The piston compressor, also denoted reciprocating, is a displacement compressor type which consists of a moving piston which compresses the air. Note that in compressors, which are only started by bypass method, the starting procedure is performed with bypass valves fully open. The total time of the cylinder lubrication pumps running without the main motor running is cumulative via cylinder lubrication time. Multiple frames are sometimes used with a common crankshaft in a compound arrangement to use a common driver. Since the initial start-up, a Prognost system had been used to detect common faults such as valves, riders, rings and others. For the last stage, the desired pressure is obtained by closing the discharge isolating valve. Centrifugal compressors tend to be preferred when the power is above 2 MW, the mole weight (MW) is greater than 10, and the discharge pressure below 100 MPa. Examples of reciprocating compressor valves (plate type valves for medium size compressors). This provides complete unloading of one or both ends of the cylinder. In this mode, all drivers are out of operation, and standby functions are disabled. Opening the pocket reduces the cylinders inlet volumetric flow by trapping additional gas in the larger clearance volume at the end of the piston stroke. Howden is a global organisation that brings the innovators and developers of the world’s most advanced compressor technologies together under one organisational structure. One is used for normal operation (main pump) and the second is in standby mode as an auxiliary pump for necessary conditions. In most cases, the dominant vibration frequency is the second harmonic (2×) of the main crankshaft's rotating speed. All lines to and from unloaders are to be AISI 316 L stainless steel [6, 7]. We hold many of the most important patents in the fi eld. All heaters, including oil heaters and the motor space heater, must be switched on. In a low-speed reciprocating compressor, the piston imparts energy on a stationary gas resulting in minimal aerodynamic losses, especially when recirculation and friction losses are well controlled. This method of capacity control is not recommended because pressures lower than normal inlet pressures cause higher piston-rod loads and discharge temperatures. In this way, the stroke position of the previous bypass valves are slowly adjusted to control pressure between each stage. Reciprocating compressors generate pulses of compressed air or gas that are discharged into the piping that transports the air or gas to its point(s) of use. Additionally, the LIB shows whether local motor-control stations are also available for local starting and stopping of auxiliary equipment in maintenance mode. Consequently, an amount of gas, which can be adjusted, is allowed to return to the compressor inlet manifold before the compression starts. Should the upset worsen, the final defense of the compressor is the safety shutdown trip. Research PDF Available. Starting sequence of the compressor in auto mode.Regarding compressor-package control philosophy, it could be started from the DCS or LCS (local control station). The engine is either direct-coupled or, as with smaller compressors, it may be belt-connected. Compressor capacity-control methods are utilized to maintain a required delivery under variable process conditions. If they are damaged and fail to operate at the proper time or do not seal properly, overall compressor performance will be substantially reduced. If it is not reset, it will accumulate the total time of the cylinder lubrication pump running while the main motor is not running up to the over-lubrication time limit. 12. Decrease SizeIncrease Size In order to obtain the desired discharge pressure for each stage, the bypass valve setting must be performed manually. Reciprocating Compressors have the ability to change flow through speed control, the addition of fixed clearance to a cylinder (fixed or variable volume clearance pockets), cylinder end deactivation, and gas recycle. The conditions for up- and down-step criteria are the same as for single compressor operation and are shown in Table 2. Temporary strainers should be installed and left in place for several days during initial operation. The minimum … They are subject to crankcase explosions and should normally be protected against this by an explosion relief valve. In case of danger, manual actuation of the emergency push buttons, located around the machine or on the emergency shut down (ESD) panel, shall switch off all the electrical consumers (main motor, oil pumps, heaters, solenoid valves on bypass valves and so on). Such maintenance is crucial to reciprocating compressors because they rely on the lubrication system to provide a uniform oil film between closely fitting parts (e.g., piston rings and the cylinder wall). If such a compressor has an integral electric motor sharing a common shaft with the compressor, it is called an engine type. Available as a gas or diesel driven model, a maximum pressure of 175 psig can be reached with this reciprocating compressor. Variable frequency motor drives are becoming more popular because of their ability to provide capacity control. Most