Fuel going thru Air Eliminators
Fuel going thru Air Eliminators
(OP)
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.
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.





RE: Fuel going thru Air Eliminators
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"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: Fuel going thru Air Eliminators
Are the operating conditions any different for this meter compared to the others?
Is the fuel more heavily air entrained than the others?
Is the float valve damaged in any way? The Neptune floats are supposed to be crush proof (they are foam filled) but is the pivot seized or is oit sticking in any way?
If the throughput is higher for this meter than the others then perhaps a different air release is necessary. The Neptune distributor in France produced their own high capacity air release units which may be more appropriate.
JMW
www.ViscoAnalyser.com
RE: Fuel going thru Air Eliminators
We have indeed examined the components for wear (Note some cases these are new installations, entirely new tank farms..). Only the ball floats are damaged. The round floats from eliminator have been found squashed like a balloon folded over on itself..
We do not have huge volumes of fuel going thru-these are for small northern communities, mostly a few vehicle per day fueling up, snowmobiles, and of of course the local fuel truck..
RE: Fuel going thru Air Eliminators
Did you discuss that problem with the manufacturer?
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: Fuel going thru Air Eliminators
RE: Fuel going thru Air Eliminators
IMO its much better to eliminate the source.
What's the source?
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: Fuel going thru Air Eliminators
If the fuel is sourced from static storage tanks where is the air coming from?
That you have several squashed floats suggests these are not the foam filled floats and also that the pipeline pressure may be excessive, crush proof floats or not.
Do your pumps have pressure relief bypass? what happens when you finish delivering fuel? is the pump linked to the shut off valve or does it continue to run? I suggest either using automatic pump stop or checking the pump relief valve settings.
JMW
www.ViscoAnalyser.com
RE: Fuel going thru Air Eliminators
These are definitely not foam-filled floats.I have one on my desk and it is half-filled with fuel.
RE: Fuel going thru Air Eliminators
I know they did a crush proof float, whether this is a special option or a discontinued option I don't know.
Are these meters with mechanical registers? If so then it is worth checking that the pump shut off switch is properly adjusted, it should stop the pump before the valve completes its closure.
If electronic there ought to be some means to trip the pump moments before the valve closes.
JMW
www.ViscoAnalyser.com
RE: Fuel going thru Air Eliminators
RE: Fuel going thru Air Eliminators
Delivery side (truck, barge and pipeline) outbounds have no eliminators. Loading basics are pump, strainer, meter, control valve. Plant operations dictate not to strip (run tank below regular suction) to loading rack. This is both for the sake of the pump (NPSHr, flush plans not designed for it, etc), air introduction into the system (measurement nightmare) and product quality (liver bottoms, water, etc.). Our pumps will push against closed valves for up to 90 seconds during operation.
Base question is where in your system, assuming is closed loop from AST/UST to loading point, are you introducing air?
As far as liquids passing through the eliminator to vent, what is the vent stack tied to? Could backpressure from the stack be holding the float out? Have also seen in steam traps where the hinge on the ball float (not sure if your equipment has this type) has softgoods in the hinge which swelled do to vapors and temperature and locked the float in single position.
RE: Fuel going thru Air Eliminators
The only results I have seen so far are for around 3% with full cappuccino effect (bubbles fully dispersed in the fuel possibly 5-10%) and pockets of air.
ALternatively, if your meters are not being damaged and you actually want mass use pulse output into a flow computer with a density input and use an EGA density meter. These will give 1% accuracy on density upto 100% air; (volume of liquid plus air)x(density of liquid plus air) = (mass of liquid plus air) and since the mass of the air is negligeable the mass is the mass of the liquid.
Now, as these are Neptunre meters, if they are not being damaged then you do not have too serious a problem (piston meters are usually more vulnerable to air due to shock loading when you get an air pocket followed by fuel.
SLiding vane meters are not too expensive but I am advised they are as vulnerable as piston meters. Best choice for entrained air and pockets of air is probably the PetrolInstrments bi-rotor meter which is fiscal standard but as a twin case meter a bit more expensive to buy but probably will give you a much higher on-stream factor due to its rugged design and geometry of the rotors which are well able to resist shock loading.
PS If you want an discussion doc on this, visit www.viscoanalyser.com and email asking for information.
JMW
www.ViscoAnalyser.com
RE: Fuel going thru Air Eliminators
We barge or truck fuel to the tank farms. Sometimes we have to switch around fuel between tanks (say LSDL from one LSDL tank to another) to allow maintenace, etc, but generally once we refuel (which is only a few times per year, or only once in some communities) the fuel stays put.... Occasionally we will use one tank farm or tank as "staging" of fuel intended to go on to another area or tank at some later date..
The tank farms then dispense fuel to private vehicles and to the community fuel truck (heating fuel). (Some facilities also have Jet A-1 fuel.) Our inital fuel fillup of tanks may introduce air but that should sort out in a relatively short while, should it not? is it possible that the routine fuel dispensing is introducing air? We have nozzles for vehicle dispensing and kamlock fittings for fuel truck fill...
RE: Fuel going thru Air Eliminators
If you were plowing a field, which would you rather use? Two strong oxen or 1024 chickens?" - Seymour Cray (1925-1996), father of supercomputing
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RE: Fuel going thru Air Eliminators
Whe we load trucks from the tanks we had been using bottom loading but are now going to top loading.
