|
Fuel Polishing again.
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 |
Fuel Polishing again.
Racor strongly recommends that filters be operated under vacuum rather
than pressure. I believe the idea being safety. Better for a leak to pull in air than spray fuel. 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. Doug s/v Callista -- 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 |
Fuel Polishing again.
Racor strongly recommends that filters be operated under vacuum rather
than pressure. I believe the idea being safety. Better for a leak to pull in air than spray fuel. 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. Doug s/v Callista -- 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 |
Fuel Polishing again.
Interesting. More tradeoffs. I have been told (by Rich H) that filters
last longer in pressure mode. I'm not using Raycor but I'm sure the issues are similar. I've also been advised that operating the engine fuel system in pressure mode is better because a leak will not kill the engine, just leak some fuel. I'd never consider such an approach with a gasoline engine, but with a diesel the risk seems acceptable. I had a minor leak this summer and enfed up with a couple gallons of bilge in the catch pan under the engine. No real danger although a pain to clean up. Doug s/v Callista "Glenn Ashmore" wrote in message news:rL%Kb.29544$JD6.12079@lakeread04... Racor strongly recommends that filters be operated under vacuum rather than pressure. I believe the idea being safety. Better for a leak to pull in air than spray fuel. Doug Dotson wrote: I am assembling my posihing system. Not clear whether it is better to put the pump on the pressure side or the vacuum side. Having no filter on the intake of the pump seems risky. I am using a 2 stage approach. maybe putting the filter between the filters is an option. Doug s/v Callista -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Fuel Polishing again.
Interesting. More tradeoffs. I have been told (by Rich H) that filters
last longer in pressure mode. I'm not using Raycor but I'm sure the issues are similar. I've also been advised that operating the engine fuel system in pressure mode is better because a leak will not kill the engine, just leak some fuel. I'd never consider such an approach with a gasoline engine, but with a diesel the risk seems acceptable. I had a minor leak this summer and enfed up with a couple gallons of bilge in the catch pan under the engine. No real danger although a pain to clean up. Doug s/v Callista "Glenn Ashmore" wrote in message news:rL%Kb.29544$JD6.12079@lakeread04... Racor strongly recommends that filters be operated under vacuum rather than pressure. I believe the idea being safety. Better for a leak to pull in air than spray fuel. 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. Doug s/v Callista -- 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 |
Fuel Polishing again.
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 |
Fuel Polishing again.
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 |
Fuel Polishing again.
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 |
Fuel Polishing again.
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 |
Fuel Polishing again.
That's why one of my thoughts is to put the pump between
the filters. 10 uM upstream, 1 uM downstream. Doug s/v Callista "Steven Shelikoff" wrote in message ... 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 |
Fuel Polishing again.
That's why one of my thoughts is to put the pump between
the filters. 10 uM upstream, 1 uM downstream. Doug s/v Callista "Steven Shelikoff" wrote in message ... 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 |
Fuel Polishing again.
Good point. I hadn't thought of that. But then I am not using Raycor
fuel/water separators for the polishing system. I am using depth filters rather than surface filters so the water should be trapped within the filters. Also, I do have Raycor on the engine system so any residual water will be handled there as well. Doug s/v Callista "Rick" wrote in message hlink.net... 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 |
Fuel Polishing again.
Good point. I hadn't thought of that. But then I am not using Raycor
fuel/water separators for the polishing system. I am using depth filters rather than surface filters so the water should be trapped within the filters. Also, I do have Raycor on the engine system so any residual water will be handled there as well. Doug s/v Callista "Rick" wrote in message hlink.net... 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 |
Fuel Polishing again.
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 |
Fuel Polishing again.
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 |
Fuel Polishing again.
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 |
Fuel Polishing again.
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 |
Fuel Polishing again.
Steven Shelikoff wrote:
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. The difference is that if the pump suction pulls water and fuel directly from the tank it will do an excellent job of mixing it up to form an emulsion that will not filter out very effectively. The path should be, a basket strainer to catch the chunks, a separarator/filter to eliminate the bulk of the water and the smaller suspended particles, the pump, then the finer stages of filtration. This is all assuming you don't have access to a centrifuge which is really the best way to handle the process. Rick |
Fuel Polishing again.
