Danfoss iSave 21, Руководство пользователя

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User manual iSave 21
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180R9221 / 521B1174 / DKCFN.PS.003.A1.02
5.7.2 Booster pump
The booster pump is a positive displacement pump, which means that the flow is controlled
by the speed of the electric motor; e.g. if the rotation speed of the electric motor is raised by
10%, the flow will be 10% higher and vice versa. The required rpm can be calculated based
on the “rated flow” of the particular iSave. See datasheet in appendix 10.3.
At low speeds you may hear some minor clicking sounds from the pump. This is normal and
is caused by the pins in the vane pump.
5.7.3 Lubrication flow
To lubricate the moving parts in the pressure exchanger there is a well defined leak be-
tween the port plates and the rotor, as well as in the high pressure bearing between the
pressure exchanger and the booster pump. This leak is typically called “lubricating flow”.
The leaks go from the high pressure side to the low pressure side of the pressure exchanger,
and from the booster pump to the low pressure side of the pressure exchanger.
5.7.4 Mixing
There is no physical barrier in the ducts between the concentrate and seawater. This means
that there will be a small amount of mixing between the two liquids. Because the two liq-
uids are in contact for a short amount of time, the mixing is relatively low.
On the RO market the mixing rate is defined as “balanced flow” when HP-in is equal to LP-in.
Experience from the market shows that the corresponding increase in membrane operating
pressure is about 1 bar.
The customer can reduce mixing by over-flushing the LP feed with excess feed water. See
figure below. Over-flushing means energy loss. Optimal over-flushing is obtained when the
energy loss on LP feed is equal to or less than the energy loss caused by the excess pressure
at the membrane.
5.7.5 How does the iSave work in an RO system?
The figure below illustrates a typical Flow Path of an SWRO or BWRO with an iSave.