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EP1861622A2 - Systeme de commande a compresseurs multiples - Google Patents

Systeme de commande a compresseurs multiples

Info

Publication number
EP1861622A2
EP1861622A2 EP06739208A EP06739208A EP1861622A2 EP 1861622 A2 EP1861622 A2 EP 1861622A2 EP 06739208 A EP06739208 A EP 06739208A EP 06739208 A EP06739208 A EP 06739208A EP 1861622 A2 EP1861622 A2 EP 1861622A2
Authority
EP
European Patent Office
Prior art keywords
compressors
distribution system
fluid distribution
compressor
loading
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06739208A
Other languages
German (de)
English (en)
Inventor
Sridharan Raghavachari
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP1861622A2 publication Critical patent/EP1861622A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B41/00—Pumping installations or systems specially adapted for elastic fluids
    • F04B41/06—Combinations of two or more pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B41/00—Pumping installations or systems specially adapted for elastic fluids
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B41/00—Pumping installations or systems specially adapted for elastic fluids
    • F04B41/02—Pumping installations or systems specially adapted for elastic fluids having reservoirs
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/02—Stopping, starting, unloading or idling control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/02—Stopping, starting, unloading or idling control
    • F04B49/022—Stopping, starting, unloading or idling control by means of pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
    • F04C28/02—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids specially adapted for several pumps connected in series or in parallel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B2205/00—Fluid parameters
    • F04B2205/05—Pressure after the pump outlet
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B2205/00—Fluid parameters
    • F04B2205/11—Outlet temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/02—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents
    • F04C18/0207—Rotary-piston pumps specially adapted for elastic fluids of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents both members having co-operating elements in spiral form
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C18/14—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
    • F04C18/16—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2270/00—Control; Monitoring or safety arrangements
    • F04C2270/18—Pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2270/00—Control; Monitoring or safety arrangements
    • F04C2270/19—Temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2270/00—Control; Monitoring or safety arrangements
    • F04C2270/20—Flow
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2270/00—Control; Monitoring or safety arrangements
    • F04C2270/56—Number of pump/machine units in operation

Definitions

  • the present invention relates to compression, distribution and control of compressible fluids to optimize supply and demand efficiently without affecting the associated process integrity.
  • Pressurized compressible fluids such as atmospheric air, carbon dioxide, helium, argon, nitrogen, freon, liquids, etc.
  • the devices that use the pressurized fluid include robots, paint applicators, turbines, power generators, jet engines, pneumatic tools, chillers, air Conditioners and others.
  • Compressible fluids are typically pressurized using a compressor, which may take one of many forms, such as a centrifugal compressor, a reciprocating compressor, a rotary screw, a stack of alternating rotors and stators, or other forms.
  • a compressor takes in a compressible fluid at an inlet, uses energy to compress a mass of the compressible fluid to a smaller volume and higher pressure, then discharges the fluid thus compressed through an outlet.
  • An individual compressor produces compressed fluid at a specified flow capacity, defined in terms of volume of free fluid at the inlet of the compressor per amount of time.
  • the individual compressor also produces a selected discharge pressure at the outlet due to the normal operation of the compressor.
  • the selected discharge pressure can typically be varied up to a specified maximum discharge pressure of which the compressor is capable.
  • the specified flow capacity and selected discharge pressure are chosen to suit the particular application for which the compressor is intended.
  • some typical compressors intended for a chemical manufacturing & packaging facility have selected discharge pressures in the general range of 90 to 125 pounds per square inch gage (PSIG), and a flow capacity in the range of 2,000 to 4,000 standard cubic feet per minute (SCFM).
  • SCFM is defined as, "cubic feet of volume per minute at the standard conditions of 14.7 pounds per square inch absolute (psiA) and 60 degrees Fahrenheit.”
  • Many other ranges of discharge pressures and flow capacity are possible depending on the needs of the particular application.
  • Each load device in turn has a demand flow rate, which is the volume rate of fluid used by the load device in its operation.
  • Each load device also has a specified incoming pressure that it requires for normal operation.
  • Demand flow rate may be fairly constant or change frequently, depending on the application. Any load device is likely to drop its demand flow rate temporarily at least occasionally for interruptions such as maintenance, breaks, etc.