Steven Shelikoff wrote:
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. The difference is that if the pump suction pulls water and fuel directly from the tank it will do an excellent job of mixing it up to form an emulsion that will not filter out very effectively. The path should be, a basket strainer to catch the chunks, a separarator/filter to eliminate the bulk of the water and the smaller suspended particles, the pump, then the finer stages of filtration. This is all assuming you don't have access to a centrifuge which is really the best way to handle the process. Rick |
Fuel Polishing again.
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 |
Fuel Polishing again.
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 |
Fuel Polishing again.
"R" == Rick writes:
R Steven Shelikoff wrote: 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. R The difference is that if the pump suction pulls water and fuel R directly from the tank it will do an excellent job of mixing it up to R form an emulsion that will not filter out very effectively. R The path should be, a basket strainer to catch the chunks, a R separarator/filter to eliminate the bulk of the water and the smaller R suspended particles, the pump, then the finer stages of filtration. R This is all assuming you don't have access to a centrifuge which is R really the best way to handle the process. R Rick Do you happen to know if there is any centrifugal separator on the market suited to small boats? I cannot really think of any technical reasons why not, but perhaps the market isn't there. Btw., I once had a Scania truck diesel engine which had a centrifuge for its lubrication oil. Judging from the amount of gunk it separated out of the oil, it worked very well. -- This page intentionally left blank |
Fuel Polishing again.
"R" == Rick writes:
R Steven Shelikoff wrote: 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. R The difference is that if the pump suction pulls water and fuel R directly from the tank it will do an excellent job of mixing it up to R form an emulsion that will not filter out very effectively. R The path should be, a basket strainer to catch the chunks, a R separarator/filter to eliminate the bulk of the water and the smaller R suspended particles, the pump, then the finer stages of filtration. R This is all assuming you don't have access to a centrifuge which is R really the best way to handle the process. R Rick Do you happen to know if there is any centrifugal separator on the market suited to small boats? I cannot really think of any technical reasons why not, but perhaps the market isn't there. Btw., I once had a Scania truck diesel engine which had a centrifuge for its lubrication oil. Judging from the amount of gunk it separated out of the oil, it worked very well. -- This page intentionally left blank |
Fuel Polishing again.
Seems to me if the filters are clean and if there is a screen or coarse
filter to protect the pump the differences between having the fine filter before or after the pump are probably academic. I don't know the pump details or characteristics, but pumps need to have their inlet pressure above some minimum figure - net positive suction head - or they don't work. And it's much easier to find leaks of fuel out of a pipe than air leaks into it. If it leaks fuel it's still working, if it leaks air in it probably isn't. So I'd think more about troubleshooting the system when there has been some bad fuel and the filter pressure drop is getting high --- I'd like to see the pump protected against things which might damage it, then a pressure gauge , then the finest filters. It might not be the best arrangement in terms of emulsifying water, but I'll bet it's the easiest one to diagnose. Mark the pressure gauge with new pump and a clean filter, second mark corresponds to max filter pressure drop. If you really want more assurance that it's running OK, either add a pressure gauge on the suction side of the pump to prove the inlet strainer is not blocked, or a delivery side sample point you can use for a flowrate check. I'd go for the flowrate check, and make the inlet strainer as coarse as possible - it's a strainer to protect the pump, not a filter .... David "Rick" wrote in message hlink.net... Steven Shelikoff wrote: 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. The difference is that if the pump suction pulls water and fuel directly from the tank it will do an excellent job of mixing it up to form an emulsion that will not filter out very effectively. The path should be, a basket strainer to catch the chunks, a separarator/filter to eliminate the bulk of the water and the smaller suspended particles, the pump, then the finer stages of filtration. This is all assuming you don't have access to a centrifuge which is really the best way to handle the process. Rick |
Fuel Polishing again.
