Using hydrostatic drive system for low opreation pressure gas meter calibrator

Nội dung text: Using hydrostatic drive system for low opreation pressure gas meter calibrator

1. HỘI NGHỊ KHOA HỌC TOÀN QUỐC VỀ CƠ KHÍ – ĐIỆN – TỰ ĐỘNG HÓA (MEAE2021) Using hydrostatic drive system for low opreation pressure gas meter calibrator Son Tung Nguyen 1,*, Kim Binh Doan 2, Thuy Pham Thi 3 1,2,3 Electromechanics Department, Hanoi University of Mining and Geology, Hanoi, Vietnam, e-mail ARTICLE INFO ABSTRACT Article history: th Nowadays, flowmeters are widely used in variety industrial fileds such as Received 15 Jun 2021 LPG, paint, oil refining, thermal power, etc. The reading value is used for Accepted 16th Aug 2021 controlling or adjusting the system. It is necessary to maintain the Available online 19th Dec 2021 accuracy of those devices. Generally, those devices are calibrated Keywords: periodically. Calibration is a comparision between the reading value of a Gas flowmeter calibration, device under test and that of the standard or reading value of a master device. The master devices must be already calibrated. The satandard device under test, test device, value is also called reference value. Reference value is determined in many volumetric method, PVTt ways. The accuary depends on the industrial standard or customer system expectations. Flowrate is the quantity of liquid (volume or mass) per unit time. Thefore, it’s evident that the total quantity of liquid and the respective collection time are basic parameters to obtain the reference flowrate. There are variaty of methods used to determine the reference gas flowrate. This paper depicts the research of using hydrostatic drive for building the low operation pressure gas flow meter calibrator. Copyright © 2021 Hanoi University of Mining and Geology. All rights reserved. 1. Introduction the reading values which are in put signals of controller and monitor system. For instance, LPG Flowmeter is a device used to obtain the quantity (Liquefied Petroleum Gas) is a flammable gas. It of fluid per unit time. Depending on the physical consists of some hydrocarbon gases. Propane property of luiquid those flowmeters are divided (C H ) and butane (C H ) are two largest into 3 categories: liquid flowmeter, gas flowmeter 3 8 4 10 percentage particle gases. The vapour pressure of and steam flowmeter. The quantity of fluid is LPG is dependent on the temperture as well as the determined by the mass or the volume. Generally, ratio of mixture of hydrocarbons (Phan Tu Bang, liquid are considered as incompressible fluid in 2003). The ratio of propane and butane is most industrial application. In contrast, the determined by the flow rate of pure propane, pure volume of certain gas/steam changes when butane flow from respective separate pipes. So pressure and temperture change. However, in the reading values of these devices are important partycular situation the gas can be considered as input signal of controller. The quality of LPG is incompressible fluid such as gas flow in pipe when strongly influenced by the accuracy of the different pressure is small enough to neglect and flowmeters. It’s necessary to maintain the the velocity is under 20 m/s. Flowmeters provide 244
2. HỘI NGHỊ KHOA HỌC TOÀN QUỐC VỀ CƠ KHÍ – ĐIỆN – TỰ ĐỘNG HÓA (MEAE2021) accuracy and the reliability of flowmeters. Mostly, volume – temperture – time) system (John D. these devices are calibrated periodically for Wright and Pedro I. Espina, 2000) or weight – adjusting the factor of the measuring instrument. time gas flow calibrator (J.O. Hylton and C. J. The period time must be accorded to the standard Remenyik, 1999). According to the Gas Flow or requirement. The calibration can be take place Calibrator Instruction Manual written by Sierra at laboratory or site. At laboratory, the flowmeter Instrument, the bell prover system was hasn’t is inserted in the test system that is also called been used for over 20 years. Sierra Instrument device under test (DUT). The reading value of designed a