Instrumentation Final Flashcards
(58 cards)
used for starting/stopping flow
used where quick operation is required
inline maintenance when needed
leak-tight service
quarter turn
body, bonnet, stem, and plug
Plug Valve
unguided as it fully opens/closes
low pressure drop/low turbulence
prevents backflow
seating and varies from 0-45 degrees
valve body, bonnet, hinged disk
Check Valve
used to stop, regulate and start flow
larger ones have gearbox type actuator, difficult to move under operating conditions
liquids, steam, cryogenics, cooling water, air gasses, firefighting, and vacuum services
rotary operation
can’t be throttled below 20-30 degrees open
types: zero offset, double offset, and triple offset
Butterfly Valve
top entry, side entry (split body), and 3-piece body
quick to open/close, bubble-tight reliable sealing in high pressure/high temperature applications
quarter turn
smaller and lighter than similar valves of same type
Ball Valve
most common
linear motion used to start/stop flow
fully open/closed
no resistance to flow
uses a flat wedge type disk that moves perpendicular to flow
Gate Valve
used with all kinds of gas/liquids
suitable for high pressure/high temperature
back pressure can effect the function
spring is subjected to corrosion
not suitable for hazardous services
body, bonnet, disk, disk holder, seat and spring
rapid pop action when opening
Pressure Relief Valve
very accurate control of flow
sliding stem valve
mostly used for throttling applications
often manually operated
used to control flow entry when sudden surges of fluid under pressure could damage the instruments
Needle Valve
low leakage when closed
commonly used for low point drains/high point vents
high percentage of pressure drop
linear actuator
noisy and require a strong actuator on larger valves
heavy
Globe Valve
sliding stem valve
slurry applications
can be used where corrosion or metal contamination of the fluid might be a problem
no internal moving parts in contact with fluid
sealing surface consists of two rubber/synthetic surfaces that close on each other
Pinch Valve
the ratio between the inertial forces moving liquid and viscous forces resisting that movement (laminar or turbulent)
commonly range from 100-1,000,000
Reynold’s Number
smooth fluid flow that has a flow profile that is parabolic in shape with no mixing between the streamlines
Reynold’s number below 2100
Laminar Flow
fluid flow in which the flow profile is a flattened parabola, the streamlines are not present, and the fluid is freely intermixing
Reynold’s number above 4000
Turbulent Flow
the ratio of the density of a fluid to the density of a reference fluid
Specific Gravity
the quantity of fluid passing a point at a particular moment
Flow Rate
the quantity of fluid that passes a point during a specific time interval
Total Flow
a primary flow element consisting of a fabricated pipe section with a converging inlet section, a straight throat, and a diverging outlet section
Venturi Tube
a primary flow element consisting of a thin circular metal plate with a sharp-edged round hole in it and a tab that protrudes from the flanges
Orifice Plate
the ratio of the maximum flow to the minimum measurable flow at the desired measurement accuracy
aka rangeability
Turndown Ratio
a variable-area flowmeter consisting of a tapered rube and a float with a fixed diameter
aka bubbler
Rotameter
a flowmeter that admits fluid into a chamber of known volume and then discharges it
commonly used for measuring total flow in homes and factories
Positive-Displacement Flowmeter
a flowmeter consisting of turbine blades mounted on a wheel that measures the velocity of a liquid stream by counting the pulses produced by the blades as they pass an electromagnetic pickup
Turbine Meter
an open-channel flow measurement device consisting of a flat plate that has a notch cut into the top edge and is placed vertically in a flow channel
Weir
a special form of open-channel flow element that has a horizontal configuration similar to a venturi tube, with converging inlet walls, a parallel throat, and diverging outlet walls
less channel elevation changes than a weir
Parshall Flume
an electrical flowmeter consisting of a pipe section with a symmetrical vertical buff body (a partial dam) across the flowing stream
Vortex Shedding Meter
