On Fri, 09 Jan 2004 00:59:52 GMT, Brian Whatcott
wrote:

On Thu, 08 Jan 2004 05:54:34 GMT, (Steven
Shelikoff) wrote:

On Thu, 08 Jan 2004 02:51:46 GMT, Rich Hampel
wrote:

NOPE!
In pressure mode, the filter will also act as a 'coalescer' (bringing
similar surface tension fluids together to make larger and larger sized
particles) and such particles will settle out into a 'drop-out-pot'
..... or usually into the bottom of the filter bowl (bowl pointing
downwards). ///

All this begs the question, why does the filter media care whether it's
in "pressure" mode or "vacuum" mode? Sure, the plumbing and filter
cases care. But the media only sees a pressure differential across it.
What's the difference to the media if the there is 14psi (atmospheric
pressure) on one side and, say, 10 psi (a 4 psi vacuum drawing fuel
across the media) on the other side vs. 18 psi (4 psi pressure pushing
fuel across the media) on one side and 14 psi (atmospheric) on the
other?

IOW, even if the pump is past the filter drawing fuel through it, the
filter is still in "pressure" mode because it's really the atmospheric
pressure pushing fuel through the filter.

Steve


Looks like the contribution that mentioned a pressure pump's tendency
to mix and chop big water drops to a clogging emulsion where the
vacuum pump sucks them into the filter intact - that idea didn't
appeal to you?

Sure did. So does the idea that I'd rather have a malfunction that lets
air into the system than one that lets fuel out. But both of those
points leads to the conclusion that you should suck fuel through the
filter rather than push it through.

However, Rich recommends that fuel be pushed through due to some
tendency of the filter media to work better in that mode. Thus my
question, discounting all other aspects at hand such as the pump
emulsifying the fuel before it gets to the filter, why does the filter
media care which side the pump is on? Fuel is being pushed through it
either way, either by the pump with a higher pressure on the inlet or
the atmosphere with a higher pressure on the inlet.

Steve

On Fri, 09 Jan 2004 00:59:52 GMT, Brian Whatcott
wrote:

On Thu, 08 Jan 2004 05:54:34 GMT, (Steven
Shelikoff) wrote:

On Thu, 08 Jan 2004 02:51:46 GMT, Rich Hampel
wrote:

NOPE!
In pressure mode, the filter will also act as a 'coalescer' (bringing
similar surface tension fluids together to make larger and larger sized
particles) and such particles will settle out into a 'drop-out-pot'
..... or usually into the bottom of the filter bowl (bowl pointing
downwards). ///

All this begs the question, why does the filter media care whether it's
in "pressure" mode or "vacuum" mode? Sure, the plumbing and filter
cases care. But the media only sees a pressure differential across it.
What's the difference to the media if the there is 14psi (atmospheric
pressure) on one side and, say, 10 psi (a 4 psi vacuum drawing fuel
across the media) on the other side vs. 18 psi (4 psi pressure pushing
fuel across the media) on one side and 14 psi (atmospheric) on the
other?

IOW, even if the pump is past the filter drawing fuel through it, the
filter is still in "pressure" mode because it's really the atmospheric
pressure pushing fuel through the filter.

Steve


Looks like the contribution that mentioned a pressure pump's tendency
to mix and chop big water drops to a clogging emulsion where the
vacuum pump sucks them into the filter intact - that idea didn't
appeal to you?

Sure did. So does the idea that I'd rather have a malfunction that lets
air into the system than one that lets fuel out. But both of those
points leads to the conclusion that you should suck fuel through the
filter rather than push it through.

However, Rich recommends that fuel be pushed through due to some
tendency of the filter media to work better in that mode. Thus my
question, discounting all other aspects at hand such as the pump
emulsifying the fuel before it gets to the filter, why does the filter
media care which side the pump is on? Fuel is being pushed through it
either way, either by the pump with a higher pressure on the inlet or
the atmosphere with a higher pressure on the inlet.

