Compressors – What Is Piping: All about Piping Engineering

Compressors are intended to compress a substance in a gaseous state. Process compressors are used to compress a wide range of gases over a wide range of conditions. Compressor Applications RefineriesNatural Gas Compression & Transportation ServicesOil Exploration – Gas Reinjection, Gas lift, etc.Gas LiquefactionAir Compression serviceRefrigerant compression serviceRefueling applications Basic type of compressors Positive Displacement CompressorsReciprocating compressorScrew CompressorsCentrifugal compressorsPipeline compressors Centrifugal Compressors Centrifugal compressor is a “dynamic” machine.Has a continuous flow of fluid that receives energy from an integral shaft impeller.Energy transformed into pressure – partly across the impellers and partly in the stator section called diffusers Refer to the Cross section & parts (Fig. 1): A. Outer casingB. Stator parts called ‘Diaphragm bundle’C. RotorD. ImpellersE. Balance drumF. Thrust collarG. HubH. Journal BearingI. Thrust BearingJ. Labyrinth SealsK. Oil film end seals Fig. 1: Cross section of a typical Centrifugal Compressor Centrifugal Compressor types Compressors with Horizontal Split casings (Fig. 2):- Consisting of half casings joined along the horizontal centerline, Employed for operating pressure below 60 bar. Fig. 2: Centrifugal Compressor with Horizontal Split Casing Compressors with Vertical Split casing/Barrel Type (Fig. 3):- Vertical split casings are formed by cylinder closed by two end covers; hence ‘barrel type’ used to refer these compressors, Employed for high-pressure services up to 685 bar. Fig. 3: Centrifugal Compressor with Vertical Split Casing The Horizontal split casings & barrel compressors are further identified based on process stages, i.e. Multistage compressors with one compression stageMultistage compressors with two compression stages (Two compression stages set in same machine/barrel casing. Between the two stages cooling of the fluid is performed in order to increase the efficiency of compression) Basic Terminologies of Centrifugal Compressor Surge: Phenomenon of instability which takes place at low flow which involves the entire system including not only the compressor but also the group of components traversed by the fluid upstream & downstream of it. Surge is characterized by intense and rapid flow and pressure fluctuation throughout the system and is generally associated with stall involving one or more compressor stages. This phenomenon generally accompanied by strong noise and violent vibrations which can severely damage the machine involved Stall: Stall in turbomachinery describes as a situation in which due to low flow values, the stage pressure ratio or head does not vary in a stable manner with the flow rate. Surge prevention: Surge prevention is effected through experimental tests in which pressure pulsation at a low flow rate is measured on individual stages. On this basis, it is possible to identify the flow values at which the stable operation of the stage is guaranteed. Capacity Control Capacity Control is used for the following: Process flow controlTo optimize fuel/power efficiencyPressure regulation Capacity can be changed several ways; below are some of them: Speed RegulationControl of Supply gas to the machineBypassing the discharge flow back to the suction side of the machine Type of Compressor Drives Following are the various types of Compressor drives: Electric Motor DrivesAC Squirrel cage Induction MotorSynchronous AC MotorGas TurbinesSteam turbinesVariable Speed drivesVariable Frequency DriveVariable speed (Hydraulic Coupling) drives Typical Centrifugal Compressor Curve (Fig. 4) Fig. 4: Typical Centrifugal Compressor Curve Compressor Sealing System Selection of sealing system is critical for Satisfactory performanceReliability The type of compressor & method of lubrication used will decide the type of sealing Technology. Sealing System can be divided into two classes based on the type lubrication: Contacting Sealing System Liquid LubricatedGas Lubricated Non - Contacting Sealing System Liquid LubricatedGas Lubricated Following are the utilities required for the Compressor: External Fuel gas for seal gas systemInstrument Air for the Instruments/Control system/Seal gas system Few more useful resources for you…Articles related to CompressorArticles Related to PumpsPiping Design and Layout BasicsPiping Stress Analysis BasicsPiping Materials BasicsArticles Related to Mechanical DesignArticles Related to Process DesignArticles Related to Heat ExchangerJob Opportunities for you…