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What Is a Tie Rod Hydraulic Cylinder?
A tie-rod hydraulic cylinder is built from a honed steel tube closed by a front head and a rear cap, held together by four or more external steel tie rods. The tie rods carry the separating force created by the oil pressure, so the heads can be bolted rather than welded. That makes tie-rod cylinders easy to dismantle, reseal and re-test, and it allows standardised mounting dimensions — which is why they are widely used in stationary industrial machinery.
Fenitsa tie-rod cylinders belong to our hydraulic cylinders range. They are built for 160 bar working pressure (240 bar test, 250 bar option), with mounting dimensions to CETOP RP 58 H, bores from Ø40 to Ø200 mm, rods from Ø25 to Ø125 mm and strokes up to 5,000 mm. Adjustable-stroke, double-rod and tandem versions are available; the FDH series is the catalogue reference for these values.
Construction
- Rear cap (cap end)
- Rear clevis mounting
- Port A — cap end (full bore side)
- Barrel (honed cylinder tube)
- Tie rods and nuts
- Piston
- Piston seal
- Wear (guide) rings
- Piston rod (hard chrome plated)
- Front head (gland)
- Rod bearing (guide bush)
- Rod seal
- Wiper (scraper)
- Port B — rod end (annulus side)
- Cushioning spear and adjusting screw
- Static O-rings
- Rod eye
Cap-side chamber — pressure acts on the full piston area · Rod-side chamber — pressure acts on the annulus area
| Part | Fenitsa specification | Function |
|---|---|---|
| Cylinder tube | Honed St52BK+S steel tube | Pressure vessel; smooth bore for the piston seals |
| Piston rod | Ck45 steel, hard chrome ≥ 20 µm, f7 tolerance; hardened + chrome (HR) and stainless (SS) options | Transmits the force; the chrome resists wear and corrosion |
| Front head and rear cap | Clamped to the tube by the tie rods | Close the tube, carry the ports, rod bearing and mountings |
| Tie rods | Steel tie rods and nuts along the tube | Hold the heads against the internal pressure |
| Seals | NBR (standard, code NS) or Viton (code VS); mineral oil, −20 °C to +80 °C, −30 °C to +200 °C with special seals | Separate the chambers and keep dirt out |
| Mountings | Front or rear flange, rear clevis (plain or spherical), foot, front, centre or rear trunnion; rod clevis or spherical rod end | Connect the cylinder to the machine |
Force Chart at 160 bar
| Bore / rod (mm) | Push kN | Pull kN | Push t | Pull t | Push lbf | Push t at 250 bar |
|---|---|---|---|---|---|---|
| Ø40 / Ø25 | 20.1 | 12.3 | 2.1 | 1.2 | 4,520 | 3.2 |
| Ø40 / Ø28 | 20.1 | 10.3 | 2.1 | 1.0 | 4,520 | 3.2 |
| Ø50 / Ø28 | 31.4 | 21.6 | 3.2 | 2.2 | 7,063 | 5.0 |
| Ø50 / Ø30 | 31.4 | 20.1 | 3.2 | 2.1 | 7,063 | 5.0 |
| Ø50 / Ø36 | 31.4 | 15.1 | 3.2 | 1.5 | 7,063 | 5.0 |
| Ø63 / Ø36 | 49.9 | 33.6 | 5.1 | 3.4 | 11,213 | 7.9 |
| Ø63 / Ø45 | 49.9 | 24.4 | 5.1 | 2.5 | 11,213 | 7.9 |
| Ø80 / Ø45 | 80.4 | 55.0 | 8.2 | 5.6 | 18,080 | 12.8 |
| Ø80 / Ø56 | 80.4 | 41.0 | 8.2 | 4.2 | 18,080 | 12.8 |
| Ø100 / Ø56 | 125.7 | 86.3 | 12.8 | 8.8 | 28,250 | 20.0 |
| Ø100 / Ø70 | 125.7 | 64.1 | 12.8 | 6.5 | 28,250 | 20.0 |
| Ø125 / Ø70 | 196.3 | 134.8 | 20.0 | 13.7 | 44,141 | 31.3 |
| Ø125 / Ø90 | 196.3 | 94.6 | 20.0 | 9.6 | 44,141 | 31.3 |
| Ø160 / Ø90 | 321.7 | 219.9 | 32.8 | 22.4 | 72,321 | 51.3 |
| Ø160 / Ø100 | 321.7 | 196.0 | 32.8 | 20.0 | 72,321 | 51.3 |
| Ø200 / Ø110 | 502.7 | 350.6 | 51.3 | 35.8 | 113,001 | 80.1 |
| Ø200 / Ø125 | 502.7 | 306.3 | 51.3 | 31.2 | 113,001 | 80.1 |
Values are theoretical (F = p × A; pull uses the annulus area, piston minus rod). Real output is lower because of seal friction and pressure losses, so keep a margin between the theoretical force and the load, and check rod buckling on long push strokes — or use the hydraulic cylinder force calculator.
