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True and Reid Vapor Pressure (by Lili Lyddon)
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Location: Blogs The BR&E Blog |
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| Posted by: BRE Blogger |
Tuesday, January 16, 2007 1:14 PM |
The Vapor Pressure Analysis in ProMax returns values for both Reid and True vapor pressures. The calculated True Vapor Pressure of the stream is based on ASTM D2889-95a(2000) Standard Test Method for Calculation of True Vapor Pressures of Petroleum Distillate Fuels. True Vapor Pressure is the pressure of the vapor in equilibrium with the liquid at 100 F (it is equal to the bubble point pressure at 100 F). The calculated Reid Vapor Pressure of the stream is based on ASTM D323-99a Standard Test Method for Vapor Pressure of Petroleum Products. Reid Vapor Pressure is the vapor pressure of a chilled sample of gasoline or other fuel as measured in a test bomb at 100 F. The Reid Vapor Pressure differs from the True Vapor Pressure of the sample due to sample vaporization and the presence of water vapor and air in the confined space resulting from the Reid Vapor Pressure test method. To presaturate the sample for the Reid Vapor Pressure test, the streams are flashed at 1 atm and 33 F, and the resulting liquid product is then combined with air at the rate of 4 parts air and 1 part liquid. Next the system is flashed at constant volume at 100 F. The resulting gauge pressure is the Reid vapor pressure. Because of this procedure, the Reid Vapor Pressure may be significantly different from the "True Vapor Pressure" if the Reid vapor pressure exceeds 26 psi. The Reid vapor pressure is applicable only for gasoline, volatile crude oil, and other volatile petroleum products. It is not applicable for liquefied petroleum gases. (The vapor pressure test method for LPG is ASTM D1267 which is not currently implemented in ProMax).
Authored by Lili Lyddon (BR&E Technical Support and Help Author) |
| Copyright ©2007 Bryan Research & Engineering, Inc. |
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Comments (53)
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By dmarshall on
Monday, February 05, 2007 4:26 PM |
Lili, I've had difficulties with Promax in exactly this area. Gas Liquids uses Promax to simulate condensate stabilizer columns with the tower spec being a bottoms liquid RVP of 12 psia (a typical stabilized condensate spec in Alberta). However, upon convergence, while the RVP is 12 psia, the TVP is around 25 psia and, as expected, dropping the liquid pressure from column pressure to atmospheric pressure (i.e. dumping it from the reboiler to the storage tank) indicates that vapors will be liberated. As a result, we are forced to use a tower spec of 12 psia TVP rather than RVP, which drives off enough light ends that no vapors are liberated in the tank at atmospheric pressure and 100°F.
A stabilized condensate at 12 psia RVP should not flash any vapor at atmospheric pressure and 100°F, but Promax does not predict this. Can you please comment on this? |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Tuesday, February 06, 2007 3:14 PM |
| The RVP is actually more of a gauge pressure than an absolute pressure due to the way the test is performed. The sample is preconditioned by flashing at 33F and atmospheric pressure to drive off the light components. Then air is added to the test vessel, the vessel is closed, and the RVP is the gauge pressure caused by vaporization while heating the sample from 33F to 100F. ProMax actually performs the preconditioning calculations by flashing at 33F, adding air, and heating to 100F. So there should be some vaporization at 100F from a 12 RVP sample that is flashed at atmospheric pressure. If you are mainly concerned about vapor in the storage tank, you should continue to use the TVP specification for the condensate. The RVP test is designed more for oils and gasoline than for condensate anyway. I would also like to note that since the TVP is just the bubble point of the liquid at 100F, there will be a greater difference between the RVP and TVP for a condensate than for an oil or gasoline since the condensate would be more likely to have lighter components in it than the oil or gasoline. The lighter the liquid composition, the greater the difference between the RVP and TVP. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Ali on
Wednesday, April 04, 2007 8:55 AM |
| Hi- The ASTM D323 has a seperate test method for liquids with an RVP of more than 26 psi, where there is no addition of air to the sample. How will this affect the RVP reading? and does the simulation address this? |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Lili on
Thursday, April 05, 2007 10:15 AM |
| Ali, thanks for your comment. ProMax first performs the Reid Vapor Pressure calculation in the normal way using preconditioning and air saturation. If the RVP is greater than 26, the RVP calculation is performed again without using preconditioning or air saturation per ASTM D323. If some vapor would be present at 32F, omitting the preconditioning step could result in a significantly higher RVP. |
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Maximum permissible RVP (Reid vapour pressure) of Naphtha in Naphtha storage Tanks as per API standard or any other standard |
By krishna on
Monday, July 23, 2007 7:37 AM |
Would please advise me on the maximum permissible RVP of Naphtha that can be stored in a naphtha storage tank as per API or some other standard. Normally 10 to 10.5 psi RVP is allowed but I want to know if 15 psi RVP naphtha can it be stored in an Atmospheric storage tanks.