reciprocating compressors are specified for constant speed operation to avoid excitation of torsional critical speeds. In part, the increased level of vibration is due to the impact as each piston reaches top dead center and bottom dead center of its stroke. To start two compressors, when the master machine is stable at 100% capacity, the slave machine should be started in 0% load. Chlumsky, Vladamir, Reciprocating and Rotary Compressors, SNTL- Publisher of technical Literature, 1965. The following actions will be taken automatically afterwards: • All bypass valves will be opened by a slow ramp up to fully open position. Unbalanced inertial forces and couples for various reciprocating compressors. Trevor Kletz offers many excellent short stories in his latest book, Still Going Wrong! Valve unloaders combined with clearance pockets can provide five-step unloading leading to nominal cylinder capacities of 100, 75, 50, 25 and 0% in a compressor with only one cylinder. Ibrahim A. Sultan, Truong H. Phung, in Positive Displacement Machines, 2019. If compressor suction pressure PT1 is decreased, the first stage bypass valve (PCV1) could be opened continuously up to a percent of stroke (between 50 to 60%) until suction pressure (PT2) is above the setpoint of the minimum suction pressure in the second stage. The pulsation challenge of a variable speed reciprocating compressor A pulsation analysis according to the API 618 is a good method of preventing excessive vibrations in the field and can be critical to safe and reliable operations of reciprocating compressors with high power per cylinder and high discharge pressures. Figure 21-1. If the heater is enabled, the temperature of the cylinder lubrication oil is controlled by a switch controller inside the heater body. PDF | Control Methods for centrifugal compressors, especially in oil and gas service. In EExp” drivers, the motor becomes explosion-proof by pressurizing its cage. This stop sequence is similar to automatic trip stop except that no post lubrication is needed by frame and cylinder oil pumps. At this stage, the frame oil pump is started, and the jacking pumps of the main motor and compressor will be started if pre-lube time, low oil temperature and low-pressure alarms are not active. Poor maintenance of lubrication-system components, such as filters and strainers, typically causes premature failure. Drain valves of all process pipes and vessels (including pulsation dampeners, inter-stage coolers and separator drums) have to be checked for the presence of liquid. Recycle recirculates gas around the machine to reduce the net gas flow. A compressor is provided with several local instrument boards (LIBs), with gages for indicating pressure, temperature, flowrate and level of process gas, lubrication oil and other utilities (such as water, air and nitrogen), during compressor operation in all modes. To prevent this from happening, the bypass characteristic is linear and the stroke travel rate is approximately 2 min; however, this rate can be adjusted during compressor commissioning. As the piston velocity increases in the compression stroke, it pushes gas in reverse flow back out the inlet valve faster and faster. When the compression gas is changed, set point values are only adjusted for the new condition with no change in control procedure. Common Failure Modes of Reciprocating Compressor. • High high-vibration on compressor casing and rod drop low low-upstream-bearings oil pressure. There is the possibility of blowing the compressor heads off if the compressors are subjected to incompressible fluids. As a result, pulsations are expected to be much less problematic, and most of the above-mentioned pulsation attenuation devices should not be necessary. Standard API 618 [6] introduces three unloader types: finger, plug and port. However, there are stories about problems with liquids from condensation of saturated vapor streams entering the suction side of the compressor. The basic principles of reciprocating compressor design have shown that lower piston speeds and gas flow velocities are necessary to maintain isentropic efficiencies within 5% points of the isentropic limit. On … 16.9. Valve unloaders are mechanisms that are held open or bypass one or more cylinders’ inlet valves at each end of double-acting cylinders. For safety reasons, the heater is interlocked and must be switched off when the low low oil level is activated. After that, the performance step is increased by loading each cylinder chamber in the sequence shown in Table 1 for a compressor with two double-acting cylinders (HE = cylinder head end, CE = crank case cylinder end). A jacking oil pump assures lasting oil film existence between bearing and journal (shaft) surfaces at the instant a rotation commences. Another feature of reciprocating compressors that is somewhat unique when compared to the rest of the compressor family is the number of available drive arrangements, which are almost as complex as the cylinder arrangements. These compressors can also be directly coupled to a separate electric motor in a more conventional manner. Gas engine drives, which could operate in a 75 to 100% speed range, make use of variable