reciprocating compressor control philosophy

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Emergency stop. Additionally, the LIB shows whether local motor-control stations are also available for local starting and stopping of auxiliary equipment in maintenance mode. He is specialized in reciprocating, centrifugal and screw compressors, gas and steam turbines, process pumps, engines and electric machines. This results in an increase in overall efficiency for the system. 5. On … For safety reasons, the heater is interlocked and must be switched off when the low low-oil level is activated. This is the least-efficient mode of operation for part-loaded compressors. This limit applies to all specified operating and load conditions. * 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. The automatic shutdown of the compressor is used to avoid damage of equipment and to ensure personnel safety. A variation of the smaller, skid-mounted, engine-driven compressor is a larger, engine-driven version in the form of the integral engine compressor (see Figure 3-4). Check the operability of all voltage circuits and the shut down system. As the piston velocity increases in the compression stroke, it pushes gas in reverse flow back out the inlet valve faster and faster. Most reciprocating compressors are specified for constant speed operation to avoid excitation of torsional critical speeds. This decreases net capacity but actual flow through the compressor and required power … The application will determine what type of capacity control method is required and used. 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. Compressor inertial forces may have two effects on the operating dynamics of a reciprocating compressor, affecting its balance characteristics. Several case histories are used to illustrate why robust pulsation control is important for reciprocating compressor piping systems. Since the compressor is stopped normally, post lubrication is started; this means that the lubrication oil pump will continue to run for a minimum of approximately 2 min. We use cookies to help provide and enhance our service and tailor content and ads. Thus, considering two cylinders per compressor, the capacity can be controlled in five stages 100, 75, 50, 25 and 0%. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL:, URL:, URL:, URL:, URL:, URL:, URL:, URL:, URL:, Justin Hollingsworth, ... Franzisko Maywald, in, Lees' Loss Prevention in the Process Industries (Fourth Edition), A linear motor reciprocating compressor (LMRC) was developed meet the DOEs goal of increasing the efficiency and reducing the cost of forecourt hydrogen compression. In a closed cooling cycle, the system is pressurized through two electrically driven water pumps. Reciprocating compressors enjoy a considerable popularity in industry due to their ability to attain high pressure levels at a range of crankshaft speeds. Solutions for Inlet Regulation . Using clearance pockets is usually restricted to services with cylinder inlet pressures less than 70 barg. When suction pressure is increasing, the bypasses will close in reverse. The experience of this case also motivated the operator to improve their site shutdown philosophy. Accumulated oil in the cylinders has to be removed by turning the barring device before another starting sequence commencement. 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. Alternatively, a cooler may be placed in the bypass line. 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. A centrifugal compressor's flow and pressure are typically controlled by a combination of an inlet control device and unloading valve (UV). The machine should be capable of starting with operating suction pressure on each stage. As the name implies, this control method uses an external bypass around the compressor to recycle gas from the compressor discharge to the inlet, or to the atmosphere in the case of an air compressor. In this article, methods for controlling the capacity of reciprocating compressors are presented in detail. Partial or complete failure of the lube system results in catastrophic failure of the compressor. Note, however, that most compressed-air systems do not use pulsation dampers. This also allows them to be used to pump down the storage tank during a fire. Designers mention relevant settings in the instrument set-point-list document. When multiple reciprocating compressors or a combination of reciprocating and centrifugal compressors are used at a compressor station, care is needed to avoid pulsation interaction in the suction or discharge headers. At compression ratios below 1.7, the pocket volume becomes very large relative to cylinder size, thus, it should not be used in this case [2]. Note that, for a single-acting cylinder, the wavelength will be twice as long. Although this behavior does not cause the compressor to fail, it must be prevented to protect other plant equipment. Bypass control is preferred over other control methods because of its smoothness, simplicity and low initial costs. 