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]

Can they be removed and replaced by manually operated vents and backpressure regulators downstream of the meters?

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

 

[jmw]

Do we presume you have examined the seals and vents for damage or wear, faulty components?
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

http://www.ViscoAnalyser.com

 

[caluna]

Thanks for the suggestions. In a pinch I guess we could use manual vents and the backpressure regulators..but it is puzzling because these eliminators are part of our standard tank farm design and in most cases they work ..

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..

 

[BigInch]

I only suggested that because we used the backpressure regulators and didn't use air eliminators at all.

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

 

[caluna]

Oh you don't use the air eliminators at all? Hmm maybe we should consider altering our design. I'm trying to contact manufacturer. Have not had any luck yet.

 

[BigInch]

Do you have air in the meter stream?
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

 

[jmw]

I'm with Biginch here. The usual need for air eliminators is where the fuel is being offloaded from tankers and can have become aerated during transit or when the tanks are pumped dry.
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

http://www.ViscoAnalyser.com

 

[caluna]

WE have PRVs on the pumps and valves. Pump is linked to shut-off valve, so it does not run when not needed. Our fuel is delivered by barge or tanker to the fuel facility, stored in tanks, then dispensed (via Neptume meter) to vehicles..
These are definitely not foam-filled floats.I have one on my desk and it is half-filled with fuel.

 

[jmw]

I have looked to see who the French company is or was that were the Neptune distributors and who made their own eliminators but without success. They don't give distributor information on their website so I guess you need to call them and ask about it.... Neptune is now Actaris, formerly they were part of Schlumberger.

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

http://www.ViscoAnalyser.com

 

[caluna]

Meter are Neptune (Actaris) mechanical Compact Type 4,c/w strainer and air eliminator.I better check about opump conrol. I am not entirely sure why we have teh air probleam at all. maybe we could just use air manual air vents

 

[JJBurdett67]

Work in several large tankfarms with varying loading equipment. Only instance where we use air eliminators is for truck off loading for biodiesel or ethanol -- maximize offload from the truck (as pump is designed to run as such) and avoid surge issues on next pump start ups. We use Brodie equipment.

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.

 

[jmw]

You could try talking to the coriolis meter guys. They are desperately trying to solve the problem of entrained air and the results are pretty encouraging. You will be especially OK if air is only an intermittent transient condition as the smart electronics can detect the air and make some form of compensation.
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

http://www.viscoanalyser.com

and email asking for information.

JMW

http://www.ViscoAnalyser.com

 

[caluna]

Thanks for all the suggestions. As far as we can tell the meters are not being damaged but the air eliminators are being broken (floats are deformed).

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...

 

[BigInch]

It could be a very high possibility that air is being introduced during transfer. Are you using bottom loading or top loading methods?

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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[caluna]

Transfer to tanks? we pump in fuel thru pipeline and in thru tank valve.
Whe we load trucks from the tanks we had been using bottom loading but are now going to top loading.

 

[caluna]

When we load from tankers I am pretty sure we use bottom loading but will check

 

[jmw]

I'd suspect that the problem occurs at some point during the loading of road tankers or the unloading of them.

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

http://www.ViscoAnalyser.com

 

[caluna]

Thanks !

I had better investigate further. We are not usually there during loading and unloading but I should be able to find out.

 

[786392]

Dear Caluna hello,
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)