Next-Level Hydraulic Diagnostics - Possibilities & Feasibility
As a diagnostician, I am always searching for faster and more efficient ways to get the job done, whatever it may be. The world of diagnostics is ever expanding yet certain areas of our industry lag behind; heavy duty and off-road is generally one of these areas, due in part to inherent design flaws. Much of the more advanced testing techniques that have become somewhat mainstream, such as pressure transducer usage, in automotive have not begun to catch on to the same extent within the diesel and off-road markets, in my experience.
I have begun some preliminary research and planning into advancing my hydraulic diagnostic capabilities. As expected, the information and case studies are somewhat lacking so far, besides brief mention on Pico's website and some white papers on engineering level vibration and pulsation analysis within hydraulic systems.
Some of the ideas that I am researching and will be testing include:
- Hydraulic Pump/Motor Health - I believe it may be possible that specific pumps (especially axial piston pumps) could have their pressure pulses monitored as a means of determining pump health (similar to current ramping a fuel pump)
- There is also a thought floating around in my head that incorporating an NVH kit may lead to some impressive results if used creatively
- Valve Stack leakage & operation
- Cylinder Operations
- Effects of Solenoid Valving on hydraulic systems
- Hydraulic system effect on engine performance in real-time and vice-versa
I am wondering if anyone, including any representatives from Pico, has some further information or experience in this undertaking? An undertaking like this will be a work in progress, perhaps one in vain, but if successful I hope to be able to help open up a whole new level of diagnostic strategies for heavy-duty technicians. Hooking up gauge sets is already a common practice, so imagine if there is a whole new level of insight that could be gained by merely substituting a pressure transducer for a gauge and building up a waveform library and some top-level diagnostic thought behind it.
As I've said, this is a thought experiment first while I figure out the logistics. My tooling for this product is limited to a Parker Serviceman with the 8,700 PSI transducer (will have to figure out how to modify the connector for my scope), Snap-On (SO) 0-500 PSI & 0-100 PSI transducers, and a Verus Edge for a scope. Like most projects worth pursuing, this will require some creativity and new thought processes but I think it is worthwhile, I welcome all who wish to join the experiment.
You seem to always have interesting post and ideas thanks for that. I have thought about using the pressure sensor on a 6.0 Powerstroke for pump heath, I have looked at one or 2 not enough to gain any knowledge though. I’m interested in your findings. I believe Frank Massey did something similar on a diesel pump, but that was in a car.
I just spend alot of my day trying to improve on what I'm doing. If I can make some use out of my ideas then great, if not then I've still learned something.
Seems only right to pay it forward after all the information others have made available to us.
I'll have to look into Frank Massey.
It may be interesting to research what production plants do. I know they have vibration sensors on hydraulic pumps and motors that can be remotely monitored. From what I can tell they do not necessarily use the data for diagnostics, more to identify failures before or as they occur. I don't work on much equipment anymore, otherwise I would be game to experiment. Is your Parker transducer the analog or CAN bus?
That's where the bulk of my research is now, technical papers and industrial usages. I'm hoping to adapt some of their principles to something a bit more useful for someone in the field.
The transducer is analog, just has a special connector I'll have to play with. Response time is 1ms which should be sufficient I imagine.
I too will try to help if i can. I have the pico 600 bar. and 500 bar. transducer.
I'm going to make a suggestion. I think it's time to upgrade to the Picoscope. The Snap-on scope has weak functionality compared to Picoscope. Does the Verus Edge scan HD vehicles, or do you have it mainly for the scope? When I check ebay, I see the Verus Edge selling for like $3,000 to $4,000. That's more than enough to get set up with a Picoscope.
Let's see what it might cost:
- $ 1800 Picoscope 4-channel Lite kit
- $ 899 WPS500X Pressure Transducer Starter Kit
- $ 700 Laptop or tablet
- $ 3399 Total
I can give you the details on how to make that if wanted, but I think it may be better to attach the scope to the backside of a laptop or something. Main reason is that the picoscope software no longer supports a stylus as well as it used to, and it's easier to just use a keyboard and trackpad anyway.
