1 Pertemuan 21 Pompa Matakuliah: S0634/Hidrologi dan Sumber Daya Air Tahun: 2006 Versi: >

2 Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : Mahasiswa dapat menghubungkan antara aliran dalam pipa dan jaringannya yang menggunakan sistem pompa

3 Outline Materi Materi 1: Sistem Pompa

4 Pompa Daya dari suatu pompa Daya = kilowatt = T  = γ Qh(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) N s = NQ 0,5 /H 3/4,N s = 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 N s < 1000 Efficiency is low for N s > 5000 Efficiency is high for medium range N s

5 Geometrically simillar pumps Q 2 /Q 1 = (N 2 /N 1 ) (D 2 /D 1 ) 2 H 2 /H 1 = (N 2 /N 1 ) 2 (D 2 /D 1 ) 2 P 2 /P 1 = (N 2 /N 1 ) 3 (D 2 /D 1 ) 5 Q=kapasitas H=Tinggi D=diameter N=Kecepatan putaran P= Daya

6 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: H p = Δz + h loss H p = Δz + f(L/D)(V 2 /2g) + ΣK(V 2 /2g) H p = Δz + (0.81/g){(fLQ 2 /D 5 )+ΣK(Q 2 /D 4 )}

7 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 γ QH HP= h Q(cfs) H(ft) γ =62,4 h =efficiency

8 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

9 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.

10 PUMPS IN SERIES VERSUS PUMPS IN PARALLEL SERIESPARALLEL 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= (H A + H B + ….) Q=Q A =Q B = …… H A + H B + h = H A / h A + H B / h B + γ Q (H A + H B + ….) P= h H= H A = H B = ….) Q=(Q A +Q B + ……) Q A + Q B + h = Q A / h A + Q B / h B + γ H (Q A + Q B + ….) P= h 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 same value of Head

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