Measurements of pressure and temperature are made for many reasons and by several methods. This paper will focus on measurements made during gas production and transportation and suggests criteria to be used in the selection and installation of the instruments used to measure these physical properties.
In this industry, pressure and temperature measurements are primarily being made for three (3) reasons: Safety
The properties of gas follow the Ideal Gas Law:
So with everything else being constant, when pressure of a gas increases, so does it’s temperature, when temperature goes up, so does it’s pressure.
In safety applications, it is important to measure pressure and temperature to understand, notify, and mitigate the possibility of dangerous situations occurring due to the physical changes of the gas, or associated equipment such as pumps and compressors. Pipelines and storage vessels are designed to contain gas only under specified conditions, when these conditions are exceeded, catastrophic events can occur. Also, motor bearings and pump seals failures also can be identified by changes in temperature and pressure, and machinery loss prevented.
In control applications, pressure and temperature measurements are made, along with other process variables, to regulate the conditions and optimize the process around a certain set of criteria.
In compensation applications, pressure and temperature measurements are made to calculate the mass/volume relationship during gas transfer and storage by correcting for density changes due to pressure and temperature variability.