How about Flow Meters?????

[budt]

When I design a hydraulic circuit I always specify Flow Meters on the Pump (Pumps) Outlet/s to indicate if there is flow and how much flow. To keep the Flow Meters in as new shape I use two 3-Way Ball valves piped with straight line flow past the Flow Meter so it can be turned on for trouble shooting only. This feature means the Flow Meter is reliable as the circuit ages since it is not continually working.

I also specify Flow Meters on all Pressure Compensated Pumps Case Drains. On Case Drain Flow Meters I specify ones with an electrical output to send a signal to the PLC when a preset flow is reached. That indicates a pump is worn and needs replaced so a pump change can be scheduled before it fails and fills the system with debris. It also reduces the Heat Load the system sees.

Does this sound like a good Idea? Is this something you would like to see on your hydraulic circuits?

BTW, I am not affiliated with any Flow Meter manufacturer or distributor.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[IceStationZebra]

You are thinking ahead ... as usual! Unfortunately in my applications in small to mid off road equipment this isn't practicle.

And thanks for the eBooks. ISZ

 

[hydtools]

I'd be concerned that when the pump delivery flow meter is not 'on', the trapped fluid will overpressure the flow meter as temperature increases. Use just one three-way valve instead of two and leave one end of the flow meter open to the circuit.

Monitoring the case drain flow sounds like a good idea. You will have to decide how much flow is too much flow considering case drain variations pump to pump or brand to brand.

Ted

 

[budt]

GOOD POINT Ted.

I overcome this with a 0.020 Orifice piped to tank from the loop. is means there is a bleed off while the Flow Meter is in service but no possibiity of trapped energy when the system is operating normally.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[RBedi]

You are right Bud from all aspects. Only thing to add here is, since these additions will add extra cost so it depend upon customer if he is ready to absorb this additional cost. If it is a small customer OR HPU is to be designed for a machine to be sold in very compititive market, I think these additions are case to case basis.
At the same time why not to put stress on better filtration techniques/clearance filtration/optimum filter locations. This will automatically enhance life of HPU including pumps. With this way, intial cost of HPU would be quite efficient & subsequent filter change/maintenance cost passed to customer. However, we should convince our customer that each filter change(since I will recommend efficient filter) could be expensive, but whole cost would be covered automatically by less breakdown of hydraulic system & long life of components by good filtration. Rather there would be net extra saving in long run.

Best Regards
Rajan Bedi
The Technical Associates

 

[Newmanite]

This sounds expensive mate two flow meters per pump unit.
Would it really be worth it?Or would it be better to spend the extra money on good filtration, oil analysis and scheduled component changeouts?
Sure in a breakdown situation these are nice to have but during scheduled servicing a good hydraulic tune every 1000hrs or so would give an indication of pump efficiency along with data from oil analysis reports

 

[jbwick]

The end customers practices will play heavily into the selection of monitoring equipment. If they are operating with the intent of having zero unplanned downtime then a case drain flow meter on an axial piston pump would be a wise choice along with the correct fluid conditioning and monitoring for the application. However in my experience the customers that truly commit to this kind of preventitive system are rare.

 

[budt]

I heard a saying many years back from a wise customer that went like this:

"Cheaper is not always Less Expensive"

So ar I have nad no trouble justifying Flow Meters to a customer after they understand their function.

A machine making $2,500.00/Hour is also losing that amount when it is not producing so justifyig $1,500.00 for installing Flow Meters is usually a no-brainer decision for most companies. Anyone who is buying on up front price is not a forward thinking person and probably does not realize a circuit can cost them the price of good trouble shooting/diagnosing tools in excess energy, parts replacememnt and downtime two to three times a year or more.

Filtering is another whole thread and should be addressed that way'

Also, no one has mentioned Wasted Energy which causes most hydraulic circuits to over heat and require the expense of a Heat Exchanger and their cost of operation. I don't consider a hydraulic circuit that requires a heat exchanger a good design in 90% of all hydraulic circuits. Designing heat out is not the Cheapest circuit up front either, but, the added cost can be recouped several times a year in reduced operating cost in many instances.

I am happy to see some interest on such oft oer looked subjects. Seems several are interested. I did'nt get this much on the other Fluid Power forums in the past.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[hydtools]

budt, I must take exception to your comment that a circuit which requires a heat exchanger is not a good design. If more circuits had heat exchangers, there would be more good circuits.

All my 30+ years experience has been with mobile circuits and I believe mobile circuits comprise more than 10% of all circuits. There is always wasted energy, energy that does not produce useful work. That heat cannot be managed properly with just a reservoir. In fact, reservoirs can be made smaller in systems with heat exchangers. Especially in mobile systems.

Heat exchangers are another fluid conditioning component just like filters and should be considered in the design of circuits.

