Outline Rainwater inflow into manholes on sidewalks or streets requires pumping water causing awesome noise which gives people lots of troubles every year. So, a study has been carried out to get rid of above troubles.
1)Environment -The water does not enter into a manhole(Water pollution and groundwater pollution prevention)
2)Safety -Fixing a assist cover (Safety ring) can prevent casualties or car accidents by its upset, leaving, breakdown or abrasion etc
3)Waterproof -The rubber pack between the fixed cover ring and the main cover works as a soldering -The rubber pack prevents water inflow and bad smell -Water proof can save cost by saving drainage flow over 20% in rainy season -No water inside manhole can save budget for maintenance and service etc.
4)No noise -Even the fixed cover ring (cast) and the main cover are inclining loaded, the mechanical couble closing structure and the rubber pack prevents a distance height and noise