How diameter, elevation, and clearance from nozzles keep maintenance safe.
Access without fighting equipment
A manway must allow person entry, inspection gear, and emergency exit without clashing with nozzles, supports, or insulation. Inside diameter and opening reinforcement are part of the shell calculation.
Common manway sizes
| Inside diameter | Typical use |
|---|---|
| 500 mm (20 in) | Common minimum for entry with basic gear |
| 600 mm (24 in) | More common standard, easier entry with inspection equipment |
| Over 600 mm | Large tanks or where internals must be removed |
For heavy manway covers, a davit arm or a hinge lets one person open and close it without a crane or extra hands — cutting the risk of injury during maintenance.