Mounting Styles and When to Use Them
| Mounting | Load path | Typical use |
|---|---|---|
| Front flange | Rigid and on the cylinder axis; keeps the unsupported rod short | Presses, clamping |
| Rear flange | Rigid and on the cylinder axis; the whole cylinder length is in the load path | Lifting, pulling, short push strokes |
| Foot | Side-mounted; creates a bending moment on the mounting bolts | Machine beds, horizontal motion |
| Front, centre or rear trunnion | Pivots in one plane | Loads that move through an arc |
| Rear clevis (plain or spherical) | Pivots at the rear | Levers, gates, platforms |
| Rod clevis or spherical rod end | Pairs with a pivot mounting to avoid side load | Any pivoting application |
Side load is the main enemy of rod bearings and seals. With a fixed flange, arrange it so the working force presses the flange face against the machine rather than pulling on the bolts. With pivoting loads, combine a pivot mounting at the rear with a rod clevis or spherical rod end. See our mounting equipment.
Tie Rod vs Welded Hydraulic Cylinders
What is the difference between tie rod and welded cylinders?
A tie-rod cylinder is clamped together by external tie rods and comes apart on the bench; a welded cylinder has its cap welded to the tube, which makes it more compact and lighter but slower to service. Tie rod suits stationary industrial machines with standard mountings; welded suits mobile equipment where space, weight and shock loads decide.
| Tie rod | Welded | |
|---|---|---|
| Construction | Tube clamped between the front head and rear cap by external tie rods | Cap welded to the tube; gland threaded, bolted or ring-locked into the open end |
| Pressure rating | Set by the tie-rod size and head sealing; peaks stretch the rods, so the series rating is fixed | Set by the tube wall, the weld and the gland retention; engineered per design |
| Serviceability | Loosen the nuts and the heads come off on the bench | Serviced through the gland, often with special tools; the welded cap stays |
| Overall size | Square heads and external rods make the envelope larger than the tube | Round body only slightly larger than the tube; fits tight spaces |
| Weight | Heavier for the same bore and stroke | Lighter; matters on mobile machines |
| Mountings | Catalogue mountings bolted to the heads | Cross tubes, clevises, lugs and trunnions welded where the machine needs them |
| Standard dimensions | Standardised mounting dimensions; replacements fit directly | Usually specific to one machine; replacements are measured or drawn |
| Cost logic | Standard parts keep catalogue sizes economical in small quantities | Economical when one design is repeated in series; one-offs need design work |
| Shock and dirt | Long tie rods are exposed and can stretch under pressure peaks | One-piece body with no external rods to catch or damage |
| Typical use | Presses, injection moulding machines, machine tools, automation lines | Excavators, loaders, cranes, tippers, tractors and implements |
The table describes the two designs in general engineering terms; the rating of any specific cylinder is the one stated for its series or in its quotation. Construction details, end types and sizes of the welded range are on the welded hydraulic cylinders page.
Tie Rod Torque and Maintenance
On a hydraulic tie rod cylinder the nuts are tightened to a specified torque so that the rods are pre-tensioned: the heads must stay clamped to the tube even at full pressure. Too little torque lets the heads lift slightly under pressure, the static seals at the tube ends extrude and the joint weeps. Too much torque overstresses the rods and threads and can distort the tube ends.
The correct torque depends on the tie-rod diameter, thread and material, so there is no single figure that fits every cylinder. Use the value specified for your cylinder; for a Fenitsa cylinder, send us the ordering code (FDH-[bore]-[stroke]-[mounting]-[seal]-[rod type]) or the bore, rod and stroke.
Tightening procedure
- Remove the load, release all pressure and support the rod. Never loosen or tighten tie-rod nuts on a pressurised cylinder.
- Clean the threads and nuts and inspect them; replace damaged or stretched tie rods and nuts instead of re-using them.
- Fit new static seals at the tube ends, seat the heads squarely on the tube and run the nuts down by hand.
