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600 kW / 850Nm hydraulic pump - need advice

600 kW / 850Nm hydraulic pump - need advice

600 kW / 850Nm hydraulic pump - need advice

(OP)
Hello all fluid power professionals!

We are in the early planning stage of designing an hydraulic engine dynamometer for internal use. We are looking at using a hydraulic pump as the load for the engine. We are planning to apply load to the hydraulic pump with a servo valve partially obstructing the flow of the hydraulic fluid. To measure power, we can either measure the pressure of the fluid and multiply with the RPM and a correction factor or measure the torque with a strain gauge and multiply with the rpm.

We need some advice on where to find a reasonably priced hydraulic pump that can transmit approx 600 kw / 850 Nm thru its shaft reliably.

The RPM of the engine is max 8500 RPM.
We might have to gear down this to a RPM the hydraulic pump can handle.

I was thinking about hydraulic pumps for dumper trucks and digging equipment like CAT or Komatsu. This kind of equipment is mass produced and I would think a lot of spare parts suppliers exist.

Also, where can we find servovalves that can handle this pressure with a fast response ?

We would like to cool the fluid via a water to oil heat exchanger. Any hints on suppliers ?

This has actually been done before in an chassis dyno application for cars.

The unit in left front of the picture looks like the hydraulic pump they use (does anybody on this forum recognize the brand of this pump by any chance?).
 http://www.flyinmiata.com/images/misc_images/rototest/DSCN0238.jpg

Looks like the unit on the right with the piping is the servovalve unit that applies load to the hydraulic pump. The black unit on top is probably the servomotor for controlling the servovalve. A pc is attached that runs some real time control software.

The brake assembly is attached directly to the driveshaft of the car.
I think there is a gearbox attached between the driveshaft and the hydraulic pump. Anyone that know a manufacturer compact of gearboxes that can handle this much power and torque (600kW / 850Nm) ?

Here is a link to a  pic of the servovalve they use
http://www.flyinmiata.com/images/misc_images/rototest/DSCN0237.jpg
Anybody recognize any of the components or is it custom?

We are not going to attach our dynamometer to the driveshafts, but directly to the engine crankshaft thru an axle. Therefore we need it to be able to handle at least double the power of this unit since the car differential distrubutes power to two driveshafts and two units.

Regards
Morten

RE: 600 kW / 850Nm hydraulic pump - need advice

From your picture the company that makes the "ROTOTEST".

http://www.rototest.com/

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Yes that is correct. However Rototest make chassis dynamometers and we are making a dynamometer to attach to an engine driveshaft directly. We have a different budget and different control software requirements. Therefore we have decided to design it in house. Any hints / tips to what type og hydraulic pump, gearbox and servovalve components that can be fasible for this application ?

regards
Morten

RE: 600 kW / 850Nm hydraulic pump - need advice

Morten;

600KW equals 805 HP if I did the math right and at 5,000 PSI that would require 276 GPM of flow which would produce over 34,132 BTU/Min. of heat. At lower pressure flow would increase but heat would remain constant.

I recently priced some pumps that would give that type flow with servo control and in quantities of 4 were $45,000.00 ea. Actually overkill for your project but real flexible as far as operating parameters.

The pump in your pictures appears to be a fixed volume Tyrone aluminum Gear pump. I'm not up on their offering so I can't say if they make a pump as large as you need. Almost any hydraulic pump you find would need some hefty gear reduction since most will not go above 2,000-2,400 RPM due to their Inlet line size not being able to get enough flow to keep it from cavitating..

You need to talk with a salesman from a local Fluid Power distributor or find a retired salesman that would help you for compensation. At present I am not able to doo any extra work.

Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com
http://www.fluidpower1.us

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Hi, did you mean the unit to the lower left ?  
Perhaps you meant using more than one hydraulic pump attached to a common shaft via a distribution gearbox ?
We have sent a mail to OEM Hydraulics to inquire.

Anybody know of fast low cost servovalves that can handle this
load ?

Regards
Morten

RE: 600 kW / 850Nm hydraulic pump - need advice

Morten;

Perhaps a Generator would be a better choice or even a large Fan such as found on a big ventilation system.

Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com
http://www.fluidpower1.us

RE: 600 kW / 850Nm hydraulic pump - need advice

That is a lot of oil for just one servo valve.  The Moog 79-200 can handle 200 GPM and it is not cheap.  This is the biggest servo valve I know of.   I would be looking for a big proportional valve to save money, not a servo valve. One could save if there were parallel paths with fixed orifices that can be switch on and off.   Only one path has a 'servo' valve for fine metering control of the oil.  The problem is the bump in the load as the orifices are 'switched' in and out.  Two or three of the bigger proportional valves will do the trick.  They are more common once you get to the 100 GPM range.

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Hi Bud, what kind of generator do you mean ? Please give more details. Did you mean to use a electric generator as the load instead of a hydraulic pump as the load?  

Large fans are used in existing aplications i have seen. Here you can see a picture of some fans that somebody doing this use today: http://www.flyinmiata.com/images/misc_images/rototest/DSCN0198.jpg
Probably the oil return have quite low pressure so there is no need for a cooling element that can withstand high pressure.
Who sells theese kinds of fans and cooling elements to a low  cost ?

Regards
Morten

RE: 600 kW / 850Nm hydraulic pump - need advice

If youare still going with hydraulics and are controlling pressure to get a load then look at a Proportional Relief valve such as found here. Look at the valves on page 54

http://hydraulics.eaton.com/products/pdfs/504300en0499a.pdf

These valves go up to around 700 GPM and are infinutely variable pressure from an electrical input signal.

Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com
http://www.fluidpower1.us

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Hello PNachtwey.
Thank you very much for your reply. You are one of many experienced people on this forum that can help ignorant beginners like me. Thank you again for your patience. I really appreciate your help !

I understand your point of using fixed orifices to switch in "load ranges" and then use a valve that is possible to regulate to do "fine regulation". However the "load bumps" is an effect that we probably need to avoid since this might impact our measuring repeatability and it might also impose transient loads that might be dangerous to internal components on a stressed turbocharged engine at high RPM and high load.

Also, your point of finding a _proportional valve_ that is not as expensive as the Moog ones is excactly the type of advice we need.

However, I dont know the difference between a servo valve and a proportional valve. Can you kindly please explain the difference ?

Who sells proportional valves at lowest possible cost ?
(We dont need a Rolls Royce for the first prototype).
How do we electronically control a proportional valve ?
How fast control response can we get ? The loop response must be relatively fast as the point is to lock the engine RPM and hold it regardless of the throttle opening (torque of the engine).

Regards
Morten



RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Hello Bud, thank you very much!
Will this valve give a fast system response enough to hold the RPM steady ? We need to control the system via a real time control software.

(An external completely independent RPM sensing safety system will shut down the ignition and fuel supply and apply full oil brake if the loop becomes unstable and the RPM surges).

Some of our engineers will do a numeric system simulation by figuring out the transfer functions of the different components in the system. Also the mass and torque of the enggine will be modelled. However I need to present a draft for a feasability study to start working on with as much details as possible.

Regards
Morten

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Btw, I know this has been done with water brakes as the load element as well. However we want a "portable" system. This means the water flow neccessary to feed a water turbine as the load element will be far too high. We will need upstream water reservoirs and that is not feasable as it is too bulky. Water resirculation might be possible but there are steam expansion problems etc.

Also the rotational mass of a water turbine system is too high I have learned. This will prevent us to see transients in the enngine torque because of the rotational inertia of the system will be too high and have a lowpass effect of the response.

The rotational inertia of a hydraulic system is probably  lower because the pump mass is smaller and the mass of the oil volume in motion (oil in the pump and in the line to the valve is smaller. This is probably the reason that the guys that sell commercial products for similar applications use oil.

Regards
Morten

RE: 600 kW / 850Nm hydraulic pump - need advice

"Hello Bud, thank you very much!
Will this valve give a fast system response enough to hold the RPM steady ? We need to control the system via a real time control software."

Morten;

Peter can tell you more about response. I have only used this valve as a way to have the PLC control presure throughout a cycle and response was not a problem for the circuit.

If you look further on the web page I sent you will also find a Propoortional Flow Control mounted on the same high flow Slip-In Cartridge valves. BTW Vickers is not the only manufacturer. Parker and Rexroth also make the same item.

Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com
http://www.fluidpower1.us

RE: 600 kW / 850Nm hydraulic pump - need advice

Hi Morten,

Many of the drive manufacturers can use a reasonably standard COTS induction motor and a power electronic drive to provide a load which can regenerate the braking power back into the mains supply. Dynos based on this technique can provide very accurate control of loading, and with remarkably fast step changes if required. The induction machine is about as robust as it gets in terms of rotating electrical plant, so mechanically it should be quite favourable. The only requirement will be an electrical service large enough to handle the braking energy - that depends where the unit is to be used.

It would be well worth speaking to the applications guys from the likes of ABB, Control Techniques, Siemens, etc.

I will post a link to this thread in the Motors forum where there are a lot of people who know more about this type of thing than I do.

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: 600 kW / 850Nm hydraulic pump - need advice

MortenHansen; I concur with ScottyUK.  Your task can be done very nicely with a VFD.  This will often allow you to return energy to your utility in lieu of heat to your facility.  Also even if you cannot use your utility as an energy sink consider that you can place a load bank(a bunch of cheap resistors with a fan)anywhere convenient to your facility, like out back.

A VFD system would allow easy ramping and profiling of your dynamometer's functions. Also since VFD are electrical/electronic animals that depend heavily on knowing about many mechanical/electrical variables they are usually very easy to interface with and control.  All the things you could want to know will generally be available by just inquiring of the VFD.

Alternatively remember that all locomotives are dyno'd regularly.  They just use the generator that is coupled to the prime-mover.  They unplug the cables going to the traction motors and hook the output to a dynamic braking load resistor unit.  They then firewall the prime-mover and read the ammeter and the volt meter, multiply the result and they have the HP.

Either way would seem eminently less expensive, more flexible, and more adept at providing data than a hydraulic solution.  

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 600 kW / 850Nm hydraulic pump - need advice

Hello MortenHansen
"Also the rotational mass of a water turbine system is too high I have learned. This will prevent us to see transients in the engine torque because of the rotational inertia of the system will be too high and have a lowpass effect of the response."
I understood that you were looking for torque response.
I understand that inertia may be a problem if you are trying for rapid speed changes, but if you are interested in torque, the higher inertia will make your system more stable.

Have you considered looking at the hydraulic retarders used on heavy equipment and some highway trucks. They will absorb a lot of horsepower in a fairly small, reasonably self contained unit. You can do most of the braking with the retarder and add a smaller unit of a different technology to give you fine control.
yours

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Hello I know some ppl use a Thelma brake to do this in fixed installations. Thelma brakes are normally used as a manually applied brake for trucks. I think those thelma brakes are quite expensive as well.

I would assume a 600 kw generator + switched control electronics is very expensive :)

Regards
Morten


RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Waross, this could  be an option.
Do you know any manufacturers of this kind of retarders ?

Btw, I was thinking of the possibility of mounting several lower cost hydraulic pumps in paralell on a common axle driving them all. Then the paralell outputs of the pumps can drive a common flow restriction mechanism. This would perhaps enable us to use mass produced pumps and thereby getting the cost down.

Anybody have experience with Taiwan / Asian suppliers of
hydraulic spareparts for dumpers etc ? I would think the price level of that kind of equipment is significantly lower than what you would have to pay in Europe ?  

Regards
Morten

RE: 600 kW / 850Nm hydraulic pump - need advice

Hi MortenHansen
I would phone up the local truck dealers and heavy equipment dealers and ask about retarder options. Pump them for as much information as you can get and then start phoning the wrecking yards looking for used units.
Kenworth, Mack, Caterpillar, and any others you can think of.
Re. the electric option. With a VFD drive, you can use appropriately sized, used, three phase induction motors as the generators. That should help hold your price down.
I suggest reading thread237-149826. Read it a couple of times and you will probably have a good idea of who the VFD experts are. You will know who to listen to when you ask for advice on choosing electric hardware to compare with hydraulic hardware.
respectfully

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Alternative solution (question - what hydraulic pump can we use for this alternative) :

What about if we wanted to take the power straight from two wheel axles instead of one and run it thru the normal gearbox and shafts / differential of the car and reduce our demand for power to approx 550 HP (412 kW).  Distrubuted over two axles this should be approx 205 kW per pump?

With 16" diamater wheels the wheel rolling distance per revolution would be (15"/2)*Pi*2 = 47 inch / rev.
This translates to 1,19 meter per revolution.

