B7510 hydraulic operating pressures

[mwzad]

Good morning all,

I have a B7510 with a LA302 loader and 4672 backhoe. I am planning on checking my hydraulic operating pressure with a gauge that I fabricated. After I verify operating pressure, if I wanted to shim the pressure up a little how would I go about doing that? Would I have to shim the hydraulic system for the tractor on the main hydraulic pump under the seat or would I go about shimming the loader on the control block? In the past I have shimmed my hydraulic system on my JD X595 garden tractor and that was on the main hydraulic system the loader did not have the option. Any feedback would greatly be appreciated. Thanks

 

[TheOldHokie]

Good morning all,

I have a B7510 with a LA302 loader and 4672 backhoe. I am planning on checking my hydraulic operating pressure with a gauge that I fabricated. After I verify operating pressure, if I wanted to shim the pressure up a little how would I go about doing that? Would I have to shim the hydraulic system for the tractor on the main hydraulic pump under the seat or would I go about shimming the loader on the control block? In the past I have shimmed my hydraulic system on my JD X595 garden tractor and that was on the main hydraulic system the loader did not have the option. Any feedback would greatly be appreciated. Thanks View attachment 72426

The first valve in the chain (one closest to the pump) will set the maximum for all downstream devices.

Dan

 

[OrangeKrush]

Wish I'd of known about OTT when I had my B7510, no problems with it just admire all the knowledge on here. I was on my own back then!

 

[Henro]

The first valve in the chain (one closest to the pump) will set the maximum for all downstream devices.

Dan

What I always wonder, is how those who adjust their hydraulic pressure can be sure the gauge they are using is actually accurate.

For electrical work I have some rather high end Fluke VOMs that I kind of trust, and can compare to other VOMs I have to get an idea if I am likely measuring accurately.

If I were to try to adjust my hydraulic pressure I would first want to know the gauge I was using was actually measuring accurately.

Have no clue how I would confirm that. Doubt that the common gauges easily purchased off Ebay or Amazon come with a traceable calibration certificate.

So my question is: How can one be sure the gauge he is using is actually giving an accurate measurement?

 

[Henro]

The first valve in the chain (one closest to the pump) will set the maximum for all downstream devices.

Dan

Another question...

Dan, if there are several pressure relief valves in the system, wouldn't each activate depending on what it saw as far as pressure goes?

So with a power beyond set up, would not different PRVs activate at different time?

I am probably misguided, but for some reason I thought the main PRV on the tractor would be the primary one, and give protection to the tractor overall. Also probably thought if there were other PRVs in the system that were set lower, they would activate before the primary one.

Not disputing anything, just trying to learn a bit more. Too easy for me to miss the point sometimes these years...

 

[North Idaho Wolfman]

Good morning all,

I have a B7510 with a LA302 loader and 4672 backhoe. I am planning on checking my hydraulic operating pressure with a gauge that I fabricated. After I verify operating pressure, if I wanted to shim the pressure up a little how would I go about doing that? Would I have to shim the hydraulic system for the tractor on the main hydraulic pump under the seat or would I go about shimming the loader on the control block? In the past I have shimmed my hydraulic system on my JD X595 garden tractor and that was on the main hydraulic system the loader did not have the option. Any feedback would greatly be appreciated. Thanks

The main Hydraulic pump is on the side of the engine not under the seat????

The relief valve to adjust the system pressure in in the control valve that is inside the rear end / Lift cylinder housing, not accessible with removing a whole lot of parts, and then finding the right combination of shims would be nothing more than a shot in the dark.

 

[TheOldHokie]

Another question...

Dan, if there are several pressure relief valves in the system, wouldn't each activate depending on what it saw as far as pressure goes?

So with a power beyond set up, would not different PRVs activate at different time?

I am probably misguided, but for some reason I thought the main PRV on the tractor would be the primary one, and give protection to the tractor overall. Also probably thought if there were other PRVs in the system that were set lower, they would activate before the primary one.

Not disputing anything, just trying to learn a bit more. Too easy for me to miss the point sometimes these years...

First I assume we are talking inlet pressure relief valves. The first valve will limit the maximum pressure going downstream. A down stream valve can decrease that but it cant increase it. The why should be obvious. With multiple valves in the circuit pressure can cascade down but never back up.

For example if the main relief is set at 2000 PSI and the 3pt is set at 1500 PSI every device between the main relief and the 3pt will see 2000 PSI. The 3pt cylinder will only see 1500 PSI.

If we put a loader valve with inlet pressure relief set to 1800 PSI between the main relief and the 3pt the loader cylinders will only see 1800 PSI. If we bump the loader pressure setting up to 2500 PSI the valve and cylinders will still only see 2000 PSI.

Think about it a bit.

As for gauge accuracy you can safely assume +/- 2% of full scale for a $20 commodity gauge. Thats more than adequate for working on a 2000 PSI tractor. Industrial quality is generally half that. If you really need it and are willing to pay there are plenty of calibration services.

Dan

 

[Henro]

First I assume we are talking inlet pressure relief valves. The first valve will limit the maximum pressure going downstream. A down stream valve can decrease that but it cant increase it. The why should be obvious. With multiple valves in the circuit pressure can cascade down but never back up.

For example if the main relief is set at 2000 PSI and the 3pt is set at 1500 PSI every device between the main relief and the 3pt will see 2000 PSI. The 3pt cylinder will only see 1500 PSI.

