As an example, the supply side requires valve adjustments to allow a controlled flow to reach a specified pressure along the length of the pipeline. A startup operation implies several actions on the supply side and at consumer points.
Advanced simulation software can help determine these conditions. For these studies, precise information on the gas composition, pipeline routing, elevation profile and weather conditions are required for different times of the year. A transient analysis allows the frequency of this procedure to be predicted, and it also allows for the gathering of other useful information, such as potential places for liquid holdup, to determine the parts of the pipeline that will require frequent maintenance. Occasionally, every gas pipeline requires a pigging procedure to clean the internal pipe walls to reduce disruption of the flow area. Gas state conditions rely mainly on the relationship between three variables: pressure, temperature and volume.ĭue to the intricate relationship of gas state condition variables, there are several problems involved in the dynamic analysis of a gas pipeline, such as: Pipeline dynamics are described by a complex hydraulic model. Users, characterized by uneven consumption. Example of consumption in a water distribution network with different These situations can be avoided with the use of transient modeling, allowing for the reproduction of usage conditions that may be present over time.įig. If the network design consideration is an average flowrate of 3 gal/min, then three users may be serviced simultaneously, however, once four or more users are accessing the system, a serious supply problem will arise ( Fig. Problems such as lower-than-expected flowrates, outages or even pulsation effects can occur.Ĭonsider the example of the design of a water distribution network system that supplies several users with even consumption. However, if the consumer’s behavior is unsteady, then the resulting flowrate will be uneven, and the consumer is more likely to experience difficulties using the pipeline network. To ease the design task, the most common method of performing an analysis is to consider a steady rate of consumption for each gas consumer.
These transitions form the basis of study for a transient analysis.
When the system is changed in a way that impacts the steady state, the entire system will change until it reaches a new steady state. In many ways, time is a variable related to the continuous pursuit of the steady state. “Transient” implies the effect of time over the operational behavior of an industrial facility. Fortunately, a wide range of computational tools exists to simplify the tedious calculations related to the design and projected operation of a gas pipeline. A quick estimate is not sufficient to define the design of a gas pipeline. In long gas pipelines, however, these assumptions are unacceptable because the range of error is greater. These assumptions are settled to simplify the calculation process. liquids under the same conditions.įor gas lines (both process lines and in-plant lines), there is a set of considerations for design that involves the definition of the ruling flow conditions as an isotherm or an adiabatic flow. Gas is more heavily impacted than liquids by changes in pressure and temperature, and this difference affects the flow behavior of gas vs. The transport of gas requires a different analysis than does the transport of liquids. Many countries have developed wide networks enabling gas transportation to highly populated areas, where the gas is used for power generation and heating. Natural gas pipelines are increasingly important pieces of infrastructure to help maintain the high momentum of gas production, especially shale gas. Perform transient analysis of a gas pipeline