Seems to me if the filters are clean and if there is a screen or coarse
filter to protect the pump the differences between having the fine filter before or after the pump are probably academic. I don't know the pump details or characteristics, but pumps need to have their inlet pressure above some minimum figure - net positive suction head - or they don't work. And it's much easier to find leaks of fuel out of a pipe than air leaks into it. If it leaks fuel it's still working, if it leaks air in it probably isn't. So I'd think more about troubleshooting the system when there has been some bad fuel and the filter pressure drop is getting high --- I'd like to see the pump protected against things which might damage it, then a pressure gauge , then the finest filters. It might not be the best arrangement in terms of emulsifying water, but I'll bet it's the easiest one to diagnose. Mark the pressure gauge with new pump and a clean filter, second mark corresponds to max filter pressure drop. If you really want more assurance that it's running OK, either add a pressure gauge on the suction side of the pump to prove the inlet strainer is not blocked, or a delivery side sample point you can use for a flowrate check. I'd go for the flowrate check, and make the inlet strainer as coarse as possible - it's a strainer to protect the pump, not a filter .... David "Rick" wrote in message hlink.net... Steven Shelikoff wrote: 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. The difference is that if the pump suction pulls water and fuel directly from the tank it will do an excellent job of mixing it up to form an emulsion that will not filter out very effectively. The path should be, a basket strainer to catch the chunks, a separarator/filter to eliminate the bulk of the water and the smaller suspended particles, the pump, then the finer stages of filtration. This is all assuming you don't have access to a centrifuge which is really the best way to handle the process. Rick |
Fuel Polishing again.
Rick wrote:
Steven Shelikoff wrote: 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. The difference is that if the pump suction pulls water and fuel directly from the tank it will do an excellent job of mixing it up to form an emulsion that will not filter out very effectively. Then it sounds like it would be better to have the pump past the filters. The path should be, a basket strainer to catch the chunks, a separarator/filter to eliminate the bulk of the water and the smaller suspended particles, the pump, then the finer stages of filtration. Well, now I have to ask why the pump should be before the finer stages of filtration. It seems to me that as long as it can maintain a sufficient pressure differential across all the stages of filtration, it wouldn't matter where the pump is. Of course if it can't do that (not enough suction for all the stages before it) then you'd have to move the pump up in the stream like you suggest above. This is all assuming you don't have access to a centrifuge which is really the best way to handle the process. I do, but it's a little big to fit on the boat.:) Steve |
Fuel Polishing again.
Rick wrote:
Steven Shelikoff wrote: 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. The difference is that if the pump suction pulls water and fuel directly from the tank it will do an excellent job of mixing it up to form an emulsion that will not filter out very effectively. Then it sounds like it would be better to have the pump past the filters. The path should be, a basket strainer to catch the chunks, a separarator/filter to eliminate the bulk of the water and the smaller suspended particles, the pump, then the finer stages of filtration. Well, now I have to ask why the pump should be before the finer stages of filtration. It seems to me that as long as it can maintain a sufficient pressure differential across all the stages of filtration, it wouldn't matter where the pump is. Of course if it can't do that (not enough suction for all the stages before it) then you'd have to move the pump up in the stream like you suggest above. This is all assuming you don't have access to a centrifuge which is really the best way to handle the process. I do, but it's a little big to fit on the boat.:) Steve |
Fuel Polishing again.
David Flew wrote:
Seems to me if the filters are clean and if there is a screen or coarse filter to protect the pump the differences between having the fine filter before or after the pump are probably academic. I don't know the pump details or characteristics, but pumps need to have their inlet pressure above some minimum figure - net positive suction head - or they don't work. And it's much easier to find leaks of fuel out of a pipe than air leaks into it. If it leaks fuel it's still working, if it leaks air in it probably isn't. So I'd think more about troubleshooting the system when there has been some bad fuel and the filter pressure drop is getting high --- I'd like to see the pump protected against things which might damage it, then a pressure gauge , then the finest filters. It might not be the best arrangement in terms of emulsifying water, but I'll bet it's the easiest one to diagnose. Personally, I'd rather diagnose a leak in a vacuum system that stops the engine due to air getting in the system than one in a pressure system that keeps running but pumps fuel into the bilge until your tanks are dry and then stops the engine. But that's just me. Steve |
Fuel Polishing again.
David Flew wrote:
Seems to me if the filters are clean and if there is a screen or coarse filter to protect the pump the differences between having the fine filter before or after the pump are probably academic. I don't know the pump details or characteristics, but pumps need to have their inlet pressure above some minimum figure - net positive suction head - or they don't work. And it's much easier to find leaks of fuel out of a pipe than air leaks into it. If it leaks fuel it's still working, if it leaks air in it probably isn't. So I'd think more about troubleshooting the system when there has been some bad fuel and the filter pressure drop is getting high --- I'd like to see the pump protected against things which might damage it, then a pressure gauge , then the finest filters. It might not be the best arrangement in terms of emulsifying water, but I'll bet it's the easiest one to diagnose. Personally, I'd rather diagnose a leak in a vacuum system that stops the engine due to air getting in the system than one in a pressure system that keeps running but pumps fuel into the bilge until your tanks are dry and then stops the engine. But that's just me. Steve |
Fuel Polishing again.
