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  3. The major differences between mechanical seals and mastic, compounds, and wet applied systems

The major differences between mechanical seals and mastic, compounds, and wet applied systems

… or 7 questions to ask your penetration seal supplier.

You can use mastic, compounds, or other wet applied methods to seal cable and pipe penetrations. If you do, remember to consider the curing time and other important aspects affecting sealing performance. You can choose mechanical cable and pipe seals instead, and benefit from several advantages. While compounds often protect against a single risk factor, mechanical seals can be used for multi-hazard protection. Here are some major differences.

1. Time

Plan your work wisely.

Mastic or compound solutions take time to install and require extensive curing time, which can cause problems for production and maintenance management. The wet applied materials do not indicate when they are dry and may even never fully cure in humid conditions. The curing depends on different environmental factors, and there is no reliable way to measure this to know when it is cured and operational. The mix often needs several days to fully harden and until then, cables and pipes must be supported. Some compound-based solutions recommend no movement of and no touching of cables or pipes until the system is fully cured. The reason is that if cables or pipes are moved during the curing process, the movement within the compound can create gaps and damage the integrity of the installation. In addition, critical project applications may require constant monitoring by fire watch until cured.

Mechanical seals are proven faster to deploy than typical compound-based methods. They are instantly fire-tight after installation – and performance is guaranteed also when urgently installed in running water conditions. Within 24 hours, the mechanical seals reach full performance levels to handle the most advanced pressure demands. You do not only save time on the actual installation work, you also avoid the need for fire-watching, the extensive time for curing and the required extra effort of rechecking of sites that may have been compromised by cable and pipe movement during the curing process.

Ask your supplier:

How long after installation can I rely on full performance?

2. Space

Manage quantity with quality.

If you use mastic or compound solutions when dealing with higher or multiple performance demands, you must be very careful with regards to the fill ratio. As there is no indication on when the certified fill ratio level is reached, there is a risk of overfilling. The result of overfilling is that certifications, approvals, and protection levels can be compromised. You may end up with a performance compliance issue that results in the need to make a larger opening or in the worst case, to reroute installed cables or pipes in another opening to gain a compliant solution. Suddenly you have an additional penetration path to take care of and seal from the risk of leakage, flames, or smoke.

Mechanical seals help you avoid overfilling. Their design makes sure you stay within the certified fill ratio. You can safely handle multiple cables and pipes, secure spare capacity for future needs and use smart software for design, planning, and long-term transit management.

Ask your supplier:

Can the fill ratio limit for full performance be verified to avoid the risk of overfilling the penetration?


3. Safety

Handle high cable and pipe density.

When using mastic, you must also consider the fact that cables and pipes laying too closely together tend to disturb each other. Normally, standards require that LV, MV and HV power cables are segregated from sensitive communication and signal cables. It is mandatory with wet applied solutions to ensure a minimum distance between cables and pipes as well as a minimum clearance to the edge of the opening to enable a full 360-degree coverage of compound between each of the cables and pipes. If the distances are not respected, the protective and sometimes certified performance becomes compromised and therefore, is no longer achieved. You will also need to ensure there is sufficient depth of material applied to guarantee a fire-tight, gas-tight, or watertight seal. Note that the material composition of the wet applied compound may require a well-ventilated workspace during application and curing to avoid exposure to fumes. If the area cannot be mechanically ventilated, the use of a respirator would normally be recommended.

Mechanical seals have a design that ensures space savings on both sides as well as spacing between cables and clearance to aperture edge. You meet all requirements for spacing and clearance automatically and can easily manage high cable and pipe density while maintaining full protective performance.

Ask your supplier:

How are the required depth, spacings and clearances guaranteed and checked?

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4. Performance

Secure certified protection.

Projects take time to finalize and must be protected against multiple hazards to operate safely for decades to come. You must respect the fill ratio and the cable and pipe density limit to achieve the required tightness. It puts pressure on the installer. It is a well-known fact that protection and ratings are compromised as soon as an opening is overfilled, or if there is not sufficient coverage between cables or enough clearance from the aperture edge.

With mechanical seals, you can simply fill up the penetration according to the cable configuration and packing plan presented by the transit design software. You know you can use the space available in line with certificates and approvals. In addition, a mechanical sealing solution provides excellent cable retention, which is important to secure tightness in areas where there is a risk of frequent ground settlement and expansion and contraction under load. A rubber module typically used within a mechanical seal is soft to the cable yet firm when it comes to keeping it in place.

Ask your supplier:

Does the final installation always comply with certifications?

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5. Lifecycle

Ensure long-term efficiency.

Note that wet applied solutions can have a shelf life as short as six months. This means a constant struggle to plan and control procurement, stock, logistics, and costs in practically all projects, and it could become an extreme issue on large complex projects stretching over years.

In contrast, there are mechanical seals with a guaranteed shelf life of five years. With mechanical seals, you have all components for a certified, quality assured solution at hand – including a frame for attachment by bolting, casting, or welding. When you have a complete sealing solution, it is much easier to manage long-term maintenance activities.

Ask your supplier:

What is the guaranteed shelf life?

6. Visibility

Simplify quality inspection.

If you use compounds, you cannot be confident on the levels of fire protection or tightness simply because it is very difficult to make a proper visual inspection after the original installation or following any changes or additional works. It is hard and time-consuming to visually inspect coverage between cables and almost impossible to check if the required depth of sealant is applied correctly. The uncertainty with regards to cable configuration makes it hard to trace cables and guarantee safe positioning and repeatability. When you want to cut or drill a hole in the compound to add a cable, there is a risk of invisible and fatal damage to the cables or other sealing materials utilized within the system.

Mechanical seals are neat, clean, and easy to inspect. Ideally, the seals are even openable for easy upgrades – making it easy to add a cable or two without any need for using knifes or other sharp tools that could cause damage to cables. There is no risk of failure in operation when the site is reenergized.

Ask your supplier:

Will this solution guarantee sufficient spacing between cables and to the aperture edge as well as sufficient depth of sealing materials?

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7. Flexibility

Be prepared for changes.

When using mastic, compounds, and wet applied solutions, you risk material waste and difficulties in handling design changes and future upgrades. If you need to add any cables or pipes, you must either add a new hole by drilling through the mastic or remove it completely, without damaging the existing cables, and then refill the hole with several additional layers of material afterwards.

With mechanical seals, on the other hand, you can plan for spare capacity without the need to cut anything or risk any damage to cables in an existing penetration. You know you bring the right materials from the start, and you are thereby prepared for modifications and additions during installation or later in the lifecycle of the asset. When you already have all the sealing materials needed on site, you do not have to worry about any additional costs. With mechanical seals, there is simply no guesswork needed: you have control of seals and safety certifications from planning and design through to construction.

Ask your supplier:

Can I add a cable without risk and without any need for extra materials and costs?

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Definition of cable and pipe sealing systems

There are many types of sealing systems for cable and pipe penetrations. In the above article, "mechanical seals" are compared to "mastic, compounds and wet applied sealing systems". Here is a description of how the different systems in the comparison are defined.  

Mechanical seals

Mechanical seals refer mainly to modular-based multi-cable and pipe sealing systems. They typically consist of a frame, rubber sealing components and a compression unit. The frame is attached to the structure to accommodate the sealing components, and the system relies upon compression by mechanical means, such as bolts or a compression system.   

Mastic, compounds, and wet applied sealing systems

Mastic, compounds and wet applied sealing systems refer to different kinds of sealing materials that has one typical feature in common: they are all applied to the cable and pipe penetration in a wet or semi-liquid state. The materials then cure or harden to form a seal.