Ships and marine technology — Manholes with bolted covers
1Key Takeaways
This document specifies requirements for watertight and oiltight manholes of the current types with bolted covers, for general shipboard use other than for pressure vessels. It specifies the dimensions for the holes in the plating and the number, size and position of the fasteners. It is applicable to manholes of raise…
2Expert Interpretation
A comprehensive interpretation of the technical requirements for bolted manhole covers in the ISO 5894:2018 Ship and Marine Technology standard, including dimensional specifications, fastener configurations, material selection, and manufacturing quality standards for six types of manhole covers. This guide is applicable to the waterproof and oil-proof design of non-pressure vessel marine equipment.
Analysis of the Standard's Core Content
The third edition of ISO 5894:2018 comprehensively revises the technical specifications for bolted manhole covers for marine applications, refining the original O/E types into six categories: AO/AE/BO/BE/CO/DO, and adding four new sizes, ranging from 450×350 to 800×600. The standard applies to general-purpose marine equipment other than pressure vessels, covering flange-mounted, surface-mounted, and recessed installation methods.
Manhole Cover Types and Size Specifications
| Type | Features | New Specifications (mm) | Number of Fasteners | Minimum Cover Thickness (mm) |
|---|---|---|---|---|
| AO/AE | Flange Type with Handle | 500×400,600×450 | 18-26 M20 | 6-12 |
| BO/BE | Surface Mounted | 450×350,800×600 | 16-26 M20 | 6-12 |
| CO/DO | Embedded Oval | 600×450,800×600 | 16-26 M20 | 6-12 |
Note: All fastener threads must comply with ISO 262 standard. The actual thickness can be increased according to classification society regulations.
Key Technical Innovations
- New Jack Bolt design (2×M20 optional)
- Mandatory gasket material
Minimum yield strength ≥235N/mm² Corrosion resistance Seawater/freshwater corrosion resistance Surface treatment No pits, flatness meets sealing requirements Manufacturing tolerances must ensure parts interchangeability, and all opening edges must be deburred.
Implementation Recommendations
- Consider installation space and maintenance convenience when selecting the type
- For large-sized manholes such as 800×600, CO/DO type embedded design should be preferred
- Special oil-resistant gasket materials should be used in the oil tank area
- Regularly check the torque value of fasteners (see Table Z for recommended values)
Analysis of the Evolution of the Standard
Main improvements compared to the 1999 version:
- Type subdivision improves design accuracy
- Cover plate thickness is adapted to the requirements of modern hull structures
- Add safety accessories (handles/markers)
- Optimize geometric parameters to improve sealing performance