After 30 years of screwing around with this stuff I cant still give a
an accurate technical reason .... my 'opinion' is the 'regime' of particle depositionIn and the formation of 'filter cake' ..... on a pressure filtration the deposition begins mostly on the upper surface or at least within 5% depth of the surface, while with vacuum filtration the deposition is essentially INSIDE the matrix of the media. Being inside the matrix causes higher internal velocities which drive the particles deeper and deeper into the matrix ... causing an exponential decrease in service life. ..... its the same for depth as well as membrane filtration. The quandy is that the fluids are incompressible and shouldnt make any difference due to the direction of motive pressure .... but in practice it does, it always does. article , 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). 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 |
Fuel Polishing again.
After 30 years of screwing around with this stuff I cant still give a
an accurate technical reason .... my 'opinion' is the 'regime' of particle depositionIn and the formation of 'filter cake' ..... on a pressure filtration the deposition begins mostly on the upper surface or at least within 5% depth of the surface, while with vacuum filtration the deposition is essentially INSIDE the matrix of the media. Being inside the matrix causes higher internal velocities which drive the particles deeper and deeper into the matrix ... causing an exponential decrease in service life. ..... its the same for depth as well as membrane filtration. The quandy is that the fluids are incompressible and shouldnt make any difference due to the direction of motive pressure .... but in practice it does, it always does. article , 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). 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 |
Fuel Polishing again.
Steven Shelikoff wrote:
Well, now I have to ask why the pump should be before the finer stages of filtration. Because you can install canned filters which are rated for high pressure downstream of the pump, on the pressure side. The filters on the suction side are fairly coarse, produce little resistance to flow until clogged, and can perform the initial separation of water and solids. wouldn't matter where the pump is. Of course if it can't do that (not enough suction for all the stages before it) then you'd have to move the pump up in the stream like you suggest above. If the pump was upstream of all filters, so that it sucked through them all, the differential available is pretty low. That is why most installations use Racors on the suction side for the reasons I have given and then the final filters are can filters on the pressure side. We seem to have gotten away from the polishing thread here but there really isn't much difference. One thing to keep in mind, this process is not designed to conserve on filters, it is supposed to clean fuel. Rick |
Fuel Polishing again.
Steven Shelikoff wrote:
Well, now I have to ask why the pump should be before the finer stages of filtration. Because you can install canned filters which are rated for high pressure downstream of the pump, on the pressure side. The filters on the suction side are fairly coarse, produce little resistance to flow until clogged, and can perform the initial separation of water and solids. wouldn't matter where the pump is. Of course if it can't do that (not enough suction for all the stages before it) then you'd have to move the pump up in the stream like you suggest above. If the pump was upstream of all filters, so that it sucked through them all, the differential available is pretty low. That is why most installations use Racors on the suction side for the reasons I have given and then the final filters are can filters on the pressure side. We seem to have gotten away from the polishing thread here but there really isn't much difference. One thing to keep in mind, this process is not designed to conserve on filters, it is supposed to clean fuel. Rick |
Fuel Polishing again.
Ole-Hjalmar Kristensen wrote:
Do you happen to know if there is any centrifugal separator on the market suited to small boats? I cannot really think of any technical reasons why not, but perhaps the market isn't there. Alfa Laval makes a cute little unit that will process about 170 liters/hour. Alfa sells it mounted on a cart with pump and controls for use as a portable oil polishing unit. The centrifuge is available by itself. I would love to have one but the cost is a bit too high to justify its use on a pleasure boat. Btw., I once had a Scania truck diesel engine which had a centrifuge for its lubrication oil. Judging from the amount of gunk it separated out of the oil, it worked very well. A "spinner" that worked off the oil itself? Those things are great. Have used them on several diesel generator sets and they do an excellent job. A little trick to make them easier to clean, line the bowl with a single layer of newspaper. Rick |
Fuel Polishing again.
