General Details The application of these types of 16â Manhole Cover is for Fuel Tanker with Top Loading. The Manhole Cover is mounted by 24 bolts on steel fabricated collar, which is welded on topside of Tankerâs shell. The Specialty of this Manhole Cover is the Mild Steel Construction of Bridges. A New well-designed Pressure & Vacuum Vent is fitted on the lower side of Fill Cap, which provides pressure releasing, and vacuum breaking.