gas pipeline financial capital cost
From the graph this comes to a value of 44 km whereas the actual section under investigation is the 48 km pipeline. The differences in actual planning a pipeline of this length may be down to a number of factors such as costs in negotiating terrain, environmental permits, location of pipeline to dwellings, suburban limits etc. However effectively the most economical length of pipeline would be achieved post the 44 km length as this is when the rate of decline in capacity begins to tailor away. Additional to these factors, as with the other variables, there is an amount of tolerance to the planned length.
Figure7. Incremental compressor arrangement
In addition, adjust the discharge pressure of the compression station so that the gas reaches the required pressure at the end location. Or we will have to move the compression station further upstream so that the pressure drop is able to decline the discharge pressure suitably to the end pressure.to acquire a suitable location for compressor station are made on a trial and error basis using the general flow equation.the taking a standard value for source pressure P1 and receiving pressure P2 we can assume that the compressor in use will be operating within its capacity:
Initial/Discharge Pressure P1 = 70 bar/Suction pressure P2 = 50 bar
∆P = 20 bar (standard Optimum)ratio = P1/P2 = 1.4: 1sizing 1.5 (centrifugal compressor)
the general gas flow equation we can overview a system such as the 48km pipeline in USA and how it could potentially use compressors to enhance flow rate to a location. For this example we estimate that the flow rate to be maintained beyond the end of the pipeline and hence the compression station will be at the 48km point.
11. Practical example of compressor planning
Where, Ts = 288,= 1.013025,
d = 750mm,= 0.7,= 48km= 288Z = 0.85= 0.000575 x x= 163.4 x x
= 1.36 mill m3/day
The daily capacity along the pipeline would be 1.36 mm3/day. To maintain this capacity into the section of 327km pipeline a compression unit could be placed at the end to rectify the pressure drop across the pipeline.yearly capacity would therefore be 496.4 million m3/year.
In compression through a closed system, the compression can be considered as adiabatic when it doesnt give any heat off to the surroundings. If the compression is heat efficient, which generally they are, then the size of the compression unit can be calculated from the gas flow (capacity) and the suction pressure and discharge pressure( pressure differential) for the unit.the work done is calculated from the equation:
Wa = x T1 [ -1]
We can therefore use the 48km pipeline flow rate and the optimum pressure differential to calculate the number of compressors needed to maintain the flow rate prescribed for the next stage of the transmission line I.e. 1.35 mill m3/day into the 327km section.simplified version of the equation for work done discounts any heat lost due to adiabatic process.
Wa = x (288) Loge = 39,162 J/Kg
The volume of gas processed per second can be found by:
1.36 x 10 6 / (24 x 3600) = 15.74 cubic metres of gas/second.
And the weight of the gas is given by 15.74/0.714 = 22.05 kg, the total work done
22.05 x 39,162 = 863,336.4 J
The total work required to transfer 21.07 kg would be 863.33 KJ.more, we can size the compressor power unit that we need.
Power = 4.0639 x 1.36 ((288) ( =
The compressor driver may have mechanical efficiency of 98% so
Driver power = = 633.91kW
Sizing the compressor units for Horse Power we can use the equation
HP = 0.0857 x 48.85 ((288) ( = 470.66
the mechanical efficiency of the driver taken into consideration as 0.98 we can calculate the break horse power of the unit.
BHP = = = 480.26 BHP
BHP required to drive the compression operation could be effectively one 500 BHP unit.units vary in size from 50 BHP up to around 20,000 BHP. This is of the smaller capacity however in further planning it would be recommended to oversize the unit.
From the results obtained it shows that due economic analysis must be carried out before pipeline development:
.Detailed market survey to ascertain peak loads, average and minimum demand of consumers in order to adequately size a pipeline
2.Detailed route survey to ascertain the nearest distance for gas supply to a customer
3.Detailed energy audit of consumer equipment in order for pressure distribution
4.Detailed engineering design to properly cost a pipeline network
With the knowledge of how the above four parameters discussed affects capacity one can properly cost and size adequately a pipeline for either transmission or distribution purpose.
1.Kadir A., University of Salford, Distribution and Transmission Lecture Notes 2011/12.
2.E. Shashi Menon, Pipeline Hydraulics, Taylor & Francis 2005.
3.Roberts, John.,1996. Caspian Pipelines. The Royal Institute of International Affairs.