About the Author: This article is written by Mr Ankur Srivastava, a Chemical Engineer with more than 32 years of process engineering experience in oil and gas, refining, polymers and petrochemical industries.eval(ez_write_tag([[300,250],'whatispiping_com-box-4','ezslot_8',635,'0','0'])); I am a Mechanical Engineer turned into a Piping Engineer. Reciprocating compressors are usually found in air cooled direct expansion (DX) systems for residential and small commercial systems. Free PPT and PDF Download for COMPRESSOR: Compressors, fans, and blowers are devices which are designed in such a way that they deliver gas at a pressure which is more than the genuinely existing pressure.The features like a rise in pressure, working pressure, mechanical design and specific speed become the basis for the classification and differentiation. The compressor compresses the refrigerant, which flows to the condenser, where it gets cooled. On low compression ratio applications (compression ratio less than 1.6, such as pipeline transmission of natural gas) adding fixed clearance will hardly change the flow. In other applications with higher compression ratios, clearance pockets and cylinder end deactivation are commonly used to regulate flow. The engine can consist of two to six pistons per cylinder, depending upon horsepower demands. The maximum compression ratio that a reciprocating compressor can handle in one stage is limited mostly by gas discharge temperature. SYMBOLS AND UNIT Designation Symbol Unit Pressure p bar A Temperature t C Absolute Temperature T K Capacity (volume flow) Q m3 / hr Power P kW Brake horse power BHP kW Gas horse power GHP kW Speed N RPM Head (polytropic) H m Gas Constant R kJ/kg.K Molecular Mass MW … Figure 21.1 shows the working principle of a centrifugal compressor. (For reciprocating, rotary screw, and centrifugal) 21 Modulation: restricts inlet air to the compressors to reduce compressor output to a specified minimum. What Are the Signs of Failed Valve Seals? For corrosive applications it is common to use stainless steel such as 17-4PH or 400 series for piston rods and compressor valve seats and guards. | Find, read and cite all the research you need on ResearchGate The technology which powers centrifugal compressors dates to the 1940’s, so, since the trial-and-error phase of testing the scientific principals which drive them are well past, centrifugal compressors tend to be more available, more reliable, and less prone to maintenance needs. link to Flange Bolt Torque Calculation and Pipe Flange Bolt Torque Chart, Difference between Centrifugal and Reciprocating Compressor, For more details about Centrifugal Compressors Click here, Click here to know more about Reciprocating Compressors, Flange Bolt Torque Calculation and Pipe Flange Bolt Torque Chart, They can be sized for an inlet flow of 680,000 actual m. Capacity is limited by cylinder size, the number of throws available, and the available driver speeds. Reciprocating compressor deliver gas with high pressure and mass of flow rate small due to reciprocation motion.it is used for less mass flow rate.etc mostly used pneumatic air. Despite their smaller size, centrifugal compressors tend to be used in industrial applications rather than in the home. Four-Stage Barrel Compressor. Materials for major components such as casings, nozzles, shafts, impellers etc. They are divided into rotary (lobe, screw, scroll, vane and liquid ring compressor) and reciprocating (diaphragm, single and double acting compressor). 3. These dynamic compressors pull in air to their centers with radial blades. On the other hand, if the pressure ratio is less than two when a centrifugal compressor is in use, its efficiency is higher. Typical reciprocating compressors in the process industry are used to generate discharge pressures as high as 800 barg. Quantity, pressure, and style of engines can also contribute to differences between the two. When the air passes through the rotating impeller it experiences force or work which is performed by centrifugal forces. The number of main casing nozzle and the type of driver (electric motor / gas or steam turbine) also affect installation time. Difference Between Rotary and Reciprocating Compressor [Notes & PDF] … The amount of kinetic energy is a function of the gas velocity and gas molecular weight. Efficiencies are primarily affected by internal leakage and mechanical losses. Although less powerful reciprocating compressors are portable, they usually consume a larger footprint than centrifugal compressors and tend to be: In general, they are less reliable than centrifugal compressors, although not by much, and they can usually be repaired quickly with common tools and parts. Centrifugal compressors operate on a constant pressure, and personnel must tend to their external environment to ensure efficient flow. The dynamic ones are further separated into centrifugal and axial. However, problems with pulsation and mechanical reliability cause these compressors to be less desirable than centrifugal compressors for … With variable speed drive or adjustable inlet guide vanes the turndown can be increased to 