How to make design choices regarding the structural forms of manholes and access holes?
Thread Content
The design choice for the structure of manholes and access holes should be determined based on factors such as the frequency of opening the hatch covers, their installation position (horizontal or vertical), the required level of sealing, the weight of the covers, and the space occupied when the covers are open. When the manhole cover needs to be opened and closed frequently, quick-opening manholes or hand holes are recommended. If the vertical plane position of the manhole axis is small, a rotary quick-opening manhole or handhole can be selected ； If rapid opening and closing is required, and it is permissible for the cover to move left and right perpendicular to the axis, a lever-type quick-opening manhole or handhole can be selected. To prevent dead zones where the medium does not flow or flows poorly due to the sections of manholes and access holes, core-equipped manholes and access holes should be used. When the weight of the manhole cover exceeds 35 Kg, a hinged manhole cover should be selected. l Atmospheric manholes and handholes are only suitable for non-toxic and non-explosive media. The selection of the nominal pressure class and seal surface type for manholes and handholes is the same as that for pipe flanges.
The above content is mainly drawn from Questions and Answers on the Design of Chemical Pressure Vessels. This book contains another point regarding this issue: Manholes located at the bottom of the vessel or at a higher position (more than 2 meters above the ground or the operating platform), or those designed for temperatures below -10°C, should have lids supported by lifting rods or hinges. What is the reason for this? The Q&A on the design technology of chemical pressure vessels states that the selection of the manhole structure should be the same as that of the vessel flange. Do you all think this rule is reasonable?
This post was last edited by ztr1118 on 2012-12-30 08:42. For manholes located more than 2 meters above the ground or the operating platform, it is necessary to use suspension rods or hinge mechanisms to facilitate operation by personnel, which is easy to understand.