  • multiple compressor systems are generally designed and installed to cater to the maximum peak demand flow rate at the required load pressure.
  • Facility operators tend to operate the maximum installed capacity of all compressors all the time at the maximum pressure, to ensure that the load devices receive enough pressure even during peaks in demand flow rate. So, the installed compressor discharge flow capacity is greater than it usually needs to be; and the compressors must be set to a higher discharge pressure than what the load devices require most of the time. Excessive compressor capacity and discharge pressure both translate into higher energy consumption, maintenance costs, and capital costs.
  • FIG. 1 is a schematic diagram of a multiple-compressor system of the prior art 1.
  • FIG. 2 is a schematic diagram of a multiple compressor control system according to an example embodiment of the present invention which includes an electronic controller.
  • FIG. 3 is a Block diagram of one embodiment of the controller of FIG. 1 according to one embodiment
  • FIG. 4 is a flowchart of an example routine used by the electronic controller of FIG 3 for controlling the multiple-compressor system shown in FIG. 2, according to one embodiment of the present invention.
  • FIG. 1 is a schematic diagram illustrating an example of a multiple- compressor system 100 according to the prior art.
  • multiple-compressor system 100 is a compressed air system within a chemical manufacturing facility, where the fluid that is compressed is atmospheric air.
  • the facility uses compressed air as energy for cycling valves, cleaning dust collector bag houses, instruments, packaging equipments, conveyors, robots, pulverizing operation, pneumatic tools etc.
  • Multiple-compressor system 100 includes a plurality of individual compressors C1-C7, which are coupled to a main fluid distribution header 102 through dryer and filter devices D1-D7, respectively.
  • Compressors Cl- C7 can be located in one or more areas of the facility.
  • Compressors C1-C7 take atmospheric air in through the respective inlets, compress the air to a higher pressure and discharge the compressed air through the respective outlets.
  • the energy for increasing the pressure of the fluid medium can be derived from one or more prime movers, which drive a shaft of each respective compressor.
  • Each compressor has a specified flow capacity and a specified maximum discharge pressure.
  • the discharge pressures of compressors C1-C7 are typically adjustable within some range up to the specified maximum discharge pressure.
  • compressor C5 is set to compress the fluid air to a discharge pressure of 115 pounds per square inch gage (PSIG). Gage pressure is the amount by which the total absolute pressure exceeds the ambient atmospheric pressure. All compressors are set to run in upper range modulation control without blow down.
  • PSIG pounds per square inch gage
  • compressors C1-C7 are coupled to the inlets of the respective dryer and filter devices D1-D7, respectively.
  • Dryer and filter devices D1-D7 remove moisture, dust and other contaminating particles from the compressed air such that dry, clean air is delivered to main distribution header 102.
  • Main distribution header 102 is interconnected by welding or other suitable means of fastening, with or without functioning or non-functioning isolating valves.
  • main distribution header 102 can include a combination of 1-inch to 14-inch diameter pipe.
  • Load devices such as Ll and L2 can be coupled to outlets along main distribution header 102.
  • load devices Ll and L2 can include cycling valves, cleaning dust collector bag houses, instruments, packaging equipments, conveyors, robots, for example.
  • Load devices Ll and L2 each have a demand flow rate, which is a volume rate of fluid (air in this embodiment) used by the load device during its operation.
  • Load devices Ll and L2 typically also have a preferred incoming pressure that is required for normal operation. In the example shown in FIG. 1, load devices Ll and L2 require a minimum of 90 PSIG pressure.
  • the total demand flow rate on main distribution header 102 may be fairly constant or may change frequently, depending on the needs of system 100.
  • multiple-compressor systems of the prior art such as that shown in FIG. 1 are generally designed and installed to cater to the maximum peak demand flow rate at the required pressure. If enough of compressors C1-C7 are not running when demand by load devices Ll and L2 increases, the outflow from the system will exceed the inflow to the system causing the density of air in the system and the resulting air pressure to decrease. The decrease in pressure can then cause a disruption in production within the facility. Excessive pressure drops in the system can also be caused by undersized cleaning equipment and piping and dirt accumulated in the system, for example.
  • Efficiency of system 100 decreases.
