Design and Analysis of Air Film Transporter

Design and Analysis of Air Film Transporter

Hardik Nayak1, Bhargav Patel 2, Kamlesh Araniya3, Gaurang Champaneri4

1,2,3,4: Assistant Professor in Faculty of Engg. Tech. & Search, Bardoli,

Abstract:- Material handling equipment are widely use in industry to handle the heavy process equipment like boiler, end shield. End shield is the component of nuclear reactor, which provides support to lattice tube and use for shielding the nuclear reactors. For that reason special type of material handling equipments are uses. Air film transporter is one of the materials handling equipment use for the movement of end shield in dust free enclosure. It is designed because of its feature like easily movable heavy loads and positional accuracy in movement.

The present work includes Design and Analysis of 100MT air film transporter. The components of air film transporter like base frame and drive unit are designed for various loading conditions. Also the selection of air casters, have been carried out.

Keywords:- Air film transporter, Design and Stress Analysis

1. INTRODUCTION

   Movement of the heavy nuclear reactor components like End shield is very critical task; because of heavy weight care should be taken care during the movement. Many of the precaution and safety rules should be considered and followed during the movement. To move the End shield from one place to another within the plant various material handling equipments are use like, cranes, low bed wagons, automated guided vehicles and air film transporter. Terry [7] has given the selection of proper material handling equipments is based on various factors. Specifically air film transporter is chosen as a material handling equipment due to the following advantages; the direct floor loading is not acting, high positional accuracy can be achieved, compact in size compare to other material handling equipments.

   1. WORKING PRINCIPLE

      Air film transporter is works on the principle of air cushion. So, it is also called as air cushion transporter. It works similar like a hovercraft. Here, the air coming out from the air caster attached at the bottom of the transporter base and makes a thin film of air. It plays an important role to reduce the friction between the floor and the transporter base. Then drive unit moves the job at required destination. Now unload the job with supporting devices and remove the transporter. For better understanding the working of the air film transporter is divided into following three steps.

      Step-1 Prior to inflation, the load is solidly supported on landing pads. These pads protect the Air casters torus bag from being crushed when load is at rest.

      Step-2 When Air is applied to the Air-caster, the torus bag inflates, creating a seal against the floor surface and raising the load.

      Step-3 When the pressure within the chamber is sufficient to offset the loads weight, air slowly and evenly escapes between the floor and transporter base and make thin film, which gives nearly friction less movement.

   2. ASSEMBLY OF AIR FILM TRANSPORTER

   Transporter base Air casters Drive unit

   Figure 1.1 Air film transporters with job. [1]

2. DESIGN OF AIR FILM TRANSPORTER

   DESIGN PARAMETERS

   Weight 150MT Diameter- 8.1 meter

   Job Height- 1.29 meters

   Job placement height- 2.1 meter

   MATERIAL

   IS 2062 (Grade B) [2]

   Ultimate Tensile Stress – 410 MPa Yield Stress – 240 MPa

   Young's modulus – 210 GPa

   Permissible bending stress – 144 MPa [3] Permissible shear stress – 94 MPa (IS 800:1984) [3] Permissible axial stress – 141 MPa (Tensile/compressive) (IS 800:1984)

   1. DESIGN CALCULATION

      Considering both fixture and end shield, Load acting on columns, 18.17 MT

      DESIGN OF COLUMN [4]

      Length of column = 1725 mm Moment of inertia I = 92.32 x 106 mm4

      Figure 2.1 Cross-Section of column Deflection, max = 0.25 mm

      Stress, max = 101.8 MPa

      2.1 ANALYSIS RESULTS OF TRANSPORTER

      Analysis of the transporter base has been carried out for two different loading conditions. [5]

      1. When the load is rested on the base frame and support provided by the plurality of the air casters.

      2. When the load is rested on the base frame and support provided by eight numbers of jacks applied at the box section. Which are use to adjust the proper location of the air caster during the movement of the air film transporter.

