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