  • Efficiency can be defined as “average SCFM of compressed air/average kW consumed,” where SCFM is the cubic feet of air volume per minute at the inlet of each compressor and kW is the rate of energy consumed, in kilowatts, by the prime mover of the compressor.
  • Efficiency of the total system can then be defined in terms of “total average SCFM of compressed air/total average kW consumed" in system 100.
  • Table 1 provides a list of hypothetical properties for compressors C1-C7 according to an example in which system 100 uses air for 8,400 hours per year and maintains around 90 PSIG in the main distribution header. These properties include for each compressor the type, model and make, the designed maximum discharge pressure, the flow capacity (SCFM), the rated energy consumed by the prime mover (kW), the maximum efficiency (SCFM/kW), and a hypothetical measured SCFM, kW and SCFM/kW.
  • Table 2 summarizes the system efficiency of multiple-compressor system 100, shown in FIG. 1.
  • the compressors in system 100 are partially loaded at an average of 51.5 percent of their flow capacity and have an average total efficiency of only 3.01 SCFM/kW.
  • FIG. 2 schematically illustrates multi-compressor control system 300 according to one exemplary embodiment.
  • System 300 generally includes a plurality of compressors C1-C7, a plurality of respective drying and filter devices D1-D7, a main distribution header 302, and one or more load devices Ll and L2.
  • Compressors Cl through 7 are coupled to main fluid distribution header 302 through optional dryer and filter devices D1-D7, respectively.
  • Compressors C1-C7 can be located in one or more areas of the facility, and any number of compressors can be used.
  • Compressors C1-C7 can include any combination of types, makes or models of compressors.
  • compressors C1-C7 can include reciprocating, rotary screw, centrifugal, scroll and vane type compressors.
  • Each compressor has a specified flow capacity and a specified maximum discharge pressure. The discharge pressures of compressors C1-C7 are adjustable within some range up to the specified maximum discharge pressure.
  • one or more of the compressors C1-C7 have a fixed discharge pressure, and that discharge pressure is selected for the particular application in which the compressor is used.
  • the prime movers for compressors C1-C7 can be driven by electricity, fossil or other fuels, or steam, for example.
  • the outlets of compressors C 1 -C7 are coupled to the inlets of dryer and filter devices D1-D7, respectively.
  • Dryer and filter devices D1-D7 remove moisture, dust and other impurities from the compressed air such that dry, clean air is delivered to main distribution header 302.
  • one or more of the devices D1-D7 can be located in other positions in system 300, such as on the outlet side of its respective compressor.
  • one device D1-D7 can be used to dry and filter air from more than one compressor.
  • Main distribution header 302 may include a pipe or a series of pipes or other functionally analogous fluid conductors that are capable of conveying pressurized fluid to at least one outlet, such as to load devices Ll and L2.
  • the fluid conductors can be interconnected by welding or other suitable means of fastening, with or without functioning or non-functioning isolating valves.
  • main distribution header 302 includes a combination of 1-inch to 12 or inch diameter pipe. Other sizes of pipes can also be used.
  • Load devices Ll and L2 can include cycling valves, cleaning dust collector bag houses, instruments, packaging equipments, conveyors, robots, for example.
  • Load devices Ll and L2 each have a demand flow rate, which is a volume rate of fluid (air in this embodiment) used by the load device during its operation.
  • Load devices Ll and L2 also have a preferred incoming pressure that is desired for normal operation.
  • load devices Ll and L2 require about 90 PSIG in main distribution header 302 for normal operation.
  • Compressors C1-C7 are coupled to main distribution header 302.
  • Pre- Engineered Air Receiver 303 is connected to the main distribution header 302.
  • a properly calibrated temperature transmitter 304 and a pressure transmitter 305 are connected to the distribution header 302 preferably at the receiver 303.
  • an electronic controller 306 is connected to the new compressor system 300 through control cables to compressors Cl through C7, Temperature and Pressure Transmitters 304 & 305 respectively.
  • controller 306 may communicate with compressor Cl through Cl by other means such as optical cables, such as through local area networks or wirelessly.
  • Electronic controller 306 can be designed to control any number of compressors as long as they are connected to the compressed air system 300 in this embodiment.
  • Electronic controller 306 can be configured to control system 300 in a closed-loop control fashion or an open-loop control fashion.
