Which one is adviceable; to use Design temperature or Operating temperature to calculate Pipeline Expansion?
The design temperature for a pipeline usually is set by the highest temperature that the pipeline can see with some safety factor. That occurs at the delivery points or on the outlet of any compressor stations that exist along the pipeline. Typically a gas pipeline’s temperature approaches the temperature of its surroundings pretty quickly; therefore, the maximum operating that much of the line sees is well below the design temperature. To design all portions of the pipeline from thermal expansion using the maxmium operating temperature or design temperature is really over kill. To truly engineer a pipeline, it needs to be broken down into segments for thermal stress analysis. To use the design temperature or the maximum temperature that can occur at only limited points on the line is not engineering.! I realize this takes some extra work and analysis but that is what engineers are suppose to do.