any comments pls forward to k.prasad@src.co.om
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Zoel on
Monday, July 23, 2007 7:37 AM |
| Hi Lili,.I'm sorry if my problems out of our topics. I have some probrems with my calculation.I have a data :RVP at 100°F of LPG is 106 psi, how to count RVP at 40°C of the same LPG..?Do You have reference data?Thanks a lot for All.. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Lili on
Wednesday, July 25, 2007 2:46 PM |
| Zoel - The RVP Test (ASTM D323) is by definition at 100°F and is not applicable to LPG. The vapor pressure test method for LPG is ASTM D1267. In ProMax you can calculate the regular vapor pressure of any hydrocarbon stream at any temperature using the Vapor Pressure Analysis. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Gede Wibawa on
Monday, September 24, 2007 3:51 PM |
Hi Lili,
If some ine give spesification of LPG with vapor pressure at 37.8 deg C (ASTM 1267) 410 KPA min and 830 KPA max, are the pressure gauge or absolute?
Thank you.
Regards, Gede Wibawa
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By mohamed elbhrawy on
Friday, February 22, 2008 3:04 PM |
| gooooooooooooooooood |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Obinna on
Friday, February 22, 2008 3:05 PM |
| To control the RVP of a fluid to be less than 10psia, an inline heater is needed, our clients recommended we place it immediately after the first stage seperator,but studies indicated placing it after the second seperator produced a better RVP.Were do recommend it be placed so that after the crude stabilization , the RVP spec will be met. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Friday, February 22, 2008 3:05 PM |
| Obinna - Thank you for your question. You can use ProMax or other process simulator to determine the best location for the inline heater as it may vary with composition and/or conditions. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Roseane on
Tuesday, March 11, 2008 1:19 PM |
Hi Lili,
Would answer if Is there some ASTM or API for Reid Vapor Pressure limit to a FPSO cargo tank? Thanks... |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Tuesday, March 11, 2008 1:19 PM |
| Roseane - RVP specifications for FPSO applications vary but are usually between 10 and 12 psi, although sometimes as low as 8 psi. An article in the December 2004 Oil and Gas Journal has a table listing the typical RVP spec for FPSO as less than 11 psi for Gulf of Mexico (shelf and deepwater) and less than 150 TVP (True Vapor Pressure) for the North Sea. |
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conversion of Reid Vapor Pressure to psia |
By Athira on
Tuesday, March 18, 2008 12:11 PM |
| I have I have Reid vapor pressure value as 10.8.But in the report my ex-senior design engineer had given the value as 14.96psia. Would you please give me how the conversion is carried out. Can you give me a proper reference to convert reid vapor pressure to psia. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Tuesday, March 18, 2008 12:11 PM |
| Athira - I don't believe there is a conversion between absolute and gauge pressure for RVP. Many times the RVP is reported as “psia” although the way the test is performed the pressure is actually a gauge pressure. The D 323 – 99a standard says “Note 1--Because the external atmospheric pressure is counteracted by the atmospheric pressure initially present in the vapor chamber, the Reid vapor pressure is an absolute pressure at 37.8C (100F) in kilopascals (pounds-force per square inch).” However, a bourdon tube pressure gauge is used to measure the pressure so the reported pressure is actually in psig. That is confirmed by procedure 5B1.4 in the API Technical Data Book. Bottom line--RVP is truly a gauge pressure and is always reported as such. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Fadly on
