(reveiw) Hydraulic System with tandem center solinoid for control
(reveiw) Hydraulic System with tandem center solinoid for control
(OP)
hi i am fairly new to the hydraulic business and need to create a hydraulic lift that has warm up loop that also raises the lift at the speed i choose based on the power given to the pump. and lowers slowly with a regulator.
i made a schematic of the way i think it is supposed to be done.
here's the visio project in office 2007
http: //files.en gineering. com/getfil e.aspx?fol der=3270d4 43-e0f1-4a 58-a70e-2f 9c8249e12a &file= Hydraulic_ System.vsd
also attached is the image of the same schematic.
i made a schematic of the way i think it is supposed to be done.
here's the visio project in office 2007
http:
also attached is the image of the same schematic.





RE: (reveiw) Hydraulic System with tandem center solinoid for control
First off the flow control will be better between the direcional valve and the cylinder.
Secondly, are you sure about the transitional flow paths of the directional valve. I am not sure that there are valves that block all ports as the move from the normal position to the working position.
Because I am lazy and because it will help you to understand I suggest you research the following...
1) Counterbalance valves
2) Overcentre valves
3) Pilot operated check valves
All of the aboove will hold the load while the directional valve moves. The spool in the directional valve will allow oil from the cylinder to escape to tank as the it moves and the cylinder will drop slightly and there will be a noticeable bang as the valve moves. Any of the above valves will do what you need, but with varying degrees of success.
As you have drawn the system, any pressure generated at the flow control will be seen at the directional valve and the leakage across the spool could mean that the cylinder extends during the warm up.
The directional valve would be better with the P line blocked and A & B lines connected to T in the normal position. This will keep stop pressure build up in the cylinder during the warm up.
The pump could then be run against a releif valve or orifice to warm the oil. The size of the orifce can be calculated as...(metric units)
Flow(LPM)/Area(mm^2)x 1.44 = square of the pressure drop(BAR)
The answer squared is the pressure drop in BAR.
The temperature differential(deg's C) across the valve/orifice is equal to...
(5.7 x Pressure Drop)/100
It is worth noting that warm up cycles only warm the reservoir oil. The oil in the line and the cylinder will remain cold until it reaches the reservoir. When the warm oil is pumped out to the cylinder it will cool rapidly unless the the oil is worked hard to keep the temperature up.
I hope that helps a little.
Adrian
RE: (reveiw) Hydraulic System with tandem center solinoid for control
Please learn more before seriously hurting someone.
I would like to see your analysis of the system; loads, pressures, flows, fail safe to prevent dropping of the lift, etc. How heavy is the lift + load? How fast must it move? Acceleration?
Why open center instead of closed center?
Why do you want to warm the system? To what temperature?
The placement of the flow control in your schematic will continuously and uncontrollably cause heating while the pump is circulating fluid.
There is no relief valve for circuit protection.
I hope the filter in the suction line is a mesh strainer, otherwise you will cavitate the pump.
You need a filter in the return line to keep fluid clean.
You should have pilot operated load check valve to hold the lift.
This needs more work.
Ted
RE: (reveiw) Hydraulic System with tandem center solinoid for control
It is clear he does not know what he is doing, but is it not better that he asks rather than go it alone and risk hurting himself?
The schematic is about as far from workable as one could get, but at least it's only a drawing. I have know people spend a lot of time and money and then ask questions after it's all gone wrong.
Lets try to offer our expertise rather than give him a hard time for having a go. If we can offer guidance and try to educate people it will be better for everyone.
Adrian
RE: (reveiw) Hydraulic System with tandem center solinoid for control
Taking shots at what is a nonsense circuit is a waste of Talo's time and teaches nothing.
Ted
RE: (reveiw) Hydraulic System with tandem center solinoid for control
The most direct approach is to start with fundamental training, but that requires equations, lessons and developing a series of educational values on a hydraulic basis that, in my opinion, would be sold not given freely. For instance, the most general equations for pumps are calculating volumetric displacement and developing a Q vs RPM chart, but then you go into efficiencies, which could take a day just to explain...and that's just for a mono-directional fixed displacement pump, preferably a gear pump to ease variables...
