CA2014276A1 - Automated vapour pressure analyzer - Google Patents

Automated vapour pressure analyzer

Info

Publication number
CA2014276A1
CA2014276A1 CA 2014276 CA2014276A CA2014276A1 CA 2014276 A1 CA2014276 A1 CA 2014276A1 CA 2014276 CA2014276 CA 2014276 CA 2014276 A CA2014276 A CA 2014276A CA 2014276 A1 CA2014276 A1 CA 2014276A1
Authority
CA
Canada
Prior art keywords
chamber
valve
chambers
vapor
pressure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA 2014276
Other languages
French (fr)
Inventor
Ronald E. Daye
Bill O. Lee
Don A. Mclean
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to CA 2014276 priority Critical patent/CA2014276A1/en
Publication of CA2014276A1 publication Critical patent/CA2014276A1/en
Abandoned legal-status Critical Current

Links

Landscapes

  • Sampling And Sample Adjustment (AREA)

Abstract

ABSTRACT OF THE DISCLOSURE
An automated vapor pressure measuring apparatus includes an elongated cylindrical casing with a valve therein separating a liquid sample receiving chamber (the liquid chamber) from a vapor decompression chamber (vapor chamber), heaters for heating the chambers separately, temperature probes extending into both chambers, a pressure measuring device connected to the vapor chamber, a device to rotate the cylindrical casing to effect mixing of the contents and a programmable controller for controlling operation of the valve between the chambers, the heaters, valves for introducing and discharging liquid sample from the liquid chamber, and a valve for discharging vapor from the vapor chamber, for monitoring the temperature probes and the pressure measuring device, for controlling the rotating device and for providing visual indications of temperature and pressure.

Description

This invention relates to a vapor pressure measuring apparatus.
While the apparatus of the present in-~ention was designed specifically for measuring the vapor pressure of liquid hydrocarbons, it will be appreciated that the apparatus can be used to measure the vapor pressure of a wide variety of liquids, both hydrocarbon and non-hydrocarbonO The analyzer may be used to determine liquid Reid vapor pressure in "gage" or "absolute" units for l.O hydrocarbon liquids as defined in procedure ANSI/ASTM D
1269-7~ and ~apor pres~ure of hydrocarbon liquid defined in procedure ANSI/ASTM D 323-79, respectively. Depending on inlet conditions such as pressure and temperature of a sample, the analyzer will measure vapor pressure o~er a wide range of temperatures thus determininy a ~apor pressure curve for each sample. The analyzer is intended for ~; operation on a batch basis with time cycles typically in the range of one to three minutes, and can produce repeatable results within the accuracy specified by the above mentioned : 20 ANSIJASTM pxocedures.
At present, the above mentioned ANSI/ASTM
laboratory procedures are commonly used to measure Rei.d -~ vapor pressure of petroleum products. Both methods are laboratory procedures which require the performance of specific steps to produce predictably accurate results.
.~ , ~ 1 --.
' æ~e Both methods require careful handling of samples, pre-conditioning of sample containers, heat bath systems, and agitation o samples during an approximate thirty minute time period to ensure mixing and vapor separation. The ANSI/ASTM D 323-79 procedure requireæ an air chamber to be preheated to lOO~F before sampling.
~ In the past, a variety of methods o~ measuring ; vapor pressures have been proposed, including the use of an apparatus consisting of a temperatule control bath, a continuous sampling device and two positive dlsplacement pumps of dif~erent capacities to cauæe vapor separation.
Vapor pressure is measured in a chamber, the~temperature of `: :
~hich is controlled by a b th at 100F. The device was designed primarily for measuring the vapor pressure of crude oil. In accordanoe with another method, the vapor pressure of blended gasoline products has been determined by measur1ng the~tempera~ture drop produced by the expansion of a llquld sample rom a high to a low pressure under substantially adiabatic conditions. In order to improve ~ ~ 20 accuracy, methods have been devised to remove a~cumulated ;; ~ixed gases ln the apparatu~ E'inally, vapor pressure has ~been measured using an apparatus including a temperature control bath~and two;sample pumps of different capacities.
In essence, a sample is continuously vaporlzed across an orifice plate into a chamber. The vapor pressure is :
~ - 2 -~: : :

