Single Acting and Double Acting hydraulic cylinders: What's the difference?
Vložit
- čas přidán 10. 07. 2024
- In this video, we will explain the difference between a single acting hydraulic cylinder and a double acting hydraulic cylinder.
Find out more at sarum-hydraulics.co.uk/
A single acting cylinder has a piston rod, a cylinder barrel, a hydraulic seal and normally a bearing to limit how far it pumps out.
When you feed oil or your hydraulic fluid into it through the inlet port, it will extend, exerting a force. In this case, lifting a mass. In this example we’re using a Micropac hand pump to provide the pressurised fluid. Hand pumps are low tech and easy but you could alternatively use an electric pump or air driven pump.
When it has done its work, you need to release the fluid back into the tank. To do this we’ve fitted a needle valve into the Micropac hand pump. You open the valve and the oil flows,letting the mass drop.
You always need a way of returning the cylinder. Either gravity return or use a spring.
So the single acting cylinder will pump out, doing its work and retract when the fluid is released back into the tank. In and out.
A double acting cylinder will allow you to push and pull under hydraulic power. You’ve got a similar piston rod with a seal on the piston. You have a cylinder barrel and a piston rod bearing with an extra seal. This forms a second hydraulic chamber.
You’ll need a four way directional control valve to operate your double acting cylinder. We’ve added one to our Micropac pump.
There are two connections on this valve, one at either end of the cylinder.
Pressurise the bottom of the ram or full bore end to generate force. You need to connect the upper chamber, or reduced bore, to the tank or the ram will jam. The oil has to go somewhere.
You can see the ram is now extending. At the end of the stroke, we are reversing the four way valve so the pressure feed is now connected to the reduced bore end. We can now retract the ram under power and pull the rod back. It doesn’t need a spring or gravity to return it.
The force generated by the hydraulics will be smaller because the area is smaller.
Now you’ve seen single and double acting hydraulic cylinders, or hydraulic rams, in action. A simpler single acting cylinder that needs gravity return and the more complex double acting ram that provides force in both directions.
At Sarum Hydraulics, we supply Micropac manual pumps to operate single and double acting cylinders. And as the hand pump experts, we’ve got solutions for a wide range of demanding applications.
Talk to us today or find our more at sarum-hydraulics.co.uk/ - Věda a technologie
Thank you very much for explanation ! I have bean looking for such tutorial since yesterday !
Thank you, Lucy. We are so pleased that you found our animation useful. It is really clear and easy to see what is happening. John
Brilliantly explained! Thank you so much!!
Good animation showing the functioning of single and double acting hydraulic cylinders. Thank you for posting such instructive content !
Thank you AGS-Tech. We are pleased that you found this animation useful.
For the double acting cylinder, is the blue fluid side of the illustration never under pressure? I'm thinking of like a loader where you are exerting force up to lift, but if you are moving fast, the loader arms would bounce up because the blue side is not pressurized?
You guys are doing great stuff for students
Thank you - if you want any other topics covered, please let us know, and we'll see what we can do!
On a hydraulic excavator with a maximum breakout force of say 40,000 pounds calculated at the tip of the appendage, the maximum return force will be on the order of about 20,000 pounds or so, would it?
Are you able to find out the efficiency of barometer ?
Can I use an off/on valve as a flow regulator on a 1 ton mini excavator if I turn it part way for auxiliary attachment?
I have one on both sides of the stick. Would I need to adjust both sides or just one side?
Is the retracting velocity is important in single acting cylinder?
Good morning J land Malakas, That is a very good question for anybody who is designing equipment with a single acting cylinder. If you are lifting a very light load, the speed of descent might be quite slow and controlled . Or might it be "a bit slow" or "ridiculously slow." If you are lifting a heavy load using a single acting cylinder and when you release the pressure back to tank, it crashes down, totally out of control, that is a real hazard. That is unacceptable for lifting/jacking and anything to do with medical applications. Your can fit a fine needle valve into the feed to the hold release valve to adjust the speed of descent to what suits the application. But what about something like a hospital bed where one day you may have a baby on it and the next day a very heavy person? We use a pressure compensated flow control valve to control the speed of descent. As long as you get the right valve flow rate, that will keep the speed of descent safe and controllable. We would say that as well as doing your calculations to sort the correct pump and cylinder for a job, you should also check out the speed of descent and not just take a chance on it being OK.
If I were to use a double pump to a single cylinder, what happens to one side if it has no where to go and the cylinder retract with gravity? Will this be enough to blow a hose?
