Natural gas from producing wells and storage facilities is typically pressurized to facilitate efficient transportation in pipelines across long distances. The pressure is stepped down at pressure letdown (pld) stations at various stages across the network. The pld station depressurizes the gas to lower levels for safe delivery through local distribution networks such as local gas mains, smaller-diameter service lines and individual meters for industrial, commercial and residential end users. Pressure reduction is most commonly accomplished through the installation of joule-thomson (jt) regulating valves, which reduce the gas pressure to the desired level. A simplified jt valve is shown in figure 1. It consists of a mechanical valve, which is throttled to create the desired pressure differential between the inlet and outlet the jt pld device is a simple and generally effective tool for pressure reduction, but a by-product is waste heat.
