Vapor Pressure (RVP) Measurement: Online RVP Analyzer
Online Reid vapor pressure (RVP/RVPE) measurement in gasoline and light product streams: ATEX-compliant process analyzer correlated with ASTM D323.
What is vapor pressure and why is it measured?
Reid vapor pressure (RVP) is a quality parameter that expresses the vapor pressure of a petroleum product at a specific temperature, and it determines the volatility of gasoline and light products in particular. Volatility matters for cold engine starting, vapor lock formation and air pollution through evaporation, so it is limited seasonally in gasoline specifications. In refineries, the share of light components such as butane in a blend directly determines RVP; online measurement helps adjust the blend in real time and keep the product from going off-specification.
Where is RVP measured?
- Gasoline blending lines: In controlling the addition of butane and light naphtha.
- In light product and naphtha streams
- On pre-shipment product lines: In quality verification.
How is vapor pressure measured?
An online vapor pressure analyzer measures the vapor pressure of a sample taken from the process stream in a closed measurement cell under set conditions, and gives the result as RVPE (RVP equivalent) by correlating it with the ASTM D323 laboratory method. The measurement cycle is repeated periodically, and the result is sent to the control system. Because the analyzer can be used with hazardous area certification (ATEX/IECEx Zone 1), it is suitable for refinery field installation.
To keep a sample containing light components from evaporating in the line, sample pressure and temperature must be kept under control and gas bubble formation prevented in the line design; otherwise the measurement deviates from the true product value.
Choosing an RVP analyzer
- Product type and expected RVP range
- Sampling and conditioning (gas bubble and cooling management)
- Plan for verifying correlation with laboratory results
- Hazardous area certification
Vapor pressure measurement with Tetra
Tetra supplies the Icon Scientific Vp online vapor pressure (RVP) analyzer. Sample system and cabinet integration, commissioning, calibration and service are provided by Tetra in Türkiye.
Frequently asked questions
What unit and temperature is RVP measured at?
Reid vapor pressure is measured at 37.8 °C (100 °F) and reported in kPa or psi. The value expresses the pressure measured at a specific vapor/liquid volume ratio, so method conditions should be taken into account when comparing results obtained by different methods.
What is the difference between RVP, DVPE and TVP?
RVP is the vapor pressure measured by the ASTM D323 Reid method. DVPE (dry vapor pressure equivalent) is a result measured by automatic methods such as ASTM D5191 and made equivalent to the Reid value, and it is used in many gasoline specifications. TVP (true vapor pressure) is the product's vapor pressure at actual temperature and is used in storage tank design.
What mistakes are commonly made in RVP measurement?
Evaporation of the sample in the line or sample container causes loss of light components and a low RVP reading. The sample's air saturation state and the temperature control of the measurement cell also affect the result. Keeping the sample cold and under pressure reduces these errors.
How is an online RVP analyzer kept in line with the laboratory?
Analyzer results are regularly compared with laboratory results for samples taken from the same point. If a systematic difference is seen, correlation coefficients are updated and the sample system is checked. Checks with reference samples of known vapor pressure can also be included in the verification plan.
Products measuring this parameter
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