Hydraulic spool valve not doing what it should

[chrismac]

I connected the spool up to the compressor, a drawing would be so much easier but I will try and type whats happening (but its clear to see)

P port is on relief side,
lever 2 (nearest relief) pull it back, it directs air to A1 which is front port then a pop and it changes to port B1, and in reverse if the lever is pushed port B1 gets air then a pop and A1 gets air, this is different orientation from the video, they must have reassembled the valves the other way round.
lever 1 pull it back and it directs air to B2 only then forwards push it directs air to A1, (working as expected)

It would seem the valve is operating exactly like the video in regards to what I dont want it to do, why can flowfit says its working as it should?

 

[Rannsachair]

So you have confirmed the issue is with the valve, need another one or that one back to flowfit and explain the fault to them. It may well be that the valve is operating as per spec, though not the functionality you wanted. Good luck.

 

[chrismac]

So you have confirmed the issue is with the valve, need another one or that one back to flowfit and explain the fault to them. It may well be that the valve is operating as per spec, though not the functionality you wanted. Good luck.

Thanks I'll give them a phone, see if the guy who I was dealing with can remember. maybe still have the emails.

 

[chrismac]

So the plot thickens, after struggling to know how these 2 spools could be operating different even when sent back and stripped and tested, I needed to pull them apart to see/make sure the internals were the same, or what was in there.

Stripped
Spool 2 2025 by chrismac2012, on Flickr

Close up
Spool 1 2025 by chrismac2012, on Flickr

Now its clear to see both are different, the issue I now have is the top one is the one functioning as I would expect(or at least its doing what I want it to do) the other has flow the wrong way before it eventually flows in the direction it should, but they (flowfit) have no idea what the top one is, have never seen anything like it and only have the bottom type available for my needs, they are sending one or two of the lower type with the 4 grooves in the first section, I have to try it and see what happens, they think the top one might be affecting the flow one way or another(not sure I believe that but I am in no position to challenge that yet) whats the thoughts here?

 

[Rannsachair]

So it looks like they only have the wrong spools!

How they each work also depends how the galleries in the housing match up with the spools, they may not be the same.

The grooves in the spool are just to balance pressure around the spool to reduce wear and prevent binding.

 

[chrismac]

I'll strip it again and fit and experiment with the replacements when they arrive, maybe with a pair the same of the lower type it will work. I'll report back once I have the bits home.

So its the distance between the ground out/machined sections obviously that allow the flow through.

So would it be possible to machine one which had metal to remove to allow, is this stuff hardened or just chrome coated.

 

[8ob]

One of the spools on a loader should have a float position.

Edit. just read through this, I think the sinking of the loader prior to lifting could be the pipes on the wrong way around on the lift spool, as in when you pull the lever back you are going through the float position. Hope that makes sense

Bob

 

[Rannsachair]

I'll strip it again and fit and experiment with the replacements when they arrive, maybe with a pair the same of the lower type it will work. I'll report back once I have the bits home.

So its the distance between the ground out/machined sections obviously that allow the flow through.

So would it be possible to machine one which had metal to remove to allow, is this stuff hardened or just chrome coated.

They should be hardened steel.

 

[m_c]

One of the spools on a loader should have a float position.

Edit. just read through this, I think the sinking of the loader prior to lifting could be the pipes on the wrong way around on the lift spool, as in when you pull the lever back you are going through the float position. Hope that makes sense

Bob

I've never known a tractor loader to have a float position.
Plus a float position, is usually in a '4th' position aka you need to move the spool past the normal spring loaded positions, into the detented float position.

When you need to lift something, you want the loader to do what you want it to do, not go the opposite direction under gravity first.

 

[8ob]

I've never known a tractor loader to have a float position.
Plus a float position, is usually in a '4th' position aka you need to move the spool past the normal spring loaded positions, into the detented float position.

When you need to lift something, you want the loader to do what you want it to do, not go the opposite direction under gravity first.

What I was getting at is to swap the pipes around on that lift spool to see if the problem is still there. If it’s not there is a good chance there is a float position on that block. I have never had a loader without a float position.

Bob

 

[chrismac]

One of the spools on a loader should have a float position.

Edit. just read through this, I think the sinking of the loader prior to lifting could be the pipes on the wrong way around on the lift spool, as in when you pull the lever back you are going through the float position. Hope that makes sense

Bob

Thats what its like right enough, spools on the back end of a tractor I have seen, have had the float to the extreme of the lever, back full pumping, forward a touch holding on the return spring pumping opposite way, then float all the way forward, where this is doing it sooner on the lever travel, I'll see what changes when I get the bits home.

 

[m_c]

What you have fits the description of a Negative Overlap spool, which according to the datasheet, shouldn't be an option.
However there is no saying how old the datasheet is on the Flowfit website, so it could be a newer option.
Or it's a custom/obsolete option, and somebody somewhere has mixed the spools up.

The valve appears to be made by GMS Hydraulics in Turkey, but they don't have any downloads available on their website - https://www.gurmaksan.com.tr/monoblock-valve-45l-gm

 

[chrismac]

What you have fits the description of a Negative Overlap spool, which according to the datasheet, shouldn't be an option.
However there is no saying how old the datasheet is on the Flowfit website, so it could be a newer option.
Or it's a custom/obsolete option, and somebody somewhere has mixed the spools up.

The valve appears to be made by GMS Hydraulics in Turkey, but they don't have any downloads available on their website - https://www.gurmaksan.com.tr/monoblock-valve-45l-gm

And the negative overlap spool is purely the internal part, the block remains the same for it to work, which it must as I am sure this does the same in either of the 2 ports.
And it looks like they are supplying me additional spools of the same type.

