Oil flushing: achieving hydraulic cleanliness before startup

Oil flushing removes construction debris, weld slag, rust, and other contaminants from hydraulic and lubrication systems before they are introduced to operational service. Contamination left in piping after construction is the leading cause of early equipment failure in rotating machinery, hydraulic actuators, and control valves.

FARAMED deploys a modular, mobile oil flushing skid that integrates high-flow pumps, multi-stage filtration, and monitoring instrumentation into a single transportable unit. The system supports hydraulic pressure testing, tubing flushing, and actuated valve operation in one streamlined process.

Why oil flushing is critical

• Equipment protection — Contaminants as small as 5 microns can damage servo valves, bearings, and seals. Flushing removes these particles before they reach sensitive components.
• OEM warranty compliance — Most equipment manufacturers require documented cleanliness levels (ISO 4406) before warranty coverage is activated.
• Reduced startup risk — Systems that start clean run reliably from day one. Contamination-related failures during startup cause unplanned shutdowns and schedule delays.
• Regulatory compliance — Many jurisdictions and operating companies require documented flushing records as part of mechanical completion packages.

Our flushing unit

Modular mobile skid

• High-flow pump package (adjustable flow rate for different pipe sizes)
• Multi-stage filtration: coarse pre-filter, fine filter (down to 3 microns), and polishing filter
• Online particle counter for real-time cleanliness monitoring (ISO 4406)
• Fluid temperature control for optimal viscosity during flushing
• Flexible hose connections for rapid hookup to system flanges
• Hydraulic fluid reservoir with capacity for large system volumes

Integrated capabilities

• Hydraulic pressure testing — verify pipe and fitting integrity before flushing
• Tubing flushing — clean instrument tubing runs and small-bore piping
• Actuated valve operation — stroke hydraulic actuators during flushing to clean valve bodies and actuator cylinders simultaneously

Flushing methodology

Step 1: System preparation

Install bypass spools around sensitive equipment (servo valves, control valves, bearings). Connect flushing skid to system flanges. Charge system with flushing fluid.

Step 2: High-velocity flushing

Circulate fluid at turbulent flow (Reynolds number > 4000) to dislodge and transport contaminants. The fluid passes through progressive filtration stages. Online particle counting monitors cleanliness in real time.

Step 3: Temperature cycling

Alternate between high and low fluid temperatures to induce thermal expansion/contraction in piping. This dislodges trapped particles from weld roots, dead legs, and crevices.

Step 4: Acceptance

Continue flushing until the online particle counter confirms the system meets the target cleanliness class (typically ISO 4406 16/14/11 or cleaner, depending on equipment requirements). Generate cleanliness certificate with continuous monitoring data.

Step 5: System preservation

After acceptance, the system is either filled with operational fluid or preserved with corrosion inhibitor, depending on the time until startup.

Cleanliness standards

• ISO 4406 — Hydraulic fluid cleanliness code (target levels defined per equipment OEM)
• NAS 1638 — Aerospace and industrial cleanliness classification
• SAE AS4059 — Aerospace fluid power cleanliness
• OEM-specific — Adapted to manufacturer requirements (Parker, Bosch Rexroth, Moog, etc.)

Applications

• Hydraulic power units (HPU) — Subsea BOP, platform crane HPUs, process valve actuator systems
• Lube oil systems — Gas turbine, compressor, and pump bearing lubrication circuits
• Seal oil systems — Compressor seal oil piping and conditioning systems
• Control oil systems — Turbine governor and trip oil circuits
• Instrument tubing — Small-bore instrument impulse lines and pneumatic tubing runs

Ready to clean your hydraulic systems?

Contact our engineering team to discuss your system scope, pipe sizes, cleanliness targets, and project timeline. We will provide a flushing plan with equipment mobilization schedule and acceptance criteria.