Pumps and Valves Flashcards
What are the most common types of valves?
Control
Pressure Relief
On-off
Check
On-off valves are used for stopping the _____.
Flow
On-off valves provide _____ _____ when being closed.
tight shutoff
On-off valves provide _____ _____ _____ when fully opened
low pressure drops
Most control valves can be used for on-off duty, especially ____ valves
ball
_____ valves are often used in of-off service
gate
Check valves prevent the _____ of flow
reversal
Check valves ____ with forward flow and _____ against reverse flow
open;close
What are three types of check valves?
lift check
swing check
tilting-disk check
Lift check valves depend on _____ for operation
gravity
Lift check work with ______ pressure services
high
Swing check valves have a closure member that swings about a _______
hinge
Swing check valves are employed along with ____ valves
gate
Swing check valves work with ____ fluid velocities
low
With Swing Check valves flow reversal is _________
infrequent
Tilting-disk check valves have a closure member that rotates about a point between the ______ and the edge of the disc.
center
Tilting-disk check valves are _______ loaded
spring
Tilting-disk check valves are more _________
expensive
Tilting-disk check valves are more difficult to _____.
repair
control valves are used to ______ the flow automatically to any desired amount
regulate
control valves help with ____ pressure drops
high
Name four different control valves.
globe
ball
butterfly
plug
Globe valves have a _____ stem motion
linear
Globe valves have significant pressure ____
drops
globe valves _____ the flow
control
globe valves are good at servicing fluids containing no ____
solids
ball valves have ______ stem motion
rotary
ball valves have _____ friction
small
ball valves have a ____ pressure drop
small
ball valves have ____ flow capacity
high
ball valves provide a ______ shutoff
tight
ball valves are well suited for _____ ____ service
on-off
ball valves are not good for _______ services
throttling
butterfly valves have _____ stem motion
rotary
butterfly valves have ____ pressure drop
small
butterfly valves can handle ______ flow capacity
large
butterfly valves provide good service with fluids with or without ______.
solids
Butterfly valves can or cannot handle on-off duty?
can
butterfly valves can or cannot handle throttling duty?
can
Plug Valves have _____ stem motion
rotary
plug valves provide a _____ shutoff
tight
______ plug valves can be used to simplify the piping system
multiport
Plug valves are well suited for ____ ____ service
on-off
What happens to temperature when mu jt is postitive
decreases
what happens to temperature when mu jt is negative
increases
pressure relief valves operate at pressures below _____
10,000 psia
Pressure relief valves operate at temperatures below ____
1,000 F
What are two types of pressure relief valves
direct-loaded
pilot operated
A positive displacement pump can be what kind?
rotary
reciprocating (pistons)
miscellaneous (peristaltic)
What are the advantages of a positive displacement pump?
self-priming
can work in two directions
can pump liquids with gases for a small amount of time
What are the disadvantages of positive displacement pumps?
most of them cannot operate with closed discharge
might produce oscillations in discharge
Peristaltic Pump is used to move tank to _____
tank
Peristaltic pumps are used in what industries?
food, batch, paper
What are some types of centrifugal pumps?
volute (shell and simple impeller)
diffuser (diffuser vanes around the impeller)
turbine pump
propeller pump
what are some advantages of centrifugal pumps?
low cost - easy maintenance do not produce a lot of noise uniform discharge (no oscillations)
What are some disadvantages of centrifugal pumps?
do not produce large heads (cannot increase pressure a lot)
do not work well with high viscosity fluids
You can change the _____ size to modify centrifugal pumps
impeller
If Hs = Hp, pick the Hs curve close to ______ open, at maximum flow
80%
Where the Pump Curve and System Curve intersect there is _____ pressure drop and the valve cannot control flow
0
The head Hs goes up as you _____ the valve
close
Hs =
-[(P4-P3)+(P2-P1)]
As the Reynold’s number increases, the _____ losses decrease
friction
To increase the pressure head, you can ____ the level of the fluid
raise
efficiencies are ______ of the impeller
independent
You can select the ______ _____ when selecting a pump.
Impeller diameter
When selecting a pump you should look at maximum efficiency and that NPSHA ______NPSHR
>
A large impeller size ______ the pressure drop
increases
Centrifugal pumps are chose because they can operate in a wider range of what?
flowrates
Using a positive displacement pump uses more _____ and ______ the fluid.
energy; heats
What kind of pump give an approximate constant flow?
positive displacement
Ps is usually what? Suction pressure
constant
You can increase the discharge pressure by ______ the vertical distance
increasing
Why do the pump curves decrease?
Friction takes over as flow rate increases.
You can calculate the suction pressure using what?
An energy balance
The available net positive suction head must be ______ than the required net positive suction head
greater
NPSHR is a required value suggested by whom?
the manufacturer
Pumps will not cavitate if what is positive?
NPSHA
What is it called when pressure increases inside the pump causing bubbles to collapse?
cavitation
Cavitation reduces _____ and _____ the pump
capacity; damages
NPSHA =
(Ps/rho gravity) - (Pv/ rho gravity)
We want Ps to be _____ than Pv
greater
If NPSHA is negative the fluid enters the pumps with what?
bubbles
Total dynamic Head =
Pd-Ps
Hydraulic horsepower W =
(Q*TDH (psi))/(rho gravity)
shaft efficiency, aeta =
Wh/Wb
saft efficiency is always less than 1 because of what?
friction losses that transform irreversibly to heat
Mechanical Energy Balance is defined as what?
Static pressure plus pressure change plus acceleration is equal to the change of work done - friction losses
What has rotating gears, lobes, or screws?
Rotary pumps
Centrifugal pumps do not have large what?
Pressure heads
Total Dynamic head of a pump is what?
The discharge pressure minus the suction pressure
What is the hydraulic power of a pump equal to?
Volumetric flow rate times total dynamic head
NPHSA is the difference between what?
The suction head and the vapor pressure head
NPHSR is provide by what?
The manufacturer
NPHSR has to be smaller than what?
NPHSA
Two equal pumps in a series have what?
Double the head
Two equal pumps in parallel have a smaller head than what?
One pump
If NPHSA is zero what can happen?
The pump can cavitation
What is the function of check valves?
To prevent the reversal of flow
Gate valves are not usually used for what?
Control
Control valves have what kind of pressure drops?
Large
Closing a control valve increases what?
The pressure drop of the system
What kind of inherent flow characteristics do we want?
Linear
What type of valve has inherently linear flow characteristics?
Globe
Why do we want linear flow characteristics?
PID controllers need linear
What kind of valve is linear when installed?
Equal percentage
