|Topic Review (Newest First)|
|01-10-2011 10:53 AM|
Originally Posted by RichH View Post
|01-10-2011 10:48 AM|
Originally Posted by noelex77 View Post
|01-09-2011 09:47 PM|
|Capnblu||How would you think the Carter would compare to the rat tat tat tat tat tat tat tat of a faucet that could suck 72 gph Maine?|
|01-09-2011 07:35 PM|
I use a Carter rotary vane pump for my dedicated fuel polishing system. It is a 72 GPH pump through a Racor 900. Works tremendously well thus far.
|01-09-2011 06:48 PM|
I'm surprised no one mentioned Facet Fuel pumps
here's one link to a marine supply. Moyers has em.. Most if not all NAPA stores have em too. I have one on my boat and carry a spare. "solid state" is actually a solenoid pump, makes a tick. unless it's pumping free flow or with air in the lines. Then it sounds like a hammer. Just under 40 bucks for the "posiflow" The cylinder type 4000 series pumps seem to be real popular also.
Facet POSI-FLO Pumps, Facet Fuel Pump Kits, Facet Gasket, Facet Marine Products - Discount Yacht Supplies, Vetus Nautical Accessories, Scandvik Parts, Garmin Marine Electronics
|01-09-2011 05:28 PM|
|Capnblu||Is A1 hose "better" than metal pipe? Now that I already have 80 feet of it...|
|01-09-2011 01:34 PM|
Originally Posted by Capnblu View Post
A pressure feed is more effective because of the motive force it can develop .... typically most fuel diaphragm pumps can easily generate up to 20-30 psi pressure before 'stalling' but can only develop about 6" Hg Vacuum or about a negative 3 psi @ 'stall' - simple pump 'dynamics'. A pressure system can produce ~10X the force of a vac. system.
Most aux. fuel pumps (not 'lift' pumps) will have an inlet screen at about 70µM which is selected by the mfg. to adequately protect the pump 'internals' (dont forget to clean the screen on a periodic basis). If your system is extremely cruddy, you might need an additional larger surface area inlet 'strainer' ~70µM ... but thats for a REAL crapped up system.
Why pressure feed is better than vac. feed (but there are 'risks')
A pressure system will have MORE 'total throughput', will last longer in service.
Filters operate on a relationship of flow vs. differential pressure (∆P) 'across' them; the higher the pressure the higher the flow rate. It takes 'work' to operate a filter and the higher pressure available, the MORE total volume you can flow and the (relative) pressure at which the filter 'clogs' will be much much higher - total 'throughput'. More importantly a vacuum fed filter when 'clogged' will 'stall' or shut down flow at ~ 6" hg. Vac. (~-3psi) while the pressure fed will still deliver fuel (depending on the amount of 'dirt loading') to upwards of 20-30 psid ... that translates to about a possible 10 times the amount of fuel filtered before total plugging in 'pressure' mode versus being in vacuum mode.
Also there is a noted difference in the way that most ('hard') debris is captured between pressure feed and in vac. mode feed. In pressure feed (with low 'velocity' and low ∆P) the debris seems to form more ON the surface of the filter media; but in vacuum feed the debris tends to deposit IN the filter media ... and can cause very short 'service life' - pump is stalling AND the filter is prematurely 'plugged'.
(Note - boat builders prefer to use vac. systems for vastly lessened legal risk as its ultimately better -for them, but not you- to have a stalled engine than have fuel oil spilling into a waterway. They dont get fines if your engine stalls and you go onto the rocks; but, if their design causes 'a sheen on the water' ..... BIG $$$$ ouch.)
Rx/Recommendation - if you are using a fuel recirc., etc. filtration system in 'pressure mode' use only metal tube with double flared connections ... or better!. Compression fittings, etc. are notorious 'leakers' and usually can only be routinely 'tightened' - a single time. All these fittings should be assembled 'dry' and with NO 'dope' nor 'tape'.
Pressure feed fuel systems on rec. boats need to be constantly monitored for leaks, including occasionally 'dead heading' the system, by closing the outlet valve to develop max. pressure to validate/test the mechanical integrity, etc. - due diligence.
For vac. feed, just use the 'positive' ∆P values.
hope this helps.
|01-09-2011 02:08 AM|
Ritch I think we are talking about the same thing at slightly cross purposes.
The fuel pump I use is rated at 60l an hour, about ¼ of the pump you recommend, but still in the same ball park.. Certainly much more than the 1-2 gph (are there pumps this small?) you mention.
With the pump you recommend at 60gph this is still very much what I would call low volume fuel polishing. I believe this is effective and I assume you feel the same.
The alternative method of fuel polishing involves much higher volume pumps. The advantage of this type of polishing is that the high volume will stir up the tank contents. (even better if it can be aimed and directed), but because of the power draw, large hoses, pumps, filtration equipment and the need to open up the tank, it is only suitable to be used occasionally (maybe once a year or less) usually by commercial operators.
Both these systems, occasional use with high volume equipment and frequent use with a low volume pump are called fuel polishing which confuses things.
Anyway to answer you questions.
Whats the ~volume of your tank?
1000L usually with only about 300l in it.
Whats the retention µM (and brand) of your recirc. filters?,
10 Micron Raycor 900-
Whats the pump? (I need to look at its output performance curve vs. backpressure, etc.)
Pump is unknown. (it came with the boat) similar to pumps rated at about 60l an hour. When in operation with fuel pumped through the filter about 50l an hour is returned to the tank.
Vacuum or pressure feed to filters?
- Whats the (clean) system gage pressure on your recirc. filter?
The gauge reads almost 0
Then I can make some generalized assumptioins/guesses and then give you a close estimate of how long a ‘moderately’ contaminated system will take to ‘clean-up’ ... based on your approximate parameters.
That would be appreciated.
The fuel is clean it looks crystal clear in the jar. (before the fuel polishing system was installed it was very slightly hazy
|01-08-2011 08:39 PM|
I have had good experience with Walbro
the pumps are made to go before the filter, and the filters are designed to have fuel pushed through and not pulled through. .
|01-08-2011 08:21 PM|
|Capnblu||Thanks RichH, I will get the Walbro pump then. I guess since you recommend putting the pump before the racors, a vacuum gauge to monitor the filter will be ineffective on the polishing circuit. I would think you would want the pump after the filter to keep it from sucking debris into it? What is the advantage to having the pressure on the dirty side of the filter?|
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