GB/T 39655.2-2020 in English

This standard applies to integral type, combined fixed pitch propellers and adjustable pitch propellers, and specifies the manufacturing tolerance requirements for products with a diameter range of 0.8-2.5m. Under special circumstances, the supply and demand parties are allowed to negotiate and adjust the deviation value.

1. Pitch measurement method

The standard stipulates three measurement methods: ruling gauge method, scale ring method and coordinate measuring machine method, with different detection points set in the radius range of 0.4R-0.95R. For S-class propellers, measurements must be made at 8 radial positions, while for Class III, only 4 positions are required.

2. Section thickness control

Thickness measurement must be carried out along the SV direction (direction perpendicular to the node line of the pressure surface), and after deducting the negative tolerance, the minimum thickness requirements of the classification society must still be met. The positive tolerance for S-class is only allowed to be +2% and not less than 2mm.

3. Blade shape verification

For Class S and Class I, a flexible template is required to verify the continuity of the section, and the leading edge/following edge profile tolerances are ±0.5mm and ±0.75mm respectively. Special templates are required for large-angle blades (>25°).

• Selection of measuring equipment: The instrument error should be ≤50% of the tolerance value or 0.5mm (the larger value). It is recommended to use a three-coordinate measuring machine for high-precision testing
• Key points of process control: For ducted propellers, special attention should be paid to radius tolerance control, and the standard value can be reduced if necessary
• CNC machining verification: The machining process can be used instead of final shape inspection after negotiation, but complete process verification records must be retained