If we put a loader valve with inlet pressure relief set to 1800 PSI between the main relief and the 3pt the loader cylinders will only see 1800 PSI. If we bump the loader pressure setting up to 2500 PSI the valve and cylinders will still only see 2000 PSI.

Think about it a bit.

As for gauge accuracy you can safely assume +/- 2% of full scale for a $20 commodity gauge. Thats more than adequate for working on a 2000 PSI tractor. Industrial quality is generally half that. If you really need it and are willing to pay there are plenty of calibration services.

Dan

Thanks. I went back and read the post that generated my question, and now see that it became a "I said what you said, and you said what I said..." kind of thing. Somehow I misinterpreted your original post...sorry. What you stated in this last post is what I thought I was saying...

On pressure gauges my weakness is that on important things I like to have full confidence in measurements. No doubt you are likely correct that a cheap gauge is likely accurate within a few percent. For me that works for tire pressure...not sure I would feel comfortable adjusting my tractor hydraulic pressure with a cheap gauge of unknown calibration though. I guess I must have bought too many cheap products off eBay in the past. Some gems, and some duds.

Just me of course...

 

[TheOldHokie]

Thanks. I went back and read the post that generated my question, and now see that it became a "I said what you said, and you said what I said..." kind of thing. Somehow I misinterpreted your original post...sorry. What you stated in this last post is what I thought I was saying...

On pressure gauges my weakness is that on important things I like to have full confidence in measurements. No doubt you are likely correct that a cheap gauge is likely accurate within a few percent. For me that works for tire pressure...not sure I would feel comfortable adjusting my tractor hydraulic pressure with a cheap gauge of unknown calibration though. I guess I must have bought too many cheap products off eBay in the past. Some gems, and some duds.

Just me of course...

They are not uncalibrated. Pressure gauges are graded and calibrated by the manufacturer just like any other measurement instrument. A $20 pressure gauge is typically ANSI accuracy class 1A or 1B.

The accuracy class is usually available from the manufacturer and if you inquire most can provide you with a calibration certificate "traceable to NIST".

That certificate is no more reliable than the manufacturer's claims of accuracy. Just FYI, for the last 25 years I worked I was a NIST researcher and I am pretty familiar with their practices. For physical metrology their certification of accuracy starts and ends with their calibration and certification of the first manufacturer instrument in that calibration chain. Once it goes back to the manufacturer it is out of their control and all bets are off. That also applies to your Fluke VOMs . They need to be recalibrated by a reliable service and on a regular basis for the accuracy claims to be meaningful.

Dan

 

[Henro]

They are not uncalibrated. Pressure gauges are graded and calibrated by the manufacturer just like any other measurement instrument. A $20 pressure gauge is typically ANSI accuracy class 1A or 1B.

The accuracy class is usually available from the manufacturer and if you inquire most can provide you with a calibration certificate "traceable to NIST".

That certificate is no more reliable than the manufacturer's claims of accuracy. Just FYI i was a NIST researcher for the last 25 years I worked and pretty familiar with thier practices. For physical metrology their certification of accuracy starts and ends with their calibration and certification of the first instrument in that calibration chain. Once it goes back to the manufacturer it is out of their control and all bets are off. That also applies to your Fluke VOMs . They need to be recalibrated by a reliable service and on a regular basis for the accuracy claims to be meaningful.

Dan

Thanks for that, good to know.

As far as calibration, for what I do electrically, being retired, not that important. But I occasionally do check the meters against a voltage source to see if they read the same or very close. They always do, so I suspect they are fairly accurate, at least within whatever accuracy they were set to, to begin with.

I would feel more comfortable having several hydraulic pressure gauges and doing the same thing. If they all read the same or very close I would have more faith they are likely correct, within the percentages you mentioned. But as you said, it likely is a non issue.

Also, I believe specified accuracy is percent of full scale on the device, and not linear over the full range, so if one is using the device at the low end of the scale range, the accuracy likely becomes worse the lower one goes.

This may or may not be true for all measurement devices...

 

[TheOldHokie]

Thanks for that, good to know.

As far as calibration, for what I do electrically, being retired, not that important. But I occasionally do check the meters against a voltage source to see if they read the same or very close. They always do, so I suspect they are fairly accurate, at least within whatever accuracy they were set to, to begin with.

I would feel more comfortable having several hydraulic pressure gauges and doing the same thing. If they all read the same or very close I would have more faith they are likely correct, within the percentages you mentioned. But as you said, it likely is a non issue.

Also, I believe specified accuracy is percent of full scale on the device, and not linear over the full range, so if one is using the device at the low end of the scale range, the accuracy likely becomes worse the lower one goes.

This may or may not be true for all measurement devices...

First lets limit the discussion to Bourdon tube type instruments as they are by far the most common.

Technically ANSI pressure gauge accuracy is specified as xx/yy/zz wher xx is the accuracy on the low end, yy is the accuracy in the mid range, and zz is the accuracy on the high end. Off hand I cannot remember the exact break down of the bands but its something like lower 30%, middle 40%, upper 30% and a typical value would be something like +/- 2%/1%/2%. So counter-intuitively when working on a 2200 PSI tractor a 5000 PSI gauge is a better choice than a 3000 PSI gauge.

Its always safer to have two (or more) instruments rather than one so you can sanity check one against the other.

Dan