Why are boiler manways and handholes oval?

The shape of boiler manways and handholes being oval is primarily designed to facilitate easier removal from pressure vessels. This oval design allows for a larger opening compared to a circular one, making it simpler to insert and remove equipment or personnel when accessing the interior of the boiler. The larger opening aids in minimizing any restrictive angles that could make it difficult to maneuver within confined spaces.

Although other factors like structural integrity, manufacturing costs, and sealing capability play roles in design considerations, they do not directly account for the specific advantage that an oval shape provides in terms of accessibility. Therefore, the oval shape primarily enhances practicality when it comes to accessing the boiler for maintenance, inspection, or repairs.