ESKS integral light/sightglass units have a quick release closure, so that they are a combination of charge/access port and light/sightglass. The integrated luminaire illuminates the interiors of boilers, tanks, bunkers, silos, mixers and other vessels in all non hazardous areas. SKS type sightglass ports are of the same design, except they have no luminaire. Both types are suitable for food processing. Usually these units come with a weld flange, but for flat vessel walls they can also be installed with a bolt-on flange.