      ANALYSIS OF ASSEMBLY FOR CONDITION-1

      Figure 2.3 Stress produces in transporter base

      Figure 2.3 Deflection produces in transporter base ANALYSIS OF ASSEMBLY FOR CONDITION-2

      Figure 2.4 Stress produces in transporter base

      Figure 2.5 Deflection produces in transporter base

3. SELECTION OF AIR CASTER

   Air caster is the pneumatic lifting device. It uses a continuous, regulated flow of air to create an air film between an inflated caster element and the floor surface. The thin film of air created between the air caster and the floor surface allows the load to lift and float, virtually friction-free and omni-directional movement is achieved.

   1. CONSTRUCTION OF AIR CASTER.

      Figure shows the construction of air caster and it consists following parts: [8]

      Circular rubber tours Landing pad

      Back plat Compressor

   2. SELECTION PROCEDURE

      Selection of air caster depends on following factors:

      1. Load carrying capacity of the caster

      2. Working floor condition

      3. Mounting specification

         Required load carrying capacity of the each caster: P = 19.8 MT

         Floor condition: Smooth epoxy painted Slide mounting casters.

         By considering above all parameters, Selection of the air caster is carried out from air caster corporation catalogue.

   3. SPECIFICATIONS OF AIR CASTER Make : Air Float Corporation, USA.

   Module : Load Modules No: B19 0048-5 (Heavy Duty)

   Material : Urethane

   Skid Size : 1220 x 1220 mm Air Bearing Diameter : 1200 mm

   Air Flow : 1.1 1.5 m3/ min

   Air Pressure : 70PSI (5kg/cm2)

   Lifting capacity : 45,000 lbs. (20.25 MT approx.)

   Air Line Requirement : 20 MM (ID) Weight of the caster : 215 kg

   Air bearing Lift : 31.7 mm

4. DRIVE UNIT

   The heavy job movement with help of the air film transporter is become easier and possible with help of the combine effect of the air caster and the drive unit. Drive unit consists of an air or electric motor that drives the air film transporter with an adjustable speed by means of a driving wheel. Drive unit having various steering and turning options are possible for the movement of the transporter.

   Here, the drive unit is divided in to two mechanisms according to its working. 1) Mechanism for straight motion. 2) Mechanism for turning motion.

   In the air film transporter drive unit doest carry any direct job load, because of the complete job load is carried out by the plurality of the air casters. Hence drive unit carry only load provided to maintain the contact with floor.

   DESIGN PARAMETERS

   Job Weight 150MT

   Velocity of the straight motion: V = 10 m/min Velocity of the turning motion: V = 1.8 m/min Here, due to the air film generation the friction between the base and the floor should be negligible. So, the motion of the transporter is resist by the air, rolling action of wheel and bearing.

   1. DESGIN OF STRAIGHT MECHANISM

      1. Power and Torque calculation [6]

         Total forces, which reist the straight motion of the transporter are, air resistance (Fa) = 1560N, rolling resistance (Fr) 211.2N & Bearing resistance (Fb) = 4N Hence, Total resistive force F = Fa + Fr + Fb

         Total Torque T = F x Rwheel = 90 Nm Total Power P = T x V/ Rwheel = 300 Watt

      2. Selection of gear box and motor Input data: T = 45 Nm , P = 150 watt Required gear ration i = 36

         Based on above parameters, Selection of the planetary gear box is carried out from oriental motor catalogue.

         Designation: – BH I 6 2 ST 36

         From the above required power and torque the

         3phase induction motor has been selected and the specification of the motor are, power 200 watt , current 1.1 Amp, torque 1.23 Nm and Tsated/Trated

         =1.25 and weight = 8 kg.

      3. Selection of Driving wheel

         Driving wheel is use for the movement of the transporter. The selection of driving wheel is depends on the following factors, load acting, material of wheel, working environment.

         Load acting on the driving wheel is 1000N

         The material of the driving wheel is taken as a 75D poly urethane, because it will not damage the floor and it h a v i n g h i g h e s t wear a n d t e a r resistance compare to other polyurethane material.