Friday, June 06, 2008 2:36 PM |
Hi Lili,
I have condensate TVP value of 188 psia. How to convert this TVP value to vapor pressure? |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Athira on
Friday, June 06, 2008 2:58 PM |
Sorry.My question was not clear.10.8psig is the RVP maximum of the given crude oil.But he mentioned a vapor pressure of 14.96psia in the data sheet.Through nomograph I could convince them that 10.8 RVP is 14.96psia at 37.8 degreeC.Hope I am correct.Now the question I have to answer is- how can we consider for design calculations vapor pressure at 37.8C eventhough maxm temp is 60Cand design temp is 93C.Please
help me. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Carl Calabro on
Friday, June 06, 2008 3:49 PM |
| Are there any reliable correlations for RVP and TBP for naphtha range samples, that is, with RVPs from 1 to 10 psig? |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Luis Gil on
Monday, June 09, 2008 8:32 AM |
| Could you tell me what are the TVP considerations for using floating roof in crude oil storage tanks?. My company is processing a 12.7 API crude oil with a RVP of 0.85 Psi and we are considering to have fixed roof storage tanks. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Friday, June 06, 2008 2:37 PM |
| Fadly - The TVP is just the vapor pressure of the condensate at 100F. The easiest way to get the vapor pressure at some other temperature is through the use of a Process Simulator such as ProMax. You must know the composition of the condensate, either as real components or with boiling curve test information. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Friday, June 06, 2008 2:58 PM |
| Athira - RVP is just a specification. If a fuel meets that specification, the process operating temperature should not be an issue. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Friday, June 06, 2008 3:49 PM |
| Carl Calabro - The RVP and TVP are vapor pressure tests and to model them is just a matter of performing bubble point calculations using an Equation of State. The RVP test simulation does include the chilling and flahsing before the bubble point pressure is determined, as stated in the test procedure. So no correlations as such are used in the calculation. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Monday, June 09, 2008 8:32 AM |
| Luis Gil - Each state has it's own regulations regarding floating roof storage tanks for petroleum liquids. You should find out what the specifications are for your state. However, in most states the strict regulations don't apply to petroleum liquids with a TVP of less than 1.5 psia. An oil with an RVP of 0.85 psi probably has a very low TVP as well. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Mike on
Thursday, February 12, 2009 8:51 AM |
Keep in mind also there is a confusion between TVP(True Vapor Pressure) and TVP(Total Vapor Pressure). There is a ASTM method for True Vapor Pressure but not perfect!. True Vapor Pressure is slightly(a few kPa) higher than Reid Vapor Pressure when high Reid Vapor Pressure(I mean 100kPa around) but lower value of Reid Vapor Pressure the difference high. Reid Vapor Pressure result is ABSOLUTE because of air and condition of vapor chamber before connected with liquid chamber. In LPG vapor pressure, there is no air traped and all vapor in the system is sample itself and therefore result is GAUGE PRESSURE.
True Vapor Pressure is mainly using in storage tank's vapor loss calculations. You can find at internet.. also you can find correlation between True Vapor Pressure and Reid Vapor Pressure based on stock temperature.
