Dr S Parthasarathy MD DA DNB PhD FICA IDRA Dip software based statistics Flow meter measures flow But we can change adjust the flow FLOW MEASUREMENT DEVICES it just measures the flow ID: 1024697
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1. FLOWMETERS & FLOW MEASUREMENT DEVICESDr S. Parthasarathy MD DA DNB PhD FICA ,IDRA Dip. software based statistics
2. Flow meter – measures flow But we can change, adjust the flowFLOW MEASUREMENT DEVICES – it just measures the flow !!
3. Let the lecture go this way ! HISTORYPRINCIPLES & TYPESNEEDLE VALVE & THORPE TUBE
4. HISTORY1868- Chameroy1876- Sir Alfred Ewing’s Ball & Tube Flowmeter1879- Joslin’s dry bobbin flowmeter
5. HISTORYCoxeter Bobbin Meterinaccuracies due to friction between the bobbin and the wall, blockade of the exit holes by dirt or dust, inability to measure fine changes in the gas flow as it could be measured only in steps from one hole to the next.
6. HISTORYHeidbrinkmeter
7. HISTORY1908- Karl Kuppers1910- M. Neu1930- Connell1937- Richard SaltCONNELL METERrota
8. HISTORY Boyle’s Water Sight Flowmeter PRINCIPLE SCHEMATIC
9. RECENT ADVANCES & FUTURE TRENDSELECTRONIC CONTROL OF FLOW Mass flow controller !! – solenoid valve and electric change ELECTRONIC FLOW MEASUREMENT
10. PRINCIPLES & TYPESCONSTANT ORIFICE, VARIABLE PRESSURE DIFFERENCETUBULARORIFICEVENTURI
11. Its variable pressure difference and not variable pressure
12. PRINCIPLES & TYPESCONSTANT ORIFICE, VARIABLE PRESSURE DIFFERENCEWater depression meterBourdon’s pressure gaugeForegger’s gas flow meterFleisch pneumotachograph
13. WATER DEPRESSION METER Gash
14. BOURDON’S PRESSURE GAUGE
15. FOREGGER FLOWMETER Only history
16. FLEISCH PNEUMOTACHOGRAPH. A bundle of parallel small- bore tubes is placed in the gas pathway, which provides a low resistance, and is called the Fleisch screen. It is electrically heated to prevent condensation of water- vapour. The pressure difference across the resistor is a measure of the flow through it. This principle is employed in many of the modern ventilators for measuring respiratory flows.
17. D- lite flow sensor( Pitot’s tube )Static pressure – opposite Dynamic pressure – same side – difference is measured
18. PRINCIPLES & TYPESVARIABLE ORIFICE, CONSTANT PRESSURE DIFFERENCEThorpe tube
19. THORPE TUBE
20. THORPE TUBE HIGH FLOWSLOW FLOWSBorosilicate glass – pyrex
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23. PRINCIPLES & TYPESOTHERSVolumetric flowmeters(Positive displacement flowmeters)Diaphragm / bellows flowmeterDrager volumeter
24. DRAGER VOLUMETERCogwheel , large internal space ; cumbersome
25. Variable Orifice SensorAisys Milar flap
26. WRIGHT’S RESPIROMETER(INFERENTIAL)
27. WRIGHT’S RESPIROMETER
28. NEWER SPIROMETERS
29. FLUIDIC FLOWMETERSThese rely on some dynamic instability in the gas which generates an oscillation whose frequency is proportional to the flow rate. employed in some Ohmeda machines, in which a swirl is created in a series of fixed vanes due to rotation of a single vane induced by gas flow, and this is sensed optically.
30. FLUIDIC FLOWMETERSVORTEX SHEDDING FLOWMETERNitrous oxide
31. ULTRASONIC FLOWMETERSPrinciples:Transit time.Doppler principle. blood flow
32. Ohmeda 5400 Volume monitors
33. ANEMOMETERSGas flow around a thin wire – heat dissipation related to flow
34. Electromagnetic flow meter Faraday’s law Flow of gases Magnetic field Potential difference
35. Electronic gas selector switch. Either nitrous oxide or air can be selected by pushing the appropriatebutton (lower left). Total gas flow and oxygen percentage are set by pushing the hard keys and rotating
36. FACTORS AFFECTING RATE OF FLOWPRESSURE DROP ACROSS THE CONSTRICTIONDIAMETER OF THE ANNULAR ORIFICEPHYSICAL CHARACTERISTICS OF THE GASTEMPERATURE AND PRESSURE EFFECTS
37. In a hyperbaric chamber, a flowmeter will deliver less gas than indicated. With decreased barometric pressure (increased altitude), the actual flow rate will be greater than that indicated
38. Flowmeter tubes are most accurate in the middle half of the tube. Accuracy decreases at the bottom and top. This is why separate tubes are often used for low flows
39. COMPONENTSFLOW CONTROL VALVE
40. SCHEMATIC – VALVE CLOSEDCONTROL KNOBVALVE SEATVALVE PININLET
41. SCHEMATIC – VALVE OPENINLETCONTROL KNOBVALVE SEATVALVE PIN
42. O2 CONTROL KNOB
43. FLOWMETER SUBASSEMBLYTUBESINGLE- TAPEREDDUAL / DOUBLE TAPERED
44. SINGLE -TAPEREDDOUBLE -TAPERED
45. FLOWMETER SUBASSEMBLYINDICATORROTATINGNONROTATING
46. Types of bobbinsNon rotatingPlumb BobSkirtedH - TypeBall - float
47. Where to read ?
48. FLOWMETER SUBASSEMBLYSTOPSCALEPLASTIC SHIELDLIGHTSON – OFF SWITCH
49. ARRANGEMENT OF FLOWMETER TUBESPARALLELSERIES / TANDEM
50. Series Skirted float indicators. Note the stops at the top of the fl ow indicator tubes. The flow indicator tubes are in series. The total flow is that shown on the higher flow tube, not the sum of the two tubes.
51. Auxiliary flow meter Upto ten litres Need not be switched on !!
52. Danger The common gas outlet should not be used to administer supplemental oxygen to a patient. This will delay conversion to the breathing system if an emergency arises. Another potential problem is that a vaporizer on the back bar may be accidentally left ON, leading to undesired administration of the agent.
53. SEQUENCE OF FLOWTUBESA,B- Oxygen upstream C,D- Oxygen downstream E – Alternative arrangementO2AIRN20E
54. PIN- INDEXING OF FLOWTUBES
55. SAFETY DEVICESCONTROL KNOBSARRANGEMENT OF FLOWMETERSMISCELLANEOUS ( dots / two colours; fluorescent screen / lights; plastic screen; protective bar; pin- indexing; downstream flow resistor)CO2 FLOWMETERALARMS
56. at low (laminar) flows, the flow rates of gases with similar viscosities would beread identically (eg, oxygen and helium have viscosities of 202 and 194 micropoise, respectively) at high flows gases of similar densities (eg, N2O and carbon dioxide, both of which have a molecular weight of 44 atomic mass units) would be read identically.
57. PROBLEMSINACCURACYPROBLEMS WITH FLOATSOBSTRUCTIONLEAKS( Tubes are leak free because of neoprene washers at both ends )
58. Dangers Sudden rise may cause to stuck it works like an assemblyClean – service engineer But one at a time Don’t screw the control knob very tightFeel the knob -- See the knob Static electricity – stuck and croxtine spray
59. MAINTENANCE & CARETHANK YOU