There are three groups of manways as divided by shape: round, oval and rectangular (including square).
Round manways are most often used as stainless steel tank lids mounted on top of tanks. They are used in various manufacturing processes where they serve a function:
- process opening (for example, to add ingredients to a mixer by a production line operator),
- maintenance opening (manway provides access for technicians to the inside of the chamber in case of emergency),
- sealing lid (to prevent unwanted release of liquid from the tank),
- inspection, control – they allow for permanent process control without opening the lid (manways with glass lid, manways with sight glass in the lid) or reading of measurement devices (inspection and measurement chambers).
Round manways are available in both non-pressure and pressure versions. The round manway range is also the most numerous and most popular category of manways.
Rectangular manways are a group of products with a very diverse range of dimensions and a wide range of applications. Among the rectangular manways there are models with side lengths ranging from 200 mm to 2000 mm. Rectangular manways are usually installed in the side wall of a non-pressure tank or one with relatively low operating pressure. On the other hand, some rectangular manways are used only as lids intended for installation in the upper part of tanks.
An important feature of rectangular manways is their typically low pressure resistance (generally not exceeding the range of 0.5-2.5 bar). Thus, rectangular manways mainly serve the inspection/inspection function of low operating pressure tanks.
Oval manways are a group of products that are almost always installed in the side walls of tanks. In addition, they mostly provide the ability to open the manway towards the inside of the tank. This means that this type of design is ideal for pressure tanks, where the forces inside will push against the manway.