Ole-Hjalmar Kristensen wrote:
Do you happen to know if there is any centrifugal separator on the market suited to small boats? I cannot really think of any technical reasons why not, but perhaps the market isn't there. Alfa Laval makes a cute little unit that will process about 170 liters/hour. Alfa sells it mounted on a cart with pump and controls for use as a portable oil polishing unit. The centrifuge is available by itself. I would love to have one but the cost is a bit too high to justify its use on a pleasure boat. Btw., I once had a Scania truck diesel engine which had a centrifuge for its lubrication oil. Judging from the amount of gunk it separated out of the oil, it worked very well. A "spinner" that worked off the oil itself? Those things are great. Have used them on several diesel generator sets and they do an excellent job. A little trick to make them easier to clean, line the bowl with a single layer of newspaper. Rick |
Fuel Polishing again.
"R" == Rick writes:
R Ole-Hjalmar Kristensen wrote: Do you happen to know if there is any centrifugal separator on the market suited to small boats? I cannot really think of any technical reasons why not, but perhaps the market isn't there. R Alfa Laval makes a cute little unit that will process about 170 R liters/hour. Alfa sells it mounted on a cart with pump and controls R for use as a portable oil polishing unit. The centrifuge is available R by itself. Interesting. R I would love to have one but the cost is a bit too high to justify its R use on a pleasure boat. Yes, you're probably right, unless you could share it with others, being a portable unit. I was thinking of a small unit which could be permanently attached to the fuel system and used either for polishing or for processing the fuel when filling a day tank. Btw., I once had a Scania truck diesel engine which had a centrifuge for its lubrication oil. Judging from the amount of gunk it separated out of the oil, it worked very well. R A "spinner" that worked off the oil itself? Those things are R great. Have used them on several diesel generator sets and they do an R excellent job. A little trick to make them easier to clean, line the R bowl with a single layer of newspaper. Yes, it used the oil pressure to spin the bowl, and you had to manually clean the inside of the bowl. The newspaper trick would have been great, but I did not think of it 25 years ago... R Rick -- This page intentionally left blank |
Fuel Polishing again.
"R" == Rick writes:
R Ole-Hjalmar Kristensen wrote: Do you happen to know if there is any centrifugal separator on the market suited to small boats? I cannot really think of any technical reasons why not, but perhaps the market isn't there. R Alfa Laval makes a cute little unit that will process about 170 R liters/hour. Alfa sells it mounted on a cart with pump and controls R for use as a portable oil polishing unit. The centrifuge is available R by itself. Interesting. R I would love to have one but the cost is a bit too high to justify its R use on a pleasure boat. Yes, you're probably right, unless you could share it with others, being a portable unit. I was thinking of a small unit which could be permanently attached to the fuel system and used either for polishing or for processing the fuel when filling a day tank. Btw., I once had a Scania truck diesel engine which had a centrifuge for its lubrication oil. Judging from the amount of gunk it separated out of the oil, it worked very well. R A "spinner" that worked off the oil itself? Those things are R great. Have used them on several diesel generator sets and they do an R excellent job. A little trick to make them easier to clean, line the R bowl with a single layer of newspaper. Yes, it used the oil pressure to spin the bowl, and you had to manually clean the inside of the bowl. The newspaper trick would have been great, but I did not think of it 25 years ago... R Rick -- This page intentionally left blank |
Fuel Polishing again.
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 |
Fuel Polishing again.
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 |
Fuel Polishing again.
I think I'll put the pump between the filters. 10 micron on
the vacuum side, 1 micron on the pressure side. Doug s/v Callista "Rich Hampel" wrote in message ... After 30 years of screwing around with this stuff I cant still give a an accurate technical reason .... my 'opinion' is the 'regime' of particle depositionIn and the formation of 'filter cake' ..... on a pressure filtration the deposition begins mostly on the upper surface or at least within 5% depth of the surface, while with vacuum filtration the deposition is essentially INSIDE the matrix of the media. Being inside the matrix causes higher internal velocities which drive the particles deeper and deeper into the matrix ... causing an exponential decrease in service life. ..... its the same for depth as well as membrane filtration. The quandy is that the fluids are incompressible and shouldnt make any difference due to the direction of motive pressure .... but in practice it does, it always does. article , 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). 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 |
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