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Flow Meters / Rotameter
Flow meters: Alat yang digunakan untukmengukur laju alir gas atau cairan
Flow: Volume cairan yang melewati titik
tertentu dalam waktu tertentuFlow Rate.
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FLOW
Laju Alir dipengaruhi oleh viskositas dandensitas.
Pada saat aliran rendah: Viskositas
Pada saat aliran tinggi: Densitas.
So,each type of gas requires diff.
calibrated flow tube. The flow tubes designed for one gas
should not be interchanged with anotherhypoxic mixtures.
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Flow tube :Conical glass tube.
Low flow tube graduated/100
ml/min. up to one liter High flow tube
graduated/1L/min.up to 10L/min.
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Control knob :when it is turnedneedle valve is opened.
Gas flows into the bottom of the flow tube& moves upward around the bobbinupward force pushes the bobbin up in the
tube .
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Float (bobbin)
It may be balls or cylindrical with slots inits upper part & tapered base to make it
to rotate in the gas stream . Non spinning bobbin that may indicate O2
is flowing while the bobbin is stucked with
no adequate flow hypoxic mixture.
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Peralatan rotameter
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The density of a gas is dependent on theambient pr .
Large diff. in atmosph. Pr. alter the calibrat.offlow tube .
At high altitudes with hypobaric condit.Flow meter setting is less than the actual
At hyperbaric condition flow setting is more thanthe actual hypoxic mixture
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The spinning movement of the bobbin can beaffected by dust , dirt & static electric charges .
Static charges can be dealt with by bimetallicstrip .
Dirts & dusts by air filter proximal to the needlevalve.
Slots on the bobbin to spin resist the effect ofstatic charges & dust.
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The twist required to turn the knobs mustbe sufficient to prevent accidental
readjustment from casual knock . If axial push _ pull forces are applied to
the needle valve spindle the flow change
must not exceed 10% .
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In modern anesth. ,there is interconnect. OfN2O & O2 flowmeters to ensure delivery of aconc.of at least 25% O2 .
There are 2 systems :-1. Pneumatic syst. ORMC (designed by
Drager).
2. Chain _link 25 proportion (by Ohmeda )
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1. The flow tube for oxygen has been on theextreme rt. Side O2 is the last gas to beadded to the fresh gas supply.
2. A color _coded flow control knob is locatedunder its respective flow tube.
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3. A color_coded cylinder pr. gauge for the gasentering the flowmeter & located under itsrespective flowmeter.
4.
A plastic screen used to prevent damage to theflowmeters.
5. In some machines , protective bar placedinfront of the flow meters to protect from
accidental bumping.
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6. Lighting system for the flow meter is valuablewhen the op.room light is dimmed .
7. Flow tube pin _indexing syst. to prevent
interchange of flow meter units hypoxicmixture.
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O2 flow can not be completely turned off. Aminimum flow rate of 200_450 ml/min isdelivered to provide sufficient O2 for the basalmetabolic needs by :
1. Applicat. Of resistor in the oxygen pipeline.
2. OR/stop screw on O2 control valve.
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The control knob of O2 has esp. shape:
Octagonal
Greater diameter
Project beyond the other knobs
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1. Electronic flow meter
a. Oscillations of pr. Drop across an orifice isproportional to the flow rate
b. Thermister flow meter :
Gas flow affects thermocouple attached to eitherend of flow tube
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2. Coxter flow meter
3. Bubble flow meter
4. Rotor meter Wrights spirometer
5. Pneumotachographs (Vitalograph)
6. Ultrasonic flowmeters
7. Electronic magnetic flowmeter
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