One more suggestion, and it may be controversial, but I recommend you buy your Picoscope kit from Autonerdz
That's just my opinion. I'm not advertising for them. The reason I recommend it is because if you buy one of the Autonerdz Custom Kits that has the PicoGroup Support package, you will have access to the PicoGroup area of the Autonerdz forums, which has a HD section with some HD techs that have been scoping diesels and HD stuff for quite a long time. The support package also has lots of other benefits as well.
This is just a suggestion. Have a good one 😎
Always appreciate your input and suggestions, and believe me a Pico scope and some accessories are at the top of my list for purchases. Unfortunately, with work cutting hours back right now it is not a viable move at this time. Got to make ends meet before I spend more 😑.
I do HD during the day, so the Verus Edge is my run and gun scope, but nights and weekends are my automotive diags and that's where utilizing the Edge comes in handy (though it has it's fair share of limitations throughout). These shortcomings are something to deal with for now until I build myself up to a better place tooling wise.
I do like the portable set-up you have there and have contemplated something similar, so I will be getting ahold of you of that without a doubt for more info on that.
As of right now, I just have to truck through with what I have and use it to hopefully generate some income for advancement.
Chris - you seem to have a very curious mind and enjoy electrical theory research way too much not to have a pico and be building your own wave form library at this point.... I personally wished and wanted a pico for way too long i didn't make the funds a top priority. I have had one for several years now and never looked back there is NO comparison and i never stopped thinking i should have got this sooner... Good Luck I enjoy reading your posts
I appreciate the kind words and glad you enjoy the posts. I'm just adding in what I find interesting in the hopes of getting some more traffic on the network here. In fact, I had put up a post to see what everyone wanted to see on the network here. If anyone posts there with some recommendations for content they want, or if they just post something up, I am committing myself to doing the research and work to help build up that topic. It gives me a bit more direction in my self-studies.
I've definitely been building up a library bit by bit, but Snap-On's Shop Stream Connect doesn't hold a candle to the capabilities of Pico when it comes to manipulation of the waveforms for research. Pico is definitely a priority, but I will just leave it at the fact that my current position isn't conducive to profit nor advancement of skills to the level I wish to achieve; I'm exploring alternative possibilities at this point, but still have to maintain steady income of some level until then.
If you were closer to me I would be looking to interview you.... Your mindset is a employers dream. Keep up the good work and find the pay you deserve! I wish you the best
Steven, love that portable setup, I haven't seen a setup like it before.
I just want to add something quickly here so I follow this up asap.
I have been proactively working with hydraulics with the WPS600 for understanding hydraulic pressure analysis. I'm sure your not but please don't think this device can be used for diesel fuel pressure. It is designed soley hydraulic fluid.
I would be interested to talk to you further about this and I will add more information to this post but I won't have an opportunity to do so today.
Axial pump health, pump efficiency and PQ tests are all very possible with Pico and I've been doing a lot of research into Fuid Bourne Noise which is gathering pace.
Please bear with me and I will reply but it would be good to talk as well.
Take all the time you need as I was expecting to go into this endeavor blind. I generally spend a solid week just on research before formulating initial testing procedure experiments. There are quite a few variables that are rolling around my head so they will take time to sort out.
I'm glad to know you've already been doing the hardwork and I'm looking forward to working back and forth, though for now I'm at a tooling disadvantage to you; I believe we can work through that though as the readings and test procedures are really the basis we want to build here.
I have contemplated the merits of common rail diesel testing methods and I've come to the conclusion that the only thing that may be of use, in addition to the standard scope tests, is using an NVH kit and trying to hone in on pressure pulses or dissonant frequencies and what their root cause might be. I have no intentions of doing direct rail pressure measurements.
I look forward to your input and I will continue to do my preliminary research in the meantime.
Chris I commend you for wanting to give this a go. I'm still wrapping my head around automotive diagnostics. Currently at my place of employment I work on some diesels here and there and diagnostics approach/available resources are a little different.
Looking forward to future posts. I'm guessing most adapters would be custom made for the pressure transducers?
