Back to filters .... HELP!

[xtal01]

So, you guys started me on the right path a couple of weeks back. Now that I a plumbing the system, I need to order a filter.

What was on the original unit was a Baldwin BT292. Hmmmm ..... from what I can tell this was the wrong filter. Rather than a hydraulic oil filter, this was a "full flow lube spin on filter".

I am thinking this means it was meant for filtering lubrication oil.

Maybe this will work for a hydraulic filter ???? It was put on the forklift by a reputable forklift repair/maintenance shop.

Just seems odd to me .... I can't even find any specification (beta) figures on it. Cheap at $12.

I tried to read up on the Beta ratio .... tell me if I got it right.

From what I read, most companies using a minimum beta ratio of 200.

So when I look at he Baldwin site they have two columns ... Beta 75 and 1000

Is the number under this columns the micron size that will be stopped at this ratio?

For example .... BT8842-MPG ... Beta 75 - 7 and Beta 1000 - 10.

So is this telling me that for all practical purposes this is a 10 micron filter (it will stop 99.9% of all 10 micron particles ... 98.7% of all 7 micron particle)?

It costs about $45

This seems "reasonable" as there is no filter offered in their charts with a Beta 1000 higher than 10. Pressure drop at 5 gpm (my expected flow)is 2 psi and at 10 gpm, 4 psi.

The next "jump up" seems to be BT8849-MPG .... Beta 75 - 5 and Beta 1000 - 10 .... $90 Pressure drop 4 psi at 5 gpm and 8 psi at 10 gpm.

To me this still looks like a 10 micron filter but will catch 98.7% of particles 5 micron. Not sure if it is worth twice the price for the same 1000 beta rating and only 2 higher at 75 Beta?

And then the question of the day ... is this clean enough?????

The two valve manufactures I am using say 1) (Parker) ISO Code 16/13 ... SAE Class 4 or better 2) (Brand) 10 micron or better

From a chart I found (hope it is correct) 16/13 is about an SAE (749D) 4 and 10 - 12 micron at Beta 100

At one point I was thinking I would filter my oil at a 5 micron level but 10 micron is the smallest particle size (assuming this is what the number in that column means) that any of the Baldwin spin on filters will stop.

So, did I get it right ????? Any filters I should look at other than Baldwin?

Thanks ..... Mike

PS .... link to the Baldwin filter page:

http://www.baldwinfilter.com/literature/english/1 brochures/Form453.pdf

 

[MikeHalloran]

For a pure and simple forklift system, you would just need a screen on the pump suction to keep chips in the reservoir from doing any damage, and a decent vent to keep rain out of the reservoir.

Since you have added a proportional valve, you should follow that valve's documentation for filtration advice.

I'm a fan of also using a pressure filter (not a spin-on) after the pump to keep pieces of the pump out of the rest of the system, but many folks would say it shouldn't be necessary. I'd plan on replacing the element once, after breakin, and never again unless there was a pump failure.



Mike Halloran
Pembroke Pines, FL, USA

 

[hydtools]

I would not spend the money on a pressure filter in this application.

Nothing wrong with Baldwin brand. Some people like Wix.

Ted

 

[xtal01]

So then the question for me becomes is a filter that stops 5 microns worth twice the price to me as one that stops 7 microns? I think looking at the valve specifications, either will work since they only mention a 10 micron rating ??????

BT8842-MPG ... Beta 75 - 7 and Beta 1000 - 10 ... $45

BT8849-MPG .... Beta 75 - 5 and Beta 1000 - 10 ... $90

I need to thank you guys for pointing me in the right direction! Originally, I looked at a Lenz filter. It had 3 micron stamped on it so I assumed it was a 3 micron filter .... after reading and looking back at the specifications it was 3 micron at a beta of 2 ... 50% efficiency! They do not even give ratings beyond beta 75 (98.7%).

