This is because the outward forces produced by internal hydraulic pressure tend to expand the steel sleeve sections.
Double- Acting — have a port at each end, supplied with hydraulic fluid for both the retraction and extension.
To accomplish the double acting feature, additional hydraulic seals are added to internally seal off the individual stages.
Choose a single acting cylinder if your press machine or other equipment only needs high-powered movement in one direction.
Higher work output When a hydraulic cylinder contains more fluid, it extends more energy during work output.
They are used in lifting applications where pressure from the hydraulic pump extends the hydraulic cylinder and a mass or a spring retracts it.