         Selected wheel parameters are,

         • Wheel Diameter: 100 mm

         • Wheel Width: 100 mm

         • Load carrying capacity: 1500 N

         • Weight of the wheel: 4.5 kg

         • Bore diameter: 31 mm

      4. Design of pulley and belt

         Belts are the cheapest utility for power transmission between shafts that may not be axially aligned. Power transmission is achieved by specially designed belts and pulleys. They run smoothly and with little noise, and cushion motor and bearings against load changes, belts are less strength than gears or chains.

         Input Parameters

         Maximum rpm provided by motor shaft = 42 Rpm Require power transmission 150 watt

         Required rpm at wheel shaft = 32 rpm Transmission ratio (i) = 1.31

         V-Pulleys are design for a type cross section belt. Table- 4.1 Dimension of the transmission pulleys[11]

         Sr. No.	Description	Motor shaft pulley	Wheel shaft pulley
         1	Outside dia.	55 mm	72 mm
         2	Pitch circle dia.	48 mm	63 mm
         3	Center hole	18 mm	25 mm
         4	Width	20 mm	20 mm

         Belts are selected based on power transmission capability, cross section and required length.

         P = 0.1 to 3.5 KW [11]

         Cross section Type A

         Wedge angle = 17 Material: Fabrics leather Density = 1000 kg/m3

         Allowable tensile strength t = 2.5 Mpa Required length of the belt (L) = 620 mm

      5. Design of shaft

         Shaft is the rotational machine element which is used to transmit power. The power is delivered to the shaft by some tangential force and the twisting moment setup within the shaft permissible limit. It is mounted in the two bearing and it supports the driving wheel.

         Load P acting on the shaft is1000N

         Twisting moment acting on the shaft 58590 Nmm Selected, Material of the shaft is selected is C40

         By considering the combine twisting and bending of the shaft required diameter of the shaft is 13.5 mm By considering the higher safety the selected diameter is (d) = 25 mm. [9]

      6. Bearing Selection

      Bearing require shaft to mounted the inside diameter and housing to support the outer casing.

      As per the required loading condition the selection of the straight roller bearing is carried out from the SKF manufactures catalogue.

      Bearing number: NUP 2205 ECP [10] Static load carrying capacity (Co) = 34 KN Dynamic load carrying capacity (C) =34.1 KN

      Just like every mechanical element, the bearings are selected based on the criterion of expected life from the bearing

      L = (1,000,000 / 60 x n) x (C/P) ^10/3 L = = 2093.17 Hours

   2. DESGIN OF TURNING MECHANISM

   Turning mechanism use for turn the transporter. It consist the following components, gear and pinion, gearbox and motor, bearing, spring.

   1. Power and Torque calculation

      Total torque, which resist the turning motion of the transporter are, load resistance (Tl) = 150Nm, rolling resistance (Tr) 0.312Nm & Bearing resistance (Tb) = 0.09Nm

      Hence, Total resistive torque (T) = Ta + Tr + Tb Total Torque T = 150.2 Nm

      Total Power P = T x V/ Rwheel = 277.82 Watt

   2. Selection of gear box and motor

      Input data: T = 75 Nm , P = 138 watt Required gear ration i = 115.38

      Based on above parameters, Selection of the planetary gear box is carried out from oriental motor catalogue.

      Designation: – BH I 6 2 ST 90

      From the above required power and torque the 3phase induction motor has been selected and the specification of the motor are, power 200 watt , current 1.1 Amp, torque 2.2 Nm and Tsated/Trated

      =1.25 and weight = 7.5 kg.

   3. Design of spur gear and pinion

   Input Parameters Geared motor rpm= 16 Required drive rpm = 13

   Required transmission ratio = 1.23 Required power transmission = 138 watt Required torque transmission = 75 Nm

   Assumption

   No of teeth in pinion Z1 = 36 Pressure angle Ø = 20 Full depth Module of teeth m = 4 mm

   Standard gear ratio i = 1.25

   By taking the above parameters the design of the spur gear and pinion pair is carried out and dimension of the gear and pinion are mention in table 4.2.

