Racor placement in system

[Zeusoftexas]

Hi,

I'm new to the forum and have a 36 Grandbanks.

My question is on fuel filter placement in system. My trawler has three Racors that are after the fuel manifold in the system. One to each motor and one to the genset. What is the reason for having the filters after the manifold and not before the manifold. If the filters where before the manifold on the supply line from each tank and the filter clogged the tank that clogged the filter would be out of service but all the motors would be running through the filter hopefully not clogged on the other tank.

Am I missing something?

Thanks

 

[Capt.Bill11]

Hi,

I'm new to the forum and have a 36 Grandbanks.

My question is on fuel filter placement in system. My trawler has three Racors that are after the fuel manifold in the system. One to each motor and one to the genset. What is the reason for having the filters after the manifold and not before the manifold. If the filters where before the manifold on the supply line from each tank and the filter clogged the tank that clogged the filter would be out of service but all the motors would be running through the filter hopefully not clogged on the other tank.

Am I missing something?

Thanks

The fuel into the manifold normally feeds each engine individually. Not as a group.

Unless you have a "log" style manifold.

Pictures please.

 

[Zeusoftexas]

Sorry not at the boat but it does have a log style manifold. The two tanks feed each end of the log and the motors draw off of three outlets.

 

[RT Firefly]

Greetings,
Welcome aboard.

 

[Lepke]

I have a 200 gallon day tank and fuel flows thru a dual Racor setup before the manifold. Vacuum gauge in the manifold. From the manifold to all diesel needs, mains, generators, boiler, stove. Then each engine has a secondary filter. Only one of the Racors is on line at any time and can be switched running. The Detroit mains pump about 72 gallons an hour, burn about 8, ensuring the fuel is filtered many times. The generators I have, Perkins and Onan alone don't pump much extra fuel so don't re-filter much fuel. A dedicated Racor would be wasted on them.
I maintain clean fuel and use a 2 micron primary. The 10 micron secondaries never clog, but I change them once a year because they can capture any water that gets past the primaries. Most secondaries can capture up to an ounce of water.
My setup is what's common in commercial boats.

 

[Ski in NC]

If you have a racor in the tank supply lines to the manifold, and both mains are supplied by the manifold, if you clog a racor you could lose both engines at once. That is one reason most installs have a racor for each engine.

But you can do it that way, not a real big difference.

 

[dhays]

I maintain clean fuel and use a 2 micron primary. The 10 micron secondaries never clog, but I change them once a year because they can capture any water that gets past the primaries. Most secondaries can capture up to an ounce of water.
My setup is what's common in commercial boats.

I would think that your setup is backwards from most. You filter at 2 microns first, then 10 microns for a secondary.... Of course the secondary never clogs. It likely isn't filtering much at all. How often do your primaries clog up?

FWIW, my setup, which is of course with a different engine and a single not a twin, is 10 micron primary and 2 micron secondary per the factory recommendation. I don't have a lot of experience but the same was true on my last diesel, courser filtering on the primary and finer filtering on the secondary.

 

[Comodave]

I use 10 micron on my primary racors and the secondaries are supposed to be 10 micron also. The racors are much easier to change than the secondaries. I don't have to bleed the racors if the fuel tanks are about 1/4 full since they will gravity fill.

 

[Bigsfish]

I've never understood the logic of not using a 2 micron in the primary Racors and let the engine filter clean up any thing that passed. Yes you might be changing those 2 micron filters more often ($10.00 per filter) but your assuring clean fuel especially for. common rail Diesels. I understand the theory, the 20 micron won't get plugged as often and the secondary traps anything that passes it. I don't see the advantage to that thinking. Some claim the 2 micron as a primary will restrict the flow of fuel. BS 2 micron won't restrict flow as a secondary but will as a primary? Really?

 

[dhays]

I've never understood the logic of not using a 2 micron in the primary Racors and let the engine filter clean up any thing that passed. Yes you might be changing those 2 micron filters more often ($10.00 per filter) but your assuring clean fuel especially for. common rail Diesels. I understand the theory, the 20 micron won't get plugged as often and the secondary traps anything that passes it. I don't see the advantage to that thinking. Some claim the 2 micron as a primary will restrict the flow of fuel. BS 2 micron won't restrict flow as a secondary but will as a primary? Really?

I'm not a mechanic and am pretty simple minded. Cummins says use 10 micron primary and 2 micron secondary, so I figure they know better than I do.

 

[Bigsfish]

Dave

I agree they are a hell of a lot smarter than me but I don't understand the logic. I don't mind changing filters at a faster rate.

 

[Jay N]

This topic has been hammered pretty hard in the past.

In my decision making, I don't want to ever have to shut down the single engine to change the secondary (on engine filter).

So, there are two primaries with vacuum gauges which can be alternated to always keep the engine going.

 

[dhays]

This topic has been hammered pretty hard in the past.

In my decision making, I don't want to ever have to shut down the single engine to change the secondary (on engine filter).

So, there are two primaries with vacuum gauges which can be alternated to always keep the engine going.

Yup. Most/many of us have that same setup. The question is on an engine like mine, a common rail diesel, is it better to filter at 2 microns on the primary or 10 microns as the manufacturer recommends?