.
, ,: .
,, :' ' ' - ' . ' :, , - ' ' '' ,' - ' ' -' .: . ~ , ' . :
., ~ : .. .
"

measured in the chamber by a bellows-type pressure gage employing a Wheatstone Bridge.
The above described methods are reasonably accurate. However, they employ elaborate sampling techniques such as time consuming manual laboratory proced~res and the use of two pumps in series to collect samples and ensure vapori2ation. The laboratory procedure includes special sampling steps and agitation of the liquid to ensure mixing. The continuous sampling device require~ a liquid, temperature controlled bath which is difficult to use in industrial applications without special consideration. Bath temperature is difficult to control within +/- 1.5F accuracy, The continuous device requires varying levels of calibration to a standard before handling liguids of significarltly different composition or physical propertiesO Moreover, the prior art devices cannot provide vapor pressure values over a wide range of temperatures durin~ each sampling cy~le.
The ob~ect of the present invention is to overcome the above-defined difficulties encounter~d with prior art devices by providing an automated apparatus which is relatively simple in terms of design, reliability and ; accuracy, and which can be used to determine the vapor pressure o~ a wide variety of hydrocarbon and non-hydrocarbon liquids.

27~;

Another object of the invention is to provide an apparatus which can be used for precise quality control of liq~lids in industrial applications, and to provide an apparatus which can be portable for use in remote locations such as pipelines.
An additional object of the invention is to provide an apparatus with a relatively short cycle for providing data of temperature versus vapor pressure for a given liquid.
Accordingly, the present invention relates to an automated vapor pressure measuring apparatus, comprising:
casing means definin~ a first liquid sample chamber and a second vapor decompression chamher; a first valve between ; said first and second chambers; first inlet means for introducing a liquid sample into said first chamber; first drain means for draining said first and second chambers;
heatin~ means for heating said casing means and consequently the contents of said first and second chambers; first probe means for measuring the temperature in said first chamber;
second probe means for measuring the temperature in said second chamber~ pressure measuring means for measuring the vapor pressure in said first and second chamber; and program~able control means for controlling said first valve, said f.irst inlet means, said first drain means and said hea-ting means, and for monitoring said first an~ second 2~

probe means and said pressure measuring means, whereby automatically to perform the steps of introducing a liquid sample intQ said first chamber, depressuring liquid sample into said second chamber, heating saicl sample in said chambers to a predetermined temperature at which vapor pressure is required, measuring the vapor pressure in said first and second chamber~ and discharging the vapor-liquid mixture from said chambers to automatically measure vapor pressure of a liquid sample.
The invention further may include means to rotate said ~asing means to effect mixing of the contents thereof, i.e. the vapor-liquid mixture.
The invention will be described in greater detail with reference to the accompanying drawing, which ~ 15 illustrates a preferred embodiment of the invention, and ; wherein the single figure is a schematic flow diagram of an apparatus in accordance with the present inven-tion.
With reference to the drawing, the apparatus of the present invention incl~des an elongated casing 1, defining a 2~ liquid sample chamber 2 and a vapor decompression chamber 4 separat~d by a valve 5. The casing 1 can, but not necessarily, be formed of 1/2 - 3/4 inch stainless steel tubing and is generally from one to two feet in tokal lengthO A first hea-ting element 6 is enclosed around the portion of the casing l defining the cham~er 2, and a second 7~

heating ele~ent 8 is enclosed around the portion of the casing 1 defi.ni.ng the chamber 4. Means can be also provided, as shown schematically at 50, to effectively rotate casing 1, one or more times, to effect efficient mixing of the liquid-vapor mixture contained within casing 1. A suitable structure could include a collar 51, extension shaft 52 and electric motor 53. The sequence o~
rotation may be manually controlled by means of a switch ~not shown), or, as shQwn, by a programmable logic controller 32. The heating elements 6 and 8 are individually controlled, and the entire casing is wrapped in an insulating materiai 9.
A liquid sample from a sample line 10 is introduced into the ~.hamber 2 through an inlet duct 12, which contains a valve 13 and a restricted orifice plate ~4. When sampling liquids such as propaner the pressure drop across the valve 13 can result in low temperatures which can cause sealing problems and leakiny at the valve. Allowing the pressure drop to occur a-t the plate 14 eliminates valve sealing probl~ms. The sample is drained to atmospheric pressure from the cha~ber 2 through an outlet duct 16 containing a valve 17 and an orifice plate 18 to a drain line l9.
Overpressure in the chamber 2 is relea~ed through a line 21 ~ and a pr~ssure relief valve 22. Vapor from the cham~er 2 ; 25 passes through the valve 5 into the chamber 4, and is :~ - 6 -:
- ~ :

