Air Elimination in Truck Offloading

[jamielahembree]

Is anyone else having issues with air elimination to prevent air entrapment in offloading pumps/false meter pulses on their offloading skids? Our standard LACT skid has a highpoint strainer (sans basket) with a small air eliminator off the top of it from FMC (

http://www.fmctechnologies.com/en/M...echnologies/LiquidSystems/FabSkid/LACT.aspx).

My thought is we likely need to just upgrade to a larger knockout tank on the suction side of the unit but that leads to further discussions about level switch settings as there is limited elevation difference between the suction of the unit at ground level and the belly of the offloading truck. FMC also offers a combination strainer/meter (

http://www.fmctechnologies.com/en/M...ducts/ValvesLineAccess/AEDeaerators/APS.aspx)

that I think might help, but was wondering if anyone had any experience with. Any thoughts on eliminating air entrapment prior to offloading pump/metering would be greatly appreciated.

Thanks!
Jamie

 

[BigInch]

It is often easier to look for and stop where air is getting in rather than trying to get it out.

 

[jamielahembree]

Unfortunately, due to truck drivers fully emptying their tankers (and the middle compartments taking longer to offload than the exterior compartments which are all still attached to the pump suction)and the coupling and uncoupling of hoses, I really have no way to eliminate any air/vapor from entering the system. Thank you for your input though!

 

[BigInch]

Are you doing bottom loading?

Hopefully all your internal pipe pressures are above 15psiA

 

[LittleInch]

Can you sketch out your system so we can understand it a bit better?

From what I gather here, you are receiving oil from tankers then pumping and metering it off the tanker into a pipeline or other storage or processing facility??

Depending on where your air eliminator is, you might just be sucking air in.

The pressure at the air eliminator needs to be > atmospheric at all times otherwise it doesn't work and most LACT skids I've seen are setup to pump from tanks.

Your other option is to bury a small tank and feed by gravity into it with a vent going at least as high as the truck top and then pumping from there stopping before your inlet pipe becomes exposed.

Connecting an offloading pump direct to a tanker is always going to suck in air at some point and always carries the risk of collapsing the tanker if the inlet vent doesn't work properly.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jamielahembree]

Drawing

 

[jamielahembree]

P&ID

Thank you all for your input!

 

[LittleInch]

Neat looking piece of kit, but your air eliminator is simply no where near big enough to cope with the quantity of air you will get either by simply having empty hoses or sucking dry one truck compartment before the other.

If you're really getting prblems then I would mount a bigger pressurised KO drum between the pump and the filter off to one side with a much larger air eliminator valve on it and an offtake off the side below the top dome or flange to give large air pockets somewhere to go before being released.

It's clear to me looking at the literature that these units are just not suitable for truck offloading unless modified to allow these large gulps of air to be captured and released prior to the meter.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BigInch]

You're right LI. They are for truck loading at remote well sites, taking relatively dead oil from field tanks.

 

[LittleInch]

No, the OP is talking about truck OFF loading from trucks to something else, tanks, pipeline whatever

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BigInch]

Yes I know.
Take oil from tank,
run through LACT,
put into truck.

But isn't he trying to do the reverse here?

 

[LittleInch]

Correct, but you keep talking about Loading INTO a truck....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BigInch]

Well you wouldn't load from a truck(?), or load out of a truck(?) ... would you?
I'm saying that it is FOR loading trucks. It is NOT for UNloading trucks.

Are you thinking like - OFFloading TO a truck???

 

[LittleInch]

That's what I'm saying - read the OPs posts - this is clearly a truck arriving at a location and OFFloading via this skid into a tank or a pipeline, i.e. it is for offloading trucks, which this skid is clearly not able to cope with.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Duwe6]

Direction doesn't really matter; the prudent folks attach a vent line in addition to the loading/unloading line. That way the purge from the receiving container refills the delivering container; you move the purge back to replace the product being delivered. Air makes for explosions; nitrogen purge is our friend.