gas flowmeter system similar to the DUT is comprared to the standard value. The piston prover design. Using the minimum length standard value is determined in certain quantity of piping necessary between the calibrator and of gas under specified condition (pressure, the gas source also minimum the distance temperture). On the other hand, site calibration between DUT and the calibrator. By practical means comparion between the reading value and implement the realized the initial pressure pulse the reference value obtained by master greater then the normal pressure 8 times. The flowmeter. There are several proposal methods to fluctuation of pressure depends on the mass of the determine the standard value. The rate of mass piston and the friction between the piston and the flow is determined inderectly from measuring the cylinder bore. Consequently, the collection travel temperture, pressure, volume then using the state of piston must be smaller the real distance motion equation for ideal gases. The volumetric of gas is (figure 3). determined by using a precision bore tube and a Similar to above designs, this design consists free floating piston which can reciprocates of a precision displacement piston type without friction inside the bore. To reduce the compressor to push the gas flows into the pipe at friction force the piston is lubricated by a ring of certain pressure and temperture. So the density is mercury. The o ring mecury also cover the seal maintained constance along the stream. The mass function. Pressure in the closed volume is equal to flowrate is calculated from the velocity of piston the static pressure created by the gravity of the and the inside cross section of cylinder. This paper piston. The schematic diagram of test system is depicts the schematic diaphgram and the illustrated as figure 1 (J.O. Hylton and C. J. specification of system to calibrate the RF1 low Remenyik, 1999) and (John D. Wright and Pedro pressure gas flowmeter. I. Espina, 2000). The similar design uses bell The structure of this paper is devided into 4 prover. Instead of using free floating piston inside sections. The brief review of gas flow meter a cylinder bore there is a bell which matches to a calibrator is represented in section 1. Section 2 cylinderical tanks. The bell can move up and move shows the RF1 gas meter specification and the down freely thanks to the annulus oil film and mathematical model of hysdraulic cylinder, counterweight (John D. Wright and Pedro I. especially the other researching of cylinder Espina, 2000). On the other hand, the quantity of friction behavior. The equations for calculating the gas is measured directly by defining the total gas flowrate is depicted at the later part of section mass of gas flows into a closed volume/tank. The 2. The section 3 shows the schamatic diagram of average mass flow is deduced from the initial calibrator and discussion. Finally, the brief mass, final mass of the tank and the collection conclusion is outlined in the section 4. time. The method is called PVTt (pressure – 2. Data and theory 2.1. RF1 gas flowmeter ___ * Corresponding author RF1 gas flowmeter is a compact residential gas E - mail: nguyensontung@humg.edu.vn flowmeter designed to measure volume of natural gas, LPG and non-corrosive gases. It is a positive DOI: displacement diaphgram gas meter. It has twin 245
3. HỘI NGHỊ KHOA HỌC TOÀN QUỐC VỀ CƠ KHÍ – ĐIỆN – TỰ ĐỘNG HÓA (MEAE2021) chamber measuring unit. The twin chambers are each fitted with a flexible and gas-tight diaphgram moved by the diferential pressure between the inlet side and the outlet side. The gas enters one side of the diaphgram plate, then comes out on the other side through a separate port on the valve. When one side is filled full, the sliding valve shifts the postion, allowing the gas flows into the empty side (RF1 gas meter instruction). Technical specification: Medium: Hydrocarbone, natrual Figure 42 – Hydraulic cylinder model gas, non-corrossive gas, External friction force is generated by air, etc