Thanks again ..... Mike

 

[hydtools]

Get two of the BT8842-MPG. Change out the first one after several hours of run time. Also after time, filters get somewhat more effective as they fill with particles.

Ted

 

[xtal01]

Awesome!

That actually lines up well with the advice the technical manager of Royal Purple gave me.

He said that with my light duty, there oil will last several years (I had asked the question if I should change out the oil once a year). He also said to change the filter as it will dissolve varnish left from conventional oil.

I would change it just because after a few hours use, I would expect it has "caught" any trash I left in the system when assembling it.

Thanks again ..... Mike

 

[MikeHalloran]

If I were building a hydraulic elevator with proportional valve for _my_ wife, it would have a pressure filter. YMMV.

Mike Halloran
Pembroke Pines, FL, USA

 

[hydtools]

If your pump is throwing pieces, you are too late.

Ted

 

[MikeHalloran]

The pressure filter would not be there to save the pump.
It would be there to keep the proportional valve, and the elevator, working,
while the replacement pump is in transit.



Mike Halloran
Pembroke Pines, FL, USA

 

[xtal01]

I just did a quick search ....

Are we talking about one of these relatively cheap inline filters ... say 25 micron, sintered metal (zoro $50)just to stop "chucks" ... or a full blown 10 micron ????

I don't mind the extra protection if it can be had "relatively" cheaply (proportional valve is $300, each of the parker valves is $200, ...) ... say $50 - $200

The only parts that are note redundant are the cylinder and the hose break valve. Right at that point ( even before the flex lines ) I split into a tee. One side goes to t may proportional control setup while the other goes to a very simple automotive lift power unit (pump, reservoir, manual lowering valve .... all in one). They are isolated by ball valves ( just after the tee, again before the flex lines) that I would need to switch over.

Except for the main lift cylinder failing, the elevator should never be "stuck" for more than a few minutes while I switch over the ball valves so I can use the backup unit.

Thanks ..... Mike

 

[MikeHalloran]

It depends on the valve.
Particles much smaller than the valve clearance will not interfere with operation.
Particles much larger than the valve clearance will be stopped by a bird screen.

OTOH, since you have a mostly redundant power supply, maybe you don't need to care about the health of the proportional valve.



Mike Halloran
Pembroke Pines, FL, USA

 

[hydtools]

Silting problems in the proportional valve will be less than 5 micron.

Ted

 

[xtal01]

I have personally never seen a gear pump fail (I have had lines break, o-rings fail, solenoid coils fail, ....).

What modes of failure are there ... seals fail ... then nothing should go down stream.

I don't know how the two fears would fail other than a bearing fail. That would allow the two gears to hit and possibly material go down stream.

Obviouly lack of oil.

Is there any other modes of pump failure I need to worry about?

There is probably about $700 worth of valves on the main panel. So it would be a question of how much it would cost to protect them ... or just replace everything if I have a "met down".

Thanks ..... Mike

 

[MikeHalloran]

In addition to seal and bearing failures, gear pumps are subject to tooth scoring and surface fatigue of the tooth faces, both of which produce hard particles that move downstream. It's easy to forget that when the pump is working against pressure, one of the gears must drive the other.

Additionally, at least one line of gear pumps (used in aircraft landing gear, but also sold for general use) are produced with an interference fit between the hard steel gear tips and the aluminum gear housing, so the gears have to be pressed into place axially, and the assembled pump has to be turned with a wrench for a few rotations before it develops _any_ clearance at the tooth tips. I think they nominally flush the pumps at the factory, but you typically find some aluminum chips downstream in the system. OTOH, because of the minimal tip clearance, the pumps are fairly efficient.





Mike Halloran
Pembroke Pines, FL, USA

 

[xtal01]

With some luck, I will have limited my tooth to tooth wear by using synthetic lubricants. If I did my homework correctly, synthetic fluids have a very high film strength and should prevent metal to metal contact ... or at least better than conventional fluids.