  • One or more sensors can be distributed throughout system 300 as desired for providing electronic controller 306 with appropriate measurements from various locations within the systems.
  • these sensors can include pressure sensors, temperature sensors and mass flow sensors.
  • Electronic controller 306 comprises a processing unit configured to generate control signals for the direction of one or more of compressors Cl- C7. In one embodiment, such control signals are generated based upon capacitance of the fluid distribution system.
  • processing unit shall mean a conventionally known or future developed processing unit that executes sequences of instructions contained in a memory. Execution of the sequences of instructions causes the processing unit to perform steps such as generating control signals.
  • the instructions may be loaded in a computer or processor readable medium 307 that may comprise a random access memory (RAM) for execution by the processing unit from a read only memory (ROM), a mass storage device, or some other persistent storage.
  • RAM random access memory
  • ROM read only memory
  • mass storage device or some other persistent storage.
  • memory 307 may be removable and portable with respect to controller 306.
  • hard wired circuitry may be used in place of or in combination with software instructions to implement the functions described. Controller 306 is not limited to any specific combination of hardware circuitry and software, nor to any particular source for the instructions executed by the processing unit.
  • Electronic controller 306 can include any control device such as a programmable logic controller (PLC), a microprocessor-based controller, or a personal computer-based controller.
  • Electronic controller 306 can be a digital-based or analog-based controller.
  • electronic controller 306 can be replaced with a plurality of individual controllers, wherein each controller controls one or more of the components within system 300.
  • electronic controller 306 can be replaced with a manual-type control, a different electrical-type control or a combination of both.
  • the receiver sizing depends on the air demand variance in SCFM over time as in the prior art, the start up time (Tl 5 T2, etc.) required by compressors Cl through C7 and the set pressure (Ps in PSIG) and the swing tolerance (for e.g. plus 3 PSIG and minus 3 PSIG) permissible by the plant operation.
  • Receiver 303 is designed to have a volume of 6,000 gallons (780 CF),. Receivers having other volumes can also be used.
  • the volume of the entire distribution header piping including the volumes of the filters, cleaning equipment is measured as 40 CF (same as the system in FIG. 2) Therefore the total volume of the system 300 is 820 CF.
  • system 300 requires an average volume rate of 2,990 SCFM of compressed air to be delivered to main distribution header 302 at a minimum of 90 PSIG.
  • Table 4 provides a list of hypothetical specifications for compressors C1-C7 according to the example.
  • compressor Cl has a discharge flow capacity of 1,500 SCFM
  • compressor C2 has a discharge flow capacity of 900 SCFM.
  • System 300 therefore requires a balance of 590 SCFM at minimum 90 PSIG and that is supplied by the Compressor C3 whose capacity is 650 SCFM.
  • Table 3 summarizes the overall efficiency of system 300, which can be compared to the efficiency of system 100, as shown in Table 3.
  • controller 306 may eliminate situations as above and automatically calculates and selects the lead time on a dynamic basis, depending upon the changing system parameters at any time.
  • control algorithms are developed based on the available capacitance, the change in demand, constantly varying sampling period and the corresponding recovery and lead periods, the permissible minimum pressure and tolerance, each available compressor capacity and the minimum time required to go on-line and load. Also, with system 300 the need for a flow controller and intrusive installation efforts are eliminated without compromising on the system pressure requirements. This greatly reduces installation cost.
  • the electronic controller 306 will immediately load the running compressor # 3 after allowing for the lead time required by C 3 for loading, say 1 second in this case.
  • the total air demand is 3,350 SCFM and the total supply capacity of all the compressors is only 3,050 SCFM which results in a short fall of 300 SCFM or 5 CF/second.
  • the pressure in the system will still be dropping.
  • the control algorithm calculates the sampling period, and corresponding recovery period and response time (instead of 5 seconds as set in the prior art) before starting and loading compressor C- 7 whose capacity is 450 SCFM.
  • the capacitance of the system 300 is 55.7 SCF/PSI.
  • the short fall is 5 CF/sec
  • the current system pressure is 91 PSIG
  • the lower pressure set limit is 90 PSIG
  • the controller has determined the short fall as 5 CF/sec. and immediately looks for the compressor whose capacity is the closest to the to 5 CF/sec. from the available compressors.