relative motion between the bushing part and Temperature -25oC ÷ 55oC guiding rod (mechanics). The mechanical force Range: gose down rapidly as piston rod and coupling Maximum 0,5 bar moment. It also counters the piston rod Operating pressure: 1,0 bar movement at the initial phase (static friction). Due Model/Measuring Range: to prevent the internal and external leakage Q = 0,016 m3/h G1.6 min hydraulic cylinder’s sealant generates a Qmax = 2,5 m3/h considering friction force between piston and Q = 0,025 m3/h G2.5 min cylinder bore and between piston rod and rod seal Qmax = 4,0 m3/h o-ring. Modeling the friction effect of cylinder is Q = 0,040 m3/h G4 min critical. Many researchers have already tried to Qmax = 6,0 m3/h model the mathematical model of friction force in Q = 0,060 m3/h G6 min both traditional approach and experiment Qmax = 10,0 m3/h approach. The friction force is built from elastic deflection of the contact surfaces, the stiffness of 2.2. Mathematical model of cylinder the microscopic deformation during the pre- sliding motion of piston and piston rod, viscous For hydrostatic drive, the differential force friction. The figure 4 depicts the theorical applying on the piston generates the hydraulic behavior of cylinder friction (Antonio et al., 2011). cylinder force which moves the piston and piston The experiment seems to be a reliable approach rod to counter the external force (figure 1). The to get the cylinder friction behavior. Inspiration of external force consists of mechanical load, inertial Antonio and his colleagues, Rozimerli and Camila force, friction force. The motion equation of piston tried to take place the experiment to obtain the is depicted by Newton laws (Michael Ruderman, friction behavior of pneumatic cylinder (figure 5). 2017): The performance curve shows the relationship p.A2 2− p.A 1 1 − Ffs − F f − F = m.a (1) between dynamic friction and linnear velocity. The dynamic friction force lightly changes as the In which: p1, p2 – respectively the gauge pressure in the piston chamber and rod chamber, speed smaller than 0,15 m/s. Similary to result of Roziment, Alexander Heinze validated the (Pa), A1, A2 – respectively the effective cross section of piston chamber and piston rod behavior of friction in his investigation of modeling and simulation the performance of chamber, (m2), Ffs – the seal ring friction force, hydraulic cylinders (Alexander, 2007). The (N), Ff – the external friction force, (N), F – the external force, (N), m – the total mass of piston, friction factor is causing of peak pressure. Smooth piston rod and external coupling component (kg), load, steady movement. On the other hand, the a – the accelaration of piston, (m/s2). 246
4. HỘI NGHỊ KHOA HỌC TOÀN QUỐC VỀ CƠ KHÍ – ĐIỆN – TỰ ĐỘNG HÓA (MEAE2021) unique performane of hydrostatic drive is the control valve, (Pa), ρ – density of the hydraulic flowrate is not depend on the pressure. fluid, (kg/m3). Because of low operating pressure, the Pressure compensation function means the compressibility of the hydraulic oil is neglected. Δp is maintained constant even though the load And the hydraulic oil is considered as changes. As the result, the Qsys is considered a incompressible fluid (Marko Orosnjak et al., constant value. That means the velocity of the 2017). In addition, the light force leads the piston is constant. requirement differential pressure between piston 2.3. State equation, gas pressure, mass flowrate chambers and piston rod chamber be small enough to minimum the leakage. If the hydraulic For ideal gas, the state equation is fluid is adressed as incompressible fluid and represented below (Bùi Hải và Trần Thế Sơn, leakage also is neglected the velocity of the piston 2008): is only dependent on the flowrate enters and p.V M= . R.T (5) come out from the servo hydraulic cylinder In which: p – the absolute pressure of the gas, (figure 2): (Pa), V – the volume of the gas, (m3), M – the mass QQ of the gas, (kg), R – gas constant, (J/(kg.K)), T – v ==12 (2) absolute temperture of the