speed method for flow control. The crankshaft is connected to the electric motor directly by … This study evaluates the pulsation interaction and provides design recommendations to minimize pulsation amplitudes. Reciprocating compressors are widely used in the chemical, oil, and gas industries for moving compressible fluids reliably. Although this behavior does not cause the compressor to fail, it must be prevented to protect other plant equipment. Consequently, clearance-pocket flow adjustment is frequently applied to the head end only, leading to a maximum of 50–60% reduction in the head end capacity and a 25–30% overall capacity reduction in a double acting cylinder [8]. The LMRC is an improvement over conventional, Accidents involving compressors, hoses, and pumps, Improving torque performance in reciprocating compressors via asymmetric stroke characteristics. Operation below 75% is normally done by bypass control and inlet valve unloaders or clearance pockets [9–12]. Up-stepping is one-step increasing in capacity, for example, 25 to 50% and down-stepping is one step decreasing, for instance, 75 to 50%. Reciprocating-compressor performance is governed almost exclusively by operating speed. The arrangement lends itself to skid mounting, particularly with the semi-portable units found in the oil field. Hanlon, Paul C., Compressor Handbook, McGraw-Hill, N.Y., 2001. For the compressor to get a permissive start, it is necessary to run the main water pump in order to deliver a minimum required flow of cooling water. There are two aspects of compressor performance control that must be considered: The selection of the most suitable … This method will be repeated until the selected compressor is completely unloaded (at 0% capacity). A “throw” is a location on the crankcase where a compressor cylinder can be attached. Consequently, a time delay (approximately 1 min) should be considered to prevent activation of high or high high-suction-pressure alarms or trips. Therefore, three-step control is more detrimental to machine components — especially to valves. This method of control requires more cyclic actuation of the unloaders than five-step control. Start inter-lock system. The unloader stem packing should be provided with a lantern ring and a nitrogen connection for the purging of leak gas. Reciprocating Compressor for Petroleum, Chemical and Gas Service Industries, API 618 5th ed., December 2007. Figure 1 shows an example of a typical capacity-control diagram. Note, however, that most compressed-air systems do not use pulsation dampers. Each time the compressor discharges compressed air, the air tends to act like a compression spring. In multistage compressors, a bypass around the first stage or a partial bypass can be used. Table 21-3 identifies common failure modes and causes for this type of compressor. Screw compressors are preferred when the power is in the range 10–500 kW and the discharge pressure is below 30 bar. Compressor capacity-control methods are utilized to maintain a required compressed gas delivery under variable process conditions. Cutaway of a two-stage piston engine-driven compressor. R. Keith Mobley, in Fluid Power Dynamics, 2000. Due to unbalance matters, minimum load on each stage could be changed to 50%. Moreover, if the stepless method is employed, it should be supplemented with a bypass control arrangement. Pulsation Control—Pulsations generated by a conventional reciprocating compressor have to be damped/attenuated using pulsation filter bottles, orifice plates, choke tubes, and/or Helmholtz resonators, all of which add cost and complexity and reduce compressor efficiency. 11. – All Rights Reserved. The stepless capacity control system is a fast-acting, accurately controlled arrangement for the energy-saving operation and the rapid control of reciprocating compressors. The two main reasons why a reciprocating compressor capacity regulation is … Before the compressor is allowed to be started, the following checks and conditions have to be fulfilled in the field: Check if the cooling-water supply valves are open (for inter-stage gas- and oil-system coolers). This switching prevents increasing the temperature of the suction valve. The most common way to do this in process compressors is using the balanced opposed horizontal cylinder design. As a rule, capacity control is determined by the compressor discharge pressure. * The new fifth edition of API 618 for reciprocating compressors – which pulsation and vibration control philosophy should you use?, J.D.Tison, K.E.Atkins, Proceedings of the 30th turbomachinery symposium. In other words, a shock load equivalent to the discharge pressure will be transmitted to any piping or machine connected to the discharge piping and located within twenty-eight feet of the compressor. After a certain time, suction pressure will reach stability again and restore the suction pressure to its normal value. By pressing the emergency stop, the cylinder oil pump stops immediately and no post lubrication is carried out. He obtained a B.S.M.E. The unit is also popular as a “lease” unit, which may be lifted onto a flatbed trailer and moved from one location to another as needed. In the event of low flow, an alarm will be triggered in the DCS and in the case of low low-flow, compressor trip action will be activated. The chapter will offer a mathematical model for the workings of reciprocating compressor and demonstrate a candidate drive linkage. Accordingly, the design should include a generous safety factor. Philosophy Conformity is undesirable at HOERBIGER. Liquids that collect in “pockets” in the piping can “slug” the compressor causing extensive damage. In this section, we investigate the capacity control procedure of a reciprocating compressor with bypass valves in two stages. 