Weight Measurement Technology

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Ophelia Miles
6 years ago
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1 Weight Measurement Technology 1

2 Definition of Terms Millivolt volts: the unit of measure of output from sensors PSI Pounds per Square Inch: Unit of measurement of stress used in the application of strain gage sensors 2

3 Definition of Terms Stress Any action on a body that results in deformation. Usually measured in pounds per square inch or Pascal's Thermal Stress Two dimensional strain caused by thermal heating (expansion) or cooling (contraction) 3

4 Definition of Terms Strain Deformation of a body or structure as a result of an applied force Strain Gage A device that converts mechanical deflection to an electrical signal 4

5 Definition of Terms Mechanics of a member in compression Compression Stress by forces pushing together Tension Stress by forces causing extension (pulling) L At Rest Add Weight W Mechanics of a member in tension L At Rest L Add Weight W L 5

6 Definition of Terms Poisson s Ratio The ratio of transverse strain to longitudinal strain -- The ratio for carbon steel is.3 Shear The component of a horizontal beam that is being measured A D Shear Area = A x D 6

7 Definition of Terms Live Load The design capacity of a vessel Dead Load The empty weight of a vessel 7

8 Definition of Terms Wheatstone Bridge An electrical circuit used to detect small resistance changes in strain gages Signal Lines In half bridge systems, these are the lines that return the signal to signal conditioners Signal Processor R c R d +EXC -EXC Red Black Note: Rc and Rd are fixed resistors Transducer R a R b White Output Signal 8

9 Definition of Terms Sense Lines In full bridge systems, these are the lines that bring in the sensed voltage Signal +Sense +Excitation -Excitation -Sense 9

10 Introduction Bolt-On Transducers attached to existing vessel structural support Direct Support Transducers are built into structural support elements Both share a common platform Silicon Semiconductor Strain Gages 10

11 Introduction Silicon Semiconductor Strain Gage Solid state resistors Manufactured from a single-crystal boule Acid etched to require resistance Glass fused to bending beam 11

12 Theory Wheatstone Bridge Signal Processor Transducer An electrical circuit used to detect small resistance changes in strain gages R c R d +EXC -EXC Red Black R a R b White Output Signal Note: Rc and Rd are fixed resistors 12

13 Theory Compression and expansion. Poisson s Ratio..3 for carbon steel 13

14 Theory Vessel support experiences small strain (length) changes in direct proportion to the change in weight of material in vessel The Bolt-On weight transducer detects and amplifies this change in length and provides a resistance change that is proportional 14

15 Rigid Piping Connections Catwalk Factors That Affect Performance Hidden Load Bearing Members Vessel goes Through Roof Tripper Conveyors or Deck Plating 15

16 Factors That Affect Poor Foundation Flexible Structure Uneven Loading Structure not level Off-center loading Wind Equipment Vibration Performance Side load causes tensiononlegson this side, which could be interpreted as decreased material weight Side Load Side load causes compression on legs on this side, which couldbeinterpreted as increased material weight Tension and compression equal but opposite; cancel each other if all legs instrumented with L-Cells. 16

17 Shock Loads Factors That Affect Performance Excessive electrical noise or heat 17

18 Bolt on Weight Measurement 18

19 Introduction Bolt-on provides continuous bulk material inventory Immune to material characteristics Provides weight not level Non-intrusive Ideal for renovations or retrofits Install without interrupting production 19

20 Microcell A half bridge strain gage device used to transform a mechanical motion into an electrical signal 20

21 L-Cell Dual axis strain gage device used to transform a mechanical motion into an electrical signal; minimizes environmental effects 21

22 Type of Legs Pipe Legs Square Tubing Rectangular Tubing H or I Beam Channel Unequal Angle Equal Angle 22

23 Type of Legs Pipe Legs 23

24 Leg Bending 24

25 Lateral Stain 25

26 Compression/Expansion 26

27 psi Calculation Legged Vessel live load per leg = live load (working capacity) number of legs load factor (psi) = live load per leg steel area calculation A D A A T A T C C B Area = 2 x B x C + {A - (2C)} x D H or I Beam Legs B Area = (A + B) x C Angle Legs B Area=(2A+2B)xT Tubular Legs B Area = 3.13 x D x T Pipe Legs 27

28 Square tubing Rectangular tubing H & I beam Channels Horizontal Location on Angle with equal or unequal legs Vertical pipe legs Vertical Legs 28

29 Vessel Free Leg 29

30 Support Legs N=0 N=0 N=2 N=2 Without X-Braces With X-Braces 30

31 Leg Accuracy Chart {± Error %} Outside N=0 Outside N=1 Outside N =2 Inside N=0 Inside N=1 Inside N= {Stress in PSI} 31

32 psi Calculation Horizontal Beam Supported Vessels live load per support point = live load (working capacity) two times the number of support beams load factor (psi) = live load per support point shear area calculation A D Shear Area = A x D 32

33 Horizontal Beams Left & Right Same Side of Web load point support point support point 33

34 Horizontal Beams Left & Right Opposite Side of Web load point support point support point 34

35 Horizontal Beams Left or Right Back-To Back load point support point support point 35

36 Horizontal Beams Left or Right Single L-Cell load point support point support point 36

37 Horizontal Beams Left & Right Back-to-Back load point support point support point 37

38 Horizontal Beams L-Cell orientation is the determining factor for reversing the excitation wiring. If the the L-Cell is located to the right of the Load Point then the excitation is reversed. i.e. red to black and black to red Excitation Wiring load point Normal Exciatation Wiring Reversed Exciatation Wiring Red to Red & Black to Black RedtoBlack& BlacktoRed 38

39 Horizontal Accuracy Chart {Stress in PSI} 4 Cells/Beam 2 Cells/Beam 1 Cell/Beam ± Error %

40 Skirted Silo Silo Layouts ' (2.7m) Diameter 9'5" (2.9m) L-Cell Spacing ' (3.7m) Diameter 9'5" (2.9m) L-Cell Spacing ' (4.6m) Diameter 9'5" (2.9m) L-Cell Spacing ' (6.4m) Diameter 9'5" (2.9m) L-Cell Spacing ' (5.5m) Diameter 9'5" (2.9m) L-Cell Spacing ' (7.3m) Diameter 9'5" (2.9m) L-Cell Spacing ' (7.9m) Diameter 9'5" (2.9m) L-Cell Spacing Legend: =L-CellSet = Junction Box = Door ' (8.5m) Diameter 8'10" (2.7m) L-Cell Spacing

41 psi Calculation Skirted Silo load factor (psi) = live load (working capacity) 3.14 x D x T T D 41

42 Skirted Silo L-Cell Sets Cable routing through 3/16" hole 42

43 Skirt Accuracy Chart {Skirt Stress in PSI} Best Case Worst Case {± Error %}

44 Bolt-On Weight Technology Evaluate customer data requirements Level-by-weight and weight-by-level systems are at best a 10% system Bolt-on not affected by Angle of repose Rat-holing Bridging Moisture content Compaction Vapors Dust 44

Bolt-On Sensors. Question. Answer. What is Bolt-on Weight Measurement?

Bolt-On Sensors. Question. Answer. What is Bolt-on Weight Measurement? What is Bolt-on Weight Measurement? What is a strain gage? KM pioneered the development and application of the type of technology that is based on the silicant, semi-conductor strain gage. The device is