What is a single acting and double acting hydraulic hand pump?

We explain the difference between a single acting and double acting hydraulic hand pump in this easy animation.
Which is better for your job? Ask the experts. sarum-hydrauli...
What are single acting hydraulic pumps and double acting hydraulic pumps?
Here’s the difference.
A single acting pump has a rod moving in and out of a bore with a seal.
There is an inlet and outlet non-return or check valves. They allow flow in one direction only.
On the suction stroke we pull in fluid through the inlet check valve. The outlet check is locked.
On the pressure stroke, the inlet is locked and flow is through the outlet check.
In, out, in out. But there is only flow on the down stroke. You will get your pressure flow of water, oil, fuel or whatever only on the down stroke.
Now let’s look at a double acting pump.
A double acting pump adds a piston with a seal on it and intermediate check valve through the piston.
On the suction or up stroke, it pulls in a shot of fluid below the piston and expels the fluid above the piston through the outlet check. The piston check valve stops flow down back through the piston.
On the pressure or down stroke, the inlet check is locked, a charge of fluid flows through the piston and out through the outlet check.
If we pump up and down, in and out we will have that shot of our fluid on both strokes.
Is the double acting pump something for nothing? Maybe. It is a little more complicated and more expensive but we like them.
At Sarum Hydraulics we manufacture both types of pump.
See what we do on sarum-hydrauli...
Or contact us on [e-mail]

[@user-op6uv5bx1r]

Thanks! excellent animation
In any case, the liquid in the container is not under pressure
as seen - It is always blue

[@oscarpena314]

On the double acting pump. Why is the outlet check valve required? Its open in both the up and down stroke. Is it just a protection method against backflow? The intermediary check valve seems to be able to also protect the tank.

[@johnfoster8624]

Good afternoon Oscar, That's a good question. I think I have seen pumps without the outlet non return valve. I think one of the Italian volume market pumps doesn't have it. We have put in this extra check valve for 40 years simply to provide that extra security. My instinct is to put it in for that reason. Thank you for the interest in our product.

[@isidoropascualmolina7381]

Hi there. In a double acting pump, if I eliminate the intermediate valve, it performs as single action? Thank you

[@majk6888]

where I can get it in KSA

[@puregold394]

shits crazy

[@munilalkumar9837]

Manilal kumar the ye pamp chahiy

[@kageyame]

This animation is wrong, there no reason for the downward stroke to generate pressure to pump the fluid.

[@johnfoster8624]

Thank you Kageyame. On a single acting pump, you are pulling in a shot of fluid from the inlet check valve in the base. The outlet check on the side is shut. The down stroke puts a solid rod into a chamber of fluid and expels it from the outlet check on the side. The double acting pump pulls a double volume slug of fluid in below the piston on the upstroke, expelling the fluid above the piston out through the outlet check valve. The piston check is shut. Now on the down stroke, it is almost working like a single acting pump. The check in the piston allows fluid up and the net effect is the volume of the rod that forces a slug of fluid out of the outlet check valve. If the area of the rod is half that of the piston, the flow on the up stroke is the same as the down stroke. That's how I see a double acting pump. Sorry, I can't see why the animation is wrong. Are you looking at the downstroke on the double acting pump? If so, think of it as a pot of fluid and you are simply pushing a displacer into it. That amount will be pushed out. Happy to discuss further.

[@kageyame]

​@@johnfoster8624
Sorry, my bad
It was hard to visualize by the animation alone, but from what you said, the upper layer have half the capacity of the bottom layer, so in the end the full stoke in both pumps send the same amount of fluid outwards, but the double action distribute the load in upwards and downwards strokes, correct?

[@sarumhydraulics1386]

@@kageyame , thank you for the message. Yes, you are right. You expel the same amount of fluid on the up and down strokes. The load on the rod is the same on up and down.

[@udaykits1]

@@sarumhydraulics1386 by the way, in terms of efficiency which one is more efficient, a single acting or a double acting when connected to an electrically driven motor?

[@sarumhydraulics1386]

@@udaykits1, thank you for the question. Whichever cylinder you use, you will only get out what you put in. Use the formula Force= Pressure x Area. If you are using the full bore side of the cylinder, the area may well be the same so the force will be the same. If you go for a double acting design, the extra pipework and valve components will give rise to some loss of energy, we would have thought. We would generally say "try to use a single acting cylinder if you can because it is simple. Some applications will need double acting in order to work, so that is what you will have to use." On your "efficiency" question it is also worth noting that using a mass or spring return to return a single acting cylinder is only stored energy. The single acting ram needs extra pressure to drive it out on the pressure stroke then that energy is used to return it. An electric pump won't be generating pressure for the return stroke for a single acting ram.