TUF multi-bolt Covers for Marine and Ship Manhole are for both oil-tight and watertight manholes like oil tanks, water tanks and many other places on ship. There are different types available like AA, AB, BA, BB, BC, BD, CA, CB, CC, CD, DA, DB, EA, EB. (Classified by nominal sizes). The rubber seal of covers for drinking water tank is made of rubber that meets the requirements of food hygiene. The surface of the manhole cover fabricated by China TUF is smooth and free of cracks, burrs, and sharp corners. China TUF Marine manhole covers of the same types and sizes are interchangeable with each other. The welding points are all of sufficient strength and tightness. The flatness deviation of the sealing surface between the cover of the manhole cover and the seat ring is not more than 1 mm. After the welding of the manhole cover, the anti-rust treatment is strictly carried out, and then covers are coated with a primer twice after derusting. Some New Products from China TUF: A. Marine Raised Manhole Cover B. Marine Sunk Manhole Cover C. Marine Flush Manhole Cover Available IACS Certs: ABS, BV, CCS, DNV-GL, KR,LR, RINA, NK,RMRS and etc.