sump sizing
Post on 05-Apr-2018
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Pump Sump Sizing
Dewatering Pumps
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Pump sump sizingThree functions of the sump:A volume V1 to certify the function of the pump/s
Prevent snoringPrevent cavitation (NPSH rec)
Cooling of the motorA working/live volume V required between start and stopA spare volume/surge capacity to take sudden inrush of water V2
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Pump cycle time
The minimum pump cycle time Tc min is determined by the number ofstarts M allowed per hour with regards to temperature rise in themotor.
For a Flygt pump the maximum numbers of starts/hour are 30.
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Pump capacity, Qp Inflow, average, Qin
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Filling phase:
Emptying (pumping) phase:
i.e.
i.e. has a minimum for
and therefore
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Example:
Qp = 40 l/s
M = 30 starts/h =>
Tc min = 3600/30 = 120 s
i.e. V min = Tc min x Qp/4
= 120 x 40/4
= 1200 l or 1,2 m3
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Clarifying / SedimentationPump sump sizing
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Clarifying / Sedimentation
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Sedimentation in water depends on:
The surface of the basin Acl (m2)
The inflow to the basin Q (m3/h)
The settling velocity of the particles - vs (m/h)
which depends on:
The size of the particles and their shape
Spec. weight of the particles
Concentration of particles (< 10 kg/m3)
Acl > Q/vs
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Calculation example:(according to graph on previous side)
Flow Q = 30 l/s or 108 m3/h
Spec.weight of the particle = 2,5 kg/dm3
Smallest particle to settle out 74 micron gives a settling velocity of 18 m/h
Clarifying surface:
Acl = Q/vS x 1,3 (safety factor)
= 108/18 x 1,3 = 7,8 m2
Clarifying / Sedimentation
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Previously
Previously
Today
Clarifying / Sedimentation
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