This practice increases the pipeline flow capacity without altering the final pressure. If temperature is close to ambient temperature, the location of a loop does not change the final delivery pressure.
However, when temperature changes substantially, then the location of a loop has an influence.
Thus, in these cases, for example, it is recommended to loop in the upstream region, where the gas is hotter.
This allows the gas to cool down faster and therefore increase the delivery pressure.
The gas pipeline section with a looping has a lower flow rate of the product being conveyed via the main gas pipeline, which leads to the reduction of the total gas pressure loss for flow resistance overcoming.
That is why, with original gas pressure remaining constant, an increase in the flow efficiency of a gas pipeline in general is directly related to the looping length.
As a rule, the length of a looping being laid is a multiple of the pipeline valves spacing (distance): 25 to 30 km.
With the looping development, its length increases and finally equals the total length of the main pipeline, therefore becoming its second string.