SOP: WELDING & CAVITATION | FRANCIS UNIT 1
SOP-WELD-018 REV 2.2

SPECIALIZED WELDING & CAVITATION REPAIR

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MANDATORY SAFETY PROTOCOL

HEXAVALENT CHROMIUM RISK

Stainless steel welding produces carcinogenic fumes. Forced ventilation and N95/P100 respirators are non-negotiable.

HOT WORK PERMIT

Verify fire extinguisher placement and fire-watch personnel before striking the arc.

EQUIPMENT SPECS

  • Auto-darkening helmet (Shade 10-12).
  • Grounding clamp directly on the runner.

METALLURGY & ARC CONTROL

MATERIAL MATCHING

Unit 1 runner is 13Cr4Ni Martensitic Stainless Steel. Using carbon steel electrodes will cause rapid galvanic corrosion and blade failure.

ELECTRODE PRIORITY

  • E308L-16 (3.2mm): GENERAL CAVITATION
  • E309L-16: DISSIMILAR METALS
  • Current: 80 - 120 A (DCEP)

7-STAGE FINISHING PROTOCOL

Roughness acts as a nucleation point for new bubbles. Ra < 1.6 μm (Mirror) is the mandatory standard.

STAGES 1-2 40 - 60 GRIT
STAGES 3-4 80 - 120 GRIT
STAGES 5-6 180 - 320 GRIT
FINAL BUFF 600 GRIT MIRROR

DIRECTIONAL RULE: Always grind parallel to water flow. Cross-grinding creates micro-turbulence.

DYNAMIC BALANCING LIMITS

THE 100g RULE

Adding metal to one blade creates centrifugal force debalans. Never exceed 100g of net added mass per blade without consult.

IMBALANCE = SHAFT FATIGUE & BEARING FAILURE

MITIGATION STRATEGY

  • Perform symmetrical repair on opposing blades.
  • Attach counterweights only in non-critical blade zones.
  • Verify shaft runout post-repair using DTI (max 0.05mm).