40-50%. Reciprocating compressors, because of their multistage operation and low discharge, can invite cracking and potentially affect the health of their operators due to their greater noise and vibrations. Both sides of the piston are utilized in compressing the air. Injection stretch blow molding process has two main different methods, a single-stage and two-stage process; these are the methods by which hollow plastic parts are formed. The common compressor cylinder materials, cast gray iron and cast ductile iron are acceptable for use at temperatures as low as -40 deg C which typically occur in refrigeration applications. When a gas-driven reciprocating compressor is experiencing failure, operators are usually warned by easily discernible symptoms. Reciprocating compressors are piston-driven; they work and look similar to combustion engines. Compressor valve and seal elements may require to be maintained in durations as short as a few months and as long as 3-5 years. Their use depends greatly on function, location, and environmental considerations. 1. The capital cost of a centrifugal compressor is typically higher than a reciprocating compressor operating at the same conditions. Refer the figure. Reciprocating air compressors, which are also called “piston” or “recip” air compressors, are widely used throughout various service industries due to their price and availability. The air is compressed only on the top part of the piston. Reciprocating compressors are used in refineries, gas pipelines, chemical and petrochemical plants, natural gas processing plants and refrigeration plants. Electrical motor driven reciprocating compressors may require longer lead times specifically if large high horsepower motors are required. Gaseous Fluid enters the center of a rotating impeller with radial blades and is pushed toward the center by centrifugal force which results in a pressure rise and increases in kinetic energy. However, a centrifugal compressor has fewer wearing parts, resulting in lower operating costs in terms of replacement parts, repairs and downtime. Also known as throttling or capacity control. Since reciprocating compressors have many more parts and more rubbing seals (pressure packing, piston rings, and rider rings) that wear and require more frequent replacement, they are considered somewhat less reliable than centrifugal compressors. Considering a centrifugal compressor with a water wash system, the end user may exhaust their reverse osmosis water supply, or the system freezes and there are extended periods without online washing. Compressors are an essential part of every industry, but what’s the difference between a centrifugal vs reciprocating compressor? Generally a reciprocating compressor will have a lower capital cost but a higher operating cost (excluding power consumption). Your email address will not be published. For centrifugal compressors compression ratio is a function of gas molecular weight, compressibility factor, stage geometry, speed, and the number of compressor stages. industries. Typical polytropic efficiencies range from 70% to 85%. For horizontally split compressors discharge pressures up to 100 barg are common. Difference between Centrifugal & Reciprocating Compressors! Reciprocating compressors have a very characteristic adiabatic efficiency curve. In the pump-priming process, the pump is filled with the liquid... Hi There! Today we will discuss about difference between centrifugal pump and reciprocating pump. Deciding between which to invest in requires research and careful study of a system’s needs and a good understanding of operating conditions. Because reciprocating compressors run intermittently and with air which pulsates at a high pressure ratio, they handle a smaller volume of air than centrifugal compressors. This bolt load for gasket sealing and flange seating is provided by Flange Bolt Torque. The number of different services on a given compressor crank case (frame) is only limited by the throws available and the number of stages required for each service. The gas in the inlet section is compressed by the reciprocating motion of the pistons. Established centers of this industry include the United States and Western Europe. It is important to note that in addition to reciprocating, rotary screw, and centrifugal compressors, other compressor types may be used. For radially split (barrel) compressors discharge pressures could go as high as 1000 barg. Mechanical Balance: Poor mechanical balance and greater vibrations due to presence of reciprocating masses. Multistaging Capability: Suitable for high delivery pressures with multistaging, delivery pressure upto 5000 bar possible. Production boosting. In this video, I explained difference between reciprocating and centrifugal pump. Major machine overhaul including bearing replacement may be required after 10 years of operation or longer. Location can also be a factor. Flange Bolt Torque Calculation and Pipe Flange Bolt Torque Charteval(ez_write_tag([[300,250],'whatispiping_com-large-leaderboard-2','ezslot_13',633,'0','0'])); Proper bolt loading is essential for ensuring proper sealing of the flanged joint