluna here, my login as myself not working..
Thank you very much for all this.

Some info meantime while I get more on the loading ..
- No separator pigs are used- each pipeline is only used for one product.
-No special strainer problems noted.
-Pipeline lengths-in the installations in which we have been seeing problems, no length is longer than several hundred metres-some are shorter.

 

[786392]

Caluna/Daianto,
Then you have to check intermittent loading/ Decanting of Tank truck, Bowsers& small barges utilizing flexible or removable systems as this may be the possible source.
• Otherwise problem of sucking-in air into your pumps suction pipelines either through vortex formation in storage tanks or
• Reduced NPSHa against NPSHr
o while pumps are tried for full throughput;
o as sometimes suction bucket strainers get some obstructing foreign materials bulky enough to reduce NPSHa
o thus inducing some air via suction pipeline gate valve seals/glands
• Beyond the handling capability of air eliminators designed for.
• Another possibility if Flow rate is somewhat reduced is screen out suction pipeline block valves open-ness
Hope this helps


Best Regards
Qalander(Chem)

 

[jmw]

I should add that if there is damage being done to the air eliminators then the meters themselves may also be suffering.

The next questions to ask are:
[ul][li] how old is the installation?[/li]
[li]Is the problem recent or has it been inherently a problem since the begining?[/li]
[li]If the latter, what changed and when?[/li]
[li]What does the meter history tell you? - how often are the meters calibration checked, serviced or repaired? what parts need replacing, is there a change in the pattern? do rotors need replacing more often or about the same?[/li]
[li]Is the current installation as per the drawings? (not all changes are necessarily well documented)[/li]
[li]Perhaps most obviously, take a look at the pump history also. It might be that the pumps were uprated at some point simply to improve turnaround times, this is worth investigating, especially in older systems.[/li][/ul]


JMW

http://www.ViscoAnalyser.com

 

[BigInch]

Pigging, shouldn't be the cause. If done properly, no air is introduced into the lines. Pig launchers should have small diameter fill line and vent lines to load the pig, fill with product and vent any air in the barrel before launching. The high available pressures for loading should be enough to force almost all of any remaining air out, as well as the barrels should have an angle forcing air towards the vent. No more than a couple of cubic feet of air at most should ever remain inside, even if done with the worst of operator skills. Not very likely IMO.

"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************

http://virtualpipeline.spaces.live.com/

 

[jmw]

By the way, when doing your witnessed loading, you might try using your ears as well as your eyes.

I went once with a flow meter engineer and he had a large old style screwdriver with a bulbous wooden handle that he used like a stethoscope to listen to what was happening in the flowmeter and fittings under normal conditions and as valves were opening and closing.... if you could get an explosion-proof microphone it would be nice to hear a recording.



JMW

http://www.ViscoAnalyser.com

 

[jmw]

Caluna, did you find the problem?

JMW

http://www.ViscoAnalyser.com

 

[Daianto]

Sorry I have been away for 2 months. We are finding some interesting things- some pRvs were installed backwards, and relief valve settings were wrong.Some equipment only rated to minus 20 and we have design temps of 1% minus 45 or worse.Still investigating and talking with meter mfgr.

 

[kenneth2]

Caluna, your question seems all to familiar to one I am presently working on. Whwen I saw you were in NWT for the GNWT I was not suprpised at the nature of the question. I am working for the GNWT as an outside consultant and am working on this very issue. Gameti just had a ball float crush as you described. Where elsewould you be referring to the probelm? I am talking to the supplier ( whom you likley know as wel) as well as Actaris Neptune in US ( now Itron)

 

[Daianto]

Hi Ken!

Yes Gameti is it! I started this thread before all our investogatins really started happening.

 

[kenneth2]

OK all. I am working along with Diaanto/Caluna on this same probelm up north. The latest si another Actaris air eliminator ball float has been found collpased at the same facility as twice before. It may be way out there, but does anyone think this may be attributable in any way to a sudden and raid cointraction of the warm air in the sealed hoolow stainless steel ball resulting in a poartial vacuum. The balls are installed from a box taken from a warm building then subject to -40deg C diesel liquid. This may be a bigger pressure than we think if the ball is already submergred in 30 feet of diesel ( only about 8 psig though. I am thinking about the Magdeburg Hemisphere experiments where two hemispheres took an extreme force to be pulled apart when in an internal vacuum. With a 5 inch dia ball and a pressure differential of say 15 psi ( 14.7 psia atm + 10 psi from liquid - 10 psia in ball)acting on the crossection the force could be as high as 300 lbs or more. Any comments?

 

[BigInch]

Crushing by pressure alone doesn't sound likely. Crushing a sphere via hydrostatic pressure isn't easy. A 5" diameter sphere made of 5 mill thick steel could be in 100 ft of diesel (w/ vacuum inside it) and still have a safety factor of 4.

Maybe its possible that rapid uneven cooling had something to do with it. I think it would tend to create shrinking of the outside surface while the inside surface tended to retain its warmer dimension, possibly increasing compression stress on the inside wall. Once losing its spherical shape, it could crush at a much lessened pressure, although 30 ft of diesel wouldn't seem like it could do it. How thin is the wall?

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[jmw]

Not at line pressure, but if there is a fast closing batch valve might the hammer effects push the peak pressure up enough?
Are the pumps properly synchronised with the shut off valve?


JMW

http://www.ViscoAnalyser.com

 

[BigInch]

Also not likely to be that high. 50% increases in pressure are a typ max.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[kenneth2]

THank you biginch and JMW for feedback. Now my theory of inernal partial vacuum resulting from rapid cooling of a room temperature ball from the box imeediately put into service in -40 deg liquid diesel is valid from a perspective of physics I think. HOwever it is a very long shot and not likley the cause, or perhaps only partly the cause. The stop/preset auto valve is just downstream of the air eliminator ( with ball) and meter. THis is the next piece of equipment I am going to check as it may slam closed thus the hammer we speak of. I appreciate your comments on the pressure you observed with a gauge. In ordet to properly identify this elusive probelm at the Gameti facility ( 350km north of Yellowknife, canada) we may need to intall test nipple and guage directly onto the drain plug fitting on the air eliminator, to observe what happens at start up of the pump. This pump cannot put out pressure emore than about 25 psig., even when deadheaded.

 

[BigInch]

Kenneth,

A 50% increase in hammer pressure is typical for a filled system (no air) and a fast valve closure. It could be higher, if a high velocity liquid slugged into an air filled pipe.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[kenneth2]

Thanks biginch- The pump can only put out 25 psi total head when blocked in so I dont think the system mpressure is anywhere near the 150 psig the meter asembly, including the ait eliminator is rated for. Still at a los to explain. Will probably have to go back, install new ball and put a pressure gauge directly on the air eliminator drain plug to monitor any spikes in pressure at start up.

Ken