pressure drop in relief valve (prince RV-1H)

[rScotty]

I'm not really sure what there is to "notice" in relief valve operation, anyway - a larger audio "pop" at the beginning of it opening iff it's "too slow" and dangerous pressure spikes build?

Usually what you notice is the noise. Relief valves deliberately make a loud screeching sound when they are releasing excess pressure. Depending on design and pressure/flow, the noise may vary from being very noticible .... on up to being a deafening screech that will set your hair on end. But you are unlikely to miss it when it happens.

Once they activate you are safe from overpressure because they open enough to handle whatever flow they are seeing. More flow results in a larger opening and louder screech. In that respect they are the same as any spring device operating in linear range.

Hydraulic pressure relief valves are designed that way so that they stay open for a few seconds to avoid the rapid on/off machine gun behavior that characterizes some other similar valves - such as automatic draft control valves in the 3pt hitch. Those have a rapid-fire on/off sequence.

 

[orangetree]

Prince got back to me, RV series with 1/2 inch ports (the smallest option) will have negligeable pressure drop. ~1/2 PSI at my 7gpm.

 

[orangetree]

Usually what you notice is the noise. Relief valves deliberately make a loud screeching sound when they are releasing excess pressure. Depending on design and pressure/flow, the noise may vary from being very noticible .... on up to being a deafening screech that will set your hair on end. But you are unlikely to miss it when it happens.

Once they activate you are safe from overpressure because they open enough to handle whatever flow they are seeing. More flow results in a larger opening and louder screech. In that respect they are the same as any spring device operating in linear range.

Hydraulic pressure relief valves are designed that way so that they stay open for a few seconds to avoid the rapid on/off machine gun behavior that characterizes some other similar valves - such as automatic draft control valves in the 3pt hitch. Those have a rapid-fire on/off sequence.

agreed on the noise. That said, there aren't that many operations in an TLB that will trigger this any more than momentarily when something reaches end of travel. And once you get used to a machine, that's not happening a ton.

 

[rScotty]

Reading again.... Do I have it right that the grapple valve is in the line going to the FEL valve? Why? Does your FEL valve not have a Power Beyond port?

Not sure I see how this is to work.

 

[orangetree]

Reading again.... Do I have it right that the grapple valve is in the line going to the FEL valve? Why? Does your FEL valve not have a Power Beyond port?

Not sure I see how this is to work.

Yep, have power beyond.

But the valves on my tractor, like virtually all smaller TLB's, are "tandem valved -VS- series"**, so i can't use my full meager flow simultaneously. I only expect to use it as such when the tools are ~unloaded (no magic here) ... but that use, like when "repositioning" is probably > 50% of the actual movement. So being able to choose to do that at "full speed" is pretty useful, IMHO. Useful enough to make some modifications.

Since i must add a 3rd function anyway, it's not that much more work here. I didn't love the mounting of the Factory 3rd function, nor the WRlong, so I also get some other benefits. What my changes do is move fluid at full flow through all downstream valves while the grapple is activated. Of course if the grapple dead-heads, flow stops. But that's fine, all of these are tradeoffs.

Concrete example:

1. Say I'm lifting & clamping. Lifting IS loaded ... but clamping is not.
2. So I can continue to lift while i clamp (close) the grapple, BOTH AT FULL SPEED
   1. ; the action of closing takes a hundred or three PSI off my system's head, sure - but i can basically use my "full power" still to lift.
3. When the grapple fully closes, i hear the screech, the lifting stops momentarily
4. ... then i immediately release the grapple button and continue.
5. I just saved 5 seconds. Repeat for 30 years (I hope) of hobby use.

Worth it? I hope so, we'll see Obviously it's a lot of work - but i also like understanding things, and now reasonably do after having to wade through all this.


** I'm linking to @Farmerford's post as I don't think these terms are really 100% standard, but he did a great job of details the options

 

[rScotty]

Do I have this right? I had no idea that any FEL or TLB used Tandem Valves in the directional control valve. Why not simply change over to a directional control valve with parallel valves like nearly every FEL out there. Is yours a home-made system? I guess I don't understand why to do it that way?

 

[orangetree]

Do I have this right? I had no idea that any FEL or TLB used Tandem Valves in the directional control valve. Why not simply change over to a directional control valve with parallel valves like nearly every FEL out there. Is yours a home-made system? I guess I don't understand why to do it that way?

Read the definition i linked.

As best i can tell, there is no name in common use w.r.t. the semantics of flow i'm talking about. Farmerford provided workable definitions that will save a whole lot of hot air.