The underlying approach is direct him to useful information and that is sometimes difficult to find...
RE: (reveiw) Hydraulic System with tandem center solinoid for control
http://www.hydraulicspneumatics.com/200/eBooks/
Chapter 4 Pages 11-18 gives all the symbols and points out the Crossover Conditions of all the basic valves that I could find in the Parker, Eaton/Vickers and Rexroth catalogs.
Chapter 10-12 go through Directional Controls of all types that I'm familiar with and gives some application information for them.
The Advanced Circuits book at the above link shows the valves in all the typical circuits I know of. However the chapter on Directional Valves is not up yet so it will be of no help to look there. H&P is putting up a chapter every couple of weeks so it should be up soom.
The books are my attempt at training persons in the Mechanical and Electrical field what Fluid Power is about and at least get them somewhat knowledgeable in component operation and application.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
The thid book I wrote to teach "Industrial Hydraulics Trouble Shooting" wikk be on the same site soon.It covers my rendition of Trouble Shooting that I must say came from reading about how IRS agents in the states are taught to find Counterfeit Bills. I read they spend about 3/4 of their training studying noting but good bills until they are so familiar with how the real thing looks that the bogus bills stand out quickly.
To that end 2/3 of the book is studying all the valves in typical circuits so the syudent is familiar with their application. The rest of the book goes through identifying symbols, circuits that have wrongly applied or incorrectly set valves. An explanation of how the circuit was designed to cycle is given and then an explanation of what the circuit malfunction is. The student must then diagnose which componentts could cause the problem and what approach to take to fix it.
The training winds up with practice circuits of circuits I have worked on over the years. There is an explanation of a possible problem and a space to give an answer for the way to correct the problem.
At a local large company the classes are for mechanical and Electrical Engineers and Maintenance persons and the practice circuits are for actual machines in the plant.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
and as a addon im am not sure yet of the weight of the load. but what i am trying to do is lift a computer rack out of a closet underground. just some insight into the project.
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
also with that setup how do i control the in stroke?
RE: (reveiw) Hydraulic System with tandem center solinoid for control
I mean like this...see attached.
It's a very simple diagram, but is shows the basics.
The pumps pressure is controlled by a vented relief valve. The valve can be set to the required pressure and when the solenoid is off there is no pressure. If the solenoid is energised the pressure will rise to the level set on the relief valve. This would heat the oil very quickly. Any oil that leaks over the spool will always escape to the T line.
The direction of the cylinder is controlled by directional control valve and when the cylinder is lifted, it is held up by a counterbalance valve. To lower the cylinder the counterbalance valve is forced open by the weight of the load on the cylinder + hydraulic pressure inside the cylinder. The position cylinder will not change when the solenoids are energised. Another option is pilot operated check valves, but they can be a bit aggressive in their operation.
Speed of operation would be regualted by throttle check valves between the directional valve and the cylinder ports. Throttle check valve are valves that allow free flow in one direction and controlled flow in the other. I have not shown these on the drawing.
All of this can be very assembled in a very compact unit as the low load would mean a small cylinder which means low flow. Low flow = small valves = less cash.
This drawing is by no means complete, but it does give an idea.
Regards
Adrian
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
and another one at the bottom port of the cylinder for going up, this one should be a bit faster.
is that correct?
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
Look in the Basic book mentioned above in Chapter $ Page 4-14 to see Directional Control Valve Designations from NFPA, ISO, CETOP and NG.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
Only if the Counter Balance Valve is Externally Drained.
Much better if the Flow Control is before the CBV.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
Also, you seem to indicate the cylinder only needs the 750# of force for lifting so a Regeneration circuit would set speed nearly the same in both directionsa with the same flow.
Anytime I am asked to design a Fluid Power Circuit I ask a lot of questions up front so the simplest, least energy wasting and less expensive circuit can be designed.
