The right insert blocks

Once the transit frames are installed, the cables and/or pipes that pass through them are kept securely in place by a sealing system that also prevents the spread of fire, smoke, hazardous fumes, water, etc. It is widely acknowledged that the most stable and safe form of sealing system consists of precision-moulded insert blocks of many different sizes that also provide the much needed application flexibility.

The stability and safety that insert blocks give to transits is derived primarily from two main features.

  • The very precise fit that modular insert blocks of different sizes achieve around cables/pipes to totally seal the space between them.
  • The toughness and robustness of the blocks, which do not deform over the long term.

These features make sure that not even gas can pass through a packed transit when it is installed correctly.

Enhancing the safety of insert blocks

For first-rate insert blocks, a lot of thought and good science goes into what may at first seem a simple transit component. The performance of blocks is a key element in assuring the safety of cable transits.

Attention to detail

Strict attention to detail in the design, development and moulding of insert blocks is essential to achieve the features needed to facilitate transit installation and ensure high performance over many years in testing environments.

Clear identification

Easily identifiable cable/pipe size should be visible on each standard insert block to ensure that the correct block is used to achieve a tight seal.

Self-extinguishing material

Blocks should be manufactured from self-extinguishing material to prevent the passage of fire.


Blocks that are self-lubricating facilitate their installation, thereby saving time and effort.

Stable material and shape

The properties of the block material should be carefully evaluated so that they do not crack, melt, harden or become brittle under adverse conditions.

Tight tolerances

The blocks should be moulded to tight tolerances to ensure correct and uniform sizing.

Inert material

The block material should be as inert as possible to prevent it from being degraded by rodents, insects or microorganisms.

No halogens

Corrosive halogens like fluorine, chlorine, bromine and iodine should not be included in material ingredients as they are released when the block is subjected to fire. The blocks should be moulded from one type of rubber. 

No displacement

The design of blocks should prevent displacement when subjected to pressure during installation.

Minimal waste

To minimize negative environmental impact, block installation should result in minimal waste accumulation during the installation of transits.

Other frame components

In addition to the frame and insert blocks, components needed within the frame to secure and complete a stable installation include:
• Stayplate
• Compression plate
• STG-Endpacking
• PTG-Presswedge
• Others

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