Steve

On Thu, 08 Jan 2004 05:54:34 GMT, (Steven
Shelikoff) wrote:

On Thu, 08 Jan 2004 02:51:46 GMT, Rich Hampel
wrote:

NOPE!
In pressure mode, the filter will also act as a 'coalescer' (bringing
similar surface tension fluids together to make larger and larger sized
particles) and such particles will settle out into a 'drop-out-pot'
..... or usually into the bottom of the filter bowl (bowl pointing
downwards). ///

All this begs the question, why does the filter media care whether it's
in "pressure" mode or "vacuum" mode? Sure, the plumbing and filter
cases care. But the media only sees a pressure differential across it.
What's the difference to the media if the there is 14psi (atmospheric
pressure) on one side and, say, 10 psi (a 4 psi vacuum drawing fuel
across the media) on the other side vs. 18 psi (4 psi pressure pushing
fuel across the media) on one side and 14 psi (atmospheric) on the
other?

IOW, even if the pump is past the filter drawing fuel through it, the
filter is still in "pressure" mode because it's really the atmospheric
pressure pushing fuel through the filter.

Steve


Looks like the contribution that mentioned a pressure pump's tendency
to mix and chop big water drops to a clogging emulsion where the
vacuum pump sucks them into the filter intact - that idea didn't
appeal to you?

Brian W

On Thu, 08 Jan 2004 02:51:46 GMT, Rich Hampel
wrote:

NOPE!
In pressure mode, the filter will also act as a 'coalescer' (bringing
similar surface tension fluids together to make larger and larger sized
particles) and such particles will settle out into a 'drop-out-pot'
..... or usually into the bottom of the filter bowl (bowl pointing
downwards). The smaller the retention size of the filter media the
more efficient the coalescing efficiency.
On the very bottom of the filter bowl, add a pigtail of oil compatible
transluscent plastic tube (Tygon, etc.) with a cock on the end ....
when you see water in the pigtail simply drain the bowl. Thats the
same way a racor with an integral clear plastic knock-out-pot works.

If you are regularly polishing the fuel the coalesced emulsions will be
removed/trapped in the inverted filter bowl .... that why you put the
dip tube for the recirc system at the VERY bottom of the tank and a
drain cock on the inverted filter bowl.

Dont want air leaks or fuel oil leaks ------ dont use compression
fittings, use flared or better fittings.

Pump should have a SCREEN (preferably integral) for protection to
prevent damage by *huge* particles that would tear the rubber impeller
or wobble plate.

I say again, if you want long service life and efficient filtration
employ PRESSURE filtration, especially on a recirculation system.

The ONLY reason I can think of why fuel systems in boats use vacuum
filtration is ........... the engine manufactures supply the lift pump
and 'guard' filter - and puts it on the engine ...... and not on the
tank (where it SHOULD BE). Cheap and dirty solution, easier for the
boat builder - less wiring, less design, less effort, ....

All this begs the question, why does the filter media care whether it's
in "pressure" mode or "vacuum" mode? Sure, the plumbing and filter
cases care. But the media only sees a pressure differential across it.
What's the difference to the media if the there is 14psi (atmospheric
pressure) on one side and, say, 10 psi (a 4 psi vacuum drawing fuel
across the media) on the other side vs. 18 psi (4 psi pressure pushing
fuel across the media) on one side and 14 psi (atmospheric) on the
other?

IOW, even if the pump is past the filter drawing fuel through it, the
filter is still in "pressure" mode because it's really the atmospheric
pressure pushing fuel through the filter.

Steve

NOPE!
In pressure mode, the filter will also act as a 'coalescer' (bringing
similar surface tension fluids together to make larger and larger sized
particles) and such particles will settle out into a 'drop-out-pot'
...... or usually into the bottom of the filter bowl (bowl pointing
downwards). The smaller the retention size of the filter media the
more efficient the coalescing efficiency.
On the very bottom of the filter bowl, add a pigtail of oil compatible
transluscent plastic tube (Tygon, etc.) with a cock on the end ....
when you see water in the pigtail simply drain the bowl. Thats the
same way a racor with an integral clear plastic knock-out-pot works.