discharged to atmosphere through a line 24 containing an orifice plate 25 and a valve 26 to ven-t line 27. Any overpressure in the chamber 4 is released through a line 29 and a pressure relie~ valve 30. Heating elements 6 and 8 are connected to a programmable logic controller 32 by li.nes 33, and the valves S, 13, 17 and 26 are connected to the logic controller 32 by line 35.
The temperature in the chambers 2 and 4 is measured using ~urface sensitive resistance thermal probes 37 and 38, respectively, which extend out of t.he casing 1 to transmitters 39 and 40l respectively~ The probes 37 and 38 should be of the surface sensi.tive type and of maximum length in order -to maintain optimum acouracy when measuring the temperature of multi-component samples. The ratio of ; 15 temperature sensing surface area to the volume of the chamber is also a factor in the accurate measurement of the temperature of a mulki-component mixture. The transmitters 39 and 40 are connected to a logic controller 42 by lines 43~ The vapor pressure in the chamber 4 is measured and transmi.tted to the logic controller 42 by a pressure transmitter 45 and a line 46. When the valve 5 is opened, and a sample is being heated to determine vapor pressure, the pressure in both of the chambers 2 and 4 is measured by the transmitter 45. Gages 48 and 49 are connected to the logic controller 42 for providing a ~isual indication of .

temperature and pressure respectively.
As mentioned above, the temperature in the chambers 2 and 4, and the introduction and discharge of fluid from such chambers are control].ed by logic controller 32, and the temperature and pressure in the cha~bers is monitored by the logic controllex 42. The controller 32 is programmed to ensure that the sampling process, timing, valve operating, and casing ro~ational sequences are properly controlled.
While the logic controllers 32 and 42 are shown as separate devices, in fact, such controls are a single device r i.e. a microprocessor.
The use of the apparatus will be described by means of two specific examples, the first being a determination of the absolute vapor pressure of volatile crude oil and non-viscous petroleum products as defined in procedure ANSI/ASTM D 323~79.
Assuming that sampling has already occurred, the vent valve 26 from the chamber 4, the liquid sample valve 13 and the drain valve 17 are closed~ and the valve 5 ; interconnecting the chambers 2 and 4 is open. In order to drain ~oth ~hambers 2 and 4, the valves 1.7 and 26 a~e opened, the valve 26 being open to atmosphere. The liquid and vapor in both of -the chambers 2 and 4 are drained or aspirat~d to a hydrocarbon drain line 19 at atmospheric -- 8 ~

'.,~ ' :

2~

pressure, As the sample is drained, air is drawn into the chambers 4 and 2~
After sufficien-t time has elapsed to permit the sample to be drained and the chamber 4 to be filled with air, and chambers 2 and 4 are both at atmospheric pressure, -the drain valve 17 and the valve 5 are closed. Heat is applied to the chamber 4 by means of the element 8 to preheat the vapor decompressi.on chamber to a base temperature at which a vapor pressure measurement is required. Normally the base temperature is lOO~F for determining Reid vapor pressure. The temperature of the vapor decompression chamber 4 is measured by the probe 38 and the transmitter 40. When the temperature in the chamber 4 reaches the required level, heating is terminated and the valve 26 is closed. Du~ing operation of the apparatus over :~ an extended period of time, residual heat in the ca~iny 1 and the insulatio~ ~ may provide suffi.cient heat for the preheat stage. Upon completion of preheating, the vapor decompression chamber 4 is at the base temperature and atmospheric pressure, which counteracts external atmospheric pressure. The net result is that the -transmitter 45 can provide an accurate measurement of vapor pressure, equivalent to the absolute vapor pressure, to the logic controller 42 for reading on the gage 49 in gage . 25 pressure. The valve 13 is opened~ and a liquid sample is _ g _ usecl to flush the chamber 2 for several seconds to ensure that the previous sample is khoroughly washed from the sample duct 12 through the outlet duct 16 to the drain line 19. When flushing has been completed, the drain valve 17 is closed to liquid fill the sample chamber 2, and the valve 13 is closed. The liquid sample is isolated in -the chamber 2 at sample process conditions. The sample may cool slightly due to pressure drop across the orifice plate 14. For the analyzer to function, the liquid sample from the line 10 must be a-t a temperature below the required base temperature. Otherwise sample conditioning will be required.
The valve 5 is opened and the vapor in the chamber 4 and the liquid sample in the chamber 2 reach equilibrium at a temperature below the base temperature, and at a pressur~ below the required vapor pressure. Also sample conditioning may be required if the sample is volume compressible at sample conditions. If, when valve 5 is opened, the liquid sample in chamb~r 2 expands under decompression into chamber 4, error could be introduced clepending on the compressibility of the liquid sample. With the vent valve 26, the sa~ple valve 13 and the drain valve 17 closed and the valve 5 openr the heater 6 i~ actuated to apply heat to -the casing 1 in the area of the chamber 2.
The rotating means 50 is actuatecl to rotate casing 1 by .
-180, one or more times to ensure complete mixing of theliquid-vapor mixture. As heat is appliecl to the liquicl sample chamber 2, the temperature rise is monitored by the probes 37 and 38, and pressure increase is monitorecl by -the pressure transmitter 45. When -the temperature reaches the base temperature, the pressure is measured and recorded by the logic controller 42 to provide the liquicl sample absolute vapor pressure in gage units at the base temperat~re~
The process can then be repeated starting with the draining step described ahove.
The same apparatus as described hereinbefore may be used to determine the gage vapor pressure of liquified petroleum gas products as definecl in procedure ANSI/ASTM D
1267-79. In this process, the line 24 and the valve 26 are connected to the liquid sampling line 10~ and there is no vent to atmosphere. During the sampling step immediately preceding drainin~, the valves 13 and 26 and 17 are closed, and the valve 5 is opened to interconnect the chambers 2 and 4. In order to drain the chambers, the valve 17 is opened to a hydrocarbon drain llne l9. I,iquid and vapor in both the chambers 2 an~ 4 are drained or aspirated to the hydrocarbon clrain line 19 at atmospheric pressure.
The liquicl sample valves 13 and 26 are open so that liquid samples can flush both chambers 2 and 4 for several 11 ~