to avoid leakage problems. Since reciprocating compressors have many more parts and more rubbing seals (pressure packing, piston rings, and rider rings) that wear and require more frequent replacement, they are considered somewhat less reliable than centrifugal compressors. Both light and heavy gases are compressed very well. 2. High discharge temperatures due to high compression ratios can usually be controlled by inter-cooling between a compression stage. Low temperature seals and O-Rings are also required. Now that you understand the pros and cons of a centrifugal vs reciprocating compressor, you can make better decisions regarding the parts and health of your compressors. Both centrifugal and reciprocating pumps are most common type of pumps used to move fluid and increase its pressure. The processing and refining of Natural Gas into a marketable products, by separating gas into pipeline-quality natural gas and a stream of mixed natural gas liquids and the transportation of natural gas to through a series of reciprocating compressor stations and pipes, and from there to end users. Reliability / availability of centrifugal compressors is typically 98 to 99%. Reciprocating compressors of capacities of a few m. This can be atmospheric or sub-atmospheric (vacuum). Where suction conditions involve sub-atmospheric pressures, adequate measures must be taken to prevent atmospheric air leaking into the cylinder through the piston rod packing. Typical turndown for a fixed speed, multi-stage centrifugal pump is approximately 20-30%. Both reciprocating and centrifugal compressors are valuable in the manufacturing world. Discharge temperature limits will depend on the application (gas compressed) and the seal element materials selected. Centrifugal compressors are used for a broad range of molecular weights including low molecular weight applications such as hydrogen recycle and high molecular weight application using refrigerant gases with molecular weights over 100. Reciprocating Compressor/Natural Gas Industry ©.Privacy PolicyKB Delta, Mfg, Valve Seat and Seat Ring Basics: What to Know, The Business Benefits of Green Manufacturing, Types of Bearings in Reciprocating Compressors, and Their Importance. I am very much passionate about blogging and always tried to do unique things. A centrifugal compressor is a popularly used in Process Industries, Oil and Gas, Refineries, Wastewater treatment plants, etc. Material selection is primarily dependent on temperature, stress (pressure / torque), and gas composition (corrosive / erosive). Polytropic efficiencies are used for centrifugal compressors rather than adiabatic efficiencies. The lowest suction temperatures required typically are in LNG boil-off applications with requirements as low as -170 deg C and there are very limited manufacturers for this application. The difference between the hermetic and semi-hermetic, is that the hermetic uses a one-piece welded steel casing that cannot be opened for repair; if the hermetic fails it is simply replaced with an entire new unit. The gas which is produced by a reciprocating compressor is either fed to a pneumatic system or immediately stored. In applications involving air compression adiabatic efficiencies are used. are primarily carbon steel, stainless steels and / or alloy steels. With this information, an educated decision can be made as to most appropriate compressor for a given need. Reciprocating Compressor. compressor types may be the best fit for their particular application. Centrifugal pump is a rotodynamic pump that uses kinetic energy to transfer fluid from low pressure to high pressure while the reciprocating pump uses a piston (suction and discharge stroke) to transfer fluid. Head is developed by increasing gas velocity to create kinetic energy and then converting the kinetic energy to pressure in the diffuser. KB Delta offers one of the most complete lines of valve internals in the industry. This energy is then converted into pressure by passing through a diffuser and volute. Before moving to further detailed explanation lets have some overview of Pump and compressor. When the compression efficiency in a system is greater than two on a reciprocating compressor, it operates at greater efficiency than a centrifugal compressor. Typical flow range might be from 100%, down to 20%, or even lower. Often the lead time is governed by the driver (electric motor / turbine) since these are generally made to order. Process plant optimization. Single-Acting Compressors: It has piston working on air only in one direction. The piston rod load generated by the compression ratio may also be a limit. For reciprocating compressors, maximum as well as minimum flow is directed by the size of its cylinder, as well as the amount of cylinders available. Other factors also impact efficiency, most significantly the compressor cylinder’s ratio of valve flow area to main bore diameter and piston speed. Reciprocating compressors are very adaptable to a multitude of gases and can handle different gases at either the same stage or at different stages in the same machine. 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