PICV Actuator Gear Material - Metal vs. Composite
By Torben W. Ibsen, President, M.Sc. (Mech.Eng.), FlowCon International ApS, Denmark - 12.2020
This Topic Letter’s focus is on key parameters used for gear material selection in the rotating FlowCon SM actuators and the linear FlowCon FN/FH actuators.
For any gears there is a wide range of various materials are available such as steel, cast irons, nonferrous alloys, various plastics, composites, and synthetic material. Hence, it is important to under-stand the characteristics - including pros and cons - of either solution to ensure selecting the proper material for the specific application. Some gear con-structions will be applicable for certain applications, whereas different gear constructions will be correct for other applications.
Hard-anodized aluminum or steel are in general having their advantage in the durability of the materials, which theoretically should increase the lifetime. This is however not in reality the full truth, as it is extremely challenging to maintain the gears lubricated throughout the actuator’s full lifetime. Once the lubrication wears off, the gears will become increasingly noisy and actuator torque will lessen.
In worst case scenario the metal gear parts will jam up over time, particularly in humid condi-tions. Risk of gear jamming is furthermore related to gear tolerance - the more accurate the gears are, the less wear and tear is seen over time and conse-quently reduced risk of gears jamming. Hence, steel gears are generally recommendable in high torque, high temperature (+180°C) conditions with slow moving operation and low noise sensitivity.
A variety of composite material was introduced in the 60’ies intended for space shuttles and space industries in general. One of these materials was DuPont’s Delrin acetal homopolymer, which was designed to act as a bridge between plastics and
metals focusing on high tensity strength, excellent fatigue endurance, natural lubrication and excellent machineability for better gear accuracy. The product was further developed into the Delrin 150 in the 90’ies, which is the time (1998) when the composite material was introduced in FlowCon SM rotating actuator gears and is still in use today......
Leakage Classification IEC60534-4 - Update
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For end-of-line or similar applications, control valves still have their justification. A word on valve authority may come useful