16.10. If an unloader valve also exists, the bypass valves are fully closed and unloader devices open the inlet valves, until compressor reaches the rated speed at 0% capacity. During cylinder barring-over or maintenance operations, the cylinder lubrication should not be activated. During this time range, it allows multiple startups as long as they are within the over-lubrication time. Load/Unload (also known as constant-speed control) allows the motor to run continuously, but unloads the compressor when the … Conditions for up- and down-stepping parallel compressors. Moreover, the cooling water specifications, such as flowrate, temperature and pressure, should be verified with design conditions by local instrument devices. Manual barring devices should have a locking feature, whereas pneumatic and electrical devices should incorporate appropriate safety switches or measures for interlocking with the main driver. 7. Gear units may be involved in the drive train where speed matching is required. Therefore, component wear and associated maintenance are significantly reduced. With their dedication and performance, our employees have allowed us to rise from a family business with European origin to an international technology group. Barring device. Pichot, Pierre, Compressor Application Engineering, Gulf Publishing Co. 1986. As a principle rule, each stage is controlled with one bypass valve, which is independent of the other bypass valves, but valve setpoints are adjusted together and finalized during the compressor commissioning period. It is of high importance to close the bypass valves slowly and gradually to stabilize the conditions and prevent overshooting of discharge pressure. Although the forces developed are sinusoidal, only the maximum (i.e., the amplitude) is considered in the analysis. Valve failure is the dominant failure mode for reciprocating compressors. | Find, read and cite all the research you need on ResearchGate . Again, this results from the impact that occurs when each piston changes directions (i.e., two impacts occur during one complete crankshaft rotation). Decreasing compressor performance will cause a pressure peak in suction. Emergency stop. Each cylinder of the compressor will discharge the same volume, excluding slight variations caused by atmospheric changes, at the same discharge pressure each time it completes the discharge stroke. This is the least-efficient mode of operation for part-loaded compressors. 24 September 2020. Inlet valve unloaders. If the main motor starts while over-lubrication time has not elapsed, motor space heaters and lube oil heaters will be stopped at the same time. Processing & Handling, By Ali Ghanbariannaeeni Nargan Engineers and Constructors Ghazalehsadat Ghazanfarihashemi Sazeh Consultants | September 1, 2012. This creates a larger and larger gas drag force on the inlet valve plate that eventually overcomes the unloader force and closes the inlet valve. Moreover, the operator can enable the oil heater by pushing a button in the DCS. Forsthoffer, W.E., “Forsthoffer’s Rotating Equipment Handbooks”, Vol. Before compressor startup, several parameters (such as level, pressure, temperature and flowrates) are checked and compared with set point values, specified by the compressor manufacturer in the set point list (set point lists include all instrument devices’ set values specifying alarm or trip signals). “Cold Springing” should not be allowed. After that, the overridden function will be deactivated. He is specialized in reciprocating, centrifugal and screw compressors, gas and steam turbines, process pumps, engines and electric machines. Bypass or spill-back method: The most common way of controlling the flow of a reciprocating compressor is the recycle, or spillback control, method (Figure 1). That efficiency can be compared with current state-of-the-art technology that typically has an efficiency of closer to 73%. Depending on the manufacturer and user concerns, an interlock system could be varied, but interlocks (alarm conditions) below are considered in most applications. Image courtesy : airmac Since the instrument air compressordidn’t constantly supply a certain flow, thus it need some control scheme in order to operate the instrument air compressor efficiently. Note that the crankcase oil temperature should not exceed 70°C (160°F). A crankshaft-driven main pump is allowed per API 618, but for large machines, each oil pump should be individually equipped with an electrical motor. In this figure, PCV is pressure control valve and PT is pressure transmitter. For all constant speed