View Full Version : Shadowless manway

06-25-2015, 08:47 AM
Can anyone explain the differences between shadowless and standard manways. Attached are 3 pictures is this a shadowless manway?


06-25-2015, 01:59 PM
That is a shadowless manway. Shadowed manways (menway?) have a perpendicular flange around them, casting a shadow on the closed manway door.

dick murton
06-25-2015, 02:25 PM
I have to disagree, simply because of the way the manway has been located in relation to the internal surface (second pikkie down). I agree that the design is in theory shadowless, but because it is set at the outside of the insulation layer, there is a deep step from the internal wall to the manway. Therefore there is a lip all the way round, the upper horizontal part of which is likely to remain uncleaned, or be poorly cleaned as there is no direct impingement from the cleaning head, or water running vertically downward at turbulent flow rates. If the manway was set in the internal surface, and the insulation casue the manway to be inset, then this would be shadowless.

Special care will have to be taken when cleaning this tank, probably requiring manual cleaning around the inside of this lip every time the tank is cleaned.

Looks like someone who thinks they know what they are doing, but .......

06-25-2015, 03:24 PM
Now I'm confused. Our DCi "shadowed" manways have a substantial flange around the outside of the door, but the door lies almost flush with the interior surface of the tanks. Our JVNW "shadowless" look very much like the one above, but also sit flush with the interior of the tank.

That must be some strange hybrid, combining the worst features of each....

06-25-2015, 06:10 PM
The bottom photo is the shadowless manway.

dick murton
06-26-2015, 03:39 AM
Manways as described with a perpendicular flange are designed so the door is flat, not curved. The flange is welded such that the vertical central line is flush, or as near as dammit, with the internal surface of the vessel. Sometimes they are welded so there is a substantial lip at the top, but this is not good hygiene practice. This flange then sticks out at the edges of the flange hoop, and creates the shadow underneath the bottom edge of the hoop. The degree of shadow varies according to how close to the vessel wall it has been welded at the vertical centre line, and the radius of the vessel. A small diameter vessel creates a larger shadow than a large radius vessel. For instance, in a 4 metre diameter vessel, the shadow is small enough not to be a major problem for most uses. But a 1.5 metre diameter vessel could create a potentially serious micro problem due to poor cleaning.

The middle picture shows a non shadow manway, which because of the installation, has created a potentially uncleanable top lip, particularly close to the manway, due to the thickness of the insulation. If the cut through the insulation had been chamfered at say 45 degrees, instead of what appears to be 90 degrees, then the shadow would probably be not worth worrying about. However of course this would give rise to poorer insulation in the chamfered area.