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PUMPS, VALVES, & FANS

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... poor throttling Gate Valve Stop Valves Butterfly Valves Used in water, fuel, and ventilation systems Adv: small, light-weight, & quick-acting Disadv: ... – PowerPoint PPT presentation

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Title: PUMPS, VALVES, & FANS


1
PUMPS, VALVES, FANS
Moving fluids
2
Objectives
  • Comprehend the basic construction and application
    of valves used
  • Comprehend the basic operation and application of
    different pumps
  • Know Bernoullis principle, the concept of
    pressure, Net Positive Suction Head
  • Be familiar with operation and application of
    centrifugal axial fans

3
Valves
  • Defn devices which control the amount and
    direction of fluid flow in piping systems
  • Typically made of bronze, brass, iron, or steel
    alloy
  • Components
  • - Valve body - Packing - Disc - Packing
    gland/nut
  • - Seat - Stem - Bonnet - Wheel

4
Types of Valves
  • Two basic groups
  • Stop valves - used to shut off or partially shut
    off the flow of fluid ( ex globe, gate, plug,
    needle, butterfly)
  • Check Valves - used to permit flow in only one
    direction (ex ball-check, swing-check,
    lift-check)
  • Special types
  • Relief valves
  • Pressure-reducing valves
  • Remote-operated valves

5
Stop Valves
  • Globe Valves
  • Most common type of stop valve
  • Used in steam, air, water, oil lines
  • Disc attached to valve stem rests against seat to
    shut off flow of fluid
  • Adv Used for throttling
  • Disadv flow resistance

6
Globe Valve
7
Stop Valves
  • Gate Valves
  • Used when there must be straight-line flow of
    fluid w/ min. resistance
  • Gate usually wedge-shaped or a vertical disc
  • Adv No flow restrictions
  • Disadv poor throttling

8
Gate Valve
9
Stop Valves
  • Butterfly Valves
  • Used in water, fuel, and ventilation systems
  • Adv small, light-weight, quick-acting
  • Disadv leaks early only low-flow throttle
  • Ball Valves
  • Similar to butterfly valves
  • Normally found in seawater, sanitary, trim and
    drain, and hydraulic systems

10
Butterfly Valve
11
Check Valves
  • Controls direction of flow
  • Operated by flow of fluid in pipe
  • Types
  • Swing check - disc moves through an arc
  • Lift check - disc moves up and down
  • Ball check - ball is located at end of stem and
    lifts to allow flow

12
Swing-check Valve
13
Relief Valves
  • Used to protect piping system from excessive
    pressure
  • Opens automatically when fluid pressure becomes
    too high (pressure acts against spring pressure)
  • Relieving pressure set by an adjusting screw

14
Pressure-reducing Valves
  • Used to automatically provide a steady, lower
    pressure to a system from a higher pressure
    source
  • Used in air, lube-oil, seawater, and other systems

15
Remote-operated Valves
  • Valves that allow operation from distant stations
  • Types
  • Mechanical - uses reach rods and gears
  • Hydraulic - uses fluid and piston set up
  • Motor - uses and electric or pneumatic motor
  • Solenoid - uses coil and core mechanism to open
    or close on an electric signal

16
Pumps
17
Pumps
  • Defn device that uses and external power source
    to apply force to a fluid in order to move it
    from one place to another
  • Must overcome
  • (1) frictional forces from large quantities of
    fluid
  • (2) difference in static pressure between two
    locations
  • Must provide any velocity desired

18
Pumps Bernoullis Theorem
  • Pressure head measure of fluids mech. PE
  • Velocity head measure of fluids mech. KE
  • Friction head measure of energy lost that heats
    fluid
  • Z1 P1/r V12/2g Z2 P2/r V22/2g (U2
    U1) W Q
  • q wshaft (h2 h1) (v22 v12)/2 g(z2
    z1)
  • Z/z fluid height P fluid pressure r fluid
    density
  • V/v fluid velocity U internal energy W/w work
  • Q/q heat transferred h enthalpy g grav.
    acceleration
  • BOTTOM LINE Total energy within the control
    volume is constant under SS conditions.

19
Components of Pumps
  • Drive mechanism (steam, electric, gear)
  • Pump shaft
  • Impeller or piston
  • Casing

20
Types of Pumps
  • Positive Displacement
  • Fixed volume of fluid is displaced during each
    cycle regardless of static head/pressure pumping
    against
  • Uses either a piston, gear, or screw type
    (reciprocating, rotary gear, rotary screw, etc)

21
Positive Displacement Pump
22
Pumps
  • Non-positive Displacement volume of fluid is
    dependent on static head/pressure
  • Centrifugal impeller inside a case (called
    volute). Impeller is a disc w/ curved vanes
    mounted radially (like a paddle wheel)
  • Suction is the Eye -gt fluid accelerated as it
    travels outward then enters volute
  • Propeller uses prop inside casing to move fluid
    -gt not used much in Navy

23
Centrifugal Pump
24
Pumps
  • Jet pumps
  • Bernoullis principle and no moving parts
  • Velocity Head vs. Pressure head

hin vin2/2 hout vout2/2
25
Jet Pump
  • Types
  • Eductor - used to pump liquids
  • Ejector - used to pump gases

26
Pump Characteristic Curves
  • Pump Parameters
  • N pump speed, RPM
  • V volumetric flow rate, GPM
  • Hp pump head (discharge pressure), psig
  • P power required, Hp
  • Centrifugal Pump Laws
  • V a N
  • Hp a N2
  • W a N3

27
Positive Displacement Pumps
N1
N2
N2 ____
Hp
GPM
28
Centrifugal Pumps
  • Parallel Pumps

V2 ____ Hp2 ____
Hp
2 Pumps
1 Pump
GPM
29
Centrifugal Pumps
  • Series pumps (called staging)

V2 ____ Hp2 ____
Hp
2 Pumps
1 Pump
GPM
30
Net Positive Suction Head
  • Defn that pressure required at the suction of a
    pump to prevent cavitation
  • So what is cavitation?
  • - the formation of bubbles due to low
    pressure area and the subsequent collapse upon
    migration to a high pressure area
  • Cavitation causes noise and damage

31
Net Positive Suction Head
  • Need enough pressure on the suction side so that
    the pump does not reduce pressure _at_ the eye to
    cause P lt Psat
  • If P lt Psat, water flashes to vapor causing
    damage to the pump
  • What are possible means of providing NPSH to
    prevent cavitation?

32
Fans
  • Same Principle as Non-positive displacement pumps
  • Types
  • Centrifugal majority used for compressors
  • Axial (like propeller) cooling fans

33
Fans
34
Questions?
Questions?
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