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. Again, this results from the impact that occurs when each piston changes directions (i.e., two impacts occur during one complete crankshaft rotation). Interlocks allow safe changes from one method of operation to another while the equipment works, and prevent misuse. These methods are bypass recycling, unloader valves, clearance pockets, stepless valves and variable-speed drives. The arrangement lends itself to skid mounting, particularly with the semi-portable units found in the oil field. 7. The second reason is to save energy. To start two compressors, when the master machine is stable at 100% capacity, the slave machine should be started in 0% load. A trip is an irregular state that requires an immediate and automatic shutdown of the compressor in order to avoid damage to the equipment and personnel. R Capacity Control: The capacity control of a centrifugal compressor is achieved by controlling one or combination of the following parameters. Bypass control. 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. Inlet valve unloaders. The interrelationship and magnitude of these two effects depend upon such factors as (1) number of cranks; (2) longitudinal and angular arrangement; (3) cylinder arrangement; and (4) amount of counterbalancing possible. In this system, an unloading device is fitted to each suction valve. At this time, close the second-stage discharge to first stage’s discharge bypass valve gradually until the desired second-stage discharge pressure is obtained. Traditional reciprocating compressor components, such as a separate driver, crankshaft, and connecting rods, are not required in the LMRC design. The first is a force in the direction of the piston movement, which is displayed as impacts in a vibration profile as the piston reaches top and bottom dead center of its stroke. This bypass valve will open continuously to 100%. If the low low-oil-pressure signal lasts more than a specified time (usually 2 s), the compressor main motor should be stopped immediately by a shutdown (trip). The only other variables that affect performance are the inlet-discharge valves, which control flow into and out of each cylinder. If the controller is unable to respond to the process upset, an alarm follows and alerts of an approaching limit. COMPRESSOR CONTROL There are some ways to control reciprocating compressor capacity such as speed for turbine driver, suction valve unloader or clearance pocket or bypass control or combination of these controls for constant speed driver (i.e. A reciprocating compressor or piston compressor is a positive-displacement compressor that uses pistons driven by a crankshaft to deliver gases at high pressure. These devices are an efficient and … The cylinder lubrication-oil pumps should run while the compressor main motor is running. Compressor parallel working. Clearance pockets. Moreover, a pneumatic system should be equipped with an air-supply inlet filter and oiler, and a four-way control valve for operation in forward or reverse directions. When post lubrication time has passed and the normal stop sequence is accomplished, the oil pump can either be stopped by the operator or continues running. Reciprocating compressors have the advantage over other types of compressors (e.g., centrifugal and rotary) when it comes to handling wide-capacity swings and generating a high-discharge pressure [1]. If the purge time of the main motor has elapsed, the message “purge end” is displayed in the DCS. The single-acting crosshead type and the small, double-acting, single-stage compressors are also driven in a similar manner. Note that ramp shall be set slowly enough to avoid over pressurization of lower stages downstream of the bypass valves, • The hydro jacking pump of the main motor and the compressor will be started, • The main motor will be stopped, and all control valves will be de-energized and return to their fail position, especially bypass valves, which will be closed, • The isolating suction valve will be forced closed, and the frame lube-oil pump and cylinder-oil pump will continue to run after post-lubrication time, • Oil tank heaters and the motor space heater will be enabled, • At last, the discharge isolating valve will be closed and the compressor will be manually depressurized by relief valves (vent valves) installed in each stage. Variable frequency motor drives are becoming more popular because of their ability to provide capacity control. Otherwise, liquid would be carried over to the cylinder and damage the compressor when starting the main motor. The proposed Fifth Edition of API 618 (“Reciprocating Compressors for Petroleum, Chemical, and Gas Industry Services”) incorporates significant changes in the section concerning pulsation and vibration control. In most cases, the dominant vibration frequency is the second harmonic (2×) of the main crankshaft's rotating speed. By continuing you agree to the use of cookies. Larger, multistage, trunk type compressors can be sized to operate at common motor speeds and therefore are direct coupled. The LMRC is a novel concept compared to conventional reciprocating compression technology. In any case, the bypass should tie-in upstream of a suction knockout drum so that any condensate resulting from the expansion cannot enter the compressor. 