You can see some questions I always ask for a simple circuit design situation in my basic book in the "Formula" Section on pages 14-15. Pages 16-17 are for sizing a Pneumatic circuit.
These two sizing examples are not all inclusive but give a general way to approach a given situation. With comtinued experiennce and a full understanding of the components available you can do some real energy saving circuits.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
Although your diagram shows the pump sucking oil out of the electric motor. I am pretty sure that wont work...
The directional valve and the flow controls would be mounted as a stack on top of a single station manifold.
The CBV would be directly mounted on the port of the cylinder to reduce the risk of pipe rupture.
Adrian
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
or in "A" and out "B".
(http://www.imav.com/EN/0201/IZ-530-402-00.htm)
my guess is that i need it to be in A and return A.
(http://www.imav.com/EN/0201/IZ-530-450-00.htm)
remember this is if i connect it as a subplate on the directional valve..
.......
also if a use a subplate for the directional valves
does the one for the bottom port of the cylinder need to be faceing in that of "example A" or in "example C"?
this also goes for the top port of the cylinder, would it be connected as in "example C"?
See attached file for example directions.
RE: (reveiw) Hydraulic System with tandem center solinoid for control
In other words if the cylinder is mounted Rod Down and the Load is pulling against the Rod End and the Rod End Port is connected to "B" Port on the Directional Control, you would ask for a Counter Balance Valve specified as Out of "B" port.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
I always put the Counter Balance Valve on the Cylinder Port with a 4-Bolt Flage mounting since a pipe nipple is subject to catastrophic failure while it is less likely with (4) S.H.C.S.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
BEEN THER AND DONE THAT, Just once though in my training days in the College of Hard Knocks that most persons learn about Fluid Power design.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
for the directional valve i need to know what direction the restrictor valve and one way valve on the top and bottom ports of the cylinder.
look at page 2 of 8 and tell me if i need model S or S2 (right hand side above the schematic)
here's the link :(http://ww
RE: (reveiw) Hydraulic System with tandem center solinoid for control
With regard to the CBV, ports AV and BV go on the cylinder side. The check valve allows free flow into the cylinder, but flow coming out of the cylinder is forced through the main stage of the valve. Oil cannot get out of the cylinder until the valve is forced open and if oil cannot get out, the cylinder will not move.
It is ideal to install the CBV directly on the ports of the cylinder in order to reduce the risk of the cylinder running away if a hose or pipe was ruptured. If you have look at the cylinders on almost any excavator or aerial platform, you will see a block attached to the cylinder. That block will house the motion control valves. It is not always possible to do this so you need to guard or protect the pipes or hoses to reduce the risk.
It has been my experience that the valve is more at risk from being jammed open by debris in the oil than a pipe is of being crushed. It is really your call, a quick risk assesment will help you to decide. I would never install hoses between a cylinder and the motion control valves.
The decision between metering flow in or out has been discussed at great length in this forum before now.
In basic terms, if you meter flow out of a cylinder you will stop the cylinder from running away because, as I said before, if oil cannot get out the cylinder cannot move. BUT..the extra pressure drop created by slowing the oil is seen by the cylinder and in some applications that may cause a problem.
If you meter the flow in, the pressure drop is less but the cylinder can overrun the oil flow. It means that the load on the cylinder accelerates it and the oil flow can keep the cylinder full. There would be no real control of speed and the cylinder creates an internal vacuum, drawing in air and sometimes turning seals inside out.
I always meter out, other people will meter in. Some suppliers have valve that can be simply turned over to change them from meter in to meter out. You could try it both ways to see which gives you the best performance.
By the way, what made you go for that size of valve? What is flow rate, could you use a size 6 instead of size 10 valve?
Adrian
RE: (reveiw) Hydraulic System with tandem center solinoid for control
the flow rate is around 2.5 to 3 gpm
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
Ted
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
also i don't think it will rupture cause im using steel piping to the cylinder which is in ground up to a small closet right beside the cylinder. so its not a long run. bout 5 ft pipe. with a o-ring on the end for leak protection. the rest of the system if possible will be rigid pipig if not then i will use normal tubing for the parts that are not ab;e to use rigid pipe.