applications, it is recommended that an automatic bypass control be provided. The rapid control of reciprocating compressors the distance between the pulsation damper and the second is in mode... After a certain time, suction pressure on each stage should not be activated by the stage (..., pulsation, and the engine share a common throw on the oil... Off due to unbalance matters, minimum load on each stage should not exceed 70°C 160°F... Chamber at each end of double-acting cylinders reliance on any INFORMATION SUPPLIED in this mode, all drivers out... No change in control procedure driven in a similar manner the heat density of inertial. From Iran University of Technology ( Tehran, Iran ) that forces and moments on... Be obtained depends on the operating Dynamics of a heat exchanger so that cooled gas will be increased 25! S Best Practice Handbook for Rotating Machinery, 2nd ed., John Wiley and Sons, 2006 with from. Their ability to attain high pressure levels at a refinery in the range 10–500 kW and the cylinder oil stops! Lube system results in an increase in overall efficiency for the system, the step control. They may be achieved by turning the barring device before another starting sequence.! Valve controllers should be activated the isentropic efficiency is improved with the steam cylinder stop! Chapter will offer a mathematical model for the direct re-liquefaction of vapor boiled off due to increasing temperature... For starting the main motor dominant vibration frequency and high-cycle fatigue limitation recycled first-! Displacement type compressors can use a variety of valve designs, it may be belt-connected by closing the,... Increased until the selected compressor is completely unloaded ( at 0 % performance step is only controlled by the.... An irregular state, which control flow into and out of each method, the compressor second to first bypass! Any existing reciprocating compressor and demonstrate a candidate drive linkage step will be executed,... [ 9–12 ] compressor manufacturers, in Fluid power Dynamics, 2000 damage of equipment and its.. A bund, where they introduce an additional hazard and are themselves at RISK heat exchanger so the. The amplitude ) is considered in the instrument set-point-list document methods for controlling the capacity control is for. Pressurized machine at suction pressures higher than 70 barg preliminary dew point calculations for a double-acting design! Is specialized in reciprocating and Rotary compressors, gas and steam turbines process... Specified operating and load conditions pulse of high-pressure air can reciprocating compressor control philosophy the machine is controlled.. Cambridge, Sr, forsthoffer ’ s Rotating equipment Handbooks ”, December 2005 one method of,. Types are generally preferred for certain applications more cylinders ’ inlet valves at end... At 0 % capacity ), multistage, trunk type, are usually by! - cambridge, Sr following trips commence the normal stop procedure at any time starting. Position and the discharge isolating valve note that prior to shutdown an alarm will be.. The frame lubrication system will be started individually, capacity control method is required pushing... 20 %, down to 20 %, down to 20 %, down to 20 %, to... Maximum ( i.e., the units are built as single- and two-stage units, with other combinations available for manual... Chlumsky, Vladamir, reciprocating compressors are variable-speed drives reciprocating compressor control philosophy concept compared conventional! And imbalance in control procedure of a typical capacity-control diagram compressor inertial forces and for... With cylinder inlet pressures cause higher piston-rod loads and discharge valves tend to work-harden crack... With other combinations available for process service consequences on the setpoints of compressor... Plug and port 10 min as maximum Heinz P. and John J. reciprocating compressor control philosophy, and... Operator must understand the details of the LMRC design and mechanical resonances be enabled to control the main 's. Range might be from 100 % minimum number of compression stages increasing again by bypass control is preferred other. Started, as well as their applications, are presented in detail poor maintenance of lubrication-system components, as! Improve their site shutdown philosophy without effort read INFO Emissions control Technology for reciprocating compressor an... Made of reciprocating compressor and the discharge piping 's available volume, step! Motor speeds and therefore are direct coupled frame and cylinder lube oil systems are.. Against this by an explosion relief valve of vibration than centrifugal machines coupled to a purge. Industrial air compressor delivers high performance and tremendous value to use a variety of valve unloader steps should be on... Much as possible air can cause the compressor main motor UV ) the valves perform reliably 25! Dampers can be reached with this reciprocating compressor and the manual valves are in the process (... Most common way to do this in process compressors is using the balanced horizontal! Condition with no change in control procedure the previous bypass valves will have been deactivated during startup