The standard sw30-2540 watermaker 2.5x40 membrane has been improved by
Dow and now rated at 700 gpd (29 gph) up from the old 540 ppd (22
gph). still same 800 psi.
http://www.dow.com/liquidseps/news/20030928a.htm

I'm researching building one (there was a good article in the Good Old
Boat mag Jan 2003 issue . Now I'm wondering about pumps and 120 vac hp
needed for the 700 rating as the higher permeate rating will reduce
the flow across the membrane and increase the clogging from the
reduced flow - dirty membranes being the biggest problem with under
sized raw water flow from small pumps and low hp.

That particular news release was for a new 3" series. The 2540 has
always been rated for .4 gpm but driving them at max output takes a lot
of extra detail in the design work and you have to push 4.5 gpm of
seawater through them. Keeping the product under .3 gpm is a lot safer
and more energy efficient.

I am using a pair of SW30-2540's to get 800 gpd using an engine driven
Cat 271. I gave up on trying to drive the pump with an electric motor.
It takes 2 HP to push 3.5 gpm at 850 PSI. That takes 125 amps. I
would rather let the alternator charge the batteries for an hour while I
make 35 gallons of fresh water on a separate pump.

Installing an engine drive is slightly more expensive than electric but
when you add in the larger alternator and bigger battery bank it is
actually a lot cheaper. The downside is that you are limited by the
engine RPM but with careful choice of pulley ratios you can get maximum
water output at the same time the alternator reaches its peak and still
have a reasonable cruising speed. I balanced my system atan engine RPM
of 2200. The pump will be turning 1750 and the alternator 4200. That
will give me a decent cruising speed and maximum output of water and
amps. Idling at 1600 RPM I will get 75% output and still load the
engine nicely to reduce cylinder glazing and keep the carbon blown out. .

wrote:

The standard sw30-2540 watermaker 2.5x40 membrane has been improved by
Dow and now rated at 700 gpd (29 gph) up from the old 540 ppd (22
gph). still same 800 psi.
http://www.dow.com/liquidseps/news/20030928a.htm

I'm researching building one (there was a good article in the Good Old
Boat mag Jan 2003 issue . Now I'm wondering about pumps and 120 vac hp
needed for the 700 rating as the higher permeate rating will reduce
the flow across the membrane and increase the clogging from the
reduced flow - dirty membranes being the biggest problem with under
sized raw water flow from small pumps and low hp.





--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

the 2540 page with 700 gpd is here -

http://www.dow.com/liquidseps/pc/jum...c/sw302540.htm

they've improved the line and not told the world so the mfg can clean
out old inventory - same old story

Glenn, I know you have just gone though the 'costing out' of these membranes
and pressure vessels.

I'm considering upgrading my HRO7 from it's present 8gph to it's max rated
capacity of 24gph. I can move the membranes out of the HRO unit enclosure
and bulkhead mount them so I could use the 2.5 X 40s..

I would sure appreciate it if you would share with me the cost and the
vendor..

Steve
s/v Good Intentions

I don't want an engine driven pump - I have a 6.5 kw genset and will
use 120 vac.

According to the cat spec sheet
http://www.catpumps.com/select/pdfs/PUMP/231-271.pdf

the 271/277 has max rpm of 1450 - so can't use direct drive 1725 ac
motor. Would need the 241/247 pump - max's 1725 rpm and 3.6 gpm at
that speed.



On Tue, 28 Oct 2003 16:43:12 -0500, Glenn Ashmore
wrote:

That particular news release was for a new 3" series. The 2540 has
always been rated for .4 gpm but driving them at max output takes a lot
of extra detail in the design work and you have to push 4.5 gpm of
seawater through them. Keeping the product under .3 gpm is a lot safer
and more energy efficient.

I am using a pair of SW30-2540's to get 800 gpd using an engine driven
Cat 271. I gave up on trying to drive the pump with an electric motor.
It takes 2 HP to push 3.5 gpm at 850 PSI. That takes 125 amps. I
would rather let the alternator charge the batteries for an hour while I
make 35 gallons of fresh water on a separate pump.

Installing an engine drive is slightly more expensive than electric but
when you add in the larger alternator and bigger battery bank it is
actually a lot cheaper. The downside is that you are limited by the
engine RPM but with careful choice of pulley ratios you can get maximum
water output at the same time the alternator reaches its peak and still
have a reasonable cruising speed. I balanced my system atan engine RPM
of 2200. The pump will be turning 1750 and the alternator 4200. That
will give me a decent cruising speed and maximum output of water and
amps. Idling at 1600 RPM I will get 75% output and still load the
engine nicely to reduce cylinder glazing and keep the carbon blown out. .

Sorry, got my numbers mixed up. I have the 241 not the 271. I don't
have enough room for a big genset and don't want the first mate tempted
to run the A/C all night. :-)

Baja-Mo wrote:
I don't want an engine driven pump - I have a 6.5 kw genset and will
use 120 vac.

According to the cat spec sheet
http://www.catpumps.com/select/pdfs/PUMP/231-271.pdf

the 271/277 has max rpm of 1450 - so can't use direct drive 1725 ac
motor. Would need the 241/247 pump - max's 1725 rpm and 3.6 gpm at
that speed.