If you are regularly polishing the fuel the coalesced emulsions will be
removed/trapped in the inverted filter bowl .... that why you put the
dip tube for the recirc system at the VERY bottom of the tank and a
drain cock on the inverted filter bowl.

Dont want air leaks or fuel oil leaks ------ dont use compression
fittings, use flared or better fittings.

Pump should have a SCREEN (preferably integral) for protection to
prevent damage by *huge* particles that would tear the rubber impeller
or wobble plate.

I say again, if you want long service life and efficient filtration
employ PRESSURE filtration, especially on a recirculation system.

The ONLY reason I can think of why fuel systems in boats use vacuum
filtration is ........... the engine manufactures supply the lift pump
and 'guard' filter - and puts it on the engine ...... and not on the
tank (where it SHOULD BE). Cheap and dirty solution, easier for the
boat builder - less wiring, less design, less effort, ....



In article k.net,
Rick wrote:

Doug Dotson wrote:
I am assembling my posihing system. Not clear whether it is better
to put the pump on the pressure side or the vacuum side. Having no
filter on the intake of the pump seems risky. I am using a 2 stage
approach. maybe putting the filter between the filters is an option.

You want to avoid having the pump act as an homogenizer. If
the pump takes suction directly from the tank it will
thoroughly mix all the water and crud that you want to
filter out. This makes it much more difficult to remove in
the filters.

The Racors operate best on the suction side because the
separator section of the filter will, when it receives one,
deposit a clean slug of water in the bowl rather than clog
the filter media with an emulsion created by the pump.

Rick

On Wed, 7 Jan 2004 17:16:45 -0500, "Doug Dotson"
wrote:

I am assembling my posihing system. Not clear whether it is better
to put the pump on the pressure side or the vacuum side. Having no
filter on the intake of the pump seems risky. I am using a 2 stage
approach. maybe putting the filter between the filters is an option.

Probably better to have the pump suck clean fuel through the filters
than force dirty fuel through.

Steve

Doug Dotson wrote:
I am assembling my posihing system. Not clear whether it is better
to put the pump on the pressure side or the vacuum side. Having no
filter on the intake of the pump seems risky. I am using a 2 stage
approach. maybe putting the filter between the filters is an option.

You want to avoid having the pump act as an homogenizer. If
the pump takes suction directly from the tank it will
thoroughly mix all the water and crud that you want to
filter out. This makes it much more difficult to remove in
the filters.

The Racors operate best on the suction side because the
separator section of the filter will, when it receives one,
deposit a clean slug of water in the bowl rather than clog
the filter media with an emulsion created by the pump.

Rick

Pull the fuel through the filter, don't push.

"Doug Dotson" wrote in message
...
I am assembling my posihing system. Not clear whether it is better
to put the pump on the pressure side or the vacuum side. Having no
filter on the intake of the pump seems risky. I am using a 2 stage
approach. maybe putting the filter between the filters is an option.

Doug
s/v Callista

Why?

Doug
s/v Callista

"Keith" wrote in message
...
Pull the fuel through the filter, don't push.

"Doug Dotson" wrote in message
...
I am assembling my posihing system. Not clear whether it is better
to put the pump on the pressure side or the vacuum side. Having no
filter on the intake of the pump seems risky. I am using a 2 stage
approach. maybe putting the filter between the filters is an option.

Doug
s/v Callista

Why?

Doug
s/v Callista

"Keith" wrote in message
...
Pull the fuel through the filter, don't push.

"Doug Dotson" wrote in message
...
I am assembling my posihing system. Not clear whether it is better
to put the pump on the pressure side or the vacuum side. Having no
filter on the intake of the pump seems risky. I am using a 2 stage
approach. maybe putting the filter between the filters is an option.

Doug
s/v Callista