Another great post. Thanks
I am still working on my automotive diagnostics, as well as my diesel and hydraulic, I am far from competent. I have one reason to start a project or research and that is to find a better way to get it done. I hate plumbing in pressure gauges and getting hydraulic oil everywhere.
As far as pressure transducers, it's up in the air. I definitely see how they can be helpful for intrusive testing. However, as Ben alluded to, and I have found in a few technical papers, there are some applications where they actually use the frequency of the pulsing tubes or harmonics of the hydraulic system in order to determine condition or type of failure. Think of the older diesel RPM pickups that clamped onto an injection line in order to pick up fuel pressure pulses and calculate engine RPM from that; I was using one yesterday and that's what got me thinking of this experiment.
It'll be interesting to see what comes of it.
Hello Chris and all interested here!
I think you have bought up a very interesting topic and for me one that doesn’t get enough coverage. Fluid power is still one of the most effective ways of ‘moving’ and despite the future of electrification in the automotive world beginning to phase out the ICE, fluid power is still going to be around.
As Pico we can provide a solution for hydraulic pressure measurements in the form of the WPS600C which comes with 2 ranges, 60 BAR (870 psi) and 600 BAR (8,700 psi). This device has been designed purely for hydraulic oil and no other fluids and please don’t mistake this device for high pressure diesel pressure transducer. As I’m sure we are all aware common rail diesel systems can and do reach pressures of up to and over 2,500 BAR (36,000 psi). This device would not handle such pressure. Enough preaching and back to the interesting stuff!
I have been using the WPS600C for some time now and still very much learning about the possibilities we can do with it from a diagnostic point of view. There is a manufacturer that has been actively using this transducer for a number of years in their workshops to diagnose and verify faults with their machines but I believe there is so much more we have yet to learn.
To start with some examples, hydraulic pump health is a common test hydraulic technicians will perform, commonly known as a PQ test. Here we have to combine both pressure and flow which as Chris mentioned, accessing these systems is not easy and normally very messy! Pico have partnered with Webtec to provide users with a flow meter that will work with PicoScope software allowing us to record, save and share captures along with adding maths to calculate theoretical flow rates and then pump efficiency. Below is a capture I have taken from a telehandler carrying out a PQ test on the accessory pump. This is standard gear pump rated at 51CC/rev.
- Engine speed – this is a math channel derived from taking the crankshaft signal.
- Pressure at the pump using WPS600
- Measured flow from Webtec flowmeter
- Theoretical flow rate based on pump displacement and pump speed
- Loading valve on flowmeter reduced
The capture starts with the pressure being high as with the flowmeter we can apply a load to the pump to simulate the system being under load. By turning in the loading valve we apply a restriction to the system and therefore increase the pressure, pressure is resistance to flow. The pump should be capable of providing adequate flow at the rated system pressure to ensure the services don’t suffer a loss of performance. As no pump is ever 100% efficient by using the theoretical flow rate, assumed 100% efficiency, and the actual we can determine the pump’s actual efficiency.
Whilst this may seem complicated Pico allows us to store and share this data as opposed to writing everything down. For pump maintenance we can easily setup a folder for a specific machine/system and then store all the saved information every time we make a measurement. Being able to share this information means we can quickly provide both customers and other technician’s results from our tests.
Due to WPS600C fast response time of 100ms, we can further analyse the pump, especially on the more common axial piston pumps. Chris mentioned the pressure pulses which are cause by FBN, Fluid Bourne Noise. I’m still researching into this as finding broking pumps can be tricky but the theory behind it makes perfect sense. The capture below was from a machine with a complaint that the engine starts to stall when the load is increased. This machine had two variable displacement pumps that both could assist with the load if needed too. By attaching two WPS600C pressure transducers to the pumps we could see the affects they were having.
Again we have added engine speed as normally the pumps will be directly connected to the engine, therefore pump speed will be the same as engine speed. The boom is being deadheaded during each of the events and we can see that as the load increases the front pump, channel B Red, comes into assist the rear pump with the lifting. We can also notice the engine speed math channel altering as the machine comes under load and off load. These speed changes can be useful in understanding where the problem lies, is it in the hydraulic side or the engine? The working pressure for this machine is set to 330 BAR and using the rulers within Pico we can determine that both pumps are achieving this. As it is a load fault not a speed issue I’m more interested in the pressure than the flow. By zooming in we can also see the pulsations created by the piston action in the pump.