- Tighten in a diagonal (cross) sequence, opposite corners in turn, in several stages up to the specified torque, so the heads pull down evenly.
- Make a final pass at full torque in the same sequence and mark each nut with a paint line, so any later loosening is visible.
- Pressure-test the cylinder or run it under load, check the head joints for weeping, and re-check the nuts after the first period of operation.
Routine checks
- Rod: scores, pitting or chrome damage ruin a new rod seal quickly; repair or replace the rod first.
- Rod seal and wiper: oil drops or a ring of oil at the front head mean the rod seal or wiper needs replacing.
- Drift: a loaded cylinder that creeps with the valve closed points to internal leakage at the piston seal or the valve.
- Tie-rod nuts: a broken paint mark shows a nut has turned; loose nuts let the heads move and leak.
- Mountings: worn pins and bushes add side load; replace them before they damage the rod bearing.
- Oil: clean mineral oil inside the seal temperature range (−20 °C to +80 °C with standard NBR seals) is the cheapest way to extend seal life.
Replacement heads are available as cylinder front and rear covers, and Fenitsa provides service and spare-parts support for 10 years.
Options
Adjustable stroke limits travel mechanically for fine-tuning a machine. Double rod versions have a rod through both heads for equal area — and equal speed and force — in both directions. Tandem cylinders put two pistons in line to increase force from the same bore. For anything outside the series, see custom hydraulic cylinders.
Tie-Rod Hydraulic Cylinders – FAQ
What is a tie rod hydraulic cylinder?
A hydraulic cylinder whose front and rear heads are clamped to the tube by external steel rods (tie rods) running along its length. The rods hold the assembly together against the internal pressure, so no welding is needed and the cylinder can be taken apart for service.
What are the advantages of tie-rod cylinders?
Standardised mounting dimensions, easy dismantling for seal replacement, a wide choice of mountings on the same body, and predictable performance in industrial machines. They are widely used in presses, injection moulding machines and automation.
Tie-rod or welded cylinder — which should I choose?
Choose tie-rod for industrial machines where standard dimensions and easy servicing matter. Choose a welded cylinder for mobile equipment where space is tight, loads are shock-type and a compact body is needed.
Is a tie-rod cylinder the same as a rotary cylinder?
No. A tie-rod cylinder moves in a straight line; a rotary actuator turns a shaft through an angle. The two are sometimes confused because the Turkish word “rotlu” (with rods) sounds like “rotary”. For rotary motion you need a hydraulic rotary actuator or motor.
Which standard do Fenitsa tie-rod cylinders follow?
Their mounting dimensions follow CETOP RP 58 H, the CETOP recommendation for the mountings of 160 bar hydraulic cylinders. That keeps flanges, clevises and trunnions dimensionally predictable when a cylinder has to be replaced.
Can tie-rod cylinders be repaired?
Yes — that is one of their main advantages. Loosening the tie rods releases the heads, so seals, bearings and even the rod or tube can be replaced and the cylinder re-tested.
What pressure can a tie rod hydraulic cylinder handle?
Its rated working pressure, which is set by the tie rods, the heads and the tube wall, not by the bore alone. Pressure peaks above the rating stretch the tie rods and can open the head joints, so the relief valve must be set at or below it. Fenitsa tie-rod cylinders are rated 160 bar (16 MPa) working and tested at 240 bar (24 MPa); a 250 bar (25 MPa) option is available.
How tight should hydraulic cylinder tie rods be?
Tight to the torque specified for that cylinder design, applied in a cross pattern over several stages. There is no universal value: it depends on the tie-rod diameter, thread and material. Too little torque lets the heads lift under pressure and leak; too much overstresses the rods and threads. For a Fenitsa cylinder, ask us with the ordering code.
Send Us Your Cylinder Data
Bore, rod, stroke, working pressure, mountings and quantity — or a drawing or photo of the cylinder you want to replace. Our engineers reply with a technical proposal and a quotation. info@fenitsa.com.
Hydraulic Cylinders · Custom Hydraulic Cylinders · Force Calculator
Related Pages
- Welded Hydraulic Cylinders — compact welded bodies with cross tube and clevis ends.
- FDH Type Hydraulic Cylinders — the catalogue series with CETOP RP 58 H mountings.
- Hydraulic Press Cylinders — tonnage table at 160 and 250 bar.
- Hydraulic Cylinder Mounting Equipment — flanges, clevises, trunnions and rod ends.
Fenitsa meets the needs and requirements of the machinery manufacturing sector, especially in pneumatics, to the maximum extent possible.
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