As Bigfish points out, it is a lot easier to change a dual Racor filter than it is changing the on-engine filter. The first you can do while underway, the second you can't. My engine bleeds itself, but many have to bleed the fuel lines if they change the secondary. The question is, if you are going to filter at 2 microns anyway at the secondary filter, why not filter at 2 microns on the primary? The more you catch in a 2 micron filter in the primary, the less the secondary has to catch. If you are running a 900 series Racor, you are likely going to be getting plenty of fuel flow for the engine.

So I certainly understand the reasons for Bigfish to run 2 micron filters in his Racors. I just think that if there weren't other, more compelling, reasons for 10 micron primary filtration, the engine manufacturers would recommend it. I just don't know what they are.

 

[ranger58sb]

I've never understood the logic of not using a 2 micron in the primary Racors and let the engine filter clean up any thing that passed. Yes you might be changing those 2 micron filters more often ($10.00 per filter) but your assuring clean fuel especially for. common rail Diesels. I understand the theory, the 20 micron won't get plugged as often and the secondary traps anything that passes it. I don't see the advantage to that thinking. Some claim the 2 micron as a primary will restrict the flow of fuel. BS 2 micron won't restrict flow as a secondary but will as a primary? Really?

I'm not a mechanic and am pretty simple minded. Cummins says use 10 micron primary and 2 micron secondary, so I figure they know better than I do.

My "logic" isn't my logic. Like Dave, I simply follow Cummins' directions (30m primary, 10m secondary, in our case; I'd guess Dave's engines are probably newer and common rail). Don't know enough about it to deviate from their guidelines.

-Chris

 

[Bigsfish]

Dave

You have my reasoning perfect. I have never had a Cummins tech explain to me a logical reason for not using a 2 micron filter as a primary (other they can sell more engine mounted filters).

 

[psneeld]

I understand the concept of progressive filtering......

On my perfect boat, I guess I would have progressive filtering to the micron size of the on engine secondary filter.

I suspect on engine filters have evolved differently. On my Lehman, it is after the fuel pump...makes sense to me. On my Cats, I don't remember for sure but I think the primaries were plumbed right to the on engine secondary.

If that's true, help me put Cat or other similar setup owners..then...what is the point of calling them primary or secondary instead of just something like "stage 1, 2, 3, whatever".

As to having too small micron sized primaries....does the engine know or care if there is no restriction in terms of vacuum?

 

[Bigsfish]

Scott

"As to having too small micron sized primaries....does the engine know or care if there is no restriction in terms of vacuum?"

Exactly, your a pretty smart guy for a Coastie. LOL

 

[catalinajack]

This topic has been hammered pretty hard in the past.

In my decision making, I don't want to ever have to shut down the single engine to change the secondary (on engine filter).

So, there are two primaries with vacuum gauges which can be alternated to always keep the engine going.

Boaters are married to Racors. I have them aboard my boat and will continue to use them cuz they work and they are there. But, take a look at Davco fuel water separators. They are used extensively on tractor trailers and other dirt diesels. No need for vacuum gauges. Your eyes will tell you when it's time to change a filter. Also, changing while underway would be no more difficult and perhaps easier than a Racor.

 

[RT Firefly]

Greetings,
Due to the fact that the CAV filters are a significant PIA to change on our Lehman 120's and I can't even imagine doing them in any sort of seaway, I run 2 micron and 2 micron. I recently changed the CAV's (at the dock) after a VERY long time (years) and not a sign of any particulate or water. Seems to work for me...

 

[Bigsfish]

Plus the money you saved on not having to but secondary filters.

 

[RT Firefly]

Greetings,
Mr. Bf. The measly amount spent on CAV filters (I think about $6 per filter, so $24 total) is secondary to the potentiality of having to change them while bopping around in the ER.

 

[cafesport]

Big fish, Before you waste a dollar on having a cummins mechanic visit your boat change both primary and secondaries back to the cummins spec and you'll probably find that missing 300 rpm. I have notes from a lugger class I took that explains why it's not a good idea and what can happen to electronic common rail engines when fuel restrictions occur. First symptom though is loss of performance as in wot.

 

[Bigsfish]

Cafesport

Thanks for the info but when new I used 2 micron Racors and it ran fine, got the proper RPMs.

I'm having Cummins to come do a service on the engines and pods and then I'll haul the boat to clean the bottom but the diver says it looks fine.

 

[Bay Pelican]

I have a fairly common dual Racor setup which feeds my main engine. I use 2mm Racors and want to trap anything I can before the fuel gets to the filter on the engine. Underway I can switch from the starboard to port Racor on the dual setup by throwing a lever. If I have to change the filter on the engine I need to shut down. Frankly, I don't ever want that to happen.

 

[psneeld]

Scott

"As to having too small micron sized primaries....does the engine know or care if there is no restriction in terms of vacuum?"

Exactly, your a pretty smart guy for a Coastie. LOL

There are a few of us.....especially those of us that took off low on fuel every mission and had to think at 120 knots instead of 10 to 30.

Like almost every discussion here on TF.....it does no good to say what works on one boat will automatically work on another...too many variables.

Depending on power plant and filter setups, those might significantly alter the equation.

Apply logic throughout the whole setup and yes even a lowly boat owner can come up with better setups than manufacturers or model techs....they are slaves to a standard, no matter how high or low it is.

Even Einstein has had his errors and been proven incorrect in certain issues....as all of us gave no matter what we are experts in.