Spectra Ventura 200T Low Flow

[MeiWenti]

We have a seven year old Spectra Ventura 200T (manual not automated) which has been used exclusively in the tropics. It has not been heavily used, probably spending 90% of that time pickled. It has performed well but on our current cruise we have noticed that the production rate is down and feed pressure is high. We have just cleaned/replaced the inlet strainer and prefilter and carried out a flow test. These are the results:

Feed pressure 88-95 psi over a cycle (should be 70-80)
Measured product flow 28 litres per hour (should be 33)
Measure reject brine flow 266 litres per hour (should be 310)
Product salinity 300 ppm (used to be 180-200)

Product ratio to feed = 28/(28+266) = 9.5% which is correct for the 200T so it looks like the Clark pump is fine.

As the feed pressure is high, it seems that the Shurflow feed pump is OK too.

Reading the Spectra literature, high pressure plus low feed flow is probably down to a biofouled membrane and that we should clean with SC-3.

Before we do this, has anybody any other ideas?

[Blackie Swart]

Hi

There's some good info from Don Wilson on Spectra that I've found very helpful

http://www.thetwocaptains.com/engine...er_OpNotes.pdf

(Hope the link works otherwise google it)

Cheers

[MeiWenti]

Thanks, Blackie. Don's notes are very good and support the view that high pressure and low flow are idue to a restriction after the feed pump, which could be prefilter (changed for new just before the flow test), a kink or other blockage in the hoses (can't find anything wrong) or the membrane itself. So I am still leaning toward cleaning with SC-3 but as any chemical cleaning ultimately reduces the life of the membrane, so I don't want to clean unnecessarily.