Weldless Accumulator Tubes

Weldless accumulator tubes made by ALTA spa, like those for cylinders, have very advanced mechanical properties and are also available in special steel grades. Dimensional tolerances, surface quality and eccentricity values are in accordance with UNI ISO EN10305-3 standards and cover a wide size range as per customer demand.

The final resulting surface in the cold drawn tubes is caused by the condition of the mother tube, because during its hot drilling the tube takes on a spiral shape (fig. A) which is maintained even when reduced, after rolling and drawing (fig. B).

Traditional finishing processes of honing and rolling follow this spiral trend and, by obtaining the requested tolerance and without modifying the spiral shape, which is in direct opposition to the coaxiality principle for the specific group: PISTON/SLEEVE. Figure C demonstrates the extreme straightness of the internal finish, known as the “ALTA finish”.

Machining a tube with a reduced internal stock allowance, is generating raw material spots (in the picture the darker spots) those areas are outside of the maximum tolerated straightness, due to the spiral shape of the tube.
To avoid these problems, ALTA uses tubes with a higher stock allowance, over and above the standard (up to 3 mm in diameter) removing the necessary material, creating a straighter, rounder, and smoother finish compared to traditional methods.