By Ruben Wansink and James P. Stahl
The average person is seemingly tethered to their electronic devices with a near compulsive need to check email, texts, or update social media profiles. The cruise lines have responded by investing millions of dollars in infrastructure to provide wireless internet access for customers. The irony of going wireless is the amount of actual wire or cable required to support sophisticated data and communication networks. Today’s cruise ships even incorporate onboard data centers to keep passengers connected. One thing is for certain when it comes to technology, and that is change is inevitable. As newer generation technology becomes available, quite often the network cabling must be modified or replaced. In structured cabling parlance, such modifications are referred to as cable moves, additions, or changes, or MAC work.
While new generation technology platforms trigger MAC work, the one area that has not kept up with the times are the cable transits through which the cables are routed through bulkheads and decks. The most common type of cable transit consists of a steel frame fitted with rubber blocks (See Figure 1). Each individual cable is routed through a rubber block and secured within the frame by wedge plates. Often referred to as a “multi cable transit”, these devices were first developed for shipboard use in the early 1950s. The designs have been refined many times over the years, and compared to the original devices, the modern versions represent marked improvement. However, when it comes to the volume of cable required to support today’s networks, these traditional cable transits can be cumbersome. To make a simple cable change requires loosening of the wedge plate assembly and rubber blocks. The new cable has to be routed and then the blocks and wedge plates need to be re-assembled and tightened. Compounding the problem can be when a greater density of cables is required to be routed through a transit frame than the frame can accommodate.
To provide greater flexibility in terms of the cable arrangement, some shipyards have replaced the traditional block and frame cable transits with welded steel sleeves and flexible sealant systems. Such systems can often increase cable fill percentage and provide ease of installation. However, they still have limitations in that the liquid-applied sealants cure to a rubber-like consistency and the cables are effectively glued together. While the cured seal can be cut into to add or remove cables, this still requires diligence to re-seal the opening to patch or repair the damaged seals.
New Cable Transit Technology
Over the past few years, a new cable transit technology has emerged. These transit devices are purpose-made to handle cables passing through non-watertight bulkheads and decks that will be subject to frequent moves, additions, and changes (See Figure 2). The new generation transits incorporate self-sealing foam pads that automatically adjust to the cable load. As cables are inserted, the pads retract, thereby allowing the cables to pass through unchecked. After the cables are installed, the pads rebound to tightly seal around the grouped cables. The soft, supple foam conforms to the cables. In the event of a fire, the pads are intumescent, which means they will expand with heat to form a dense, insulative char that resists passage of flames, hot gases, and smoke in accordance with IMO FTP requirements.
These cable transit devices feature mounting plates that can be welded or screw-attached to bulkheads or decks. Individual cable transits can be ganged together to increase cable capacity. The convenient design of the transits and the associated mounting plates also maximizes the volume of cable that can be installed into a given area, which means the openings in the bulkheads or decks can be reduced both in terms of size as well as the number required
Self-Sealing Cable Transit Advantages
Ship owners and operators benefit long term. Since self-sealing cable transits always remain sealed, there is no risk that they would ever be left unsealed like traditional cable transits, thereby eliminating compliance issues during safety surveys while safeguarding passenger safety. The added benefit is that cable changes can be made remotely by leaving pulling strings inside the cable transits. This can be a major benefit by reducing trips up the ladder and avoiding damaging overhead ceiling tiles. Cable moves, adds, and changes are made quickly and efficiently, without the need to re-open transit frames or make new openings in the division during refurbishment.
Selecting the Right Environment for Self-Sealing Cable Transits
As advantageous as self-sealing cable transits can be, they are specifically intended for use in non-watertight divisions. Cable penetrations in watertight divisions should still use cable transit products that provide a hermetic seal such as a traditional block and transit frame or a liquid-applied sealant. The self-sealing cable transits provide an excellent air and smoke seal, but it is not a hermetic seal and thus they are not rated for use in watertight divisions. Nevertheless, in cruise line construction, a great deal of the penetrations will occur in non-watertight divisions and therefore, shipyards and ship owners can expect substantial cost and time savings.
Self-Sealing Cable Transits Are Here to Stay
Shipyards have clamored for a better way to address cable penetrations in non-watertight divisions for decades. With the introduction of self-sealing cable transits, such as STI Marine’s EZ-Path Marine Cable Transit (See Figure 4), the dream is now reality. Certification and Classification Societies, including DNV GL, ABS, BV, and others, have rigorously examined this new class of products. In fact, IACS published a document in February 2013 identified as FTP6, which included additional provisions for evaluating non-traditional cable transits. Beyond that which is required for the traditional cable transits, self-sealing cable transits have been evaluated to the additional testing and design criteria to verify performance. The resulting published Type Approvals validate conformance to both the IMO FTP as well as the additional criteria imposed by FTP6, assuring ship builders and owners of the safety and compliance of the devices. As shipyards continue to integrate self-sealing cable transits, and owners demand their use, this new class of products is quickly becoming the benchmark standard for cable penetrations in non-watertight divisions.