- , ' '. , :

seconds to ensure that the previous sample is thoroughly removed through the duct 16 and the line 19.
Following flushing of -the chambers 2 and 4, the valves 13 and 26 are closed and both chambers 2 and 4 drain.
~pon completion of the flush and drain, the drain valve 17 is closed.
Both chambers are thus isola-ted in a vapor phase at atmospheric pressure. The valve 5 is closed. The valve 13 is opened to introduce liquid sample into the chamber 2 at liquid sample process conditions. The sample may cool because of the pressure drop across the orifice plate 14.
In order for the analyzer to function, the liquid sample must be at a temperature below the required base temperature. Otherwise, sample conditioning will be required.
The valve 5 is opened and the vapor in the chambex 4 reaches equilibrium with the liquid sample in chamber 2 at a temperature below the base temperature and a pressure below the required vapor pressure.
With the sample valves 13 and 26 and the drain valve 17 closed) and the valve 5 open, heat is applied to the chamber 2. The rotating means 50 is again activated, following which, the temperature and pressure in the apparatus is monitored, such tha-t when the temperature reaches the base temperature, the pressure is measured and . .: . : . .
, : ' , , ' ' ' '' ,~

recorded by the logic controller 42 as the sample gage vapor pressure at the required base temperature. The process can then be repeated starting with the draining step.
The accuracy of the above described apparatus when carrying out the above defined processes has been found to be at least equal to the accuracy set out in procedures ANSI/ASTM D 323-79 and ANSI/ASTM D 1267-79, The ~pparatus has been tested with a wide variety of liquids over a wide range of vapor pressures, and determined to be ~
accurate. Accuracy of the apparatus is at present dependent upon the volurne ratio of the vapor decompression chamber 4 : to the liquid sample chamber 2, the length to diameter dimension ratio o~ each chamber, and the rate of heat input. Al 1 of these values are variable and dependent upon the physical properties and composition o~ the liquid being tested.
; Both o the processes described herein are carried ; out on a batch basis.
For industrial use, when the analyæer is -to be used to measure vapor pressure o one or more liquids, the apparatus can be permanently mounted in a heated, weather ; resistant cabinet. The logic con-trol can be mounted either in the cabinet or remotely in a control room, For portable use, the apparatus can be mounted in a metal case which contains the analyzer and the logic controller, requiring a power supply .for operation.