Jeremy, You can use a double acting pump with its two hoses to operate a single acting cylinder, but just connect one hose to the cylinder feed and feed the other hose back to tank. Pump the cylinder up then to let it down, turn the valve through 90 degrees to connect the cylinder to tank. The pump is more complicated and expensive than a unit with a simple hold release valve, but it does work. If you don't connect the hose to tank, the cylinder will simply not descend. It won't burst, provided it is rated to the correct pressure. Using a single acting pump to operate a double acting cylinder is another interesting question. Thank you for watching our video.
Can I move a single acting cylinder manually if needle is open? Its in a situation where the cylinder would be fastened between two points that will move away and towards each other so I want cylinder to freely move with them.. but also close needle and actuate when needed
Nick, make sure the drain from the needle is below the level of the oil in the reservoir and that the flow paths are big enough and you can do exactly what you say. Actuator manufacturers use this sort of method for damping or speed control. You can move the cylinder freely then add power when you need to. Keep in mind that if there is spring return, that can be a fair force to overcome. Thank you for the watch and the question. Sarum Hydraulics
@@johnfoster8624 Appreciate the answer John
How to get (liquid) from the reservoir into the small cylinder piston through the valve and not replace it with something else?
I mean you can not take any liquid from the reservoir or even open the valve if it’s completely sealed. Unless the reservoir tank shrinks?
Sammy, thank you for viewing our video. A reservoir will normally breathe to atmosphere so you can take fluid out and put it back in. Some applications do use a breather bag on a reservoir or even seal the fluid in a rubber bladder. That is required when you are carrying kit around upside down and don't want oil to spill or you don't want dirty air or water to enter the reservoir, as in an underwater hydraulic system. You can leave an air space in a reservoir and have it sealed, but we are careful with this. We hope this explanation makes sense.
Hi, do you have a hydraulic jack whose displacement can be controlled? For example, applying a deflection of 1mm/minute.
Superb explain
Thank you, Lokesh V. We have more videos like this in the future.
@@sarumhydraulics1386 are you able to make a turbine which is run by hydraulic pressure and we got lots of electricity and stored it in battery so we can power my microwave and cook my food
1200 watts microwave
For one hour
50 hz
250 volt
16 amp
We use a spring which is made of steel and stored 500000 joules a flywheel which store 1000 joules gears and pulley system
A dynamo synchronise motor
So we do some exercise and electricity production become easy
Like we turned the earth with our weight also by leavers so we produced electricity in very large quantities so we going grid free
Hi. I wanted to know which software was used for simulating this and if you have any suggestions how to simulate a model like this. Thanks. Appreciate the video.
Thank you for watching the video, Shubham Sharma. I believe that our animation guy uses After Effects. I drafted up some ideas of how I would explain how it worked in Coreldraw and he did the rest.
which works on aircraft shock strut means double action or single action?
Raka MS, Thank you for the view and question. Aircraft shock struts are complex because they mix oil and nitrogen. Not our thing, but this link may help. www.aircraftsystemstech.com/p/there-are-many-different-designsof.html . I thought that aircraft landing gear also used regenerative cylinders as well, which is worth looking into if you are designing hydraulic systems. I might be wrong. A regen cylinder can provide rapid extension- take a double acting cylinder and pressurise both ports. We've used them on some of our kit over the years for specific reasons. Our vid doesn't discuss them, just as we haven't talked about how telescopic cylinders work. Plenty of stuff on the web. Thanks.
Thank you
Radhika chauhan, thank you for watching our video and your comment.
Dear Sir............Example Problem I have a single acting hydraulic cylinder with a stroke of 300 mm, a bore of 18 mm and a rod of 10 mm
if the press weight is 10 mm on the Piston Head what is the pressure.....Please explain the calculations
Thank you Zulferi Syahputra for watching our video. We will explain the basics of cylinder calculations. These are just the fundamentals. A hydraulic cylinder is based on the formula Force =Pressure x area or rearranged, pressure = force/area. Work in pounds force and square inches or Newtons and square cm. We suggest not to mix metric and imperial units when calculating, but remember that you can simply convert pounds force into newtons at the final stage if you need to know an answer in imperial and metric units. 14.5psi = 1bar, 2.2lb=1kg, 9,81kgf=1 Newton and 25.4mm= 1 inch. Square for mm2 to inches2. Cube for mm3 to inches3. One more important point before you work out your cylinder force. A double acting cylinder is easy. The area applicable when the cylinder extends is the full bore area of the piston/bore it is running in. Use Area = pi x radius squared. On the area as the cylinder retracts, it is the ANNULAR area that you need to use. Work out the rod area and take that away from the full bore area, giving you the area of the annular “ring.” A single acting cylinder is very easy apart from one complication. Most designs will include some sort of piston to give the cylinder stability and also stop the rod popping out at full stroke. You MUST find out whether the hydraulic seal is in the bearing (so your area is that of the rod) or on the piston (so your area is that of the piston diameter.) This is fundamental. You have given us two diameters of 18mm and 10mm. The areas are 2.54cm2 (0.394in2) and 0.785 cm2 (0.122in2). Your load is quoted as 10kgf/22lbf (I am assuming), so the pressure is either 22/0.394=55.8 psi (3.84bar) or 22/0.122=180.3 psi (12.4 bar) depending upon the construction of the cylinder. Finally, how to work out the displacement or amount of fluid shifted over a full stroke. On a single acting cylinder, take the effective area (which you do unfortunately have to decide) x the stroke = so many cubic centimetres or cubic inches. A double acting cylinder simply uses the full bore area or the annular area x the stroke. Expect the displacement on the retract stroke to be around half of the extend displacement depending on the design. Your single acting cylinder has a displacement of 76.2cc/4.65cu.in. or 23.5cc/1.43 cu.in depending upon the effective diameter. Finally, look at the figures and check they are sensible. This is vital. If you are converting from mm to cm or ibf to newtons, people can easily make careless mistakes. I hope this very basic explanation in a few lines is helpful to you.