On Tue, 28 Oct 2003 16:43:12 -0500, Glenn Ashmore
wrote:


That particular news release was for a new 3" series. The 2540 has
always been rated for .4 gpm but driving them at max output takes a lot
of extra detail in the design work and you have to push 4.5 gpm of
seawater through them. Keeping the product under .3 gpm is a lot safer
and more energy efficient.

I am using a pair of SW30-2540's to get 800 gpd using an engine driven
Cat 271. I gave up on trying to drive the pump with an electric motor.
It takes 2 HP to push 3.5 gpm at 850 PSI. That takes 125 amps. I
would rather let the alternator charge the batteries for an hour while I
make 35 gallons of fresh water on a separate pump.

Installing an engine drive is slightly more expensive than electric but
when you add in the larger alternator and bigger battery bank it is
actually a lot cheaper. The downside is that you are limited by the
engine RPM but with careful choice of pulley ratios you can get maximum
water output at the same time the alternator reaches its peak and still
have a reasonable cruising speed. I balanced my system atan engine RPM
of 2200. The pump will be turning 1750 and the alternator 4200. That
will give me a decent cruising speed and maximum output of water and
amps. Idling at 1600 RPM I will get 75% output and still load the
engine nicely to reduce cylinder glazing and keep the carbon blown out. .




--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Ah, I see. They raised it about 20% from .4 to .48 gpm. I will have to
update my Rosa program and see how that will effect my flow. I have
everything built but will not buy the membranes until the boat is
launched. It would have to be compatable because there are to many
systems out there tuned for the old product rate. I can see one thing
that I do need to check. I sized the diverter solenoid for .6 gpm at 5
psi. If it puts out much more the product side back pressure is going
to rise and I will have to up the pump pressure to compensate.

Baja-Mo wrote:

the 2540 page with 700 gpd is here -

http://www.dow.com/liquidseps/pc/jum...c/sw302540.htm

they've improved the line and not told the world so the mfg can clean
out old inventory - same old story



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

They say you're not allowed to have any product/permeate side back
pressure. Was prob the case on the older version as well.


On Tue, 28 Oct 2003 19:18:41 -0500, Glenn Ashmore
wrote:

Ah, I see. They raised it about 20% from .4 to .48 gpm. I will have to
update my Rosa program and see how that will effect my flow. I have
everything built but will not buy the membranes until the boat is
launched. It would have to be compatable because there are to many
systems out there tuned for the old product rate. I can see one thing
that I do need to check. I sized the diverter solenoid for .6 gpm at 5
psi. If it puts out much more the product side back pressure is going
to rise and I will have to up the pump pressure to compensate.

Baja-Mo wrote:

the 2540 page with 700 gpd is here -

http://www.dow.com/liquidseps/pc/jum...c/sw302540.htm

they've improved the line and not told the world so the mfg can clean
out old inventory - same old story

Without knowing the details on the new spec SW30-2540 I can only guess
but you will need somewhere between 2.5 and 3 gpm out of the high
pressure pump to run. 24 gph would be running the older 2540 at maximum
output so the new version might work to your advantage. If you shop
around and lie a lot (i.e. Good Intentions Marine Services, Inc ;-) )
you should be able to get an A&M pressure vessel for about $230 and the
membrane for about $160. You can reuse most of the fittings because the
ports are 1/4" on both 2.5" vessels. You will have to get new hose. I
had a fairly long run from the pump to the membranes so I went super
delux and used oversize -8 Aeroquip Teflon hose to reduce pressure drop
as much as possible. Stainless JIC fittings are expensive. My hose and
fittings cost as much as a pressure vessel but believe it or not
McMaster had the best prices.

Steve wrote:

Glenn, I know you have just gone though the 'costing out' of these membranes
and pressure vessels.

I'm considering upgrading my HRO7 from it's present 8gph to it's max rated
capacity of 24gph. I can move the membranes out of the HRO unit enclosure
and bulkhead mount them so I could use the 2.5 X 40s..

I would sure appreciate it if you would share with me the cost and the
vendor..

Steve
s/v Good Intentions



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

That is not physically possible. THe best you can do is minimize it.
It takes almost 2 psi to push half gallon a minute through the 1/4"
fitting at the end of the pressure vessel. Beyond that you have the
flow meter, diverter valve and piping. Not to mention the hose to the
tanks. About the best you can expect is 5 or 6 PSI total. High volume
commercial systems run 10 to 15 psi on the product side. The important
thing is the difference in pressure between the brine and the product
side.

wrote:

They say you're not allowed to have any product/permeate side back
pressure. Was prob the case on the older version as well.


On Tue, 28 Oct 2003 19:18:41 -0500, Glenn Ashmore
wrote:


Ah, I see. They raised it about 20% from .4 to .48 gpm. I will have to
update my Rosa program and see how that will effect my flow. I have
everything built but will not buy the membranes until the boat is
launched. It would have to be compatable because there are to many
systems out there tuned for the old product rate. I can see one thing
that I do need to check. I sized the diverter solenoid for .6 gpm at 5
psi. If it puts out much more the product side back pressure is going
to rise and I will have to up the pump pressure to compensate.

Baja-Mo wrote:


the 2540 page with 700 gpd is here -

http://www.dow.com/liquidseps/pc/jum...c/sw302540.htm

they've improved the line and not told the world so the mfg can clean
out old inventory - same old story





--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com