about pumps, valves, & fans by deva

ENGINEERING LESSON GUIDE 4

PUMPS, VALVES, AND FANS

VALVES

TYPES OF VALVES

Globe valves - common type of stop valve– the disk seats on the seating ring– commonly used in, steam, air, water, and

oil lines– also used as throttle valves

TYPES OF VALVES

Gate valve - used for straight line flow and when minimum flow restriction are needed– not used for throttling– rising stem or nonrising stem– steam systems have flexible gates

TYPES OF VALVES

Butterfly valve - light weight, relatively small and quick-acting– has a body, resilient seat, butterfly disk, a

stem, packing, a notched position plate, and a handle

– very versatile - can be used for fresh water, salt water, JP-5, lube-oil, and chill water systems

Relief Valve

VALVE OPERATING DEVICES

Manual

Hydraulic

Motor (electric or air operated)

Solenoid

PUMPS

PUMP COMPONENTS

Drive– Steam, electric, or gear

Pump Shaft Impeller or Piston Casing

PUMP TYPES CENTRIFUGAL

– Single Stage– Multi-staged centrifugal pumps

POSITIVE DISPLACEMENT– Reciprocating– Rotary Gear– Screw– Moving vane

JET PUMP– Eductor– Ejector

POSITIVE DISPLACEMENT PUMP

Fixed Volume Volumetric Flow rate is

proportional to speed of the pump A relief valve will always be on the

discharge end of the pump

EXAMPLES

PRESSURE HEAD(Hp = ft lbf/ lbm)

CAPACITY(V=GPM)

N1 N2

ActualIdeal

Reciprocating PumpCharacteristic Curve

NON-POSITIVE DISPLACEMENT PUMPS

BERNOULLI’S THEOREM

Z1 + P1/D + 1/2(V12/g) =Z2 +P2/D +

1/2(V22/g) + gc/g(wk) + HL

Where: Z : Elevation (ft) P : Pressure (lbs/ft2) D : Density (lb/ft3) V : Velocity (ft/sec) g : acceleration (32.2 ft/sec2)

wk: work (ft-lbs) HL: Head Loss = f(L/D)(V2/2Zg) where f : friction factor L: Length D: Diameter

BERNOULLI’S PRINCIPLE

Basically: as the velocity (speed) of a fluid increases, its pressure decreases, and visa versa

PUMPS

Net Positive Suction Head: that pressure required at the suction of a pump to prevent cavitation.– cavitation: the formation of bubbles due to

area where P < PSAT, and the subsequent collapse of those bubbles.

• causes noise and damage due to erosion and fatigue failure.

PressureHead

V = GPM.

HP =(ft lbf)/ lbm

V NHp N2

Pw N3

. Where V = volumetric flow rate N = Speed of rotation Hp= Pump Head (discharge pressure Pw= Power required (prime mover)

N2 = 2N1

Characteristic curve for centrifugal pump

N1

N2

PUMPS

– Centrifugal:• Parallel pumps:

1 pump

2 pumpsHP

VGPM

V2 = 2V1

HP2 = HP1

PUMPS

• Series (called staging):

HP

VGPM

1 pump

2 pumps

Fans

Same Principle as Non-positive displacement pumps

Types:– Centrifugal: majority used for compressors– Axial (like propeller): cooling fans

QUESTIONS