VAPOR PRESSURE IN CRUDE OILAVAILABLE TECHNOLOGIES

Vapor Pressure Significance

• Government regulations

• The vapor pressure of fuels determines:• Engine starting characteristics• Environmental emissions of stored products• U. S. EPA blending requirements to meet altitude and

seasonal changes for RVP• RVP for transporting liquids

• Vapor pressure information is used for:• Blending fuels• Emissions standards compliance• Storability• Safety/Handling for transportation and storage

Definition: What is Vapor Pressure ?

Vapor pressure is defined as “The pressure exerted by a vapor on the solid or liquid phase with which it is in equilibrium”

Practically vapour pressure is used as a measure of how volatile a sample is and how easily it will evaporate.

Vapor pressure is measured in the same units as any other pressure.

Vapor pressure is temperature dependant and increases with temperature

The Precision Behind The Process

The Precision Behind The Process

The Precision Behind The Process

ASTM D323 Reid Test

Summary:

• Cooled, air saturated sample (0-1°C) is placed in the liquid chamber.

• The liquid chamber is attached to the pre warmed (100°F 37.8°C) air chamber

• The assembly is shaken and placed into a 37.8°C (± 0.1°C) water bath

• The assembly is removed and shaken and then replaced in the bath twice at 5 min intervals

• The pressure gauge connection is opened and the vapour pressure is read off

The Precision Behind The Process

The Precision Behind The Process

The Precision Behind The Process

Principle of Operation

Pressure Transmitter

Sample In

Sample Out

Purge InCell Vent

Air Operated Spool

Ultrasonic Agitator

Sample In

Sample Out

Purge InCell Vent

Air Operated Spool

Ultrasonic Agitator

Pressure Transmitter

• Continuous sample flow

• Automatic air / N2 purge of measurement chamber before every measurement cycle

• Pressure readings automatically zeroed before every measurement

• Air-operated spool automatically meters sample into measurement chamber

• 10 cc Metered sample volume50 cc Total measurement cell volume4:1 vapor to liquid ratio

• Ultrasonic agitation speeds equilibrium

• Maintain temperature at 37.8 °C (100 °F)

• Typical measurement cycle 6 minutes

Principle of Operation

AGITATOR ON

AGI

TATOR

OFF

MEASURERVP

SPOOL

UP

PURGE BLANKCHECK

TIME

TIME ENDERRORCHECK 0 1.5 3 MIN. 4.5 6 MIN.

Principle of Operation

NECK OF AIROPERATOR

ULTRASONICAGITATOR

ANNULAR SAMPLEVOLUME 10cc SAMPLE

OUTLET

SPOOL VALVE DOWN(SAMPLING POSITION)

SAMPLE CHAMBER50cc TOTAL

LIQUID LINE

SPOOL VALVE UP(MEASUREMENT POSITION)

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The ATAC Model 1354 Kinetic Vapor Pressure Analyser

Fluid under high pressure is converted into a high-velocity jet at the throat of a convergent-divergent nozzle which creates a low pressure at that point.

In an ejector/eductor this low pressure is used to draw a suction fluid into the convergent-divergent nozzle where it mixes with the motive fluid.

In the 1354 the motive fluid is the sample itself and the suction fluid entry is closed off.

How does the model 1354 work?

The model 1354 works on the Venturi Effect (Bernoulli’s Principle) and is similar in operation to a paint spray-gun or steam ejector or eductor

The Precision Behind The Process

How does the model 1354 Vapour Pressure Analyser work?

• The analyser uses Bernoulli’s Principle based on the conservation of kinetic energy (Kinetic energy = velocity x pressure)

• Under constant flow when the velocity of the flow increases the pressure must drop to conserve the kinetic energy

This effect is maximised by using a venturi and forms the basis for the steam ejector, the jet pump and a whole range of aspirators, ejectors and eductors and the model 1354

The Precision Behind The Process

• In an ejector the suction is normally used to draw another fluid in and mix it with the incoming fluid

• In the 1354 the suction inlet is capped off and we measure the suction created

• As the pressure reduces it will reach the vapour pressure of the sample. The sample will vaporise and prevent any further pressure drop as the ejector becomes overloaded. The measured pressure is then the vapour pressure

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Schematic of 1354 Vapour Pressure Analyser

The Precision Behind The Process

1354 Main assemblies

The Precision Behind The Process

The Precision Behind The Process

Temperature Control Box

• The temperature control box houses the temperature controller and motor on/off switch

• This item is the same for the ATAC viscometer range with the exception of a motor control circuit which is not fitted to the vapour pressure analyser.

• The temperature controller is an AC based two term controller with adjustable fine and coarse set point controls, and adjustable proportional (Gain) and integral (Reset) settings

• Proportional and integral settings are factory adjusted

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1354 Electrical Controls

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Options

The following options are available for the vapor pressure analyser:

• Cooling coil in Hastelloy C or Monel (high chlorides, salt water)

• Choice of pressure transmitters including ‘Smart’

• Configuration for CSA local approval

• Bath temperature transmission

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Sample Conditioning Requirements

The following sample conditioning requirements must be met to ensure accurate vapour pressure analysis:

• Sample pressure minimum of – [outlet pressure x 2.5] + 101psi

• Sample temperature 27 to 50°C – fluctuations <5°C

• Sample Flow 55 to 230 litres per hour (depending on back pressure)

• Sample must be free from entrained solids

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Installation Requirements

Environmental conditions:

• Ambient temperature limits 5 to 55°C

• Protection from direct sun and rain

• Relative humidity not exceeding 80%

Utilities:

• Cooling water <30°C, 135 litres per hour max. (if required)

• Power 100 to120 or 200 to 240 Vac, 50/60 Hz, 2.0 kVA maximum

• Separate supply for transmitter – typically 24Vdc

The Precision Behind The Process

The Precision Behind The Process

NEW Vapor Pressure Analyzer

26The Precision behind the Process

The Precision Behind The Process

The Precision Behind The Process

The Precision Behind The Process

The Precision Behind The Process

The Precision Behind The Process

The Precision Behind The Process

The Precision Behind The Process

The Precision Behind The Process

The Precision Behind The Process

THANK YOU

The Precision Behind The Process