 

[oldnslo]

Rscotty
I believe what is happening is that orange is using industrial valve terminology for mobile valves. Industrial valves like D03, D05, etc. have 4 flow paths and a tandem center allows flow from P to T with A & B blocked n center condition. Difference is mobile parallel flow have have six flow paths in their schematic. They have a power beyond or pressure carry over and separate tank that industrial valves do not have. At least this is what I saw in looking at previous posts. Orange wants series so can multifunction easier with higher speeds. Some mobile valves also offer series circuit but they are not very common.

 

[orangetree]

Rscotty
I believe what is happening is that orange is using industrial valve terminology for mobile valves. Industrial valves like D03, D05, etc. have 4 flow paths and a tandem center allows flow from P to T with A & B blocked n center condition. Difference is mobile parallel flow have have six flow paths in their schematic. They have a power beyond or pressure carry over and separate tank that industrial valves do not have. At least this is what I saw in looking at previous posts. Orange wants series so can multifunction easier with higher speeds. Some mobile valves also offer series circuit but they are not very common.

Thanks for the clarification. FWIW i haven't found as clear of terminology in the "mobile" world, vs the "industrial" community [definitely standard names, btw]. I'm sure it exists, maybe it's just more-specialized/smaller user group (of folks actually engineering things that is).

Which would also make sense because they (mobile) often come fully integrated as in an off-the-shelf tractor, vs the every-system-is-custom of the industrial world such as manufacturing plants etc.

Also correct, the D05 etc valve format has 4 ports. "return to tank" is full pressureized, analogous to power-beyond - except there is no atmospheric-return-to-tank that accepts flow from the exhausting cylinder. For anyone catching up, I am going D05 because the "steady state" pressure loss of just one D03+manifold would be over 100psi (that's a lot of wasted heat & pressure, just while sitting there)

Last, note that industrial are pretty common in aftermarket - WRLong's 3rd function is simply a D03 valve & manifold, nothing more or less; and much of Summit's line is industrial as well.

 

[rScotty]

Rscotty
I believe what is happening is that orange is using industrial valve terminology for mobile valves. Industrial valves like D03, D05, etc. have 4 flow paths and a tandem center allows flow from P to T with A & B blocked n center condition. Difference is mobile parallel flow have have six flow paths in their schematic. They have a power beyond or pressure carry over and separate tank that industrial valves do not have. At least this is what I saw in looking at previous posts. Orange wants series so can multifunction easier with higher speeds. Some mobile valves also offer series circuit but they are not very common.

Thank you. Yes, I believe you are right. I had just about come to that same conclusion. He and I are talking on two different levels here. Orange is using an industrial flow terminology that is more often seen in regenerative and pressure saving circuits that define and use every bit of the full range of spool valve movement as opposed to our tractor controls with their simple parallel flow valves - or even the ones that use a series/parallel tractor control valve.
In his considerations - which are complex - I believe that Orange is trying to utilize some some recovery of normally wasted pressurized flow in the Control Valve itself .... and perhaps even couple that with some degree of regeneration. And over a full range of motion.

This thread has quite opened my eyes to something else which I had always wondered about in our TLBs.
It has helped me to look deeper into control valve spool and edge geometry and understand why some control valves are so good at high speeds and others so good at delicate control.

Here's an example: Our JD310SG TLB has a backhoe control that will swing a bucket fast enough to pound a post into the ground. But try as I can, it is not dependable when what I want is to slide a two ton stone a quarter inch into a better position when building a stone wall. The Kubota TLB's backhoe is just the opposite. It does not work nearly so fast even at full throttle, but can apply full force to move that same stone a fraction of an inch with confidence. Both the JD and Kubota will hold a load in position for half an hour with only slight droop, so bore wear in the control valve is not the answer.

I had always thought that difference in those two control valve operations was due to internal spool wear, or maybe simple manufacturing tolerance - but this thread has exposed me to my own ignorance on the subject. There are other ways to accomplish control or speed. For example, by using sophisticated internal features of the spools, lands, and passages in the control valve to emphasize hybrid parallel/series/tandum fluid flow. Some features in the shape of the valve guts may be microscopic applications of geometry that I would not understand if I was looking right at it. I'd have to use a CFD (computational fluid dynamic) program to even get started on the path Orange wants to explore.

However, just studying the concepts helped me understand why some Control Valves are accurate at partial opening and others so fast.

Thanks again to both of you. I'll have to study up some more before I can bring anything of value here.

rScotty