Parts of a Hydraulic Cylinder – 15 Labeled Parts, Cut Open

All 15 parts on the diagram

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Start here: 6 main parts 6

Barrel (tube) Holds the oil pressure; the piston runs inside it.
Piston Divides the barrel into two chambers; oil pushes on it.
Piston rod Carries the force from the piston out to the load.
Cap (end cap) Closes the barrel’s blind end; welded on here.
Head (gland) Guides the rod and holds its seals.
Port Where the hose connects; one opens into each chamber.

Cut open 8

Piston seal Stops oil passing the piston from one chamber to the other.
Wear ring (guide ring) Keeps piston and barrel wall apart.
Rod seal The main seal that keeps oil in round the rod.
Wiper (scraper) Scrapes dirt off the rod as it comes back in.
O-ring (static seal) Seals the fixed joint between head and barrel.
Cushion (cushion spear) Slows the piston at the end of its stroke.
Clevis Pins the cap end of the cylinder to the machine.
Rod eye (rod end) Pins the rod to the part being moved.

Tie-rod cylinder 1

Tie rod Hold the square end caps onto the barrel.

How this list was compiled: Read 2026-09-24. (1) Wikipedia, Hydraulic cylinder, https://en.wikipedia.org/wiki/Hydraulic_cylinder : barrel; cap (cap end, with cap flange, trunnion or clevis mounts; a static seal or O-ring between cap and barrel except in welded construction); head with the seal gland and an O-ring between head and barrel; piston dividing the cap end and rod end chambers; piston rod with mounting attachments; piston seal, rod seal and wiper; ports; cushions; clevises, trunnions, flanges and lugs; tie rods. (2) A hydraulics supplier's Hydraulic cylinder parts page, https://hydrauliconline.net/hydraulic-cylinder-parts/ : barrel, piston, piston rod, gland, end cap, seals, wiper, wear rings, ports, eye and clevis mounts. (3) A cylinder maker's Parts of a hydraulic cylinder, https://lichydraulic.com/parts-of-a-hydraulic-cylinder/ : barrel, blind end cap with the rear mount (clevis ear, trunnion or flange), gland (rod end head), piston, rod, piston seals, rod seals, wiper, wear bands (wear rings, guide rings), O-rings, a port at each end, cushion plungers. (4) A hydraulics supplier's Hydraulic cylinder parts guide, https://isohydraulic.com/hydraulic-cylinder-parts-guide/ : barrel, end cap, gland, piston, rod, piston seal, rod seal, wiper or scraper, O-rings, wear rings, ports, rod end (clevis, eye), cushion spear, tie rods. Licence: own work

The drawing: Drawn for this site by script, 2026-09-24. Licence: own work

How it works

A hydraulic cylinder is a barrel closed by a cap and a head. Oil through a port pushes the piston, and the piston rod carries the force out. Seals keep the oil in and dirt out.

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Seals from the inside out

The piston seal stops oil passing the piston, with a wear ring either side keeping it off the barrel. In the head (gland), the rod seal keeps oil in round the rod, and the wiper at the outer face scrapes dirt off. An O-ring seals the head to the barrel.

Ends and mounts

A welded cylinder has its cap welded to the barrel; a tie-rod cylinder holds square caps on with tie rods. A clevis on the cap and a rod eye on the rod pin it to the machine. A cushion slows the piston at the end of its stroke.

Questions and answers

What are the main parts of a hydraulic cylinder?

The barrel, the cap and head that close its ends, the piston and piston rod, the ports where the oil goes in and out, and the seals: piston seal, wear rings, rod seal, wiper and O-rings.

What is the gland on a hydraulic cylinder?

The head at the rod end. It guides the rod as it slides and holds the rod seal and the wiper, with an O-ring sealing it to the barrel.

What are the parts of a pneumatic cylinder?

Much the same: a barrel, end caps, a piston and rod, ports and seals, but it runs on compressed air instead of oil. A single-acting one has a spring to push the piston back.