Metering Pumps
Check the settings of both “stroke speed＂ and “stroke length＂, one of them may be set to the minimum.
Both of them may be adjusted clockwise to a higher value, and the pump will function normally.
Air chamber capacity(L) = Coefficient / Pulsation rate(%) x Stroke capacity(L/stroke) x Working pressure of air chamber(MPa)
* Cofficient : 5.5 (Simplex type)
2.2 (Duplex type)
1.1 (Triplex type)
* Pulsation rate : Normally 10% or 5%
* Working pressure = Feed point pressure + Piping resistance + Throttle resistance(0.1~0.2MPa)
It is necessary to take the inertial resistance caused by pulsation into consideration.
There is no need to apply the safety factory, however, it is essential to keep NPSHa > NPSHr.
NPSHa = (Pa – Pv) ± Phs – Pis (or Pfs, whichever is larger)
** Pa : Absolute pressure on liquid surface at suction side (0.1013 MPa for atmospheric pressure)
Pv : Vapor pressure of liquid temperature at suction side (MPa)
Phs : Converted suction pressure(MPa) = Height from the lowest liquid surface at suction side (m) x 0.0098 x S.G.
+ for flooded suction
- for lift suction
Pis : Inertial resistance at suction side (Mpa)
Pfs : Pipe resistance at suction side (MPa)
