بحث كيفية اختيار الزيت الملائم في بيرنات الأفران الدوارة

Abstract

The rotary kiln considers the spine of economy in the cement industry. The cement production needs continuous working without sporadic. one of the majority problems on the operating kiln is the increase of the friction coefficient between the rollers’ journal and bearing which causes increase the Ampere of the main and thus leads to discontinuity in kiln operation. To overcome this problem, this study has been proposed to allocate the appropriate oil that depends on the viscosity, speed and the stress on bearings.As result, the oil of grade (1000) is the suitable type for bearing kiln and which made the kiln works on an ongoing basis.

Keywords:- Dynamic viscosity,shear stress, stress on bearing, summerfield number, kinematic viscosity.

Introduction Producing cement reliably and safely while reducing downtime is a continual challenge faced every day. Machines in the cement industry are subject to extreme operating conditions like high contamination, temperatures, vibrations and shock loads. These conditions make maintenance and repair of your machinery a very challenging task. In the extreme environment in which drives, bearings, conveyors and other components have to function, the lubricant has to meet the highest demands. First, the right lubricant has to be selected, as there is no standard solution for many of the applications in this industry. Depending on the mode of operation and the location of use, you have to use different lubricants that are made up of different base oils, additives, viscosities and consistencies. Making the wrong decision can lead to premature component failure or even production stoppages, resulting in high maintenance costs and production losses. In addition, your plant must run efficiently and cost-effectively with minimum impact on the environment. The objective of lubrication is to reduce friction , wear and heating of machine parts that move relative to each other .There are five distinct form of lubrication may be identified (Hydro dynamic ,Hydrostatic , Elastohydro dynamic ,Boundary and solid film ).the first type “Hydrodynamic lubrication is used in kiln bearing .the load carrying surfaces of the bearing are separated by a relatively thick film of lubricant , so as to prevent metal to contact, and the stability thus obtained can be explained by the fundamentals of fluid mechanics . Hydro dynamic lubrication depends on the existence of an adequate supply of lubricant at all times rather than having lubrication under pressure .the film pressure is created by moving surface itself pulling the lubrication into a wedge –shaped zone at a velocity sufficiently high to create the pressure necessary to separate the surfaces against the load on the bearing [1] .In this research the mathematical calculations have been done to specify the appropriate oil that depends on the viscosity, speed and the stress on bearing and guarantee the kiln to work continuously and in steady state.

Theoretical Section In order to select the appropriate lubricating oil for the rotary kiln journal bearing, the equations (1-21) (refer to references [1,2]), Figure (1) that contains three parameters (velocity of journal, kinematic viscosity and stress applied on bearing), and Tables (1 and 2), the oil’s grad and viscosity has been calculated using the actual parameters of the kiln in the AL – Najaf Alashraf plant. The first step is to study the specifications and dimensions of the rotary parts to determine the velocity and stress. The linear velocity and the stress of bearing can be calculated and specified on the curve of stress in Fig1to obtain the kinematic viscosity. By applying the equations (1-10)[1,2], the kinematic viscosity would be obtained and compared using the Table1 of oil viscosities to find the grade number of oil. The other various parameters of surface density can be calculated and determined using equations (Table2).

Result and Disuussion Based on the calculation’s procedure that has been illustrated in the Appendix, the result states the oil of grade (1000) is the suitable type for bearing kiln. From the practical point of view, using the oil of grade (1000) in the field has made the kiln works on continuous, stable and steady state. The bases of supporting rollers in the operated kiln were filled with the oil of grad (1000) and the results can be summarized as below:- 1- In starting main motor the ampere is decreased from (900 – 200Ampere). 2- The feed of material to the kiln increased (28 m3/h) to (43m3/h) . 3- The temperature of bearing reduces to (45°C) compared with (100°C) before. 4- The rotary parts are working safely without wear or pitting. 5- The rotary kiln continuous working without problems.

Conculsion In this work, a procedure of calculating the oil’s grade for the rotary kiln journal bearing in the AL – Najaf Alashraf plant has been introduced using mathatical equations and empirical curves and tables instead of using arbitrary or true and error methods. The results showed that the oil of grade (1000) in the field has made the kiln works on continuous, stable and steady state

References 1- Dr.R.KBansal – Fluid mechanics, 1st ed. LAXMI PUPLICATIONS (P) LTD, 2008. 2- Ferdinand Leon Singer, Andrew Pytel. Strength of material.Harper & Row, 1980. 3- www.lifetime-reliability.com. Last entry 1/7/2017. 4- kinematic viscosity for industrial oils according to ISO3448. 5- viscosity-temperature chart in US customary units (Rrimondi and Boyd).