  • the controller selects C 7 whose capacity of 7.5 SCF/sec. is the closest (from Table 3) to the short fall of 5 SCF/sec. from the Table 3.
  • the controller 306 After selecting C 7 it compares the response time required by C 7 and matches that with the determined sampling period and the maximum response period. If the response period of C 7 is less than the maximum response time determined by 306, it sends a signal to start and load C- 7 and the appropriate time. For example the start and load response time is 5 seconds, the controller 306 will start the compressor at the 6 th second of the available 11.14 seconds. Then, the supply capacity is 3,490 SCFM as against the demand of 3,350 SCFM. The surplus 140 SCFM will raise the pressure of the system 300 from around 90.5 PSIG to 96 PSIG (set pressure of 93 PSIG plus 3 PSIG tolerances) in 131 seconds unless the Air Demand in the system increases further during the pressure rise.
  • multiple-compressor system 300 is made stable and this situation is conducive for the operator feeling secure about the stability of the system (as against the previous example where three compressors follow a load/unload cycle in a short period of time).
  • compressor C-4 was the floating trim compressor for a demand of 2,990 SCFM and compressor C-7 was the floating trim compressor for a demand of 3,350 SCFM. Likewise, for any change in demand either lower or higher, multiple compressor controller will maintain only one floating trim compressor.
  • FIG. 3 is a block diagram illustrating a control function of electronic control 306 in greater detail.
  • electronic control 306 includes a programmable logic controller (PLC) 400 having a program 401 and a database 402.
  • Program 401 is tailored to perform the desired control function for the multiple-compressor system based on data stored in database 402 and input parameters received from the pressure sensor 307 and temperature sensor 308, for example.
  • Program 401 can be implemented in software, hardware or a combination of both.
  • Database 402 includes system-specific data, such as the specifications of each component in the system. These specifications can include the maximum discharge pressure, the selected discharge pressure, the maximum discharge flow capacity and the rated energy consumption of each compressor, the pressure consumption of each drying and filter device, the flow capacity of each dryer and filter device, the total system flow capacity, the "total volume" of system 300, etc.
  • FIG. 4 is a flowchart illustrating the steps performed by PLC 500 in controlling the various components within multiple-compressor system 300 according to one embodiment.
  • step 500 data is provided to the multiple compressor controller from database 402(shown in FIG. 4) and from the various sensors in the system.
  • step 501 the system is turned on and initialized. The controller is powered-up and selects the desired compressors to be started and loaded. Step 401 can be performed at the start of each work day in a facility or at less frequent times if the facility operates 24 hours per day.
  • the multiple compressor controller 306 calculates the mass rates of change, the response time to start and load or unload and stop based the capacitance in the system, at which point of the dynamics the action is to be taken, by using the system data from 500.
  • This calculation is based on inputs to the multi-compressor controller 306 from sensors, transducers, available time, an internal memory storage, a network-hosted database, or other input sources.
  • the inputs represent values for the system pressure, temperature, set pressure, the tolerances, the capacitance, and the starting characteristics of the compressors C 1 to C 7 available at that time of sampling time and time to reach the upper or lower limits of the set pressure.
  • a method of calculating air density is used wherein a standard air density under arbitrarily chosen conditions forms a STANDARD value, which is subjected to correction terms such as temperature and pressure to reach an accurate value for local conditions.
  • a calculation of air mass in the system 300 can therefore take the form of:
  • M t (D s *V t )/[(Pa*(T+460))/((Pa+P t )*(T s +460))]
  • M t is the mass of air in the system 302 (receiver 303 and the piping)
  • D s is a Standard air density at standard conditions of temperature and pressure
  • V is the system total volume, which is the volume of the receivers, the filters, dryers, and the piping etc.
  • T is the measured temperature of the air in degrees Fahrenheit
  • T 8 is standard air temperature in degrees Fahrenheit
  • Pa is the standard ambient pressure in psiA
  • Ps is the system pressure in psiG.
  • the term of 460 added to both temperatures sets them to an absolute scale by compensating for absolute zero being 460 degrees below zero in the Fahrenheit scale. Details of the equation would change in other embodiments, such as if temperature were measured in the Kelvin or Celsius scale, or if additional corrective terms were included, according to well- known methods of calculating a mass based on values of pressure, volume, density, etc. In an alternative embodiment, the rate of change in mass is calculated for the receiver only. In this embodiment, V represents the receiver volume.
