... the tanks or vessels can be locked up.YAC:arc manhole cover,which can sustain a Max. ... of 2bar(under the temperature of 20°C)YAC-1:arc manhoe cover,has higher bracket,suitable ... for big vessels with lagging material.YAC:flat manhole cover,lower bracket.YAC:flat manhole over,,higher bracket,suitable ... for big vessels with lagging material.YAC-P:can sustain a Max.Working pressure of ...