I love you
Which works best on a hydraulic elevator that carries a load of 1000kg and what pipe diameter should I use for the pipes connecting from the pump to the piston?
Good morning Nhlanhla Khumalo, Thank you for your comment. If you can use a single acting cylinder, the designer will be much simpler and cheaper. You do need gravity return or spring return to make it work. The design has to be reliable. For example, friction in pivots or slides over time could cause a problem. Also check that there is not a need to lock the elevator hydraulically for operational or safety reasons. That is difficult with a single acting ram. If it is a hand pump that you are using, the flows will be small. -4 or 1/4" sizes are often adequate on the pressure line, subject to the temperatures you are working at. There are lots of different elevators all with their own designs. Always have a look how other people do things first. Good luck on your project.
@@johnfoster8624 thank you so much is it okay if I ask you anymore questions that I may stumble upon
Why am I binge watching these
I'm not an engineer
Thank you for watching our vid, LUX 03. Engineering is our life. We're passionate about hydraulics. Keep watching.
what is the type of cylinder required to withstand a load of 200kg?
Good morning Bingoman. Use the formula Pressure = Force/Area. If you know the pressure that your electric, air driven or hand pump will generate and you know the force as 200kgf, you can work out what area you need on the full bore side of the piston. Then look at standard rams to start with and select one with the right size. I would start with the Enerpac or HiForce catalogue. Those are 700 bar cylinders. Or you may be able to use a more basic ram from lots of catalogues, often running at 200 bar. Those will probably be cheaper. Lots of other considerations. Spring or gravity return? Or double acting? Mineral oil, water or something more specialist? interface on the ram body and piston rod? Materials? Good luck with sorting out the right cylinder for your application.
@@johnfoster8624 actually i wanted to design a stair to ramp convertor using double acting electric hydraulic cylinder that can lift 200kgf or more. what type of fluid should be used and can u suggest how to find the power?
@@johnfoster8624 Which works best on a hydraulic elevator that carries a load of 1000kg and what pipe diameter should I use for the pipes connecting from the pump to the piston?
But... thats a 2/2 directional valve not a 4/2. also manual jacks dont extend on pull up, only down push.
Good morning Alvin, Thank you for looking at our video. If a manual jack is lifting a load and uses gravity return, it will invariably use a single acting cylinder as in our left hand view. You are pressurising the full bore area under the piston and lifting the load. You release this pressure back to tank when you want to lower the load. The right hand graphic showing the double acting cylinder does correctly show an acceptable graphic for four way two position directional control valve (a 4/2 valve.) We could have shown this as a circuit symbol for a spool valve, but our kit uses a very low leakage four way ball valve, so that explains more clearly exactly what our Micropac pump does. We hope that explains.
Las letras, no dejan ver el vídeo...
Thank you for your comment, Emilio. We will ask our designer.
⭕
How much energy a 60 kg man can provide maximum
It depends on the length of the lever.
it depends on a lot of things, like the cylinder bore diameter, the pump displacement, hose diameter will effect flow but that is a smaller factor, and of course the torque needed to actuate the lever and the load or force counter acting the cylinder. The torque for the lever could be determined by the distance of which the force is being applied on the lever and how long the lever is. If a man is 60kgs or 132 lbs and the lever is exactly one foot long, then you apply all of your energy "feet off the ground" you would have 132 ft lbs of torque. How much torque is needed for the pump based on it's displacement, it's probably not 60 kgs/132lbs.
to be honest i still don't get what's the difference 😂 ...
Good morning James. Have a look at a garbage wagon or tail lift. Some hydraulic cylinders only need to be powered in one direction and use gravity or a spring to return them. Others need to be powered on the out and return strokes. That's the difference. It is a big thing for hydraulic designers.
@@johnfoster8624 ah i see. thanks a lot man