Appendix Diameter type of kiln ( DT = 4325mm) Diameter supporting roller ( DR = 1300 mm) Rotary speed of kiln ( NK = 1.4 r.p.m ) Length of bearing ( L = 615 mm) Journal diameter ( Dj = 430mm) The load exerted on the bearing ( W = 1212 KN ) Nt= Revolutions per minutes ( r.p.m) =1.4 r.p.m NR= Revolutions per minutes ( r.p.m) Bearing length =615 mm A=0.615×0.43=0.26445 m2 journal diameter =430 mm =16.92 inch R= radius = (430/2) = 215 mm Choose the type of ( kinematic viscosity ) and coefficient of FRICTION for journal and bearing in Hydrodynamic W5=316.22x1.5=474.33T …………………………………………………(1) F=(W/2)=(474.33/2)=237.165T ……………………………………………..(2) FR=Roller supporting force =F+10T =237.165+10 =247.165 T ………….(3) FR=247.165x1000x9.81=2424688.6N ……………………………………..(4) Fb=Bearing load = (2424688.6/2) =1212.3443KN ………………………….(5) l=615mm ----- d=430mm A=0.615x0.43=0.26445m2bearing area σ=(Fb/A) = (1212.3443/0.26445)=4584.74KN/m2 = 4.585 M pa ……….…..(6) DT=tyre diameter = 4325 mm NT=Tyre speed = 1.4 r.p.m DR=Roller outer diameter =1300mm NR= Roller speed (NR/NT)=(DT/DR) ……………………………..………………………….…..(7) (DT/DR).NT=(4325/1300)x1.4=4.648 r.p.m=0.0776 r.p.s …………………..(8) NR=(DT/DR).NT=(4325/1300)x1.4=4.648 r.p.m=0.0776 r.p.s .……….… (9) V=∏ DR .NR= ∏x0.430x0.0776= 0.1 m/s ………………………………..…(10) σ=4585 KN/m2 According to speed and σ pressure have selected on Fig 1:- μ=0.9 pa.s ρoil= density of fluid = 861 Kg/m3 ν =kinematic viscosity = (μ/ρ) =(0.9/861)= 1.04529x10–3 m2/s 1.04529x10–3x 106 = 1045.29 mm2/s = 1045 C St According to the Table1, ISO Viscosity Grader this number between (900 – 1100 ) Cst The ISO Viscosity Grade number is (1000) radial clearance c= ( 3.6 n0.25 x D1.25) /105 ……………………………….(11) n= 4.648 r.p.m D=430mm C= ( 3.6 x(4.648)0.25x( 430)1.25 ) /105 ……………………………………..(12) C=0.103 mm summerfeld number S = (r/c)2 ( μ nj/σ) …………………………………….(13) r=(430/2)=215mm C= 0.103 mm μ=0.9 pa.s nj=0.0774 r/s σ=4.584 M pa (r/c)=(215/0.103)=2087 …………………………………………………….(14) S = (2087)2( 0.9x0.0774/4.58474x106) =0.0661 …………………………..(15) l/d)=(615/430)=1.43 this called long bearing and consider (l/d)=∞ in Table2 and S= 0.0661 Lies between (0.0636 – 0.123) to find the following : excentric ratio e=c – h0 ………………………………………………………………(16) excentric ratio e=0.2–(0.2–0.4)x[ 0.123–0.0661)/(0.123–0.0636)] e=0.2+0.2x(0.0569/0.0594) e=0.2+(0.2x0.95) =0.39 (ho/c)= 0.8–(0.8 –0.6)x0.95 =0.8–0.2x0.95 =0.61………..………………(17) ho=0.61 x0.103 =0.062 MM (r/c) x f= 2.57–(2.57–1.52)x0.95 = 2.57–(1.05x0.95) =1.57 = ( C F V) ….(18) f=(c/r)x1.57 =(0.103/215)x 1.57 =0.0007 (Q/rcnl)= 2.83–(2.83–2.26)x0.95 = 2.83–(0.570x0.95) = 2.83–0.54 =2.29 …(19) Q= 2.29x215x0.103x0.0774x615=2414 mm3/s =2.41 cm3/s =145 cm3/min p/pmax=0.814–(0.814–0.764)x0.95 =0.814–(0.050x0.95 =0.77 ………………(20) p max=(p/0.77) =(4.58MPa/0.77) =5.95 M Pa T=8.3x10–6xσ x (C F V/F V) ……………………………………………………..(21) (C F V)=1.57 F V=2.29 T=8.3x10–6x4.58x106 x (1.57/2.29) =26◦C Ta =Ti + ( T/2) =30+(26/2) =30+13 =43◦C ………………………..(19) Ta =Average temperature . The oil of grade (1000) is the suitable type for bearing kiln.

Figure 1: the curve of stress with vertical line, the surface speed and the kinematic viscosity

Table1: ISO Viscosity Grade

Table2; Various parameters of surface density