Units

All measurements, in order to be complete, require you to state the unit in which that measurement is made. For example, the Pour Point value of “10” is meaningless, unless you specify whether you measured that value in °C or °F (or some other temperature unit).

In Process Model Manager Reference Manual, units of measurement are considered to be subdivided into Unit Categories, each of which corresponds to a physical quantity being measured. Within each Unit Category are a number of units, which are used to specify measurements for physical quantities falling under that category.

Relating this to the Pour Point example, we would say that the Unit Category for measurements of pour point is Temperature (this is the physical quantity that we measure), and that possible units for the measurement of temperature might be Celsius (°C), Fahrenheit (°F), Kelvin (K) and Rankine (°R).

There are two specific unit categories worthy of a special note:

• Dimensionless. Use this unit category when the measurement is purely numerical (for example, Cetane Index or other crude indices). There is only one unit in this unit category.

• Proportion. Use this category for measurements of the amount of substance, as a proportion of the whole (for example, the proportion of aromatics as a percentage of the product). This unit category has a number of units, such as:

  • ratio: for example, 0.45.

  • percentage: for example, 45%.

  • ppm: for example, 450 ppm.

By default, the following Unit Categories, and associated units are available in Process Model Manager Reference Manual.

Note: Your version of Process Model Manager Reference Manual may have more units than this already configured.