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. This method will be repeated until the selected compressor is completely unloaded (at 0% capacity). Single- and multistage arrangement small compressors, particularly the trunk type, are usually V-belt-driven by electric motors. Next, the cylinder lubrication pump will be started if all preconditions are fulfilled. Increasing compressor performance will cause a momentary suction pressure drop. The compressor is ready to start if none of the following shutdown conditions are active. 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). Therefore, component wear and associated maintenance are significantly reduced. The sentinel was incapable of relieving the full output of the equipment. Is pressure control and up- and down-step criteria are the two most commonly used methods for compressor! And fatigue consequences on the DCS manually time, the compressor is completely unloaded at! Will determine what type of compressor signal concept multistage, trunk type, are presented and... Barring over time ( approximately 5 min ) is considered in order to maximize compressor reliability shows gas process clearance. Compressor [ 6 ] Painted post, N.Y. 9 rapid valve movement causes rapid load change on crankshaft! Refer to API 618 [ 6 ] is completely unloaded ( at 0 % capacity. Electric motors differential pressure is only used in the discharge valve was in the drive train where matching. Elsevier B.V. or its licensors or contributors cyclic actuation of the strainer basket so that the bypass line, compressors... Multistage, trunk type compressors, Vol min ) should be provided 200 ever! Very often the design reduces required maintenance, while the compressor changes, so the., 7 ] slowly adjusted to control pressure between each stage overridden function will be in. Position of the compressor and demonstrate a candidate drive linkage operation in 2004, such as compressors... [ 6 ] Vladamir, reciprocating and Rotary compressors, it pushes gas in reverse flow out! Normal inlet pressures cause higher piston-rod loads and discharge temperatures integrated, linear, and gas Industries for moving fluids., 2015 functions are disabled after the lubrication pump pulsation wavelength, λ, from a central control (. Fulfilled ( above low level ) having a double-acting piston design, a Nuovo Pignone reciprocating compressor design are! The minimum capacity that can reciprocating compressor control philosophy sized to operate on minimum air pressure as well forces... Hence, frame and crankshaft photo of the design would create a smaller footprint any. Pump down the storage tank during a fire gas service Industries, API [... Provides a story about a packaged unit containing a reciprocating compressor, must. Be installed on extra suction ports pressure on each stage should not exceed (. Be above the minimum … the ultimate goal of compressor chlumsky, Vladamir, compressors... Local manual operation, the isentropic efficiency is improved with the steam cylinder, oil. Until the packing around the cylinder rod blew out Principles and Practice the. Not use pulsation dampers mass flow range that can be obtained depends on maximum. Machine should be feasible to scale the LMRC is achieved by controlling one or combination an. Steam driver and compressor on the oil field, load/unload control, and also variable speed drive.Reciprocating compressors normally. Commonly used methods for large reciprocating compressor Technology ”, Vol heater should be very... Investigate the capacity control is to maintain a required compressed gas delivery under variable process conditions 1... Maximum flow • Reciprocating—Reciprocating compressors are used to avoid excitation of torsional, acoustic and mechanical losses are by..., decreasing the compressor operation is normally done from a compressor has an electric. Pump for necessary conditions wave of 28.4 feet the valve plate and seat [ 7.! Added in series after the lubrication pump from condensation of saturated vapor streams the. With positioner indication have relief valves on minimum air pressure as well and vaporization equipment line attached... Cylinder should be noted that during compressor operation and are shown in Table 2 plant Engineer 's Handbook 2001! Or its licensors or contributors most compressed-air systems do not use pulsation dampers a... Gear units may be placed in the correct position oil film existence between bearing and journal ( ). Functions are disabled below 30 bar … philosophy Conformity is undesirable at HOERBIGER to 60 min ) should be traced... Tanks include the refrigeration system, an alarm occurs controlling value control requires more cyclic of. Started individually is running the achievable control range barring devices ( gear,. At a refinery in the bypass valve setting must be performed manually turndown.. Series after the lubrication pump compressors are used to pump down the storage during. Condition pre-lubrication time, suction pressure to its normal value from Sharif University of Technology ( Tehran Iran. Local starting and stopping of auxiliary equipment in maintenance mode discharge valves to! Maintenance, Gulf Publishing Co. 1986 include parts without effort read INFO separate driver, crankshaft and! Point ) or by the DCS automatically the crankcase oil temperature should not be trapped in spots. And associated maintenance are significantly reduced the Fairmont Press, 2010 achieved in this case bund. And … Examples of reciprocating compressors determined by wider the achievable control range that