gas, (K). AA12 For single piston compressor (figure 5): In which: v – velocity of the piston, (m/s), Q and 1 V A= . x (6) Q2 – respectively the flowrate enters the piston chamber and the flowrate come out from the In which: V – the volume of closed chamber/the volume of the gas, (m3), A – the efficetive cross piston rod chamber (m3/s), A1, A2 - respectively 2 the cross section of the piston chamber and the section of the cylinder, (m ), x – the coordinate of the piston surface, (m). cross section of the piston rod chamber, (m2). Unfortunately, the positive displacement pumps The necessary moment of the piston for can not provide the constant quantity of liquid per increasing the pressure from pab1 upto pab2 is unit time. The flowrate always fluctuates due to detected below: x2 M .R.Tdx the geometry of the rotor. Therefore, it is unable pp. −=− to pump flow directly into the system. It’s abab21 2 x1 Ax necessary to add a press relief valve at the Deduction: discharge port of the pump to maintain the certain M .R.T pressure and system flowrate. The excessive flow xx12−= (7) is directed to the tank via pressure relief valve. A.p In which: x1, x2 – respectively the initial position or QQQsyspv=− (3) later position of piston surface, (m), M – the mass In which: Q – flowrate enters the system, sys of the gas, (kg), R – the gas constant, (J/(kg.K)), T (m3/s), Q – flowrate of hydraulic pump, (m3/s), p – the absolute temperture of the gas, (K), A – the Q – excessive flowrate goes to tank via pressure v efficetive cross section of the cylinder, (m2), Δp – relief valve, (m3/s). the differential pressure between initial point and The flowrate goes through the pressure beginning collection time point, (Pa), (figure 5). compensated flow control valve: Density of the gas: 2.p pab2 QCsysvv= .A . (4) = (8) 2 R.T In which: Qsys – flowrate enters the system, The average mass flowrate during the 3 (m /s), Cv – the valve factor, Av – total cross collection time is defined: section of the throtting port, (m2), Δp – differential between inlet port and outlet port of the flow 247
5. HỘI NGHỊ KHOA HỌC TOÀN QUỐC VỀ CƠ KHÍ – ĐIỆN – TỰ ĐỘNG HÓA (MEAE2021) g p .A g p . A m= 2 .v (9) m .v= 2 (10) R.T R.T g g In which: m - the average mass flowrate of the gas In which: m - the instant mass flowrate of the gas flow, (kg/s), pab2 – later absolute pressure, (Pa), A flow, (kg/s), pab2 – later absolute pressure, (Pa), A 2 – the efficetive cross section of the cylinder, (m2), – the efficetive cross section of the cylinder, (m ), R – the gas constant, (J/(kg.K)), T – the absolute R – the gas constant, (J/(kg.K)), T – the absolute temperture of the gas, (K), v - the velocity of temperture of the gas, (K), v - average velocity of piston. piston. If the piston is considering smooth motion during the collection time, the instant flowrate value is equal to average value: Figure 43 – Constant pressure volume flow calibrator (J.O. Hylton and C. J. Remenyik, 1999) 248
6. HỘI NGHỊ KHOA HỌC TOÀN QUỐC VỀ CƠ KHÍ – ĐIỆN – TỰ ĐỘNG HÓA (MEAE2021) Figure 44 – Piston prover pressure performance (Sierra Instrument) Figure 45 – Theorical friction behavior (Antonio et al., 2011) Figure 46 – Experiment pneumatic cylinder friction behavior (Rozimerli et al., 2014) 249
7. HỘI NGHỊ KHOA HỌC TOÀN QUỐC VỀ CƠ KHÍ – ĐIỆN – TỰ ĐỘNG HÓA (MEAE2021) 1 – Hydraulic oil tank, 2 – Suction filter, 3 – Hydraulic pump, 4 – Unloading valve/Solenoid operated pressure relief valve, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6 – Check valve, 6 – Pressure relief valve, 7 – pressure compensate flow control valve, 8 – Directional control valve, 9 – Hydraulic cylinder, 10.1, 10.2 – Compressor, 11.1, 11.2, 11.3, 11.4 – On/off manual valve, 12 – Sequence valve, 13 – Meter, 14 – Return filter Figure 47 – Schematic diagram of gas flow meter 250