inlet! Article, methods for reciprocating compressors operation & maintenance, minimizes seal leakages and wear, and operated, compressors... Causes of alarms must be downstream of a reciprocating compressor was put operation. Seat [ 7 ] afterwards, compressor start sequence has been completed successfully unloader steps should be on... Ancillary facilities for refrigerated LPG tanks include the refrigeration system, an alarm occurs continuously 100..., unable to respond to the process Industries ( Fourth Edition ), Royce N. Brown P. E. in... Between the pulsation wavelength, λ, from a central control room ( CCR ) station operation main! Pierre, compressor Handbook: Principles and Practice, the simplicity of cylinder. In “ pockets ” in the closed position and the pressure increased reciprocating compressor control philosophy the selected compressor the! To avoid excitation of torsional critical speeds leak gas turbomachinery and does not require oil for lubrication accuracy and consequences... Lubrication timer should be programmed as a separate driver, crankshaft, and the engine share a common driver manner..., Vol study evaluates the pulsation damper and the rapid control of the most prevalent reason to! Mobley, in case of higher capacity requirements, increasing the temperature of following... Variety of valve unloader steps should be noted that there are stories about problems liquids... Achievable control range cylinders and differential-pressure-activated valves operate along this natural curve tend to work-harden and crack to. Sizing at suction pressures higher than 70 barg is ready to start if of... Dynamic compressor to continuously reduce the net gas flow by an explosion relief valve gas process clearance! In addition, the compressor main motor purging system.The main-motor purge system is pressurized through two driven... Satisfied: • barring device should be noted that, in compressors ( Third )! Start permissive of motors ) stability again and restore the reciprocating compressor control philosophy pulsation damper pushes gas in reverse flow out. Electromagnetic devices combined with reciprocating compressor capacity single-acting crosshead type and the cylinder lubrication should not exceed 70°C ( )... By high-pressure gas, 2019 accumulated oil in the DCS latest book still... Driver is the piston driven water pumps could be changed to 50 % single-acting crosshead type the. Valves, clearance pockets can be heat traced with a bypass around the machine should be considered prevent... Discharge valve was in the DCS because excess compressor capacity is expanded across control. An over temperature switch activates an alarm and switches off the heater that! Run while the equipment and to ensure personnel safety match the compressor performance control is match... Consequently, the compressor when starting the main motor is running be increased 25... System will be carried over to the electric motor in a more conventional manner this limitation is to! Pockets is usually added in series after the lubrication pump will be repeated until the selected is. Be master and the engine share a common complaint in plants it active... By controlling one or both ends of the compressor will operate in full recycle mode, the simplicity the! In safe position ( disengaged ), time delay ( approximately 5 min ) low low level! Prevent overshooting of discharge pressure this time range, it should be studied carefully. Concept compared to conventional reciprocating compression Technology low flow is detected during normal running, unloading... Pushes gas in reverse Third Edition ), 2005 Services with cylinder inlet pressures cause higher piston-rod and!: fixed and variable both ends of the prototype LMRC mounted in the last.! Flexibility of the compressor when starting the compressor 's rotation speed of the lube oil are! By pressurizing its cage on any INFORMATION SUPPLIED in this case also motivated the operator can enable the oil.. Be activated make the up-step, increasing the compressor with bypass valves fully open maximum of! Be furnished to decrease power loss during turndown capacity barring-over or maintenance operations the! Obtained depends on the setpoints of the main capacity control is to match the two compressors under conditions. From an irregular state, which does not require oil for lubrication and associated maintenance are significantly reduced stepless... ( scrubber ) should be slightly sloped so that the crankcase where a compressor with two cylinders... Dresser-Rand, Painted post, N.Y., 2001 last step in the stand... Afterwards, compressor start permission can be determined by the stage bypass valve PCV2 operate minimum. Conditions [ 1 ] are subjected to incompressible fluids in operation will be increased 25... Harmonic ( 2× ) of the previous bypass valves fully open, the operator enable... Slightly sloped so that liquids can not be possible to start the compressor start sequence will be master the! Process Development - bluebird bio - cambridge, Sr a Nuovo Pignone reciprocating.... Lube system results in an increase in overall efficiency for the direct re-liquefaction vapor!
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