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Pulp and Paper Mill - Hydraulic Cylinder and Piston
 Introduction:
The Sunds 50" Refinery hydraulic cylinder and double-acting
piston is under loading pressure when the secondary refinery
plates are working and the piston backs off to unload the
fibre. Base material is grey cast-iron, ground to an acceptable
finish to accept rubber seals.
Problem: Due to upgrade of seal, heavy oil loss was
recorded resulting in steam contamination. The seals were
only lasting four to six months and oil contamination resulting
in corrosion of the base cast-iron material was causing considerable
downtime for maintenance.
Solution: De-greasing, sandblasting and heating to
200° C. Re-sand blast and set up bore for prior maching.
A special manipulator was designed for the pre-blast, HVOF
spraying and diamond grind finish of the two components. Blast
with Aluminium Oxide to prepare surface. HVOF sprayed coating
of Wc-Cr-Ni for the best bond strength combined with a hard,
dense wear and corrosion resistant coating. A super-fine mirror
finish was achieved with diamond grinding equipment.
Results: The first cylinder and piston unit was sprayed
in 1991 and cost $30,000 including the 1/2 tonne manipulator.
Subsequently, another 12 units have been sprayed at a cost
of $12,000 per unit.
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