Matakuliah
Tahun
Versi
: S0634/Hidrologi dan Sumber Daya Air
: 2006
: <<versi/revisi>>
Pertemuan 21
Pompa
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Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Mahasiswa dapat menghubungkan antara aliran dalam
pipa dan jaringannya yang menggunakan sistem pompa
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Outline Materi
• Materi 1: Sistem Pompa
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Pompa
Daya dari suatu pompa
Daya = kilowatt = T = γQh(satuan internasioanal)
Q= debit , h= tinggi hisap bersih
Specipic speed
Pump performance parameters (vary from to pump)
•Rotational speed
•Discharge capacity
•Pumping head
•Power applied
•Efficiency
Kombinasi dari 3 parameter diatas merupakan kecepatan spesifik
•Specific speed is the same for geometrically similar pumps (homologous)
Ns= NQ0,5/H3/4,Ns = kecepatan spesifik, N=kecepatan putaran (rpm), H=tinggi total
Nilai kecepatan spesifik daapat berubah dibawah kondisi operasi. For classification
we use the specific speed at maximum efficiency
Features of specific speed:
•Efficiency drops for Ns < 1000
•Efficiency is low for Ns > 5000
•Efficiency is high for medium range Ns
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Geometrically simillar pumps
•
•
•
•
•
•
•
•
Q2 /Q1 = (N2/N1) (D2/D1)2
H2 /H1 = (N2/N1)2 (D2/D1)2
P2 /P1 = (N2/N1)3 (D2/D1)5
Q=kapasitas
H=Tinggi
D=diameter
N=Kecepatan putaran
P= Daya
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Istilah tinggi dalam pompa
• Tinggi isap statis (static suction lift) : Jarak vertikal dari
muka air dalam tanki air sampai pusat pompa.
• Tinggi debit statis (static discharge head) : Jarak vertikal
dari pusat pompa sampai muka air tanki keluar
(discharge tank)
• Total static head: sum of total static suction lift and static
discharge head
• Total dinamic head: sum of total static head and friction
and minor losses:
• Hp = Δz + hloss
• Hp = Δz + f(L/D)(V2/2g) + ΣK(V2/2g)
• Hp = Δz + (0.81/g){(fLQ2/D5 )+ΣK(Q2/D4 )}
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Pump characteristic curves
Derived from actual test (pump factory):
• Pumping Head vs. Discharge
• Brake HorsePower vs. Discharge
• Efficiency vs. Discharge
Curve shape varies with pump size, speed,design.
Increase in head reuces capacity.
There is capacity where efficiency is MAX
There is capacity where HP is MAX
•
γQH
• HP=--------•
550h
• Q(cfs)
• H(ft)
• γ =62,4
• h =efficiency
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Single pump and pipeline system
• SUITABILITY OF PUMP:Superimpose
System Head Curve (Piping System) on
the Head-Capacity Curve (pump).
• Intersectin is operating point.
• Check efficiency at this point. If too low
consider another pump
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Multiple pump system
• Single pump: Suitable for narrow range of
head and discharge.
• Multiple pumps: Fluctuations of operating
conditions are considerable or Head or
Capacity requirement is too high for a
single pump.
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PUMPS IN SERIES VERSUS PUMPS IN
PARALLEL
SERIES
PARALLEL
Pump in series: Substantial head
change take place, not much
difference in discharge
Pump in parallel: Conciderable
discharge variations but not
appreciable Head change.
H= (HA + HB + ….)
Q=QA=QB= ……
H= HA = HB = ….)
Q=(QA+QB+ ……)
HA + HB +
h= -------------HA/ hA + HB/ hB +
γQ(HA + HB + ….)
QA + Q B +
h= -------------QA/ h A + QB/ h B +
γH(QA + QB + ….)
P=---------------------550h
P=---------------------550h
Composite head curve: Add ordinates
of individual head curves for same
value of discharge
Composite head curve: Sum up the
abscisas (discharge) of all pumps for
10
same value of Head
<< CLOSING>>
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