Blending crude w/condensate

[ivymike]

Hello,

I've recently come across a setup which makes me worry a bit. A contractor is blending crude with condensate to achieve a desired API gravity. They have been using a cylindrical trailer-mounted mud tank and a small diesel pump for this purpose. Short version is they hook up a truck of condensate, pump it in, hook up a truck of crude, pump it in, run the mixer, check the gravity, pump it out into several trucks. Often some of the mixed product is left in the tank overnight. To me this seems like a fire risk - I expect the tank will be full to the brim with flammable gas when they start pumping fluids into it in the morning, and that the displaced gas will potentially find oxygen and a source of ignition in the surroundings. Can anyone here provide comments w/r/t (1) how common this sort of process is, (2) whether I'm right to be concerned, and (3) what precautions are recommended to prevent ignition at such a site?

I have a copy of API RP 500, it seems like "Combustible Liquid Storage Tank in a Nonenclosed Adequately Ventilated Area" might be a representative scenario?

 

[BigInch]

Right the problem with condensates is the vapor pressures. Normally we would take the condensates out of the crude, to sell them at a higher price and to "stabilize" the crude to permit a pump of single phase flows. The guy is most likely devaluing the condensate by mixing it with the crude, then sending it to a refinery to separate it again???? Wasting money, time and energy. Maybe he needs to blend the crude to pump it into his trucks. How heavy is the original crude? If it is sellable as is, get in there, buy both, keep them separate and make your profits.

Sure the high vapor pressures are more dangerous. They should have hazardous area classifications and conduct operations within accordingly. No lights, cell phones, engines.

Independent events are seldomly independent.

 

[ivymike]

A bit mysterious to me, to be honest. I was told they use the mix for mixing mud at drilling sites. Apparently they're trying to get the gravity up to 48 (but not above, so they can still ship by rail). I'm not aware of the gravity of the crude .. but they get both "light" and "heavy" in and have separate storage for each.

Another failure mode that comes to mind is foaming if the centrifugal pump cavitates during operation (restricted lines, closed valves, etc) - does anyone know what would happen in the event that a pump used to recirculate a mix of condensate + crude in/out of a tank should happen to have its flow (inlet or outlet) obstructed? I'm imagining a foamy "milkshake" filling up the tank in short order & pouring out the top - but don't know whether that's plausible or not.

 

[ivymike]

cavitation or air entrainment, perhaps ... I'm thinking of this:

http://www.plantservices.com/articles/2010/07LubeFoaming.html

 

[BigInch]

So that's what's going into the aquifers?
Take pictures and see if you get shot at.

Cavitation and foaming is possible, but I doubt they're worried about that.
Least as long as the pumps keep running.

Independent events are seldomly independent.

 

[ivymike]

only reason I heard about it was that a pump isn't running anymore, and the failed unit included some of my company's parts. One of my first thoughts after I saw a picture of the site was "who thought THAT was a good idea?" ... I think the answer is that nobody really thought about it beforehand. Someone mentioned fluid coming from the top of the mixing tank and I'm trying to think of why that would be occurring (besides overfilling - the tank should have been nearer empty than full, based on the story), hence the remarks about foaming and/or cavitation. They also said that the pump unit sounded like it sped up, and it made a lot of noise before eventually stopping (I ought not to give details of how exactly it stopped, but it was reportedly stopped from the power end not the driven end, and the story makes me believe that pump power input was very low before the failure). The unit's predecessor was swapped out a few days earlier due to "sounding funny." I hope to see the hardware in person someday ... but it may not happen.

thanks for the input so far - if you've got any more thoughts I'm interested in hearing 'em.

 

[BigInch]

Oh! Cavitation is likely and goes hand in hand with "sounding funny", low power and the low flow theory. Air entrainment reduces efficiency and builds heat. Possibly making things vaporize that much quicker, of course foam is possible with air entrainment. What kind of pump, centrifugal, positive displacement?

Independent events are seldomly independent.

 

[ivymike]

centrifugal. fluid intake directly below outlet (maybe 3 ft apart), and I can't guarantee that the inlet was very deep in the fluid when the pump was running (supposedly less than half full tank).

 

[BigInch]

With higher viscosity, frictional pressure drop is a larger proportion of the total drop to the pump, again not helping the NPSHA situation, especially when tanks are not full.

Independent events are seldomly independent.