 

[m_c]

Yes, the bodies are generally common between all the normal valves.

The datasheet does have a couple cross sectional drawings on page 63 showing flow for a standard three position spool, which I've copied one off, and marked the P/T galleries-

The 3 right most oil galleries, the right most will be another tank return to ensure there's no pressure build up behind the seals.
However I'm not sure about the other two ports. They're possibly alternate A/B ports (the internal galleries on a spool are quite elaborate, and not all straight through passages), to allow for the other spool options like float/motors.

 

[chrismac]

So the saga continues,

The rouge spool part number 3501- CF 240/21, (larger section with 6 score line) should not be in the block or the manufacturer said its one of either 3501 or 3501-CF but not a mixture.

The other which was its mate does not have a part number on it but is the same as 3501 170/ 23 supplied as a replacement, strangely 2 were sent they were both different 3501 420/22 but this does not fit, its too tight and the hole for the lever is too small.

I have reassembled with one original and 3501 170/23 and hooked up to a compressor to try and I am not convinced its doing what it should.... when 3501 CF was in it was simple air one way or the other, the other current combination seems to be doing strange things, so much so I cant even clearly see or feel whats going on,

If I block the power beyond port can I try it then which I guess is a yes but asking first seems the right thing to do, this might help as the low flow from the compressor is nothing like the flow from the hydraulic pump.

 

[chrismac]

So the plot thickens, after struggling to know how these 2 spools could be operating different even when sent back and stripped and tested, I needed to pull them apart to see/make sure the internals were the same, or what was in there.

Stripped
Spool 2 2025 by chrismac2012, on Flickr

Close up
Spool 1 2025 by chrismac2012, on Flickr

Now its clear to see both are different, the issue I now have is the top one is the one functioning as I would expect(or at least its doing what I want it to do) the other has flow the wrong way before it eventually flows in the direction it should, but they (flowfit) have no idea what the top one is, have never seen anything like it and only have the bottom type available for my needs, they are sending one or two of the lower type with the 4 grooves in the first section, I have to try it and see what happens, they think the top one might be affecting the flow one way or another(not sure I believe that but I am in no position to challenge that yet) whats the thoughts here?

I just got round to refitting this spool block with the now correct spools, lower one in the photo above in both ports.

now this is what happens

Untitled by chrismac2012, on Flickr

as you can see it drops unless you pull the leaver back slightly which is not normal position in rest.

I refitted the incorrect spool as before and at least it stays up, although it drops before it raises as before, not great that way but at least I can put the mower on and cut the grass.


Untitled by chrismac2012, on Flickr

I sent an email to the supplier and they have advised I need to fit check valves on each cylinder, why do I not need these check valves when my original spool valve is used, I wish I could get replacement spools for that, this is the old one below.

I would appreciate the thoughts of the knowledgeable folk on here.
Thanks

 

[m_c]

I wonder if you've got a leaking ram seal.

If the internal/piston seal was leaking, the ram would essentially act as a displacement ram.
If that was the case, when you move the spool, it'll most likely open the 'vent'/rod side first, which would release the pressure from the rod side, and if the piston seal has failed, would allow the loader to drop.

There are a couple ways to check.
Blank the cylinder end of the ram (for twin rams, you'd just want to blank the common pipe/hose), and pressure the rod side. If the rams extend, a seal has failed.
Take off the rod hose, stick it in a bucket to catch the oil, and lift the loader. When you release the lever, the oil flow out of the ram should stop, and the loader remain in place. If the oil continues, and the loader drops, then a seal has failed.
You need to try and replicate the condition where the loader drops, as depending on how the seal has failed, it may only bypass under light load/pressure, and seal up when under higher pressure.

I've seen a loader fail in this way before, albeit with a far slower drop rate, and it transpired the piston had unscrewed from the rod a few turns.
I never dealt with the ram repair, I only done the removal and refitting, but the report back from the hydraulic place was the piston had unscrewed a few turns.

 

[chrismac]

I wonder if you've got a leaking ram seal.

If the internal/piston seal was leaking, the ram would essentially act as a displacement ram.
If that was the case, when you move the spool, it'll most likely open the 'vent'/rod side first, which would release the pressure from the rod side, and if the piston seal has failed, would allow the loader to drop.

There are a couple ways to check.
Blank the cylinder end of the ram (for twin rams, you'd just want to blank the common pipe/hose), and pressure the rod side. If the rams extend, a seal has failed.
Take off the rod hose, stick it in a bucket to catch the oil, and lift the loader. When you release the lever, the oil flow out of the ram should stop, and the loader remain in place. If the oil continues, and the loader drops, then a seal has failed.
You need to try and replicate the condition where the loader drops, as depending on how the seal has failed, it may only bypass under light load/pressure, and seal up when under higher pressure.

I've seen a loader fail in this way before, albeit with a far slower drop rate, and it transpired the piston had unscrewed from the rod a few turns.
I never dealt with the ram repair, I only done the removal and refitting, but the report back from the hydraulic place was the piston had unscrewed a few turns.

Thanks for this,
And this is a possibility even though when I have the old spool valve block on it operates as expected? Its just when I fit (now fitted) the replacement valve block its not operating like I had hoped.

 

[Ace Paul]

Can you get valve of something else

Forklift. Tow truck. Tail lift etc

 

[chrismac]

Can you get valve of something else

Forklift. Tow truck. Tail lift etc

I have the old one it works its just leaking as the internals are corroded/pitted, I bought a replacement and its been nothing but bother, had the new one for 3 years but only had it on twice, went back to using the old leaking one, but now I am trying to get to the issue, but its not looking like I will with out getting another spool.