LNG Cargo Hold Cable Penetration Sealing Module Selection Scheme

LNG (liquefied natural gas) carriers impose extremely stringent safety requirements on cargo hold areas due to the extreme low temperatures (-163°C) and high flammability of their transported medium. Cable penetration sealing modules, as key components maintaining the airtightness, fire resistance, and explosion-proof integrity of the cargo hold, must be selected in accordance with international maritime regulations and meet specific operational requirements. The following is a systematic selection scheme for cable penetration sealing modules in LNG carrier cargo holds:

1. 1. Core Design Requirements and Challenges
   2. Adaptability to extreme low temperatures

Cargo hold temperature: -163°C (LNG boiling point);

Sealing materials must maintain their elasticity and sealing properties at low temperatures, without becoming brittle or shrinking and cracking.

1. 2. Gas-tightness

Prevent methane (CH₄) from leaking into non-hazardous areas;

Leakage rate requirement: ≤1×10⁻⁴ atm·cm³/s (helium mass spectrometry leak detection).

1. 3. Fire and Explosion Protection

Passing through the A60 fireproof bulkhead;

Meets IEC 60079-0/14 explosion-proof standard (Ex d IIC T6).

1. 4. Corrosion resistance and durability

Resistant to seawater salt spray, LNG boil-off gas (BOG), and cleaning agent corrosion;

Design life: ≥25 years (same life cycle as the ship).

1. 1. Applicable Standards and Specifications

⚠️ Certification Requirements: Products must obtain classification society certification (such as DNV, ABS, CCS) and explosion-proof certification (ATEX/IECEx).

III. Sealing Material Selection Guide

🔑 Golden Combination:

Main seal: FFKM O-ring + metal retaining ring;

Auxiliary sealing: Expanded graphite spiral wound gasket (fireproof + airtight redundancy).

1. 1. Typical Structural Design

▶ Dual-redundant sealing system

[Cable] → [FFKM Main Seal] → [Monitoring Chamber (Optional Pressure Sensor)] → [FFKM Secondary Seal] → [Fireproof Packing]

Advantage: Even if the main seal fails, the secondary seal can still maintain airtightness;

Monitoring chamber: can be connected to nitrogen positive pressure monitoring for real-time early warning of leaks.

▶ Quick-install modular frame

Material: Austenitic stainless steel (316L/904L) or nickel-aluminum bronze;

Structure: Supports independent sealing of single or multiple cables, facilitating maintenance and replacement;

Installation: Tighten with bolts, no welding required (to avoid corrosion in the heat-affected zone).

1. 1. Mainstream Suppliers and Product Series

1. 1. Installation and Verification Requirements
   2. Installation process

Through hole machining accuracy: H7/g6 fit;

Torque control: Use a hydraulic torque wrench and tighten according to the manufacturer’s specifications;

Cleanliness: Clean the sealing surface with anhydrous ethanol before installation; grease is prohibited.

1. 2. Acceptance Testing

VII. Selection Decision Flowchart

Determine the penetration location

Did it penetrate the A60 bulkhead?

Select A60+ dual airtight certification module

Select a dedicated airtight module

Confirm the number and outer diameter of the cables.

Choose FFKM or metal seal.

Verification of classification society and explosion-proof certification

Complete the selection

The following principles must be adhered to when selecting cable penetration sealing modules for LNG ship cargo holds:

🔒 The “Triple Protection” Principle:

Reliable materials (FFKM/metal);

Structural redundancy (double seal);

All certifications are complete (classification society + A60 + Ex d).

No compromises allowed: Any cost or weight savings should not come at the expense of airtightness and fire resistance.