8. HỘI NGHỊ KHOA HỌC TOÀN QUỐC VỀ CƠ KHÍ – ĐIỆN – TỰ ĐỘNG HÓA (MEAE2021) 3. Result and discussion experiment of cylinder behavior as a proof to ensure the realiability of obtained theorical design 3.1. Result of this researching. Next, we are going to build the This design includes 3 components: hydraulic real calibration device for experiment. For gas, it’s system, compressor & piping and controller. The necessary to focus on the error between the theory hydaraulic system consists of a double acting and practice. Addion, the performance of the hydraulic cylinder, a directional control valve hydraulic cylinder is also investigated carefully. which leads the hydraulic cylinder to extend or Acknowledgments retract, a pressure relif valve, a pressure compensated flow control valve and a hydraulic Be half of authors, I would like to power unit. The compensated pressure function is thanks Electromechanics department and our carried out by pressure reducing valve. The colleagues who inspire us to complete this paper. hydraulic pump is the single acting vane pump, 4 I would like to thanks Mrs Thuy for studying the cm3/revolution driven by an asynchronous electric properties of gas. I am grateful to Mr Kim Binh motor, 3000 rpm. The second component consists for his effort in this studying. of 2 servo pneumatic cylinders play as single acting Contribution of authors piston compressors, non-return valves, vent This study is completed by authors effort and valves, block valve and piping. The flowrate of gas discussion. Mr Tung is in charge of writting, is adjusted by detecting the speed of piston and gathering the consultant of other authors. unloading one compressor or any. The controller consist of PLC module and pressure transmitter. References PLC controller is used to detect the collection time Alexander Heinze, (2007). Modeling, Simulation and pressure performance (figure 6). and Control of Hydraulic Crane. School of 3.2. Discussion Technology and Design, Russia Antonio Carlos Valdiero, Carla Silvane Ritter, To take the priority of speed control of Claudio Fernando Rios and Marat Rafikov, hydrostatic drive, the smoth motion of the piston, (2011). Nonlinear Methematical Modeling the gas compressor could offer the instant flowrate in Pneumatic Servo Position Application. for calibration the meter. Mathematical Problems in Engineering Regarding the safety and protection, the Volume 2011. design deals with the drawback of piston prover Bùi Hải, Trần Thế Sơn, (2008). Kỹ thuật nhiệt. using the mercury as sealant. Because of no NXB KHKT mercury metal, this desing is safer and easier to Gas flow calibrator instruction manual, Sierra operation than other. Instrument Cooperation. At low pressure and temperture, most of the Marko Orosnjak, Mitar Jocanovik, Velibor gases can be considered as ideal gases. So, the all Karanovic, (2017). Simulation and Modeling equations in section 2.3 are ideal gas equation. In of hydraulic system in FluidSim. 17th constract, the tolerance of flowmeter can be reach International Scientific Conference on upto 2%. That means this design is realiable. Industry System. However, it is necessary to carry out the Michael Ruderman, (2017). Full and Reduced- experiment to ensure the performance of this order Model of Hydraulic Cylinder for design. Motion Control. IEEE Conference. 4. Conclusion John D. Wright and Pedro I. Espina, (2000). Flow Calibration Services at NIST, National Basing on the volumetric calibration method Institute of Standard and Technology, USA and comparision to other designs which are J.O. Hylton and C. J. Remenyik, (1999). An applied in the industry and the result of instrument for gravimetric calibration of 251
9. HỘI NGHỊ KHOA HỌC TOÀN QUỐC VỀ CƠ KHÍ – ĐIỆN – TỰ ĐỘNG HÓA (MEAE2021) flow device with corrossive gas. 4th Rozimerli Raquel Mibeier Richter, Camila International Symposium on Fluid Flow Valandro Zamberland and Antonio Carlos Measurement, Denver, Colorado. Valdiero, Luiz Antonio Rasia, (2014). Phan Tu Bang, (2003). Giáo trình công nghệ lọc Friction Dynamics Mathematical Modeling dầu và chế biến khí. NXB GTVT. in Special Pneumatic Cylinder. ABCM RF1 Residential Diaphgram Gas Meter, Thorne & Symposium Series in Mechatronics – Vol.6 Derrick Cooperation. 252