Claims (10)

1. An automated vapor pressure measuring apparatus, comprising: casing means defining a first liquid sample chamber and a second vapor decompression chamber;
first valve between said first and second chambers; first inlet means for introducing a liquid sample into said first chamber; first drain means for draining said second chamber;
purge or atmospheric means for introducing a gas into said first and second chambers; heating means for heating said casing means and consequently the contents of said first and second chambers; first probe means for measuring the temperature in said first chamber; second probe means for measuring the temperature in said second chamber; pressure measuring means for measuring the vapor pressure in said first and second chamber; and programmable control means for controlling said first valve, said first inlet means, said first drain means, said purge or atmospheric means and said heating means, and for monitoring said first and second probe means and said pressure measuring means whereby automatically to perform the steps of introducing a liquid sample into said first chamber, depressuring said liquid sample into said second chamber, heating said sample, measuring the vapor pressure in said first and second chambers, and discharging the vapor-liquid sample from said first and second chambers to automatically measure vapor pressure of a liquid sample.
2. An apparatus according to claim 1, wherein said heating means includes a first heating element for heating said first chamber and a second heating element for heating said second chamber.
3. An apparatus according to claim 1, wherein said first and second temperature probe means include surface sensitive probes extending into said first and second chambers.
4. An apparatus according to claim 1, including a second valve in said first inlet means for controlling -the introduction of the liquid sample into said first chamber;
and a third valve in said first drain means for controlling the discharging of vapor-liquid mixture from said first and second chambers.
5. An apparatus according to claim 4, including first restricted orifice means in said first inlet means between said second valve and said first chamber; and second restricted orifice means in said first drain means for preventing sealing problems in said second and third valve.
6. An apparatus according to claim 5 including second drain means for draining liquid from said first and second chambers.
7. An apparatus according to claim 6, including a fourth valve in said second drain means; and third restricted orifice means in said second drain means downstream of said fourth valve in the direction of liquid travel for preventing sealing problems in said fourth valve.
8. An apparatus according to claim 1, including transmitter means for transmitting temperature measurements from said first and second probe means to said control means, and pressure measurements from said pressure measuring means to said control means.
9. An apparatus according to claim 1 including pressure release means in said casing means for releasing any overpressure in said first or second chambers,
10. An apparatus according to claim 1, including means to rotate said casing means for mixing the liquid-vapor mixture contained therein.
CA 2014276 1990-04-10 1990-04-10 Automated vapour pressure analyzer Abandoned CA2014276A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA 2014276 CA2014276A1 (en) 1990-04-10 1990-04-10 Automated vapour pressure analyzer

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA 2014276 CA2014276A1 (en) 1990-04-10 1990-04-10 Automated vapour pressure analyzer

Publications (1)

Publication Number Publication Date
CA2014276A1 true CA2014276A1 (en) 1991-10-10

Family

ID=4144730

Family Applications (1)

Application Number Title Priority Date Filing Date
CA 2014276 Abandoned CA2014276A1 (en) 1990-04-10 1990-04-10 Automated vapour pressure analyzer

Country Status (1)

Country Link
CA (1) CA2014276A1 (en)

Similar Documents

Publication Publication Date Title
EP0284262A2 (en) Temperature compensation in differential pressure leak detection
US4543819A (en) Vapor-liquid ratio analyzer
US5158747A (en) Apparatus for identifying and distinguishing different refrigerants
US5563339A (en) Self-correcting autocalibrating vapor pressure analyzer
AU603032B2 (en) Low pressure refrigerant contaminant tester
US2722826A (en) Continuous vapor pressure recorder
US3037375A (en) Continuous vapor pressure apparatus
KR100570552B1 (en) Moisture analyzer
US3528440A (en) Vapor-liquid ratio monitor
EP0759168A1 (en) Fluid analyser
US5022259A (en) Automated vapor pressure analyzer
EP0554380B1 (en) System for determining liquid vapor pressure
EP0307265B1 (en) Gas generating device
CA2014276A1 (en) Automated vapour pressure analyzer
US2540377A (en) Apparatus for determining vapor pressure
US2564892A (en) Viscosimeter
US4610169A (en) Variable temperature trap
US2939312A (en) Continuous flash point monitor
US3597979A (en) Metering valve for introducing a fluid under pressure into an analytical apparatus
US3780565A (en) Fluid vaporization tester
US4292837A (en) Liquid testing apparatus
US3191428A (en) Vapor pressure measuring apparatus
US3253454A (en) Apparatus and process for continuous determination of percentage boiling point
US4344316A (en) Method and apparatus for indicating the air content of concrete in situ
US3435663A (en) Dynamic filter press

Legal Events

Date Code Title Description
FZDE Dead