SOP: Hydraulic Fluid Management

Critical SOP: Hydraulic Fluid Management

Viscosity, Temperature & Hygiene Standards

⚠️ THE SILT THREAT

Mechanism: Micro-particles (quartz/silt) suspended in oil act like sandpaper on valve spools.

  • Consequence: "Stiction" (Static Friction). Valve blocks, then releases suddenly.
  • Danger: This unpredictable movement destroys closing time logic, leading to Hydraulic Hammer.
Risk: P = ρ · c · Δv (Rapid Δv = Pipe Burst)
SOP 1: Fluid Specification Standards

Not all hydraulic oil is equal. You must match fluid to system pressure.

1.1 Viscosity & Class Selection

  • Role: Oil must transmit power, lubricate moving parts, and dissipate heat.
  • Selection Rule:
    • Pressure ≤ 12.5 MPa: Use L-HL (Oxidation & Rust protection).
    • Pressure > 12.5 MPa: Use L-HM (Anti-wear additives mandatory).
SOP 2: Hygiene & Filtration Protocol

Filtration system (kidney loop) or high-quality pressure filters are the only defense against silt.

2.1 Monthly Filter Check

  1. Inspection: Check "Differential Pressure" (Delta-P) indicator on filter housing.
  2. Trigger: If indicator enters RED zone (typically > 3-5 bar drop), element is saturated.
  3. Action: Replace immediately. Do not clean disposable elements.

2.2 Annual Lab Analysis (ISO 4406)

  • Sample: Take 100ml from middle of tank (warm oil).
  • Analyze For:
    1. Particle Count: Target ISO 18/16/13.
    2. Water Content: Max 500 ppm.
    3. TAN (Total Acid Number): Oxidation check.
SOP 3: Temperature Operating Window

Oil viscosity changes with heat. Too hot = too thin (leakage). Too cold = too thick (cavitation/sluggish).

  • Golden Window: Maintain bearing and tank temperature between 18°C and 60°C.
  • Cold Start: If temp < 15°C, use tank heaters before starting pumps.
  • Overheating: If temp > 60°C, oil degrades rapidly (oxidation doubles every 10°C). Check cooling water flow.
Technical Audit Table

Use this table for regular rounds.

Parameter Frequency Method / Action
Oil Level Daily Check sight glass. Top up if below halfway.
Filter Status Monthly Check Delta-P indicator. Replace if Red.
Water Contamination Annually Lab Analysis or "Crackle Test" on hot plate.
Temperature Daily Log HPU & Bearing temp. Target: 18°C - 60°C.
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