PQ Measurements

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ben.martins
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PQ Measurements

Post by ben.martins »

Hi all,

Hope all are safe and well.

Just to follow on from this post topic22592.html regarding the use of XY for motor and resolver measurements. This can of course be used in hydraulics where we can capture both pressure and flow.

When it comes to pump testing the PQ graph helps us to understand the condition on the pump and spot any signs of change. Current methods typically involve a pen and paper to write the down the values at certain pressures. This process can be sped up with Pico when you combine the WPS600C and either the 300lpm or 600lpm flowmeters.

The principle is the same as the motors where we use XY view to change the X-Axis from displaying the signals in relation to time but instead to another channel. This means we can replicate the PQ graph by plotting the measured flow rate against the pressure. How to set this up is described in the link above but below is an example of what it might look like.
PQ Test.png
This PQ test was done on a JCB JS220 with the pumps only regulated by the internal galleries. The working outline of these pumps can be seen here - topic22508.html.

Here we can see that there are two stages to reducing the flow rate inside this pump. Around the 250 Bar mark we can see the that the flow changes to dropping at a more dramatic angle. We believe this is the action of the pumps self regulation.

XY is only available in PS6 Automotive at the moment but should be coming to PS7 very soon.

Hope this helps.

Kind regards

Ben

muttnjeff
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Re: PQ Measurements

Post by muttnjeff »

Hello Ben,

Thanks for the post, couple questions.

Would this be considered a pump efficiency/performance test, and can this PQ test also have engine rpm added to show pump performance at a given rpm?

Neil

ben.martins
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Re: PQ Measurements

Post by ben.martins »

Hi Neil,

RPM can of course be added in. I usually always try to include the crankshaft sensor in any of the hydraulic captures I do, purely to get the RPM.

We talk about more about hydraulic pump efficiency calculations in the maths is cool topic - viewtopic.php?p=98250#p98250. Here we look at the theoretical pump flow based on pump speed (typically engine speed) and pump displacement. This gives us the theoretical pump flow which can then be compared to the flow rate from the flowmeter. The ability to load the pump is only an option on the 300lpm and 600lpm flow meters which include the loading valve.

Hope this helps and as always happy to discuss further if needed.

Kind regards

Ben

lastvagn8
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Re: PQ Measurements

Post by lastvagn8 »

Hi, thanks for a good post and lesson.

Is this pump replaced since it drops around 30 Lpm when at max pressure? A good thumbrule is to accept around 10% loss of flow at max pressure. That's of course that the rpm on the motor is maintained.
Do you have a opinion about this?

Best regards
Jim

ben.martins
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Joined: Tue May 16, 2017 1:02 pm

Re: PQ Measurements

Post by ben.martins »

Hi Jim,

Completely agree with the 10% of most pumps as a given loss due to internal leakages. This capture was taken from a K3V pump which has some internal control of the swash plate based on the back pressure generated through the pump. This gives this a pattern the appearance the flow dropping off rapidly at a certain pressure point. The pump control can be seen in more detail in the following link - viewtopic.php?p=101592#p101592

If you take a look at page 8 on the following document - http://www.kpm-usa.com/wp-content/uploa ... _K5V_e.pdf, you'll see a more dramatic impression of the capture I have. The position of this internal flow control can be adjusted and actually with the machine the capture was taken from, this was what needed to happen. Using the scope and this technique we could plot where this point was and make live alternations to the pumps to ensure the pump wasn't lugging the engine down to the point of a stall but also ensuring the machine still had enough digging power.

I hope this helps but any questions please ask!

Kind regards

Ben

lastvagn8
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Re: PQ Measurements

Post by lastvagn8 »

Thank you, as always very good information and no guesses! You are an inspiration.

/jim

ben.martins
Pico Staff Member
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Joined: Tue May 16, 2017 1:02 pm

Re: PQ Measurements

Post by ben.martins »

That's very kind of you Jim! Not sure I would say an inspiration though! More someone that hopefully helps to make life a bit easier!

Thanks again and as always let me know if you need any support on this subject.

Kind regards

Ben

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