This may require engineering investigation to ensure bus bracing is adequate. Field data gathered by all manufacturers has confirmed the probability of vacuum loss to be negligible. While this has been successfully carried out by at least one major manufacturer, it can be a very complex undertaking. It involves changing select mechanism parts to reduce the closing stroke, and force balancing other components for opening and closing speeds. Plus there is a possibility that some of the more crucial components subjected to mechanical wear will be reused.
Extensive tests have to be carried out to verify the performance of the hybrid design.
The modules are self-contained, fully tested to ANSI or other applicable standards. All safety interlocks to meet the requirements of ANSI standards are included. When replacing a solenoid operated device with a modern spring operated device, an additional safety interlock is required to ensure the complete assembly is not withdrawn from its compartment with the closing spring charged. This is specified in the applicable standards.