If the max test speed would be set to 300km/h then the rolling speed of the wheel surface would be maximally approx 5000 meters / minute. This would mean 5000(m/min) /1,19(m/rev) = 4200 rev/min max pump RPM. Then we would probably have to use a 2:1 reducing gearbox.

It looks like this is what is done here : http://www.flyinmiata.com/images/misc_images/rototest/DSCN0238.jpg
When I look closer at the pic. it looks like there are TWO pumps in series on this application. It appears to be one valve control block at the output of one of the pumps (the inner) and one pipe feeding the valve block from the outer pump.

There are two hydraulic lines going to the right. -Looks like those are return lines that go to the cooler. Perhaps there is a fixed orifice in the small block on the body of the front pump that feeds some of the output from the front pump to the control block and the rest to the cooler.

What do you think ?

regards
Morten

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Btw I meant two pumps in paralell !

Regards
Morten

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Hallo Waross, I will check that out. Thank you.
However I have the feeling that a genrator that powerfull will be very harvy. The equipment must be movable by hand.
What do you think ?

Regards
Morten

RE: 600 kW / 850Nm hydraulic pump - need advice

Morten,

I think that a hydraulic solution will be in the $ 50,000 - 100,000 range. And you will have to deal with lots of waste energy. Most car and truck manufacturers use generators and inverters instead. The control is very good and the accuracy also. And the energy can be fed back to the mains - you can actually get paid for it instead of paying for getting rid of it. If you are in a big enough factory, the energy doesn't have to be fed back to the utility but can be used by your other equipment.

budt, ScottyUK, itsmoked and waross have all mentioned this possibility and I second that. A dedicated brake from Siemens with all its measurement and automation gear will surely cost a lot. But rolling your own motor/inverter will not cost much. I can guarantee that the all electric solution is cheaper than the hydraulic one. And you get rid of the heat - perhaps even get paid for it.

Gunnar Englund
www.gke.org

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Hello Gunnar, thank you for your answer.

I don't think feeding energy back to the net is so easy as it sounds. It is AC and the generator will not be in sync with the net at all. The engine is the "master" The output had to be rectified and then switched with the correct 50 Hz frequency. Switching 600 KW will take a VERY big stack of IGBT transistors and possibly some hefty transformers and capacitors as an energy storage for storing the exess energy until you can feed it in phase into a cycle. Also I think the genrator(s) will be very heavy.

I must admit that I think that paralell connecting a number smaller hydraulic pumps with a control valve will be the lightest and most portable unit. The unit will be run for only minutes at a time and only intermittently and there will be no connection for us to the net at all locations that could handle 600 (!) kw. This should be a portable system that can operate from 220V 10A auxiliary supply for the neccessary electronics. The hydraulics will have to do the work.

I know this has been done with hydraulics as the pictures show.  We want to make a similar system to this or a bigger one with just one axle.

I start to think that separating the load on two axles will be the best.

Regards
Morten

RE: 600 kW / 850Nm hydraulic pump - need advice

OK, I can understand that energy is not an issue in your case. And that a hydraulic solution is better suited because of the portability needs. And if there isn't a grid stable enough to receive the energy - it just can't be done.

But you really need to update yourself on the electronics side! I see dynos that do what you want to do more or less daily in the Volvo, Saab and Scania development labs. And I do some commissioning on them as well.

A big dyno with something like 1200 HP braking power is not very big. And the motor isn't either. About the same size, or smaller, as the diesel engine it is coupled to. And the rectifying/synchronizing part is taken care of by standard inverters. Your concern about different frquencies and synchronizing to the grid is understandable - but completely unnecessary. It is being done in thousands of installations day and night. All around the world.

Gunnar Englund
www.gke.org

RE: 600 kW / 850Nm hydraulic pump - need advice

Morten;

Another far out thought:

Get a propeller from a DC-6 that has variable pitch for your resistance. A prop that size could be chopped to reduce its diameter since they were driven by over a 1,000 HP if I remember correctly.

The variable pitch would give some latitude on torque also.

Did you find the Tyrone site. I believe they are owned by Parker now Here is a site that also makes them:

http://www.perfhyd.com/products/hotdeals/TP6700121001.htm

They make single and double pumps that could be big enough for your setup.

Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com
http://www.fluidpower1.us

RE: 600 kW / 850Nm hydraulic pump - need advice

Have you checked this one out.
http://www.taylordyno.com/eng/maineng.html

You might also check out this one.
http://www.hbus.haldex.com/products/fds.htm

The hydraulic dynamometer that you are looking at doesn't use the hydraulic power to really measure the output, it uses a load cell setup with their software for the power measurements and dissipates the hydraulic power and heat  through the fans and cooler.   Their literature also states that they use a high speed servo valve (patented by them).   

RE: 600 kW / 850Nm hydraulic pump - need advice

Re one or two units; I wouldn't trust the spider gears to last for very long if you locked one wheel and ran your power through the differential to the other wheel.
I agree with the figure that someone posted that your heat output at 600 kw will be over 34000 BTUs per minute. That's enough heat to boil about 34 Lbs of water a minute. (15.5 liters).
If cost is an important consideration, consider using the brake drums from a piece of heavy equipment and water cooling them. The technique was used in the logging industry for years. It's a good idea to start the water sprays on the outside of the brake drums before the heat builds up. Boil the water off and vent the steam.
Re portable; That is a challenge. Anything that has enough mass to stay in place and stay together while disipating 34,000 BTUs a minute will be too big to pick up. One man can move a very large load by himself with a pallet jack. If you have to move from site to site I suggest a dedicated truck with a small crane to load, unload and place the dynos, whatever method you choose to disipate the energy. Another old but cheap and dependable device is a water cooled (By sacrificial vaporization if necessary) eddy current brake.
respectfully

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Waross, there is a real time control unit that adjusts the load on each of the sides so that the spider gear in the differential is not seeing any different RPM. This way the spider gear will not be stressed.

I have actually found out now that the system is cooled via some fans that are driven by hydraulic motors. There is one 30 HP hydraulic motor on each fan ! This will cool the system down. I spoke to somebody that has this system in use.

If anybody knows if this is a piston pump or another type of pump, that would help. It doesnt look like a piston pump to me.

regards
Morten



RE: 600 kW / 850Nm hydraulic pump - need advice

Another hydraulic approach might be to use a variable displacement pump driving against a fixed restriction.

Some of the cost of going to a more expensive pump can be offset by the fact that if you want to use a servovalve to control the pump stroke (to maintain required rpm), the valve need only be pocket sized.

You've still got to lose all that energy somewhere - if your duty cycle is low enough, the answer to this might simply be to use a much larger tank.

A.

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Hello Zeusfaber, thank you for your input.
That might very well be a good idea. I dont know how a variable displacement pump works. Does the stroke of a piston pump change by the control input or something like that ?

However we have also found a very low cost way of making a very fast servo valve. The response of the system must be very fast. This is neccessary to be able to control the rpm of the load load.  The load can have a very high torque gradient in some RPM ranges. Therefore we need to apply load very fast. I dont know what loop response you will get with a variable displacement pump ?

Regards
Morten Hansen

RE: 600 kW / 850Nm hydraulic pump - need advice

Morten,

Yes, a variable displacement pump works by varying piston stroke.

A typical axial piston design will have seven or nine cylinders in a spinning barrel (like the chambers in a six shooter.  The ends of the pistons stick out the bottom of the barrel and engage with a swashplate.  When the plate is perpendicular to the spin axis of the barrel, the pistons don't stroke at all.  As soon as you tilt the plate, the pistons stroke up and down the cylinders with the rotation of the barrel.  The other end of the barrel mates with some fixed ports and valve gear to connect each cylinder to flow and return at the appropriate stages of their journey.

The tilt on the swashplate is often controlled by a small hydraulic servo system, and can be very responsive.

Details of one model on the Denison website (notes: Document is 6 MB+ and link is ftp:).  This particular pump looks not far off the size you'd need, and appears to promise a 10% to 90% flow response of under 100 ms.

Downside of these pumps is that they are never really "low cost"

A.

RE: 600 kW / 850Nm hydraulic pump - need advice

(OP)
Hello Zeusfaber.
That is interesting. However we might need faster response than 100 ms. I havent done 100% of the loop calculations yet but we will definately take a look at that unit there.
Thank you again.

Regards
Morten

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