PLC BASED RECIPROCATINGCOMPRESSOR CAPACITYREGULATION SYSTEM

R.Poornima1, V.Sivachidambaranathan 2, P.S.Mayurappriyan3

1M.E. KCG College of Technology,Chennai.2Professor Head of EEE Dept,

Sathyabama Institute of Science and Technology,Chennai.3Professor Department of EEE,

KCG College of Technology, Chennai.

January 22, 2018

Abstract

The Reciprocating Compressors are widely used for com-pressing air and it is satisfactory for all ranges of pressures.In this study, an attempt has been made to regulate the ca-pacity of reciprocating compressor, by controlling the speedof the AC motor and also to reduce the heat produced bythe motor, to save the energy conservation. The proposedregulation system has been realized employing a proxim-ity sensor. The Programmable Logic Controller (PLC) ismainly used in designing the ladder logic and it controls theregulation system. Omron platform is used for analyzingthe PLC and display the ladder logic.

Key Words: Proximity sensor, Pressure sensor, Com-pressor (model), Programmable Logic Controller.

1 Introduction

The reciprocating compressor that consumes large amount of en-ergy. Suitable methods should be developed to regulate the ca-

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pacity of the reciprocating compressor within a certain scope. Thiswill meet the requirements of production process and satisfy energysavings.

The number of cylinders used in reciprocating compressors maybe more than one. In single stage reciprocating compressor pressureratio is kept 5 to 8, and the speed varies from 100 to 1500 rpm.

Reciprocating compressors are driven by electric motors, or I.C.engine. It is not driven by gas turbines because turbines have highrotational speed. The air/gas coming from reciprocating compres-sor is not continuous but intermittent. So the air/gas is stored inreceiver from where continuous flow of gas can be supplied. It isgenerally seen where there is requirement of high pressure and lowflow. Mostly where the air is used for hand-tools, cleaning dust,small paint jobs, commercial uses, etc.

Dacheng Li et al have presented design of capacity regulationsystem for reciprocating compressor based on programmable logiccontroller. The advantage of this method is that achieves continu-ous step less capacity regulation and decreases unnecessary energylosses [1]. Hong et al presented theoretical analysis on realizationof step-less capacity regulation for reciprocating compressor. It hasto reduce energy consumption [2]. Zhi et al presented an analysison capacity regulation method of reciprocating compressor. It con-sumes low power and cheap to manufacture [3]. Yu et al presentedan analysis on reciprocating compressor. It reduces the power con-sumption by using novel rotary valve. [4]. High frequency is suit-able for low values of filter components [5].

In this work, an attempt has been made to develop the regu-lation system by using silicon pressure sensor, window comparatorand programmable logic controller (PLC). The small plastic tubetransmits the pressure difference to the pressure sensor, where asensor converts the pressure signal into a changing voltage that iscompared with reference voltage by window comparator and varia-tion of speed of ac motor that is indicated by incandescent lamp.

2 METHODOLOGY

The block diagram of the proposed system is shown in Figure 2.1.The system consists of power supply unit, programmable logic con-

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troller, pressure sensor, A.C. Motor, proximity sensor and signalconditioning unit.

Fig. 2.1. Block diagram of proposed system

In this study, an attempt has been made to regulate the ca-pacity of reciprocating compressor, by controlling the on-off timeof actuator and also to reduce the heat produced by compressorto save the energy conservation. The proposed regulation systemhas been realized employing a proximity sensor. It senses a metalobject and provides necessary electrical signal to the window com-parator then it controls the speed of ac motor. The ProgrammableLogic Controller (PLC) is mainly used in designing the ladder logicand it controls the speed of the ac motor.

Figure 2.2 shows the snapshot of the inductive proximity sen-sor. In this work, an inductive proximity sensor used to sensesthe metallic object nearer the sensor and provides an impedancechanges due to presence of eddy current induced by coil. The char-acteristics of this sensor are to detect objects with the objects ashort distance, ranging from 1 mm to several centimetres metersaccording to type of sensors used. Proximity sensor has a workingvoltage of 10-30 Vdc and there is also a voltage 100-200VAC.

Fig. 2.2. Snapshot of the proximity sensor

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The speed of AC motor can be controlled by programmablelogic controller, where a sensor converts the pressure signal into achanging voltage that is compared with reference voltage by windowcomparator. Omron platform is used for analysing the PLC anddisplays the ladder logic. Figure 2.3 shows the complete view ofdeveloped hardware.

Fig. 2.3 Developed PLC based reciprocating compressor capacityregulation system

3 RESULT AND DISCUSSION

The completely developed regulation system assembly together withactuator, proximity sensor, pressure sensor, plc and ac motor andOmron software are tested with ladder logic. The ladder logic isdesigned to displays connection of proposed system and output isdisplayed as shown in Figure 3.1

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Fig. 3.1 output shows the ladder logic of the proposed system

Testing of PLC based regulation system:

Condition 1:When the air pressure in the blower becomes very high then

the window comparator provides high resistance which makes themotor to run slowly or lamp glows very dim as shown in figure 3.2

Fig.3.1 High air pressure vs Slow speed

Condition 2:When the air pressure in the blower becomes very low then the

window comparator provides less resistance which makes the motorto run fastly or lamp glows very brightly.

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Fig.3.2 Low air pressure vs Fast speed

4 CONCLUSION

Monitoring reciprocating compressor is an important task when us-ing programmable logic controller (PLC). In this work, an attempthas been made to plc based reciprocating compressor capacity reg-ulation system. The regulation system can be designed by usingsilicon based inductive proximity sensor, compressor, actuator andlow cost programmable logic controller. The Omron software hasbeen developed with a view to display significant motor speed inreal-time. The results shown that the various parameters like pres-sure, volume and speed are measured.

In future, such systems are implemented in multi-cylinder ca-pacity regulation system instead of single cylinder capacity system.Extensive trials need to be performed by using PLC to gather statis-cal data for further analysis.

References

[1] J.D Li, Z Jiang, L Cui, Design of capacity regulation systemfor reciprocating compressor based on programmable logic con-troller, WSEAS Transactions on Systems, ISSN: 1109-2777,Issue 8, vol. 10, August 2015.

[2] W. Hong, J. Jin, and R. Wu. Theoretical analysis and realiza-tion of stepless capacity regulation for reciprocating compres-sors, Process Mechanical Engineering (Part E), Vol.223, No.4,2009, pp. 205-213.

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[3] R. Zhi, and C. Z. Wang, Analysis on Capacity RegulationMethod of Reciprocating Compressor, Petro-Chemical Equip-ment Technology, Vol.24, No.4, 2003, pp. 21-23.

[4] Y. Liang, Principle and application of the infinitely variablecapacity regulation system for reciprocating compressor, Com-pressor Technology, Vol.203, No.3, 2007, pp. 13-17.

[5] Sivachidambaranathan.V (2015), High Frequency Isolated Se-ries Parallel Resonant Converter, Indian Journal of Science andTechnology (ISSN 0974-6846) Vol 18 (15), 52311, July 2015,pp 1-6.

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