Ted

 

[budt]

Good point Hydtools. My experience has been 99.9% Industrial hydraulics so that is where I was coming from.

Mobile hydraulics is another story, but, they are the ones who came up with Load Sensing. I think the original idea was fuel savings 9HP savings) which automatically reduces heat.

From my experience with Load Sensing pumps on several Hydraulic Trim Presses, they can run 24/7 without a heat exchanger and never get above 130 Deg.F. in the summer weather in a building that is not air conditioned.

The circuits usually run about 10-20 Deg.F. above ambient.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[RBedi]

Bud

Don't you think say if a customer has multiple HPUs(many pumps) in his factory & in this case rather than installing two flowmeters & two high pressure ball valves on each pump, better to have a one off-line Flow/Pressure/Temp Tester which can be used in all HPUs(many pumps) of the factory in case of any trouble shoot. This separate Tester can also be used additionally at other various places of circuit while troubleshooting(like between valve & actuators etc). So I agree with your suggestion only in case where difference of cost of breakdown hours when there is a online flow meter & when there is a offline Tester along with number of HPUs(pumps) in that factory + if you have to troubleshoot between valve & actuator(then really you need a separate tester) is justified. I believe, it is ok if only one HPU is there. But if there are many, then better to have separate Tester which would have multi usages while troubleshooting.

In nutshell, everytime we have to see COST/BENIFIT RATIO & convince customer accoringly. I hope, you will agree.

Rajan Bedi
THE TECHNICAL ASSOCIATES

 

[budt]

Rajan;

An Off Line Tester is another way to trouble shoot and would probably be used after all the standard trouble shooting procedures were exhausted.

I would consider Off Line Testers as second best and only as an option for the experienced Fluid Power person but not much use to the average Mechanical Maintenance person or Mechanical Engineer who has been to a 2 week Hydraulic Course 7 years back. They can't read a schematic and have only a vague idea of what that blue painted thing on the left is supposed to do so how would they know where to install the Off Line flow meter?

My approach may not be the ultimate but has worked well for all the customers who have implemented it in their circuits.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[horsefeather]

I stumbled across this thread while researching this very question. One of the operator's swears by flow meters on the case drains. I've been somewhat skeptic, believing anything in the case drain line that can clog will blow my pumps up.

What type of flow meter would be recommended?

I'm using Denison P16 pumps at 90gpm/3000 psi. I'm nervous about paddle sensors and variable area flow meters. My understanding is any case drain pressure exceeding 25 psi is damaging my pumps and the VA flowmeters I've seen add 1-5 psi in use. I just had a pump go bad with 50 gpm in the case drain so I can be convinced that monitoring the drains can be a good diagnostic tool but am concerned that adding any restrictions in the line that can catch debris will blow the seals on the good pumps.

Any opinions would be appreciated.

 

[budt]

horsefeather;

I have used Hedland and Lake variale orifice flow meters on dozens of pumps from Eaton/Vickers, Rexroth, Denison and Parker without a shaft seal problem.

I always use the Proximity Switch option with the output connected to the PLC or Control Panel to give a warning when a pump is bypassing over about 10% pump flow. This will usually give enough warning to schedule a pump change before it fails and it usually makes repair possible and less expensive.

I seldom have a problem covincing a user to pay the extra cost when they understand its function in trouble shooting. I have worked with most of these customers 20 years or more and they usually do'nt ask questions just give purchasing the BOM and say this is what I want.



Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[horsefeather]

Thanks for the reply.

I was looking at the Hedland flow meters with the proximity switch option; I had trouble getting the Lake website to work.

I was thinking there may be some sort of pitot type fluid flow meter, but nothing jumps out at me in a google search.

I'm guessing that a flowmeter on each of my high value pumps and motors would be the way to go. Rather than one on a common drain line leaving me puzzled regarding which pump/motor was going out. That also eases my apparently unfounded concern that a chunk of debris would lodge and back up into all my pumps and motors.

I have a number of other questions I'll post in separate threads.

 

[budt]

horsefeather;

Here are a couple of Flow Meter providers that I've colleted that use sensors in the flow path that measure temperature diference to give flow amount. Very Non-Invasive and fair accuracy. I have never applied these but if they do what they claim it would be a great way to monitor flow without any restriction and electronic interfae to thePLC. Below are a couple of links that may be helpful.

http://www.flowmeterdirectory.com/flowmeter_thermal_mass.html

http://www.flowmeters.f2s.com/

Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[horsefeather]

I've never seen the thermal mass type before, I'll research it.

The ultrasonic requires a physical shape (contamination or bubbles) to reflect the ultrasound off of. I'm curious if it would work in a hydraulic fluid application.

Thanks for the leads