ARCA’s MF0 actuator from the proven 812/813 series is a pneumatic actuator that was spe-cially designed to be compatible with sterile and fine chemical applications and is particularly well suited to the tight space requirements associated with prefabricated system components.
This diaphragm actuator is the first to integrate the fully welded construction of the actuator chamber as used on piston actuators in sterile process technology. The design facilitates ex-tremely small dimensions and maintains a specified effective diaphragm surface of 143 cm². To this end, the circular formation of bolts that affix the diaphragm in conventional diaphragm actuators has been eliminated to lend the actuator a smooth, easy-to-clean surface that is free of bolt heads and other sharp edges. The smooth surface also minimizes the risk of injury when maintenance work is performed.
The new diaphragm joint and welding gap ensure that the surface pressure on the diaphragm is precisely defined and evenly distributed, and the low thermal influence exerted by the diffu-sion weld never impacts the diaphragm.
The MF0 meets all requirements of a modern actuator for the process industry despite its fully welded construction. These include:
- Easy replacement of the actuator stem and all dynamic sealing elements
- Easy, on-site reversal of the direction of operation without the need for additional parts
- Direct mounting of the 827A positioner and similar devices with integrated air ducting for the ”fail close” direction of operation
- Adjustable feedback lever for use on valves with a stroke of less than 20 mm
- Optional positioned mounting as per VDI 3847 requirements, including the variant with the OPOS® interface, which offers an additional shutoff device for the instrument air so that the positioner can be replaced during operation
- Optional blanket protection of the spring housing using the positioner exhaust air to avoid moisture and corrosion under extreme operating conditions (even without external piping for fail close” direction of operation)
- Use of the same actuator yokes and stem couplings as found on larger MFIs (ensures direct compatibility of the MF0 with all ARCA valves up to DN 65 as well as with a large number of valves from other manufacturers)
- Additional NAMUR interface (IEC 60534-6-1) on the actuator yoke enables mounting all positioners and auxiliary devices that comply with this standard
The actuating force (closing force of the spring) is 3 kN despite the compact dimensions of the actuator chamber, which measures just 170 mm in diameter. This allows the MF0 to safely close a DN 50 valve with maximum rated Cv against r a differential pressure of 13 bar. Higher values are possible when with reduced Cvs.. The MF0 thus is a good all-rounder for many chemical applications and is a versatile aid in general mechanical and process engineering environments.