Very interesting on the pump assembly with no clearances. Obviously would think there would be no way of getting tighter clearances than letting the gears cut the minimum that they need. I am sure they have this down to a science ... the only thought that comes to my mind are the chips being taken around if they are not flushed and scoring or galling against the housing.

Just for my own interest, I will have to look this up on the web some time.

Thanks ..... Mike

 

[hydtools]

The final process of running in the gears to the housing is primarily a burnishing process rather than a cutting process. The gears were not a press fit. The pre-runin interference is the result of hydraulic forces pushing all the running parts to take up all the manufacturing clearances of the rotating parts. The gear to chamber clearances were less than the accumulated clearances of the assembled parts and the gear teeth tips would contact the gear chamber walls. The run-in process would progress in steps from no load to maximum load.

Ted

 

[xtal01]

Thanks for the info!

As a machinist, I am always fascinated by just how close some one can build parts.

When I worked at Westinghouse Nuclear, depending on the part, I was able to manufacture parts +/- .0002 (working on a new ... well it was 10 years ago .... quarter million dollar wire EDM).

They sent me on a couple of courses put on by Penn United Technologies. Grinding on manual surface grinders .... shooting for +/- .0001!!! I remember for our final test, having to take the parts to a clean room and let them sit overnight before someone would check them and see how close we got. I will have to check back on my notes sometime, I don't remember how close I got on my 123 blocks.

Just FYI ..... the reason for the redundancy on my hydraulics is not just the mechanical issues. For about 15 years, I was part of a plant facilities group. I designed a lot of control panels (and still build a couple each year for various clients). If it is electrical, I have seen it fail. PLC's die, relays fry, contactors weld on, ....

Thanks again ...... Mike

 

[xtal01]

Sorry, just to add .... when I say Westinghouse Nuclear, it was not a nuclear plant. We produced the fuel bundles. I worked there for several years as a contractor with the plant facilities group (I tell everyone I pretended to be an engineer ... I only have a three year college diploma) and then took a full time job with them in the machine shop (I was 45 and thought maybe it was a good time to find a full time job and save for retirement). Then I ended up meeting a woman in VT, quitting, selling everything and moving up here.

Mike

 

[MikeHalloran]

Of course, it's possible to make excellent gear pumps without interference fits by just machining the parts properly. The Gold Standard for that used to be J.S.Barnes of Rockford, IL, which appears now to be a part of Haldex:

https://www.hydraulic-supply.com/html/productline/mfgprod/barnes.htm

I don't think you'll find their stuff at a log splitter store.



Mike Halloran
Pembroke Pines, FL, USA

 

[HPost]

Gear pump manufacturers will bed pumps in at a given pressure. The torque at the drive shaft is imparted onto the pumping gears. This causes them to try to separate and as they do this, the tips of the gears remove material from the housing. This makes the pumps very efficient in volumetric terms, but only when they are running at the pressure at which they were bedded in. Running them at lower pressure causes them to be less efficient. Running them over pressure causes excessive separation of the gears to the point where the tips dig into the housing and the torque spikes and the shaft shears under high torsion.

I know for a fact that Haldex, now called Concentric AB, do this...I used to work there designing gear pumps.

I also that Casappa do the same as we used their pumps on our machines.

The pump should not pump debris into your system, not if you have specified the pump correctly anyway.

If you have proportional valves, then the best practice is to have an in-line pressure filter. There are a long list of pros and cons in using suction strainers. In any case, they only remove the big bits and only single dimension filters, so can still let long and thin debris through. Return line filter work also, but do not protect the more sensitive valves from debris that is system generated.

Getting back to the ISO 4406 standard from which the cleanliness codes are derived, it is based on 4, 6 and 14 micron particles. It is purely intuitive to see that the a 10 micron filter will not catch the 4 and 6 micron particles, so it will not be able to keep the system sufficiently clean.

If it were my system, I would go with a 5 micron element in a pressure filter. The Beta 75 element from Baldwin will fit.

Cheers

Adrian