Different Types Of Flowmeters Flashcards
Is a thin disk placed in the path of fluid flow with a sharp-edged opening in it.
Orifice Plate
Oriface plates are typically sandwiched between ____ of a pipe joint, allowing form easy installation and removal.
Two flanges
T or F. The precise location of the vena contracta for an orifice plate installation will vary with flow rate.
True
The simplest design of orifice plate is the
Square-edged, concentric orifice
T or F. Square-edged orifice plates may be installed in either direction, since the orifice plate “appears” exactly the same from either direction
True
If the orifice place is relatively thick, it may be necessary to bevel the downstream side of the hole to further minimize contact with the fluid stream.
Square-edged Concentric orifice plate with downstream bevel
Hole is located off-center to allow the undesired portions of the fluid to pass the orifice rather build up on the upstream face
Square-edged, eccentric orifice plate
Hole is not circular but rather just a segment of a concentric circle
Segmental Orifice Plate
An alternative to offsetting or re-shaping the bore hole of an orifice plate is to simply drill a small hole near the edge of the plate
Orifice plate with Vent and drain holes
Looks like a beveled square-edge orifice plate installed backwards, with flow entering the conical side and exiting the square-edged side
Conical Entrance Orifice Plate with upstream bevel
Flanges may be manufuctured with tap holes pre-drilled and finished before the flange is even welded to the pipe, making this very convenient pressure tap configuration
Flanges Taps
Offer the greatest differential pressure for any given flow rate, but require precise calculations to properly locate the downstream tap position
Vena Contracta Taps
Are an approximation of vena contracta taps for large pipe sizes (one-half pipe diameter downstream for the low-pressure tap location)
Radius Taps
Must be used on small pipe diameters where the vena contracta is close to the downstream face of the orifice plate that a downstream flange tap would sense pressure in the highly turbulent region (too far downstream)
Corner Taps
(Also known as full flow tap) standard calls for a downstream tap location eight diameters away from the orifice: to give the flow stream room to stabilize for more consistent pressure readings
Pipe taps or full flow taps
Design for flow measurement consist of cylindrical probe inserted into the process pipe. The probe is bent at 90 degrees angle so that it points toward the source of fluid flow, parallel to the pipe wall
Pitot Tube
Also known as Annubars, are also available, with designs that include several measurement ports over the entire diameter of the pipeline. The annubar port design yields a much more accurate flow measurement than the regular pitot tube.
Averaging Pitot Tube
T or F. An annubar is an averaging pitot tube consolidating high and low pressure sensing ports in a single probe assembly
T
Are inserted in the process pipe to create a wedge obstruction on the inner wall of the pipe. A differencial pressure is created as the fluid flows past the obstruction
Wedge Flow Element
Is a high-accuracy, normally lab-calibrated flow meter, For customers who have room for straight-piping requirements .
V-cone
Useful because it works equally well both with short and with long straight pipe requirements
V-cone
When a venturi flow meter is placed in a pipe carrying the fluid whose flow rate is to be measured, a pressure drop occurs between the entrance and throat of the venturi meter.
Venturi Tube
Place in a pipe carrying whose rate of flow to be measured, the flow nozzle causes a pressure drop which varies with the flow rare
Flow nozzle
Flow nozzles consist of two main section
Eleptical inlet and Throat
Another way we may accelerate a fluid is to force it to turn a corner throught a pipe fitting called an ___.
Elbow Flow Element
Also known as variable area flowmeters, are tapered glass, plastic or metal tubes that must be mounted vertically
Rotameter
The traditional means of implementing the necessary signal characterization was to install a “_____” function relay between the transmitter and the flow indicator
Square root
Also called magmeters provide obstructionless flow measurement ant conductive process fluid
Magnetic flowmeter
Magmeters consist of two main components
Sensor
Flow transmitter
The operating principle of magmeters is based on __________, which states that a voltage will be induced in a conductor moving through a magnetic field
E= kBDV
Faraday’s Law of Induction
Is a bluff body, or shedder, placed in the fluid flow stream that causes vortices to form. The shedder acts as the primary device
Vortex flowmeter
Consist of a section of pipe that contains a multiblade rotor and a magnetic pickup coil
Turbine Flowmeter
T or F. The fundamental design of turbine flow meter is to make the turbine element as free-spinning as possible, so no torque will be required to sustain the turbine’s rotation
True
A cut-away demonstration model of a turbine flow meter. The blade sensor may be seen protruding from the top of the flow tube, just above the turbine wheel
Turbine Flowmeter
Two different methods are currently used to make this velocity
Time of flight
Doppler effect
Operate on the principle that the speed of an ultrasonic sound wave ( sound at frequency too high to be heard by the human ear ) will increase when directed with flow and decrease when directed against flow.
Time of flight Ultrasonic Flowmeter ( Clean Liquid )
T or F. The transit time meter utilizes transducers that function as both ultrasonic transmitters and receivers. The transducers are clamped on the outside of a closed pipe at a specific distance from each other.
T
Refers to the change in the frequency of sound waves. The frequency increase or decrease based on the velocity of the fluid.
Doppler Effect Ultrasonic Flowmeter
Different types of mass flowmeters
Coriolis Mass Flowmeter
Thermal Mass Flowmeter
Use a curved tube as a sensor apply Newton’s Second Law of Motion to determine the flow rate. An electromagnetic drive coil is located in the center of the bend of tube that causes the rube vibrate like a turing fork
Coriolis Mass Flowmeter (vapor bubbles, suspended particles)
The opposing forces of the dluid and the vibrating tube causes the tube to twist. The twising is referred to as the coriolis effect. T or F
T
Coriolis Mass Flowmeter. According to Newton’s Law of Motion, the angle of twist is directly proportional to the mass flow rate of the fluid flowing through the tube. T or F
T
Coriolis Mass FlowMeter. Two identical U tubes nedt to each other and shaken in complementary fashion ( always moving in opposite dierection) . T or F
T
The flow meter measures the temperature of the fluid at resistance temperature detectors (RTD’s) located upstream and downstream of the meter. The temperature variation ( change in temperature between the two points upstream and downstream of the meter ) is inversely proportional to mass flowrsre.
Thermal Mass Flowmeter
Thermal Mass Flowmeter (manufactured by sage) sense the amount of gas sent to a fare. T or F
T
Flow merer is cyclic mechanism built to pass a fixed volume of fluid through with evey cycle
Positive Displacement Meter
Is an example kf a positive displacement meter. Consist of two touching oval gears that rotate as fluid flows through them.
Oval gear meter