Looking more closely at the pulsations we can see they’re all even with no abnormality in the pattern. I have yet to see a bad one but the theory would be if maybe a piston slipper had fallen away or there was excessive wear inside the pump this would appear in this waveform. For now though I am relatively happy that this is ok. I would have liked to have seen the two pumps looking slightly more similar but bearing in mind channel B is assisting C this may alter the pattern. Hopefully though you can see this being useful when determining the pumps integrity but also getting an idea of what is good and what is bad.
Using NVH is something I am currently looking into. By utilising either the NVH software with PicoDiagnostics or using the spectrum mode in PicoScope 6, there may well be more diagnostic value here which if it can be applied non intrusively then there is not as much reason to get as dirty anymore!
This is just a bit of an overview and it is still very much in its infancy as to what we are looking at but there is so much to discover and I know I’m only scratching at the surface.
Please feel free to add any experiences you may have had and if I can be of any help then please get in touch either here or at picoauto.com With regards to the maths channels there is more information on the Pico forum, picoauto.com/support/topic2….
Thanks for the update. Pretty exciting stuff as the pressure pulses are exactly what I was expecting to see. I am even more curious as to what can be figured out via the vibrations inherent to a hydraulic system, especially when compared to the regular pressure pulsations shown above.
I have a couple ideas as far as failing pumps and getting waveforms, but we will discuss that later.
I most look forward to the possibilities of non intrusive testing using Fluid Borne Noise (FBN) or Structure Based Noise (SBN).
We shall see where it all leads.
For those following this thread, after reviewing Ben's captures and some other data and research, I've formulated a rough outline of how this could all work in a diagnostic procedure.
I have to type it all up and proof read it, but it should be up within a week or two I think. I want to prove out a couple conjectures first. If you run into me at the TST big event, and dont mind some napkin drawings, I can explain there as well; Ben will get first crack at reading my write up and then I will be posting it here for discussion.
Stay tuned for some exciting stuff; at least it is to me.
A rough draft will be up at some point in the near future here.
A thought and a suggestion.
This could be useful in diagnosing sticking poppet valves in steering gears. It could eliminate the threat of "burning out" the gear through the use of a "T" valve.
The suggestion? sae.org/publications/j…
Perhaps, even this: sae.org/news/2019/02/c…
I like the poppet valve thought, I see potential usage in any hydraulic system, be it abs, steering, trans, etc.
As far as SAE goes, the paper needs lots of work and structure, an experienced guide to help me through as I didn't follow any standard format. I'd like to put something professional together as I'd love to get something published.
For this, I just needed to somewhat organize thoughts on paper, but I want to prove out some of these theories
I'll quote Kant here "Experience without theory is blind, but theory without experience is mere intellectual play."
Experience is what you get from screwing up. :)
The second link has some resources on submitting a paper. While it is referencing the young guns (I don't know how old you are. Therefore, I don't know if you qualify.) Still, I think they make for a good starting point. Keep in mind that there is a drop dead date for the young guns in a l'il over a week. Here are some direct links.
Haunt around those for a bit to see if you wish to submit it. They way that I see it, nothing ventured; nothing gained. Besides, what's the worst that can happen? You'll gain experience. You've got a good subject with some decent material. It's up to you.
I'll give it a shot. Like you said, nothing ventured, nothing gained.
As far as age, I'm old enough that I was using command prompt in MS-DOS when I was little but young enough that I'm part of the much maligned millennials [definitely need a cooler name than that].
I rewrote the whole paper, twice actually, sans screenshots, and made it a write up in theory of application. It took most of yesterday as I had to learn Chicago Style paper writing.
There were no open calls for the subject matter in any journal, but I submitted to the SAE International Journal of Commercial Vehicles as of yesterday evening.
Not sure anything will happen with it, probably just have it returned, but one never knows. I appreciate the push either way.