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Mansh P.Patel on
Thursday, February 12, 2009 8:51 AM |
| In my company, condensate has 69 kpa RVP.Is it safe for transferring by Tankers? |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Maarten Boer on
Thursday, February 12, 2009 8:51 AM |
Lili, on Feb 26th 2006 you noted: "The lighter the liquid composition, the greater the difference between the RVP and TVP"
I note however that for crude, the difference between TVP and RVP is much greater than for nafta (where TVP at 100F and RVP are almost equal??? |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Bhagyashree on
Thursday, February 12, 2009 8:51 AM |
| If I have distillation data of a stream, can its RVP be calculated? |
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vapor pressure of gasoline |
By anindya on
Thursday, February 12, 2009 8:52 AM |
| i want to design a debutanizer where the feed is considered as butane &gasoline.but i can't calculate the vapor pressure of gasoline at various temperature.i want to know this with antoine parameters. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Thursday, February 12, 2009 9:20 AM |
| Mike - I agree with what you are saying, however, if the pressure on the gauge at the start is 0 and it is not a vacuum gauge, then the pressure at the end of the test is a gauge pressure. If the pressure at the strart it 14.696 (or whatever the local atmospheric pressure is), then the pressure at the end is an absolute pressure. From ProMax Help files: "Often the RVP is reported as “psia” although the way the test is performed the pressure is actually a gauge pressure. the D 323 – 99a standard says “Note 1--Because the external atmospheric pressure is counteracted by the atmospheric pressure initially present in the vapor chamber, the Reid vapor pressure is an absolute pressure at 37.8 C (100 F) in kilopascals (pounds-force per square inch).” However, a bourdon tube pressure gauge is used to measure the pressure so the reported pressure is actually in psig. That is confirmed by procedure 5B1.4 in the API Technical Data Book." |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Thursday, February 12, 2009 9:20 AM |
| Maarten Boer: I should have said "the greater the content of light components in the liquid the greater the difference between RVP and TVP". This is due to the pre-conditioning. You are correct, the natural gasoline from the top of a crude tower might have a TVP of 15.5 and an RVP of 13.0 whereas the crude oil feed might have a TVP of 17.3 and an RVP of 11.0. The greater difference between TVP and RVP for the crude is that it has not yet been processed to remove the lighter compounds whereas the gasoline has been processed such that the lightest compounds have been removed. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Thursday, February 12, 2009 9:20 AM |
| Bhagyashree - Proceess Simulators such as ProMax can model a crude oil based on distillation data, then a vapor pressure analysis can be used to calculate the RVP of the stream. These calculations can proabably be performed by hand using API procedures, however, it is much easier and faster using a simulator. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By lili on
Thursday, February 12, 2009 9:24 AM |
| Anindya - As i mentioned to Bhagyashree, calculations are much simpler if you use a process simulator. You can easily generate vapor pressure curves for gasoline or any other stream if the composition is known. Tower design for debutanizers or other fractionators is also very easy using a simulator such as ProMax. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By vishy on
Thursday, September 08, 2011 8:14 AM |
| We want to measure TVP of condensate. Is it possible to directly measure TVP @ 45 degC. Our sample has traces of water and stream Temp areound 45 degC. Our cooling water Temp is 40 degC. We cannot bring the sample to 37.8 degC as our CW temp is more than that. please advise |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Zack Adam on
Thursday, September 08, 2011 8:21 AM |
| Lili; some people take 45C to calculate TVP, Do you have any idea why? appreciate your advice |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Venugopal R pillai on
Thursday, September 08, 2011 8:21 AM |
ASTM D2889 is very elaborate and gives a feeling that the accurate true vapor pressure cannot be determined as we depend on many charts.
I need the following clarifications.
1.Whether any emperical relationship between True vapor pressure and Reid vapor pressure is available?
2. For a naphtha sample with RVP 12.0 psi, what could be the True vapor pressure?
2. What is the relationship between True vapor pressure and total vapor pressure(ASTM D5291). |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By hamed on
Thursday, September 08, 2011 8:20 AM |
Dear Friend
I have a difficulty to understand the difference between RVP and TVP. In determining RVP procedure, at first oil is in lower tempereature and then it is heated to 100F, because of this some volatile hydrocarbon evaporate and enter vapor phase so the pressure should increase but RVP is lower than TVP or first pressure ,can you explain this?. I mean that RVP should be more than TVP
Best Regards |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Vusal Baku on
Thursday, September 08, 2011 8:19 AM |
Hi Lili
I understood RVP and how it is measured at the laboratory.But TVP for me a little bit diffucult how is it identified.
