5 replies to this topic

[Goga]

Dear All,

 

Tried to search in the forum about the topic but couldn't get anything hence posting.

 

Our laboratory want to measure RVP of the Crude Oil. They are doing open sampling from the pipeline in the field and sample is exposed to atmosphere while sampling. Means whatever gases are there in oil are gone off while sampling. The container in which they are taking sample is chilled one with ice and chilled water around. They are also using a cooling coil in bucket to cool the sample before coming to sampling container.

 

My understanding is that the sample shall be taken in close environment and it should not be exposed to atm. or else all gases will be vented and the RVP reading will not be the correct one. After all they (gases) only will be contributing for RVP reported at 37.8 °C.

 

I just want to know that while taking sample for RVP measurement exposing it to atmosphere is okay? Will it still give correct RVP?

 

Request you all to throw light on this.

 

Goga. 

[P.K.Rao]

Please use ASTM D 6377 method

[Wilson]

What you described is the RVP. So to answer your question yes you will get a correct RVP. If you are worried about losing the light ends you are looking for TVP.

 

RVP following ASTM D323 is always measured at 37.8C and V/L ratio of 4:1. As the sample is air saturated at the start of D323 there is no need for a pressurized container.

TVP following ASTM D6377 can be measured between 0-100C and V/L ratio between 0.02:1 to 4:1. The sample is not air saturated and therefore must be collected in a pressurized sample container.

[Goga]

Thank you very much Wilson. Sorry for late reply.

 

That answers my query.

 

So for RVP no need to have  closed sampling as sample need to be air saturated and for TVP only it should be closed pressurised sampling.

 

 

Regards,

Goga.  

[rdcrags]

Why does the lab want a VP of any kind of the crude? As you said, components are lost during sampling. After a crude sample is taken for a distillation, the light ends are reported one by one and included in the assay. However, since some of each is missing, the assay quantity will be low. To design a plant, or to rate an existing plant, the engineer needs to double each light end quantity before starting further calculations. Otherwise, the designed light ends plant will be too small in capacity or the indicated quantity to the existing LEP will be two low.

[Goga]

Lab wanted to check whether the Crude Oil is stabilised or unstabilised. It different thing that later on we came to know that it should be judged (whether stabilised or unstabilised) by TVP and not by RVP. Our original plan was we will co-relate measured RVP with TVP using the graph given in GPSA but later on I came across some article that mentioned that there can be a huge difference and the prediction by graph can go too much wrong!

 

Goga.