Racor Micron Rating

[sailak]

I'm in the process of swapping out the Dahl filter for a Racor 200 series unit. It came with a 2 micron filter. I understand that a 2 will clog up sooner than a 10, but is there any problem with running a 2 micron primary filter? Will the 2 micron filter cause a fuel flow problem since the filter is on the suction side of the pump. The engine is a Yanmar 3GM30F.

Unless folks here convince me to continue with a 2 micron filter I plan on using a 10 micron for the primary, they just don't have any in stock today.

Thanks in advance.

[capttb]

I used a 2 micron on a smaller 18hp Perkins for 9 months (~100 hours) without problem, tank was clean and fuel was fresh at the start, Also a 200 series Racor.

[JimsCAL]

The Racor 200 series filter used as a primary on my 3GM30F had a 30 micron element on it when I bought the boat. I have continued that practice. I wouldn't go below 10 micron for the primary since if you get some bad fuel it will clog quickly.

[chef2sail]

I am with Jim...30 on my primary...2 on my secondary

[HUGOSALT]

Have heard that the 2 micron on primary filter puts a strain on fuel pump leading to premature failure. So I use
30 on primary. Been meaning to call Mack Boring to confirm.

[sailak]

As follow up...

I was able to talk to an experienced live-aboard here and he uses a 2 micron as his primary and hasn't had any issues.

I have a couple 10 micron otw, will most likely switch to the 10 just for peace of mind.

We tend to get good quality fuel here in Seward. My boat,until today, was equipped with a Dahl primary. After the Dahl was a "mystery filter". This MF was appeared to be a standard water separator type filter. It has a metal can with a drain plug on the bottom. The PO (had the boat 6 years) never had this MF open, I've not been able to open it in the 2 years I've had the boat. (Scary huh )

I installed the Racor and removed the MF. When I dumped the contents of the MF in a pan there was a considerable amount of clear water followed by brown water with particles and finally what had the appearance of cottage cheese. The MF appears to have been original equipment on the boat (1986).

Thanks for the replies.

[r.furborough]

the yanmar secondary on-engine filter supplied with their engine is, as i recall 19 micron. this is what yanmar specify to protect the fuel system on the engine. a 30 micron is all that is required. no point in using a filter to protect a filter!

[Maine Sail]

Originally Posted by r.furborough

the yanmar secondary on-engine filter supplied with their engine is, as i recall 19 micron. this is what yanmar specify to protect the fuel system on the engine. a 30 micron is all that is required. no point in using a filter to protect a filter!

I think many of the aftermarket filters for Yanmar are 19 nominal but the Yanmar brand are spec'd at 10-15 micron nominal. A 30 micron to protect a 10-15 micron on-engine is a good option for multi-stage filtering. You can also use a 10 but then you really have just one filter doing all the work.

Racor marks the 2 micron filters as R12S. The "S" stand for secondary. The 10 micron is marked R12T which is suggested for a "primary" or "secondary" applications and the 30 micron is marked R12P or "primary" for primary filtering..


Here's a link to Torresen which rates the Yanmar filter as 10-15 Micron.
Yanmar 104500-55710 Sailboat Supplies, Engine Parts and Boat Parts


The Yanmar filter specs out of the manuals I have are as follows:

Micron Rating: 10-15μ
Material: Cotton Fiber
Filtering Area: 333 cm<sup>2

The engine is designed to run at a 15 micron nominal filter mesh rating. Using a 2 micron filter can work your pump harder and potentially lead to a plugged filter but only when you absolutely don't want it to plug.. It never plugs when tied to the dock, Murphy makes sure of that..</sup>

[saildog1]

I work for a large construction company and all the diesel mechanics say go with the 3 micron or you'll have injector issues down the line. I always use a 3 micron for 30 years now. No pums or injectors have been replaced.

[RichH]

Ive been deeply involved in 'filtration engineering' for over 40 years, including indirect work with and for the 'parent' of Racor.

The acknowledged most damaging particle in a marine diesel is ~20µM.

Typical set up for marine diesel engines (unless otherwise specified by the engine mfgr.) is tank --> 30µM --> 10µM --> 15-17µM for the (very small) engine 'guard' filter --> engine.
It takes a lot of WORK to make such filters operate. A 2µM (of equal surface area) will have 1/5th the flow rate capacity (vs. differential pressure across the filter) of a 10µM. To operate at the designed (WOT) flow rate of a 10µM a 2µM will have 5 TIMES the pressure drop across it; OR, must have 5 TIMES the surface area to equate to the resistance or on stream service life of the 10µM.
High differential pressure across a 2µM can lead to 'exponentially earlier' plugging with debris and significant work load on the lift pump and may cause premature lift pump diaphragm FAILURE. There are exponentially MORE particles at the 'finer' µM distribution size range ... .

Simple speak: putting a 2µM (nominal) filter in place of a normally used 10µM will cause premature plugging (approximately 10 times 'faster' or at ~1/10 of the total amount of fuel filtered before plugging), undue load on the lift pump, etc. etc.

The small engine mounted guard filter should be LARGER in µM retention size the next 'upstream' filter in the sequence. Its there 'only' to stop debris if the upstream filters FAIL... a 'last chance' filter.

If you somehow erroneously feel that using a 2µM is required for 'your' system, it should be preceded by a 10µM, the 10µM should be preceded by a 30µM .... all these 'prefilters' are to extend the onstream service life of the immediate downstream filter. All filters add to the overall workload on the engine's lift pump.

Modification of the 'typical' system should only be based on system operational history of total gallons filtered before plugging (in accordance to recorded 'history' of total gallons filtered vs. WOT volumetric flow in gallons per hour vs. differential (gage) pressure across each filter).

On most marine diesel engines a 2µM filter HAS NO TECHNICAL REASON to be in the filter train.

Maintain and clean the internals of the tank on a regular basis, buy only 'fresh' fuel from high turnover supply sources .... and you wont be 'challenging' the filters with a lot of debris.