Equilibrium Vapor Pressure
CRT Services
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The Equilibrium Vapor Pressure (EVP) value at a given temperature is an indication of when the fluid begins to boil or evaporate.?This causes the fluid to change state and start converting to a gas or start developing entrained gas bubbles in fluid. As one can imagine, this state causes very poor measurement and can severely damage equipment. For this reason a flowing pressure higher than the EVP must be applied to maintain the fluid in a liquid state.?A good rule of thumb is to maintain a pressure 25% greater than the EVP. The EVP is also used in the calculation of the Correction for Pressure on a Liquid (CPL) factor.
In the FlowX, this calculation is used with NGL/LPG (GPA_TP15), ethylene and propylene. To set each product to calculate properly the Vapor Pressure Mode can be configured by going to HOME / CONFIGURATION / PRODUCTS and set the ”Vapor Pressure Mode” to??Calculated.
In the Omni 3000/6000 flow computer, when measuring LPGs and NGLs, enter the "Vapor Pressure at 100 degF" setting as a negative value of -999 and the flow computer will calculate it for you and use it in its calculations, otherwise enter a positive value for the flow computer to use.
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