   Table- 4.2 Dimension of the gear and pinion [11]

   	Gear	Pinion
   No of teeth (Z)	45	36
   Module (m)	4 mm	4 mm
   Face width (b)	16 mm	16 mm
   Gear Ratio(i)	1.25	1.25
   Bottom clearance, c	1 mm	1 mm
   Pitch circle diameter, d	180 mm	144 mm
   Tip diameter, da	184 mm	148 mm
   Root diameter, df	175 mm	139 mm

   1. Bearing Selection

      As per the required loading condition the selection of the straight roller bearing is carried out from the SKF manufactures catalogue.

      Bearing number: 32210 [10]

      Static load carrying capacity (Co) = 122N Dynamic load carrying capacity (C) =100 KN Life of bearing, L = 5860.10 Hours

   2. Spring Design

      Spring provides the sufficient amount of force on drive unit to maintain continuous contact with floor. These spring are to be designed for the total amount of force provided by spring must be higher than the total pulling force required, then only the wheel will not slip.

      Input Parameters

      Load acting on spring = 700 N Assume Spring Index C = 10 Deflection of the spring () = 100 mm

      Minimum outside diameter (Di) = 60mm Mean diameter (Do) = Di + d

      Material Selection:

      Carbon steel C55 Cold Drawn [11] Tensile Stress (u) =1138 MPa Allowable shear Stress (s) = 420 MPa Young's Modulus (E) = 210 GPa, Modulus of rigidity (G) = 80 GPa, Hardness number, HRC = 55

      Density = 7850 kg/m3

      Now by considering the Whals factor, calculate the mean diameter of the spring.[9]

      Whals factor.

      K = 1.1415

      Now calculate required wire diameter of spring

      d = 6.8 mm ~ 7 mm Mean diameter (D) = 70 mm Number of coil required

      n = 11 mm

      For flat and ground ended spring no of turns n = 13 Free Length of spring Lf = nd + + 0.15

      =216 m

      Pitch of the spring P = Lf / n-1

      = 17.1 mm

      Sr.No.	Description	Dimension
      1	Wire diameter	7 mm
      2	Mean diameter	70 mm
      3	Outside diameter	77 mm
      4	Free length	216 mm
      5	Pitch of coil	17.1 mm

      Sr.No.	Description	Dimension
      1	Wire diameter	7 mm
      2	Mean diameter	70 mm
      3	Outside diameter	77 mm
      4	Free length	216 mm
      5	Pitch of coil	17.1 mm

      Table 4.3 Dimension of the spring

5. CONCLUSION

   As define in problem manual design for various components like base frame, drive mechanism of air film transporter have been carried out. Based on the obtained design data 3D modeling and assembly of various components have been done.

   After the modeling, static structure analysis of the base frame has carried out with Ideas NX-12 software and results have been compared with the permissible value taken from IS 800:1984 and the result shows that stress are well under permissible stress limit.

   In addition to the above calculation for the movement of air film transporter the value of torque and pulling force is obtained. The value of require pulling forces compare with the allowable literature and it has a close agreement with available literature.

6. REFRENCES

1. Solid Edge ST-2, Software for 3d modeling and 2d drafting.

2. IS: 2062-2006, Code practice for general structural steel. December 2006.

3. IS: 800-1984, Code of practice for general construction in steel.

4. Robert Mott, Applied strength of material, Pearson/Prentice Hall.

5. I-deas NX-12, Software for surface modeling and analysis.

6. Rudenko N.F. Material handling equipment. Technology and engineering, edition-1964.

7. Terry D. Malvin Air film pallet. United state patent 3871708.

8. Bjork Petter and Jakostand finalind. Air cushion element for air cushion transport equipment. United state patent. 3822652.

9. J. E. Shigley and C. R. Mischke, Mechanical engineering design, Tata McGraw-Hill Publishing Company Limited, sixth edition, 2003.

10. SKF manufacturers catalogue for bearing selection.

11. PSG Tech. Design data book, Kalaikathir Achchargam, Arptil,2007.