Tank pressure manways are available in stainless steel SS304 or SS316 (some are special order). Manways are either top or side mounted, depending on the size of the tank or the function of the manway.
Oval/Elliptical manways are often found on brite beer tanks and fermenters, and offer both an inward and outward swinging door.
Shadowless manways are designed to be mounted flush with the exterior of the tanks, thus creating no interior protrusions, or a lip inside, where unsanitary conditions can build up; they are recommended instead of their oval counterparts. Shadowless manways open inward.
Rectangular manways are typically side-mounted on mash tuns to facilitate the removal of grain.
Round manways are simply designed to be an access port for pressurized brewing systems.
Duane Teach
Michael C