  • step 504 determines if the downwards slope is negative, positive or the same respectively. If 504 is determined no action to start and load a compressor is needed and accordingly the loop completes back to 402. If 505 is determined then step 506 determines if the downward slope is due to the floating trim compressor, then step 507 takes "No Action" to start and load another compressor and the control loop goes back to 502. If step 506 determines that the mass rate of change slope is not the same as that of the downward trend of the floating trim compressor, the step 508 is directed to step 509.
  • Step maps the rate of change of mass and determines the load the unloaded floating compressor (if it is in its unload cycle), calculates the response time, and accordingly loads the floating compressor at a comfortable time based on the capacitance and available mass, the load time characteristics of the floating compressor. If the rate of change of mass is still downwards, step 505 takes over and the process of comparing the mass short fall, available sampling and response times and mapping with the available compressor in step 502. Step 510 then determines rate of change upwards and compares with the floating trim compressor and unloads the floating trim compressor when the system pressure is reaches its upper tolerance level.
  • the process is continuous and the cycle of calculating the sampling period, response time etc. is repeated maintaining the system pressure within the tolerance level and at the same time controlling to sustain only one compressor as the floating trim.
  • step 512 compares the slope with that of the floating compressor in its loading cycle and if the calculated slope is same, no action to unload the floating compressor is taken. If the upwards slope is not the same and depending the then current sampling period, time to unload any compressor, it unloads the floating trim compressor. Then step 515 waits for the selected stop delay period for the floating compressor and stops the prime mover (motor or generator). If one particular floating compressor is unloaded, then the multiple compressor controller selects one of the remaining running compressors as the floating compressor and maintains stability in the system and prevents frequent load and unload cycle of the more than one compressor.
  • Steps are dynamic as the system air flow changes.
  • the particular steps taken by the multiple compressor to maintain pressure within the main distribution header are provided as example only. Numerous modifications can be made in alternative embodiments of the present invention. Further, representations of the mass rate of change can be calculated in a number of ways. For example, the multiple compressor can calculate the rate of change of mass or pressure.
  • the multiple-compressor control system of the present invention provides an economically feasible, much less expensive and practical solution to the problem of improving operating efficiency of the system as indicated by the "total average compressed SCFM/total average kW consumed.” This translates to reduction in the energy consumed by the system, the cost of components used in the system, maintenance expenses and other ancillary costs.
  • the system also provides a stable pressure within a close tolerance to the desired pressure in the plant header. A stable pressure reduces production disruption and increases productivity.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Positive-Displacement Pumps (AREA)
  • Control Of Positive-Displacement Air Blowers (AREA)

Abstract

Au moins une pluralité de compresseurs (C1-C7) connectés à un système de distribution fluidique sont chargés et/ou déchargés sur la base d'une capacité du système de distribution fluidique.
EP06739208A 2005-03-22 2006-03-22 Systeme de commande a compresseurs multiples Withdrawn EP1861622A2 (fr)

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US11/086,527 US20060216159A1 (en) 2005-03-22 2005-03-22 Multiple compressor control system
PCT/US2006/010328 WO2006102372A2 (fr) 2005-03-22 2006-03-22 Systeme de commande a compresseurs multiples

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JP5646282B2 (ja) * 2010-10-29 2014-12-24 アネスト岩田株式会社 圧縮装置及びその運転制御方法
US20130025304A1 (en) * 2011-07-27 2013-01-31 Dorman Dennis R Loading and unloading of compressors in a cooling system
JP6220303B2 (ja) * 2014-03-27 2017-10-25 株式会社神戸製鋼所 圧縮装置および圧縮装置の制御方法
CN106150996B (zh) * 2016-08-30 2018-05-18 深圳市新环能科技有限公司 基于需求用气量计算的空压机群控控制方法
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US20060216159A1 (en) 2006-09-28
JP2008534842A (ja) 2008-08-28
MX2007000698A (es) 2007-04-17
CA2574338A1 (fr) 2006-09-28
WO2006102372A3 (fr) 2006-12-21
WO2006102372A2 (fr) 2006-09-28

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