Marine & Offshore
Lift Cylinders
Corrosion · Stainless · Certification

HFDU PHOSPHATE-ESTER

Most common on FPSO and platform lifting equipment

HFC WATER-GLYCOL

Used where phosphate ester is cost-prohibitive; lower fire resistance

QUARTERLY

Inspect all lift cylinder exposed rod surfaces for corrosion pitting, paint blistering on outer body, and coating defects at weld seams. Apply corrosion-preventive wax to all stainless steel rod surfaces. Check all cathodic protection anodes for depletion — replace when 50% consumed. Record inspection results in the cylinder’s maintenance logbook.

ANNUAL

Full seal kit replacement on all deck lift cylinders — rod seals, wipers, and static O-rings. Take phosphate ester hydraulic fluid sample for acidity (acid number), water content, and particle count. Acid number above 0.5 mg KOH/g is the mandatory change trigger for HFDU offshore fluids. Inspect and touch-up any outer coating defects identified in quarterly inspections.

5-YEAR SURVEY

Full disassembly inspection of all safety-critical lift cylinders — rod surface measurement (pit depth gauge, chrome/SS thickness), bore inspection, weld examination by MPI, and pressure re-test to 1.5× current working pressure in the presence of the classification society surveyor. All findings documented and submitted with the survey documentation package. Any lift cylinder with rod pitting exceeding 0.1 mm depth or wall thickness below the minimum calculated value must be replaced before the vessel returns to service. The full range of certified replacement configurations is available from the lift cylinder product range.

Q 01

Can a standard industrial lift cylinder be used temporarily on a vessel while waiting for a classified replacement?

This depends entirely on the function of the cylinder and the vessel’s class rules. For a non-safety-critical auxiliary application — a workshop hatch that does not form part of the vessel’s watertight integrity and is not involved in cargo or personnel safety — a standard lift cylinder may be temporarily acceptable under a Temporary Repair Notation from the classification society, subject to a formal risk assessment and written permission. For any safety-critical application — hatch covers that seal against flooding, crane boom or hook cylinders, ramp lifting cylinders, or any personnel-carrying equipment — there is no acceptable temporary measure. The vessel must either not operate that system or remain in port until the correct classified cylinder is available. A classification society surveyor must assess the specific case and issue a written notation before any temporary arrangement is put into service on a classed vessel.

Q 02

How do I convert an existing mineral oil hydraulic system on a vessel to fire-resistant fluid?

Converting from mineral oil to HFDU phosphate ester requires a systematic approach across the entire circuit. First, commission a compatibility survey of all seals, hose materials, and metal components in the circuit against the specific HFDU fluid grade — this must be done before any fluid change. Then: drain the mineral oil completely; flush the entire circuit including all lift cylinder bores with a small volume of the new HFDU fluid; drain the flush volume; replace all seal kits in every lift cylinder in the circuit with FKM-grade seals; remove and replace any incompatible hose assemblies (HFDU attacks many standard hydraulic hose inner liners); refill with fresh HFDU fluid; and commission the system at low load before returning to full duty. The fluid change must be documented in the vessel’s maintenance record and the classification society notified if the fluid change affects a classified system. Phosphate ester requires specialist disposal — it cannot be discharged overboard and must be handled as hazardous waste at port.

Q 03

Is 316 stainless steel rod sufficient for a lift cylinder on a supply vessel operating in the North Sea?

For deck equipment in the atmospheric zone on a North Sea supply vessel — such as the lift cylinder for a deck hatch or cargo door that is above the maximum wave wash height — 316L stainless steel rod is generally adequate, providing the installation geometry does not create stagnant water accumulation points at the rod gland entry or mounting brackets. For any position that experiences regular wave wash or spray — such as the ramp lift cylinder on an offshore supply vessel, or any cylinder in the splash zone — 316L stainless shows measurable pitting corrosion in North Sea conditions within 2–4 years. Super-duplex SAF 2507 rod extends service life to 10–15 years in these positions and is the preferred specification for any new installation on North Sea offshore support vessels where cylinder removal for inspection or replacement requires significant crane and scaffold time. The increased material cost of SAF 2507 is typically recovered within the first service cycle through avoided inspection and replacement costs.

Q 04

What documentation must accompany a replacement marine lift cylinder supplied for a classified vessel?

The minimum documentation package for a replacement lift cylinder on a classification-society-surveyed vessel is: EN 10204 3.2 material certificates for the barrel steel, rod material, and all structural weld filler materials; a hydrostatic pressure test certificate showing test pressure (1.5× working pressure minimum), test duration, and confirming zero leakage, signed by the classification society surveyor who witnessed the test; dimensional inspection report confirming bore, rod, and stroke dimensions match the approved drawing; NDT reports (MPI of welds) signed by a Level 2 certified technician; and a declaration of conformity to the applicable classification society rules chapter. For cylinder positions that were originally design-approved by the classification society, the replacement must be confirmed as “like-for-like” — any design change to bore, material, or seal specification requires a new design approval submission before the replacement cylinder can be fitted. Ensure you specify the classification society, vessel name, and rule edition when ordering to ensure the correct documentation package is prepared.