Please can you give explanition to it and main difference between them by showing example. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Lele on
Thursday, September 08, 2011 8:19 AM |
| Dear Lili, I have a question on how to calculate RVP. I have on hand only the %mol of each compistion of LPG, and my Boss ask me to estimate the RVP even he knew that I am not process engineer :|? which software, method should i use to calculate? Please advices, thanks alot |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Ahmad on
Thursday, September 08, 2011 8:19 AM |
| Why do you add air to the test sample to get RVP? Why not measure RVP without adding air? |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By masoud on
Thursday, September 08, 2011 8:18 AM |
i think the RVP is strictly in gauge because of the atmospheric pressure is 14.7psi and how we can have 10 psia for condensate gas for example?
it is gauge pressure friends no absolute the chamber is closed and there is no atmospheric pressure... email: masouds_ce@yahoo.com |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By A on
Thursday, September 08, 2011 8:18 AM |
| Thank you for the article. i was just wondering, how KVP is related to RVP? |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Agugua Godbey on
Thursday, September 08, 2011 8:17 AM |
| please can you suggest equipment that i can use to measure True vapor pressure of Crude Oil to be stored in a storage tank |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Suehs on
Thursday, September 08, 2011 8:17 AM |
if ASTM D5191-4a reflect RVP as psi is it absoulute or guage, if can be clarfied.
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By bwsailin@yahoo.com on
Thursday, September 08, 2011 8:17 AM |
Could you please help clarify the difference between True vapor pressure and RVPE...If the RVPE value at ambient temp less than 100F, then why is it possible for the TVP value to be higher when the product temp is less than 100F. Given the ASTM test method brings the product temp up to 100F to calculate the RVP pressure?
Thanks |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Sung on
Thursday, September 08, 2011 8:16 AM |
| I have a question about Crude Oil RVP calculation methods. I found that there are deviations between calculated RVPs from ASTM D323 and API 5B1.2. Sometime the deviations are great!. So I am curious that which method is more reliable. Generally API method has a greater value. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By jyin on
Thursday, September 08, 2011 8:22 AM |
I used ASTM D2889-95 to calculate TVP's for Jet A and Jet A1 fuels manually. It was time consuming and not repeatable. Do you have any small software package just doing this calculation? Where did you get the line equations on those charts in D2889?
Thanks,
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Robert grandduke on
Tuesday, September 27, 2011 1:20 PM |
| I do agree with you as I used ASTM D2889-95 |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Adel on
Wednesday, March 21, 2012 9:15 AM |
| Please tell me how can to convert RVP to TVP |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Mohsin Harooni on
Wednesday, March 21, 2012 9:15 AM |
| Do you know any digital equipment can test TVP of crude oil. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By raghav kumar on
Wednesday, March 21, 2012 9:15 AM |
| clearly true vp(vp of pure sample) is greater than indicated RVP(vp of sample +air+water vapor) as in case of latter less molecules of sample are available for vaporization at the surface.. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By zara on
Wednesday, March 21, 2012 9:16 AM |
| can i knw what is the actual RVP for gasoline, diesel and lubricating oil.. |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Risda on
Wednesday, March 21, 2012 9:16 AM |
| How can we calculate TVP at 55 deg C? Is TVP similar with vapor pressure (by defining the vapor fraction to be zero (0))? |
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Re: True and Reid Vapor Pressure (by Lili Lyddon) |
By Adrienne PdB on
Wednesday, March 21, 2012 9:16 AM |
Hello,
We're working on the condensate stabilization process. We use PROSIM which a software to modelize engineering process. We need to calculate the TVP of the final liquid. Could you please give us a method to do it?
Thanks. |
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