Tags: Centrifugal Compressors

Gas Turbine Driven Centrifugal Compressors

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While the majority of natural gas field and transmission compressors are reciprocating machines, a sizable minority are centrifugal compressors driven by gas turbines. Only on rare occasions can electric, steam or deisel oil drives compete with natural gas as compressor fuel in pipeline service. A gas turbine works on the same principle as a jet …

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Centrifugal Compressors – Suction and Discharge Shutdown Valves and Discharge Check Valves

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These devices are required to isolate the compressor for the same reasons they are required for reciprocating compressors. Discharge Check Valve (Each Stage) In reciprocating compressors the compressor valves themselves act as check valves, preventing backflow from high-pressure stages to lower pressure stages. Multistage centrifugal compressors require check valves on each stage to isolate each …

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Centrifugal Compressors – Slowdown Valve

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Slowdown valves must be installed in centrifugal compressors for the same reasons as in reciprocating compressors. They must be designed with more care than those on reciprocating units, since centrifugal compressors have oil film seals where the shaft goes through the case. These seals only work if the shaft is rotating. If the compressor shuts …

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Centrifugal Compressors – Speed Controller, Inlet Guide Vanes

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Speed Controller A speed controller is needed in conjunction with the surge control system. A new head-capacity curve is established for each speed, as shown in Figure 10-14. Inlet Guide Vanes The performance curve can also be shifted to match the process requirements by variable inlet guide vanes. Located at the compressor inlet, these vanes …

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Centrifugal Compressors – Flare Valve, Suction Pressure Throttle Valve

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Flare Valve As suction pressure increases or discharge pressure decreases, the compressor head requirement will decrease and the flow rate will increase. A flare valve will avoid stonewalling or overranging driver horsepower. Suction Pressure Throttle Valve A throttling device can also be placed in the suction piping to protect against overpressure or to limit the …

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Centrifugal Compressors – Recycle (Surge Control) Valve

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A recycle valve is needed for surge control as well as for the conditions listed above for reciprocating compressors. At constant speed the head-capacity relationship will vary in accordance with the performance curve. For a constant compressor speed: • If the flow rate to the compressor decreases, the compressor approaches the surge point and a …

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Centrifugal Compressors – Surge Control and StoneWalling

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Surge is the most important process design consideration for centrifugal compressors. The surge condition occurs when the compressor does not have enough flow to produce sufficient head. At this point, the gas in the discharge piping flows back into the compressor momentarily. This lowers the back-pressure of the system, establishing forward flow at a temporarily …

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