Oil and gas production handbook An introduction to oil and gas production

Figure 11. Gas pipeline 
 
Block valve stations (or vine valve stations) are required to allow closure of 
off flow at regular intervals to limit accidental release of gas in case of 
pipeline rupture. This will be determined by the maximum permissible 
released gas volume. A valve station is normally operated by remote 
telemetry and in addition to the closing valve, at least contains pressure, 
temperature and some level of flow measurement. These will feed back into 
the pipeline modeling system. Even if methane (CH
4
) is lighter than air and 
will rapidly rise, other gases such as propane (C
3
H
8
) are present in up to 8% 
by volume, and are heavier than air. They will sink, and rapidly create a large 
volume of combustible gas mixture.  
 
In cases where multiple producers and pipelines feed into a larger pipeline 
grid, the pressure balancing to maintain required flow and observe 
contractual volume allocations back to individual production sites presents 
additional challenges for the pipeline balancing system. 
5.4.3 Liquid pipelines, pump and valve stations 
Liquid crude or product pipelines are handled much the same way, with 
pump stations and block valve stations along the pipeline. However, when 
the pipeline goes up or down over hills and mountains, they behave 
differently. Liquid, due to the much higher specific gravity, will experience 
much higher pressure drops uphill, and increases downhill, than gas. This 
often requires additional pumping capacity uphill and corresponding 

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pressure-reducing turbines (or braking stations) downhill. In case electrical 
power is used, the braking power from the turbine can be fed back into the 
grid.