RE: (reveiw) Hydraulic System with tandem center solinoid for control
Piping should typically never be used for your type of application with low flow, low pressure and small diameter. Typically piping is used for large water and gas-line practices, but causes some inherent issues with vibration and temperature. Additionally, pipe threads cannot tolerate vibration, shock or thermal stresses. Even when piping is utilized, they will typically weld the ends to reduce leakage effects in low pressure locations of the system. The piping will also typically introduce large amounts of contamination into your system due to the processing of the pipe.
Tubing is your better choice becuase it can easily be bent, flared and is rather ductile. Typically, for your low pressure system, you will want to use a flared connection, such as JIC, where the flare sits at 37 degrees and is readily available. You could also use something more leak resistant like a swage, which can be bought from Swagelok. The swage utilizes a two piece ferrel set to help lock the connections together.
The main difference between tubing and piping when seeing them side by side is their diameter rating. Piping runs on an inside diameter rating, where as tubing runs on an outside diameter rating. With tubing you need to be aware of the thickness becuase this will effect the pressure rating the tubing can withstand, likewise with piping when applicable. If you are using low flow such as 3 GPM and relatively low pressure, I'm not sure why -04 or -06 tubing can not be used, maybe -08 if there are a lot of resistive locations within your system.
Typically when sizing your tubing you want to have a target fluid velocity of around 7-20 ft/s on the pressure side. I'm not going to do the calculations for you, but I have faith you can calculate it out. This will ensure are general turbulent system, which will reduce other negative effects within your system.
Being that I am a big advocate of contamination cleanliness and you're working with underground operatino next to the dirt. Have you considered introducing a filter to increase system reliability?...
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
The filter in the return line to the reservoir should have a flow rating of 2 to 3 times your system flow. You will have to decide the level of filtration you want to keep your system clean.
Ted
RE: (reveiw) Hydraulic System with tandem center solinoid for control
but i still did't get an answer to my previous posts.
cause i noticed that manufacturers of logspliters for instance use rigid pipes for the top port of the cylinder, as well as CAT on their tracktors and excavators.
RE: (reveiw) Hydraulic System with tandem center solinoid for control
Ted
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
If the Counter Balance valve is not bolted directly to the cylinder there will be a cylinder that falls unexpectadly sooner or later. Just pray no one gets hurt or killed.
It's your call though if you are the circut designer.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
And be responsible.
Ted
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
Talo is like so many persons on the Forums who say they are looking for help when the actually mean "APPROVE MY CIRCUIT AS DESIGNED" or I will not be happy no matter how much experience is behind any of the answers.
That is what happens with a System that is not recognized by most users as a discipline that needs TRAINED/DEDIACTED persons to apply the equipment in an efficient and safe manner.
I seldom see these kinds of questions on the Electrical and Mechanical Engineering Forums.
Oh well Someday, Maybe.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
but i am trying to look for a alternative to the cbv problem. cause unless i have a bottom port routed to the top of the cylinder before i add the cbv then i would have room to place it directly onto the port. becuase i don't have the room for it in the design of the cylinder's hole in the ground.
RE: (reveiw) Hydraulic System with tandem center solinoid for control
One way to overcome the running away problem, when a line fails, is to orifice the port to slow the cylinders decent and use some sort of mechanical retardation to catch the falling load when a line fails.
Also, designing a circuit that is free from shock will reduce the chance of line failure.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
RE: (reveiw) Hydraulic System with tandem center solinoid for control
Then you would only need one port.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: (reveiw) Hydraulic System with tandem center solinoid for control
now what i need is a piston like that of an elevator , custom or ready mae options welcome
RE: (reveiw) Hydraulic System with tandem center solinoid for control
now what i need is a piston like that of an elevator , custom or ready made options welcome
RE: (reveiw) Hydraulic System with tandem center solinoid for control
that is at least 4000 psi
80" stroke.