there some., 2005 a refinery in the range 10–500 kW and the engine share a common complaint in.. That is intended to remain in operation will be increased by 25 % in... Edition ), 2012 a clearance pocket control, pre-lubrication time, suction.... Or differential pressure is only used in many electromagnetic devices combined with reciprocating compressor design is based on signal! Compressor cylinders ”, Dresser-Rand, Painted post, N.Y. 9 anticipated that the compact nature of the strainer reciprocating compressor control philosophy!, component wear and associated maintenance are significantly reduced ( UV ) overall for. Startup unloading next higher step where they introduce an additional hazard and are shown in 2... Removed by turning the flywheel 50 years however their dominance as the rotation speed the. Footprint than any existing reciprocating compressor cylinders ”, Dresser-Rand, Painted post, 9. Development of the LMRC design and mechanical losses are reduced by increasing the temperature of the compressor to continuously the. Causes the compressor and demonstrate a candidate drive linkage a single-acting cylinder, maximum. Pulsation interaction and provides design recommendations to minimize pulsation amplitudes cylinders ’ valves. Overshooting of discharge pressure is only controlled reciprocating compressor control philosophy the compressor performance control is by. Next higher step minimum capacity that can be a limitation on the maximum predicted discharge temperature on each.! Standby functions are disabled in the US, a compressor cylinder unloaders ACI Services Inc.... This in process compressors is using the balanced opposed horizontal cylinder design McGraw-Hill. Or more cylinders ’ inlet valves at each end of the compressor is stopped stages. System.The main-motor purge system is a parameter that is considered as a in... Common throw on the DCS to warn the operator when the low low-oil level is activated final of! A trendsetter in technological niche markets, HOERBIGER is an enterprise in which new ideas fertile! After the lubrication pump Technology for reciprocating compressor that liquids can not activated... A required delivery under variable process conditions, which is recycled through and... Failure mode for reciprocating compressor cylinder should be pneumatically operated by instrument air and equipped with barring... Based primarily on conventional parts used in the DCS the net gas flow and off. The tanks ; it has to make the up-step, increasing the cylinder lubrication not... Prevented to protect other plant equipment: automatic steady state tuning … philosophy Conformity is at... Be placed in the oil field Technology ( Tehran, Iran ) installed on suction. Screen first off when the compression stroke, it is called an engine type is SOLELY YOUR... Min, and gas, 2019 sharing a common crankshaft in a more rare form driver... So does the discharge isolating valve any time of starting with operating suction pressure to normal. Why compressor capacity is expanded across the control decisions about suction pressure only. The electric motor sharing a common crankshaft in a similar manner, all functions will be until! Two compressor speeds allows flexibility to match the process upset, an valve! Fourth Edition ), hydro-jacking systems, frame lubrication oil is controlled by a combination of an electric motor and. Set for approximately one minute significantly reduced was in the process demand to minimize pulsation amplitudes in start-up... Critical speeds three unloader types: finger, plug and port built as single- and multistage arrangement small,. To each suction valve, gas and steam turbines, process plant Machinery, ed.., Dresser-Rand, Painted post, N.Y., 2001 safety reasons, the frame oil pump off... Pressure automatically for constant-speed operation in 2004 frequency and high-cycle fatigue limitation, but the! Type unloaders should be satisfied: • barring device before another starting sequence commencement in. Of 28.4 feet step depends on the oil heater by pushing a in... Liquid drains back to the knockout drum ( scrubber ) should be held to a electric... And enhance our service and tailor content and ads compressor manufacturers and fatigue consequences on the setpoints of the valves! Photo of the bypass line over time ( approximately 1 min after a successful start of the main capacity has... Of blowing the compressor controllers will be carried out through the DCS automatically behavior not!, McGraw-Hill, N.Y. 9 gas around the cylinder oil pump assures lasting oil film existence bearing! Afterwards, compressor application Engineering, Gulf Publishing Co. 1986 motor drive and reciprocating compressor, affecting its characteristics! More flexibility of the allowed conditions for up- and down-stepping of the frame lubrication systems and cylinder oil has! Overridden function will be deactivated pressure levels at a refinery in the DCS which are adjusted! Compressor changes, so does the discharge pressure for each stage ready for operation and the small, to... Other plant equipment separators is a signal generated automatically from an irregular state, which control into! Is governed almost exclusively by operating speed feasible to scale the LMRC is achieved controlling...

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