‘Mill’ cylinders deliver high performance under harsh conditions

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‘Mill’ cylinders deliver high performance under harsh conditionsParker Hannifin’s 160 bar and 250 bar hydraulic ‘mill’ cylinders are a favourite in hostile environments and arduous applications. Originally designed for use in steel mills, Parker’s mill cylinders are of heavy duty, all-steel construction and are fatigue-free at their maximum rated pressure. New for 2012, the latest generation of these cylinders extends the standard fitment of induction-hardened piston rods, offering excellent resistance to damage in tough applications. A new, wider range of mounting accessories offers versatility for the designer, while web-based CAD models and an online configurator speed and simplify the selection process.

Parker’s standard mill cylinders are available in two ranges. The MMA series is rated at 250 bar working pressure and conforms to ISO 6022 and DIN 24 333, while the MMB series of 160 bar cylinders conforms to ISO 6020/1. Both MMA and MMB series cylinders incorporate features such as removable glands and separate bodies with detachable heads and caps to ensure ease of maintenance and low whole-life operating costs. Steel and aluminium mills, paper mills and plastic injection moulding machines are just some of the applications where Parker mill cylinders have been used.

Both the MMA and MMB series are available with a range of gland and piston seal options to suit differing application demands. Each offers different combinations of attributes, allowing the designer to select the desired blend of load holding, contamination resistance, fine positioning control and seal life to suit the application.

The seals fitted as standard to mill cylinders provide excellent low-speed and break-out performance, and deliver exceptional working life in high-cycle applications. The detachable, corrosion-resistant steel gland houses a heavy duty wiper seal, polyurethane lipseal and bearing rings with, additionally, a PTFE stepped seal on the 250 bar MMA series cylinder. On both MMA and MMB series, the piston carries a heavy duty filled polymer seal with broad bearing rings, preventing metal-to-metal contact and helping to protect the piston seal from contaminants.

For the most arduous conditions, where long life and durability are critical, traditional chevron piston and gland seals are a popular choice. Secured by a corrosion-resistant gland retainer, the chevron packing set and bearing rings are protected by a heavy duty wiperseal, while the two-piece piston features a wide bearing ring mounted between chevron seals, for high resistance to side loads.

Load-holding performance

Where load-holding performance is critical, the load-holding option combines the all-round performance of the standard gland assembly with the resistance to cross-piston leakage of the chevron piston, giving an optimised combination of wear resistance, seal friction and load-holding properties.

A low-friction gland with stepped seals is offered for applications where very low friction and an absence of stick-slip are important. The matching piston employs PTFE seals and wear rings, chosen for their low-friction performance and high resistance to wear. Low-friction seals are offered as a standard option for the MMA series and are available to special order for the MMB range.

Parker’s mill cylinders are available in a wide range of bore sizes up to 320mm diameter and in stroke lengths up to 5m. Standard features include precision ground, hard chrome plated and polished piston rods, which are induction hardened as standard on bore sizes up to 200mm diameter. Detachable threaded flanges for head and cap retention simplify maintenance, while heavy wall steel tubing honed to a high surface finish ensures a long seal life. Optional features include adjustable cushions at both ends for shock suppression and high-speed cycling performance, air bleeds, gland drains and special modifications for water service. Where precise control over performance and positioning is required, feedback devices and non-contacting position switches can be specified.

Mill cylinders can be used at operating temperatures of between -20degC and +150degC and generate up to 2000kN, making them suitable for high force applications in the toughest conditions.

For further information about MMA and MMB series hydraulic ‘mill’ cylinders, go to

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