RE: Fuel going thru Air Eliminators
RE: Fuel going thru Air Eliminators
It might be worthwhile to check the operating procedures laid down and witness a couple of operations.
How are the connections made? Do the lines have self sealing (Hansen style) couplings or drain down flexible hoses?
What happens when he tanker runs dry during unloading or when filling a tanker is complete?
If it is usual to blow air through the lines to clear them, is this air also going through the meters and air release heads?
If I had to guess the problem occurs either when blowing down lines with air or when starting up with empty lines such that the air valve is full open and then slams shut when fuel enters the chamber at full pump rate.
The air releases are normally intended to vent small amounts of air dispersed as bubbles in the flow and hence the air release also often is combined with a filter where the filter element helps separate the air from the fuel.
Big pockets of air or air blowing may be outside of the design capability of these release units.
PS any problems with strainer screens?
JMW
www.ViscoAnalyser.com
RE: Fuel going thru Air Eliminators
I had better investigate further. We are not usually there during loading and unloading but I should be able to find out.
RE: Fuel going thru Air Eliminators
If this is a long Pipeline having many higher elevation and lower elevation segments without proper design to arrest air pocketting,then there may be such occassional problems.
Such problems do get aggravated if some portion(s)of pipeline are bare aboveground exposed to solar radiant heat input,whereas part is underground.
Problem might be addressed upto a great extent through provision of TRV(thermal relief valve) upstream of air eliminator.
Best Regards
Qalander(Chem)
RE: Fuel going thru Air Eliminators
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
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RE: Fuel going thru Air Eliminators
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)
RE: Fuel going thru Air Eliminators
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/
RE: Fuel going thru Air Eliminators
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)
RE: Fuel going thru Air Eliminators
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.
RE: Fuel going thru Air Eliminators
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)
RE: Fuel going thru Air Eliminators
The next questions to ask are:
JMW
www.ViscoAnalyser.com
RE: Fuel going thru Air Eliminators
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/
RE: Fuel going thru Air Eliminators
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
www.ViscoAnalyser.com
RE: Fuel going thru Air Eliminators
JMW
www.ViscoAnalyser.com
RE: Fuel going thru Air Eliminators
RE: Fuel going thru Air Eliminators
RE: Fuel going thru Air Eliminators
Yes Gameti is it! I started this thread before all our investogatins really started happening.
RE: Fuel going thru Air Eliminators
RE: Fuel going thru Air Eliminators
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?
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"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/
RE: Fuel going thru Air Eliminators
Are the pumps properly synchronised with the shut off valve?
JMW
www.ViscoAnalyser.com
RE: Fuel going thru Air Eliminators
**********************
"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/
RE: Fuel going thru Air Eliminators
RE: Fuel going thru Air Eliminators
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.
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"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/
RE: Fuel going thru Air Eliminators
Ken
RE: Fuel going thru Air Eliminators
The fact is they have experienced crushed floats previously and they did develop and produce a "crush-proof" foam filled float.
This suggests the problem has a relatively common cause (and possibly related to hammer or large amounts of entrained air - liquid following through after air can have a significant shock effect and is one of the major causes of damage to PD meters) and one that required a product design solution rather than an operational solution, at least, in many cases.
The point being that many installations and operations are not ideal but are reasonable and that if normal conditions creates situations where the standard float is vulnerable then the crush-proof float is a solution i.e. survivability was considered more practicable than remedial action to prevent what is probably an occasional transient condition (the floats don't crush on a daily basis).
However, from your investigations so far, there is a possibility that the cause is not an acceptable transient condition; you have reported that some PRVs were installed wrongly and this may indicate other problems that can and should be remedied.
I would hope that Neptune can give some greater insights based on their experience. Or, you could try one of the other manufacturers for their experience (they'd love the opportunity to be able to supply alternative equipment if they can show it is an equipment design fault and they'd need to be sure their own equipment doesn't suffer a similar fate). You might try some of the other manufacturers for their advice e.g. such as Liquid Controls, Smiths etc.
JMW
www.ViscoAnalyser.com
RE: Fuel going thru Air Eliminators
RE: Fuel going thru Air Eliminators
I've always been told that you have to maintain a backpressure on meters, holding them full of liquid when they are shut down, so you don't get the slugging into air filled lines and impacts on the turbines when you restart flow. If they were down for servicing, and drained, we fill them manually, venting all air out before restarting flow. As I have always designed, operated and worked with metering systems that did have about a 25 psig minimum backpressure held against them, I can't really say if not having that backpressure could be responsible.
**********************
"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/
RE: Fuel going thru Air Eliminators
what do they say about the foam filled float?
Incidentally, I see something new to me on their website which is a differential valve installed downstream of the meter and connected to the air release;
http:
This is for use where there is more air than the air release can handle and which would therefore flow through the meter if flow were to continue.
I'm just trying to figure out if, where there is a situation of crushing floats, this would help or amplify the problem.
In the O&M Manual I find this:
[quote[Air Release Valve Troubles
Troubles with this unit may arise from:
a) Collapsed ball float allowing vent to remain open.[/quote]
http:
In other words, this happens and hopefully they should be able to diagnose the common causes.
JMW
www.ViscoAnalyser.com
RE: Fuel going thru Air Eliminators
RE: Fuel going thru Air Eliminators
sorry for late comments
Best Regards
Qalander(Chem)
RE: Fuel going thru Air Eliminators